Epidemiology and Burden of Astigmatism: A Systematic Literature Review

SIGNIFICANCE

This is the first literature review to report the epidemiology, patient burden, and economic burden of astigmatism in the general adult population. The unmet needs of astigmatism patients with coexisting ocular conditions (cataract, glaucoma, dry eye, presbyopia, or macular degeneration) and risks associated with untreated astigmatism are also reviewed and reported.

PURPOSE

This study aimed to identify, report, and summarize the published literature on epidemiology, patient burden, and economic burden of astigmatism using a systematic literature review.

METHODS

MEDLINE, EMBASE, and Cochrane Library databases were searched (January 1996 to May 2021). Search results were limited to the English language. Proceedings (2018 to 2021) from ophthalmology congresses were searched along with gray literature using the Google Scholar platform.

RESULTS

The literature search yielded 6804 citations, of which 125 met the inclusion criteria (epidemiology, 68; patient burden, 60; economic burden, 6). Astigmatism prevalence in the general population varied from 8 to 62%, with higher rates in individuals 70 years or older. The prevalence of with-the-rule astigmatism was higher in individuals 40 years or younger, whereas rates of against-the-rule and oblique astigmatism increased with age. Astigmatic patients experienced decreased vision quality, increased glare (53 to 77%), haloes (28 to 80%), night-time driving difficulties (66%), falls, and spectacle dependence (45 to 85%). Astigmatic patients performed vision-related tasks slower (1 D, 9% slower; 2 D, 29% slower) and made more errors (1 D, 38% more errors; 2 D, 370% more errors) compared with fully corrected individuals. In cataract patients with astigmatism, the annual mean per-patient productivity loss costs ranged from €55 ($71) to €84 ($108), and mean informal care costs ranged from €30 ($39) to €55 ($71) with a mean of 2.3 to 4.1 hours spent on informal care.

CONCLUSIONS

Uncorrected astigmatism decreases patients' vision-related quality of life, decreases productivity among working-age adults, and poses an economic burden on patients and their families.

Refractive errors (myopia, hyperopia, or astigmatism) affect all age groups and are the most commonly reported ocular conditions globally.^1,2 If left uncorrected, refractive errors can lead to social and economic consequences for both patients and their families.^1–3 In 2010, uncorrected refractive errors affected an estimated 108 million individuals worldwide.⁴ According to the 2019 World Health Organization report on vision, uncorrected refractive errors were responsible for moderate to severe distance vision impairment or blindness in 123.7 million individuals globally.⁵

Astigmatism is a common refractive error caused by a meridional asymmetry in the curvature of the eye's cornea or lens, leading to a corresponding asymmetric refraction of light rays.⁶ In a recent systematic review and meta-analysis, Hashemi et al.¹ identified astigmatism as the most common refractive error, with an estimated pooled prevalence of 40% in adults. Although the exact cause of astigmatism is still not known, age, race/ethnicity, genetic factors, environment, extraocular muscle tension, visual feedback, and eyelid pressure have been found to influence the development of astigmatism.^7–9

Astigmatism can be classified as with-the-rule, against-the-rule, and oblique based on the orientation of the strongest power meridian.^10,11 In with-the-rule corneal astigmatism, curvature is steepest in or near the vertical meridian, and in with-the-rule refractive astigmatism, the vertical meridian is the most myopic. The opposite is true for corneal and refractive against-the-rule astigmatism. In oblique astigmatism, corneal curvature is steepest, or myopia is greatest in the oblique meridian.^10,11 The overall or refractive astigmatism is a result of corneal and lenticular astigmatism.¹²

Astigmatism affects patients' visual acuity and contrast sensitivity at all light levels.^8,13 Astigmatism correction is generally achieved using spectacles, contact lenses, toric intraocular lenses, toric implantable collamer lenses, or corneal refractive surgery.^14–16 If left uncorrected, patients may suffer from distorted vision, eyestrain, and diplopia.⁸ Furthermore, patients with uncorrected astigmatism also suffer from decreased vision-related quality of life, increased risk of falls, night-time driving difficulties, and decreased overall well-being.^8,17–22

Astigmatism leads to increased productivity losses among patients and their caregivers.¹³ Because of decreased vision quality, astigmatic patients are more prone to making errors at their workplace.²³ In patients undergoing surgery for astigmatism correction, post-operative vision care, visits to optometrists and ophthalmologists, transportation costs, and time spent receiving informal care are the major contributors to the economic burden.^24–26

The epidemiology of astigmatism and associated patient and economic burden have been recognized in the literature. Anderson et al.¹³ conducted a systematic review using data published between 1996 and 2015 and reported the global epidemiology and economic and humanistic burden of astigmatism. However, Anderson et al.¹³ assessed the outcomes of astigmatism in cataract patients only and did not include studies of general population. Several other systematic literature reviews in the past have independently reviewed and analyzed astigmatism-related outcomes. However, these reviews were focused on one of the three outcomes—epidemiological, humanistic, or economic outcomes, and none of these reviews summarized all three astigmatism-related outcomes.^1,13,27–30 Thus, the present systematic review was conducted to address the gaps in existing literature and identify data related to astigmatism epidemiology and burden in the general adult population and patients suffering from eye diseases with coexisting astigmatism.

The specific objectives of this systematic review were the following:

• to identify and report the prevalence, incidence, mortality, and risk factors associated with astigmatism in general adult population and patients suffering from eye diseases with coexisting astigmatism;

• to identify and report the patient burden of astigmatism in terms of health-related quality of life, visual disturbances, patient safety in navigation, spectacle dependence; and

• to report the economic burden associated with astigmatism in terms of direct and indirect costs incurred by patients and families, health care resource utilization, caregiver burden, and loss of work productivity.

METHODS

To meet the objectives, this systematic review was conducted following the principles outlined in the Cochrane Handbook for Systematic Reviews.³¹ The findings from the systematic review were reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines.³²

Systematic Literature Search

The systematic literature searches were conducted using structured search strategies in three electronic medical literature databases: Medical Literature Analysis and Retrieval System Online (MEDLINE), Excerpta Medica Database (EMBASE), and Cochrane Library (search period: January 1996 to May 2021).

The key search terms for retrieving relevant studies of interest were as follows: disease (“astigmatism”), epidemiology (“incidence,” “prevalence,” “risk factor,” and “mortality”), patient burden (“vision-related quality of life,” “health-related quality of life,” “activities of daily living,” “patient satisfaction,” “risk of falls,” “night-time driving difficulties,” “spectacle independence,” and “dizziness”), and economic burden (“direct costs,” “indirect costs,” “cost analysis,” “loss of work,” “resource utilization,” and “caregiver burden”). The searches were restricted to articles published in the English language. The detailed search strategy for EMBASE database is presented in Appendix Tables A1 to A3, available at http://links.lww.com/OPX/A589.

In addition, conference proceedings from key eye congresses for the past 3 years (2018 to 2021) were manually searched to retrieve studies that were not yet published in medical journals as full-text publications. Key ophthalmology congresses were searched for evidence related to astigmatism: American Academy of Ophthalmology, American Society of Cataract and Refractive Surgery, European Society of Cataract and Refractive Surgeons, Association for Research in Vision and Ophthalmology, World Ophthalmology Congress, Royal College of Ophthalmologists UK Congress, and European Association for Vision and Eye Research. Finally, a gray literature search was conducted using the Google Scholar platform to identify relevant studies not captured through database searches.

Inclusion and Exclusion Criteria

The studies retrieved from database and gray literature searches were reviewed following the Population, Interventions, Comparators, Outcomes, Study Design, and Time Frame criteria listed in Table 1. Studies evaluating astigmatism patients 18 years or older, with or without coexisting conditions, such as cataract, glaucoma, presbyopia, dry eye, and macular degeneration, were reviewed. Studies conducted in the following geographical regions were included: North America (the United States and Canada), South America (Brazil), Asia-Pacific (China, Japan, South Korea, and Australia), and Europe (Germany, United Kingdom, Italy, Spain, the Netherlands, France, and Sweden).

TABLE 1.

PICOS-T criteria

	Inclusion criteria	Exclusion criteria
Population	• Adult patients (18 years or older) diagnosed with astigmatism • Studies conducted in following geographies/regions: United States, Canada, Brazil, China (including Hong Kong and Macau), Japan, South Korea, Australia, Germany, United Kingdom, France, Italy, Spain, the Netherlands, Sweden • Subgroup population: patients with various other eye diseases such as glaucoma, cataract, age-related macular degeneration, presbyopia, dry eye, and reporting pre-existing astigmatism	• Nonocular diseases patients • Patients suffering from the following eye diseases: strabismus, keratoconus, lower eyelid epiblepharon, Terrien marginal degeneration, nystagmus, and ptosis • Studies evaluating diseases other than ocular and comparing outcomes with normal population • Animal/in vitro studies • Studies conducted in focused groups: athletes, homeless population, doctors/physicians, and other such specific populations
Interventions/comparators	• Studies focusing on the following interventions of interest: IOLs, contact lenses (including ortho-k), LASIK, spectacles	• Studies evaluating oral medications, such as vitamins, massage, physical activity, or any new technology, such as goggles with medicine, or visual therapies • Studies evaluating corneal surgeries except for LASIK • Studies evaluating a new technology or surgical method without any relevant comparator
Outcomes	• Incidence, prevalence • Mortality/death • Risk factors • Total costs: medical costs, costs associated with spectacle use, contact lens use, refractive surgeries, and post-surgery management such as eye drops; indirect costs • Health care resource utilization: hospitalizations, length of stay, physician visit • HRQoL changes • Patient burden: disturbances in visual acuity (glares and haloes), inconvenience, headache, fatigue, spectacle dependence, safety aspects such as risk of falls and night-time driving difficulties, and other related measures	• Studies not reporting on any one of the outcomes of interest
Study design	• RCTs/single-arm trials • Observational studies • Cross-sectional studies • Economic evaluations • Systematic reviews and/or meta-analysis	• Editorials/commentaries • Case reports or case series • Narrative reviews • Observational studies with <20 patients and RCTs with <10 patients in each treatment arm • Optical bench simulation studies
Time frame	• Studies published during the year 1996 or later	• Studies published before 1996

HRQoL = health-related quality of life; IOL = intraocular lens; PICOS-T = Population, Interventions, Comparators, Outcomes, Study Design, and Time Frame; RCT = randomized controlled trial.

There is no consensus on a standard classification of astigmatism in the published literature. Although some classify astigmatism as mild (<1.50 D), moderate (1.50 to 2.00 D), and severe (>2.0 D),³³ others classify it as mild (<1.50 D), moderate (1.50 to 2.50 D), and significant/severe (>2.50 D).^34,35 This review presents astigmatism outcomes for mild, moderate, and significant astigmatism, adhering to the classification based on previously published studies.^34,35 The findings of this review suggest that visual acuity is unaffected by astigmatism of less than 0.5 D. This implies that the visual benefit of astigmatism correction for less than 0.5 D would be restricted in clinical settings and would not be considered as visually significant.³⁶

Selection of Eligible Studies and Quality Appraisal

The titles and abstracts of all the citations retrieved from database and gray literature searches were screened by two reviewers independently. After completion of the title and abstract screening, full-text articles of potentially relevant or unclear citations were screened by two independent reviewers. A third independent reviewer reconciled any discrepancies between the two reviewers during the title and abstract screening or full-text screening. Data were extracted into a specially designed Microsoft Excel (Microsoft Corp., Redmond, WA) template for each included study. Relevant data from all included studies were extracted by a single independent reviewer and checked for quality and accuracy by a second independent reviewer.

Each included study was appraised for quality using the following checklists: Cochrane Risk-of-Bias Tool 2 for randomized controlled trials,³⁷ Newcastle-Ottawa Scale for nonrandomized/observational/cross-sectional studies,³⁸ Consolidated Health Economic Evaluation Reporting Standards checklist for economic evaluations,³⁹ and Critical Appraisal Skills Program checklist for systematic reviews.⁴⁰

RESULTS

Search Results

The literature search yielded a total of 6804 citations. During the title and abstract screening, 1601 duplicate citations (within the three electronic databases) were identified and removed manually. The titles and abstracts of the remaining 5203 citations were screened according to the Population, Interventions, Comparators, Outcomes, Study Design, and Time Frame criteria listed in Table 1.

After completion of the title and abstract screening, 443 citations were found to be relevant for full-text screening. After the completion of full-text screening, conference searching, and gray literature searching, 125 studies (113 studies from database searching, 11 studies from gray literature searching, and 1 presented at conference) met the inclusion criteria and were included for data extraction. Of the 125 studies, 68 studies reported data on epidemiology, 60 studies reported data on patient burden, and 6 studies reported data on the economic burden. The summation of study numbers in each category exceeds 125, as some of the studies evaluated multiple relevant outcomes. Three of the included studies were systematic reviews and/or meta-analyses.

The Preferred Reporting Items for Systematic Reviews and Meta-analyses flow diagram summarizing the process and results of systematic literature searches is presented in Fig. 1.

FIGURE 1.

Preferred Reporting Items for Systematic Reviews and Meta-analyses flow diagram summarizing the process and results of the systematic literature review.

Prevalence

Astigmatism Prevalence in the General Population

Astigmatism was identified as the most common refractive error with an estimated pool prevalence of 40% (95% confidence interval [CI], 34 to 47%) in adults across the World Health Organization regions (Africa, Americas, Southeast Asia, Europe, Eastern Mediterranean, and West Pacific) in a recent systematic review and meta-analysis.¹

The summary of studies (n = 14) reporting the prevalence of astigmatism in the general adult population across countries and geographies is presented in Table 2. The reported prevalence across different countries and regions was as follows: Northern and Western Europe, 27%⁴⁸; South Korea, 31 to 58%^46,47; Germany, 32%⁴⁹; Spain, 54%⁵⁰; Japan, 54%⁵⁴; United States, 11 to 46%^51–53; and China, 8 to 62%.^41–45 Among the countries/regions included in this review, the highest astigmatism prevalence was reported in China (62%). The estimates of prevalence presented herein should be compared with caution because these studies differ in terms of magnitude of astigmatism (varying from ≥0.5 to ≥1.0 D).

TABLE 2.

Characteristics of studies reporting prevalence of astigmatism in the general adult population

Country/region	Study	Design	Astigmatism criterion by cyl magnitude (D)	Age group (range, and mean/median if applicable) (y)	Sample size (patients)	Prevalence (%)
China	Li et al.41	Cluster sampling and survey	≥0.75	50–96 (mean, 61)	4979	8
	He et al.42	Cross-sectional (clustered sampling)	>0.75	50–93 (mean, 64)	1269	48
	Liang et al.43	Cross-sectional (clustered sampling)	>0.50*	≥30 (mean, 52)	6491	28
	Wang et al.44	Cross-sectional	≥0.50	40–80	2090	62
	Wang et al.45	Cross-sectional	≥0.50	40–80	1626	58
South Korea	Yoon et al.46	Cross-sectional	>0.75	3–95	14,606 (≥3)	58; (≥3 y)†; 54; (19–29 y); 50; (30–39 y); 52; (40–49 y); 63; (50–59 y); 79; (60–69 y); 92; (≥70 y)
	Rim et al.47	Cross-sectional	≥1.00*	≥5	33,355 (≥5 y)	31; (≥5 y)†; 32; (≥20 y); 36; (≥40 y)
Northern and Western Europe	Williams et al.48	Meta-analysis of population-based and case-control studies	≥1.00	Median age across studies, 44–78	61,946	27
Germany	Wolfram et al.49	Observational	>0.50	35–74	13,959	32
Spain	Antón et al.50	Cross-sectional	≥0.50	40–79	417	54
United States	Vitale et al.51	Epidemiological survey	≥1.00	≥20	14,213	36
	Sandhu et al.52	Cross-sectional	≥0.75	≥40 (mean, 55)	4272	11
	Varma et al.53	Cross-sectional	>0.50	≥50	4144	46
Japan	Sawada et al.54	Cross-sectional	>0.50	≥40 (mean, 58)	3021	54

Variations in the prevalence rates across studies could be further attributed to different age groups evaluated in studies, differences in examination techniques (such as using no cycloplegia for refractometry), variation in study sample size, different sampling techniques, residential area (urban vs. rural), and genetic differences between the populations. *Astigmatism definition reported in Liang et al.⁴³ is <−0.50 and in Rim et al.⁴⁷ is ≤−1.00 D, which have been reported as >0.50 and ≥1.00 D to align with the reporting norm of other studies included in this review. †Mentioned only for presentation purpose; pediatric population was not included in the analysis. Cyl = cylinder.

Variations in the overall prevalence across studies could be further attributed to different age groups evaluated in studies, differences in examination techniques (such as using no cycloplegia for refractometry), variation in study sample size, different sampling techniques, residential area (urban vs. rural), and genetic differences between the populations.^41,42,44,53

Astigmatism Prevalence in the General Population: Age- and Sex-wise Distribution

The prevalence of astigmatism in the general population was found to increase with advancing age, mainly because of age-related changes in refractive index gradients within the crystalline lens.^{41,42,46,47,50,53,55,56} The age group–wise prevalence of astigmatism in the general population across studies is presented in Fig. 2.

FIGURE 2.

Age group-wise prevalence of astigmatism in the general population.

Included evidence from four epidemiology studies showed that astigmatism rates were higher in males than in females (34 to 54% for males vs. 30 to 54% for females).^42,49,53,54 A reverse epidemiological trend was observed in three studies, wherein astigmatism rates were higher in females compared with males (54 to 59% for females vs. 41 to 58% for males).^41,46,50

Astigmatism Distribution According to Orientation: With-the-rule, Against-the-rule, and Oblique

Across countries, the distribution of against-the-rule astigmatism ranged from 1 (China)⁵⁷ to 58% (China),⁵⁸ and with-the-rule astigmatism ranged from 4 (United States)⁵³ to 98% (China).⁵⁷ The prevalence of oblique astigmatism ranged from 2 (China)⁵⁷ to 61% (South Korea).⁵⁹ The distribution of against-the-rule, with-the-rule, and oblique astigmatism across studies is summarized in Table 3.

TABLE 3.

Distribution of against-the-rule, with-the-rule, and oblique astigmatism

Country	Study	Sample size (patients)	Age group (range, and mean/median if applicable) (y)	ATR (%)	WTR (%)	Oblique (%)
Canada	Michaud et al.60	19	18–40 (mean, 35)	—	63	37
	Wallerstein et al.61	65	18–51 (mean, 30)	29	67	4
China	Guan et al.62	827	16–98 (mean, 73)	50	32	18
	Chen et al.58	2849	40–95 (mean, 71)	58	25	17
	Yuan et al.63	6908	30–97 (mean, 70)	52	30	17
	Cui et al.64	4561	40–101 (mean, 70)	53	29	18
	Feng et al.65	1975	18–95 (mean, 72)	49	31	20
	Yu et al.66	2821	32–95 (mean, 71)	48	37	15
	Wu et al.67	5662	40–97 (mean, 68)	44	37	19
	Hu et al.57	7829	18–40 (mean, 25)	1	98	2
	Han et al.68	356	5–45 (mean, 17)*	5	84	10
Germany	Hoffmann and Hütz69	15,448	Median, 74	34	47	19
Italy	De Bernardo et al.70	380	33–96 (mean, 71)	39	44	17
	De Bernardo et al.71	729	18–96 (mean, 58)	29	57	14
Japan	Fujimoto et al.72	41	18–71 (mean, 48)	—	75	25
United Kingdom	Young et al.73	11,624	8–70*	29	33	NR
	Schallhorn et al.74	18,648	26–99 (mean, 59)	54	26	20
United States	Varma et al.53	4144	≥50	17	4	25
South Korea	Eom et al.59	180	39–93 (mean, 66)	23	17	61

*Majority of the subjects were older than 18 years and therefore discussed using the combined population. ATR = against-the-rule; NR = not reported; WTR = with-the-rule.

Astigmatism Distribution According to Severity: Mild, Moderate, and Significant

When classified according to severity, the distribution of mild astigmatism (<1.50 D) in the included studies ranged between 33 (China)⁶⁸ and 82% (Italy).⁷⁰ In comparison, distribution rates up to 39% (United States) and 34% (China) were recorded for moderate and significant astigmatism, respectively.^35,68 The distribution of mild, moderate, and significant astigmatism across studies is summarized in Table 4.

TABLE 4.

Distribution of mild, moderate, and significant astigmatism

Country	Study	Sample size (patients)	Age group (range and mean/median if applicable) (y)	Mild (<1.5 D) (%)	Moderate (1.5–2.5 D) (%)	Significant (>2.5 D) (%)
China	Guan et al.62	827	16–98 (mean, 73)*	80	16	5
	Chen et al.58	2849	40–95 (mean, 71)	81	15	4
	Yuan et al.63	6908	30–97 (mean, 70)	75	19	7
	Yu et al.66	2821	32–95 (mean, 71)	78	17	5
	Jiang et al.75	1976	3–100 (mean, 62)*	78	18	4
	Hu et al.57	7829	18–40 (mean, 25)	81	14	4
	Han et al.68	356	5–45 (mean, 17)*	33	33	34
Italy	De Bernardo et al.70	380	33–96 (mean, 72)	82	13	5
	De Bernardo et al.71	729	18–96 (mean, 58)	76	NR	NR
Spain	Ferrer-Blasco et al.76	2415	32–87 (mean, 61)	70	11	6
	Arriola-Villalobos et al.77	3332	30–97 (mean, 75)	80	NR	9
United Kingdom	Khan and Muhtaseb78	746	30–104 (mean, 76)	80	10	8
	Lyall et al.34	1814	18–99 (mean, 75)	80	15	5
	Collier Wakefield et al.79	2247	10–109 (mean, 72)*	78	16	6
United States	Heidary et al.35	217	0.5–91 (mean, 37)*	39	39	22
South Korea	Yoo et al.80	1215	40–99 (mean, 62)	76	19	5

*Majority of the subjects were older than 18 years and therefore discussed using the combined population. NR = not reported.

Mild astigmatism was more prevalent in both sexes than moderate/significant astigmatism.^65,71,77 The magnitude of astigmatism is significantly (P < .001) correlated with age.⁵⁸ Prevalence of moderate and significant astigmatism increased after 70 years of age, whereas the prevalence of mild astigmatism increased until 70 years of age.^62,63,77

Risk Factors

In the included studies, the following risk factors were reported to contribute to the development of astigmatism in adulthood: age, sex, race, education status, pre-existing refractive errors, and various other factors, such as urban versus rural population, degree of nuclear and cortical cataract, axial length, and presence of internal astigmatism.^{31,35,41,43,46,47,50,51,53–55,58,62–64,66,71,79,81–92}

Age played an important role and showed a positive correlation with overall astigmatism, corneal astigmatism, and against-the-rule astigmatism.^{31,35,41,43,46,47,50,51,53–55,58,62–64,66,71,79,81–92} Individuals 70 years or older had higher odds (odds ratio [OR], 2.5) of astigmatism compared with individuals in the 50- to 59-year age group.⁴¹

The rate of with-the-rule astigmatism was negatively correlated with age,^{50,56,63,64,66,79,84–86,93} whereas the rate of oblique astigmatism increased up to 60 years of age and subsequently remained stable.^82,85 A higher prevalence of overall astigmatism and against-the-rule astigmatism was observed in males compared with females.^{46,47,49,53,64,71,86,89,94} On the other hand, females had higher odds of corneal astigmatism and with-the-rule astigmatism than males.^{56,63,81,93,94} The mechanisms underlying the age-dependent change remain unclear. Studies have hypothesized the change to be related to changes in upper eyelid tension, intraocular pressures, and underlying changes in corneal structure.^56,71,79,86

Mexican Americans had higher odds of with-the-rule astigmatism than non-Hispanic Whites.⁹³ The prevalence of astigmatism was found to be slightly higher in the White compared with the Black population.⁸⁸ Individuals with lower educational status had significantly higher odds of with-the-rule astigmatism.⁹³ Astigmatism prevalence declined slightly with increasing years of education in the Black population studied, whereas this was not the case for the White population.⁸⁸ Higher academic level (high school/university) lowered the risk of astigmatism compared with elementary school education (OR, 0.84),^47,89 whereas individuals with a higher monthly household income had a lower risk of astigmatism than low-earning individuals (OR, 0.81).⁴⁷ It was also the case that astigmatism of ≥1.00 D was associated significantly with residing in urban area and degree of cortical cataract.⁸⁹

Higher magnitudes of pre-existing myopia significantly increased the risk of with-the-rule astigmatism (low to moderate myopia: OR, 1.91; high myopia: OR, 3.96).⁸⁴ Myopes (≤−1.50 D) had 53% higher chances of against-the-rule than emmetropes.⁹³ Magnitude of against-the-rule was negatively related to the eye's axial length.⁷⁹ The magnitude of astigmatism was significantly correlated with decreasing best-corrected visual acuity and uncorrected visual acuity.⁸⁹

Patient Burden

Astigmatism affects patients' visual performance, vision-related quality of life (vision clarity, visual disturbances, and spectacle dependence), and health-related quality of life (difficulty in performing day-to-day activities, driving difficulties, and risk of falls), leading to decreased overall well-being.¹³ In the present systematic review, 68 included studies evaluated the patient burden due to astigmatism. Of 68 studies, 41 used disease-specific and generic questionnaires to evaluate the impact of astigmatism on patients' vision-related and health-related quality of life (Appendix Table A4, available at http://links.lww.com/OPX/A589). The following subjective questionnaires were most commonly used to assess patients' vision-related quality of life: standardized 42-item National Eye Institute Refractive Error Quality of Life questionnaire, 25-item National Eye Institute Visual Functioning Questionnaire, 14-item Visual Function Index (VF-14), Near Activity Visual Questionnaire, Visual Tasks Difficulty Assessment (VISTAS) questionnaire, and generic questionnaires specific to individual studies (e.g., Likert-type questionnaires). For the different questionnaires, patients self-rated their quality of life and level of difficulties, both qualitatively (through descriptive summaries) and quantitatively (providing scores on a scale).

Our review identified a study reporting subjective perception of patients receiving ortho-k lenses. However, the study included myopic patients with astigmatism ≤0.5 D.⁹⁵ Because of the low magnitude of astigmatism of study population, the results of the study were considered to be nonrepresentative of changes due to astigmatism and were thus considered clinically irrelevant for our review. Hence, the results of this study have not been presented and discussed.

Vision-related Quality of Life

Uncorrected Astigmatism and Quality of Life

Patients with uncorrected astigmatism suffered from increased vision difficulties and decreased vision-related quality of life (Fig. 3).^20,52,96 In presbyopic patients with astigmatism of up to 4.00 D using spectacles for vision correction, the subjective rating of vision clarity was found to be decreased significantly with increasing uncorrected baseline astigmatic power when the subjects viewed a mobile phone (P < .001) or a computer screen (P < .01).⁹⁷

FIGURE 3.

Distribution of patients according to vision difficulty: near versus distance vision. Source: Sandhu et al.⁵² Note: More difficulty indicates QoL score of less than 75; mild difficulty, QoL score between 75 and 99; and no difficulty, QoL score of 100. QoL = quality of life.

In the study by Bissen-Miyajima et al.¹⁸ and Knorz et al.,¹⁹ vision-related quality of life among cataract patients with pre-existing astigmatism were evaluated using VISTAS and modified VF-14 questionnaire, respectively. Post-operatively, in both the studies, patients experienced increased vision-related quality of life across all major domains of the questionnaires compared with pre-operative (uncorrected) values.^18,19

On the other hand, in the study by Wallerstein et al.,⁶¹ pre-operative and post-operative vision-related quality of life in astigmatism (≥2.00 D) was compared in patients undergoing laser in situ keratomileusis (LASIK) surgery, using a subjective vision quality questionnaire. In this study, post-operative scores for majority of the quality-of-life domains improved compared with pre-operative values.⁶¹

Vision-related quality of life associated with ortho-k lenses (Euclid Emerald; Euclid Systems Corp., Herndon, VA) was evaluated by Ren et al.²⁰ using the 42-item National Eye Institute Refractive Error Quality of Life; the authors found a significant improvement in 1-month post-baseline (67.8 at baseline to 73.3 at 1 month).

Mingo-Botín et al.⁹⁶ found similar post-operative visual function (VF-14 index) in toric (Alcon, Madrid, Spain) and spherical intraocular lens group (Alcon), with the toric intraocular lens group demonstrating greater improvement in mean VF-14 index from baseline.

Visual Disturbances

Several ophthalmologic conditions and disorders cause different types of visual disturbances (glare, haloes, double vision, ghosting, etc.), which can either be temporary (usually relieved with treatment) or permanent.⁹⁸ Visual disturbances interfere with normal sight and affect patients' daily activities and night-time driving abilities.^98,99 Patients with uncorrected astigmatism experienced increased rates of glare (53 to 77%)^18,100 and haloes (28 to 80%)^18,100–102 across studies.

Toric intraocular lenses (Abbott Medical Optics, Santa Ana, CA) demonstrated slightly higher glares and haloes as compared with other intraocular lenses,^21,103 but most of these studies reported that these visual symptoms did not cause any disruption in patients' general activities and improved overall vision related quality of life.^104,105 Thus, patients reported being comfortable with this trade-off of visual symptoms and optical independence.¹⁰⁴

In the included studies, the frequency of glare and haloes was also analyzed according to their severity. In cataract patients with pre-existing astigmatism undergoing implantation with different intraocular lenses, the frequency of glare/haloes decreased with increasing severity.^18,100,101

An increase in post-operative ghost images by 1% was seen in myopic patients (including those with astigmatism), post-correction with LASIK.¹⁰² No post-operative ghosting was reported in cataract patients with pre-existing astigmatism implanted with AcrySof toric intraocular lens (Alcon Laboratories, Fort Worth, TX) and Tecnis toric intraocular lens (Johnson & Johnson Vision Care, Jacksonville, FL).¹⁰⁶

Spectacle Dependence

In astigmatic patients, the spectacle dependence rates across included studies varied from 45 to 85%.^{18,19,22,96,107} Ninety-seven percent of patients with toric intraocular lenses (Alcon Laboratories) reported distance spectacle dependence.¹⁰⁸

Patients with pre-existing astigmatism receiving LASIK showed a substantial reduction in distance correction spectacle dependency 1 year post-operatively. The post-operative spectacle dependence was found to be lower in patients with a lower magnitude of pre-existing astigmatism than those with a higher pre-existing astigmatism magnitude (less than 34% in patients with pre-existing astigmatism <1.00 D compared with less than 58% in pre-existing astigmatism >1.00 D).^109,110

Health-related Quality of Life

Night-time Driving Difficulties

Driving at night has different challenges than driving during the day. Road crash fatality rates might be up to three times greater than daylight driving rates, when adjusted for travel distances, especially for pedestrian accidents, and accidents are frequently ascribed to night-time poor visibility.¹⁷ Patients with uncorrected astigmatism suffer from increased night-time driving difficulties.¹⁷ In cataract patients with pre-existing astigmatism (<1.00 D) and undergoing correction with the AcrySof IQ PanOptix nontoric (TFNT00) trifocal intraocular lens (Alcon Laboratories), night-time driving difficulties were observed in 59% of patients post-operatively compared with 66% of patients pre-operatively.¹⁰¹ In myopic astigmatism patients treated with LASIK, 59% rated night-time driving to be less complicated.¹⁰²

Risk of Falls

In cataract patients with pre-existing astigmatism and undergoing surgery with monofocal intraocular lenses, the 6-month self-reported pre-operative fall rate was 23% and had decreased to 20% post-operatively; however, the difference was statistically nonsignificant (P = .35).²² Greater oblique astigmatism changes are an important risk factor for dizziness; therefore, astigmatism correction during cataract surgery could help reduce dizziness and the risk of falls.²²

The most important risk factors for post-operative falls were pre-operative falls (OR [95% CI], 7.28 [3.48 to 15.21]) and change to multifocal spectacles (30% increase in falls rate) (OR [95% CI], 3.56 [1.34 to 9.43]).²²

Patient Preferences for Astigmatism Correction

In patients showing astigmatism of ≥0.75 D, 85% preferred toric over spherical contact lenses (Alcon, Geneva, Switzerland).¹¹¹ A similar finding was observed in patients showing astigmatism of <1.75 D; 72% preferred toric over spherical contact lenses (Johnson & Johnson Vision Care).¹¹² Toric contact lenses were preferred over spherical contact lenses because of their increased stability in the eye.¹¹² In astigmatic patients (≥0.75 D), 75% preferred rigid permeable lenses (Blanchard Contact Lens, Sherbrooke, Quebec, Canada) over soft toric (Cooper-Vision, Fairport, NY).¹¹³ However, this finding was not consistent across all included studies. A study conducted by Lipson and Musch¹¹⁴ demonstrated more patient comfort with soft toric lenses (56%) (Bausch & Lomb, Rochester, NY) versus rigid gas-permeable contact lenses (44%) (SynergEyes, Carlsbad, CA) in patients with astigmatism. However, this difference was not statistically significant.¹¹⁴ In addition, these studies evaluated patient's preference over a short period (2 weeks to 1 month as duration of wear); hence, the effect of long-term wear should be explored in future studies.^113,114

Multifocal intraocular lenses (Physiol S.A., Liège, Belgium) are not typically designed to provide optimal intermediate vision and may provide lower patient satisfaction rates. To overcome these limitations, trifocal intraocular lenses have been developed.¹¹⁵ In cataract patients with pre-existing astigmatism (spherical intraocular lens group, ≤1.00 D; toric intraocular lens group, >1.00 D) and undergoing trifocal intraocular lens implantation, 97% of patients would have the surgery with the same spherical trifocal intraocular lens compared with 89% of patients implanted with the toric trifocal intraocular lens (P = .38).¹¹⁵ The refractive and quality-of-life outcomes were similar in both intraocular lens groups.¹¹⁵

Patient Satisfaction

Patient satisfaction is an important measure of the quality of treatment being offered to the patients and helps in determining the unmet needs of patients related to the post-correction visual outcomes.¹¹⁶ Patient satisfaction with different correction techniques was evaluated using either of the following questionnaires: subjective satisfaction questionnaire,^{101,102,117–119} self-rated visual analog scale,¹²⁰ VF-14 scale,¹²¹ and VISTAS questionnaire.¹⁹ In the included studies, a higher proportion of patients undergoing correction were satisfied with their post-correction visual outcomes.^{19,101,102,117–121}

Toric intraocular lenses demonstrated high patient satisfaction (greater than 70%) in patients with pre-existing astigmatism, which was comparable with the patient satisfaction rate of other intraocular lenses. The satisfaction rates were found to be similar in patients with varying magnitude of pre-existing astigmatism.

Correction of astigmatism with LASIK in patients with concurrent myopia resulted in a patient satisfaction rate of 92%.¹⁰²

Economic Burden

Patients with uncorrected refractive errors suffer from increased economic distress and reduced educational and employment opportunities.^122,123 Globally, the annual economic impact due to uncorrected refractive errors is estimated at $202 billion.¹²³ There is paucity of published evidence evaluating the economic impact of astigmatism in the general population. In this systematic review, six included studies evaluated astigmatism's direct and/or indirect economic impact on patients and their families.^{23–26,124,125} Organization for Economic Co-operation and Development Data exchange rates to the costing year were used to convert publications' costs, which are not stated in dollars.¹²⁶

The details and characteristics of the included studies are presented in Table 5.

TABLE 5.

Characteristics of studies reporting economic burden

Study	Design	Country/region	Cost year	Patients (N)	Age (y)	Astigmatism (D)
Laurendeau et al.25	Cost-consequence analysis	France, Germany, Italy, and Spain	2006	NR	70	NR
Pineda et al.124	Cost-effectiveness analysis	United States	2008	NR	≥65	1.50–3.00
Shah et al.125	Randomized, masked, comparative study	France, Germany, Italy, the Netherlands, United Kingdom, and Spain	NR	208	70.4 (mean)	≤2.50
Simons et al.24	Cost-effectiveness analysis	The Netherlands	2012	77	Toric IOL group, 74.2 (mean) Monofocal IOL group, 73.8 (mean)	>1.25
De Vries et al.26	Cost-consequence analysis	The Netherlands	2007	NR	68.8 (mean)	≤1.50
Daum et al.23	Economic evaluation alongside RCT	United States	NR	39	24.9 (mean)	≤2.75

IOL = intraocular lens; NR = not reported; RCT = randomized controlled trial.

The majority of included studies evaluated the economic impact in cataract patients with pre-existing astigmatism undergoing surgery. Evidence from included studies highlighted that post-operative spectacle cost, optometrist/ophthalmologist visits, transportation costs, and time spent caring for visual acuity contribute to the overall economic burden.^24–26

Laurendeau et al.²⁵ compared the lifetime costs and consequences of reducing post-operative spectacle dependence in cataract patients with pre-existing astigmatism and undergoing surgery with either monofocal intraocular lenses or toric intraocular lenses (Alcon, Fort Worth, TX) in four European countries (France, Germany, Italy, and Spain). In a simulated Markov model developed from the societal perspective, astigmatic patients were followed up from cataract surgery until death. Model results revealed that fewer patients implanted with toric intraocular lenses required spectacles post-operatively than monofocal intraocular lenses. More than 66% of patients implanted with monofocal intraocular lenses required complex spectacles compared with <25% with toric intraocular lenses. The discounted lifetime cost savings associated with toric intraocular lenses over monofocal intraocular lenses were €691.7 ($965) (France), €646.4 ($902) (Germany), €693.9 ($968) (Italy), and €308.2 ($430) (Spain).²⁵

Pineda et al.¹²⁴ conducted a cost-effectiveness analysis from the U.S. health care perspective to compare toric intraocular lenses and monofocal intraocular lenses (with or without intraoperative refractive correction) (Alcon Laboratories and STAAR Surgical, Monrovia, CA) in cataract patients with pre-existing astigmatism (1.50 to 3.00 D). Implantation of toric intraocular lenses led to higher first-year costs ($5739) compared with the monofocal intraocular lenses with ($5634) or without ($4687) intraoperative refractive correction. Toric intraocular lenses provided mean incremental lifetime savings of $195 per patient compared with monofocal intraocular lenses with intraoperative refractive correction and $34 per patient compared with monofocal intraocular lenses without intraoperative refractive correction. Toric intraocular lenses also resulted in lifetime cost savings of $393 per patient, achieving uncorrected distance visual acuity of 20/25 or better and $349 per quality-adjusted life-year compared with the monofocal intraocular lens without intraoperative refractive correction. The cost savings with toric intraocular lenses were mainly attributed to reduced post-operative spectacle or contact lens dependency compared with monofocal intraocular lenses.¹²⁴

Shah et al.¹²⁵ performed a cost analysis using data from a randomized, double-blind, 6-month follow-up study conducted in 20 centers across Europe. Nonastigmatic and astigmatic patients (≤2.50 D) underwent cataract surgery with either multifocal intraocular lens implantation (AcrySof IQ ReSTOR toric or nontoric) or monofocal intraocular lens implantation (nontoric only) (Alcon Laboratories). Multifocal intraocular lenses provided good vision across a range of distances, decreasing patients' need for spectacles. The per-patient post-operative spectacle cost was significantly (P < .001) lower with multifocal intraocular lens implantation ($40.1) compared with monofocal intraocular lenses ($151.5).¹²⁵

Simons et al.²⁴ conducted a trial-based cost-effectiveness analysis of toric versus monofocal intraocular lenses (Alcon Laboratories) in the Dutch cataract patients (with pre-existing astigmatism of >1.25 D) undergoing surgery. From the societal perspective, the total per-patient cost of bilateral cataract surgery was €407 ($523) higher in the toric intraocular lens group (€3203 [$4117]) than in the monofocal intraocular lens group (€2796 [$3594]). From a health care perspective, the total costs were €635 ($816) higher in the toric intraocular lens group. However, with toric intraocular lenses, the mean per-patient productivity loss costs (€55 [$71]) and informal care costs (€30 [$39]) were lower compared with monofocal intraocular lenses (€84 [$108] and €55 [$71], respectively) with a mean of 2.3 to 4.1 hours spent on informal care. Furthermore, compared with monofocal intraocular lenses, toric intraocular lenses provided higher post-operative spectacle independence, resulting in higher patient satisfaction and vision-related quality of life.²⁴

De Vries et al.²⁶ compared lifetime costs and consequences (from the societal and Dutch national health service perspective) with implantation of monofocal intraocular lenses and multifocal intraocular lenses (ReSTOR or Array-SA40) (Alcon Laboratories). A simulated cohort of cataract patients with pre-existing astigmatism (≤1.50 D) undergoing surgery was followed for a lifetime (30-year horizon) in a Markov model. Over the lifetime, spectacle independence rates were higher for ReSTOR intraocular lenses (86%) and considerably lower for monofocal intraocular lenses (9%) and Array-SA40 intraocular lens (9%). The lifetime discounted costs (for the society) with the different intraocular lenses were as follows: ReSTOR, €3969 ($5437); monofocal intraocular lenses, €4123 ($5648); and Array-SA40, €5326 ($7296). From the national health service perspective, the lifetime costs were as follows: ReSTOR, €2415 ($3308); monofocal intraocular lenses, €2555 ($3500); and Array-SA40, €2556 ($3501). Cost savings were higher for ReSTOR intraocular lens because of higher spectacle independence than monofocal or Array-SA40 intraocular lenses. Over the lifetime, patients implanted with ReSTOR spent less on spectacles and cleaning materials, visits for refraction, and transport, compared with patients with monofocal intraocular lenses or Array-SA40.²⁶

Daum et al.²³ conducted a cost-benefit analysis alongside a clinical trial in patients with mean astigmatic correction ranging from 0.00 to 2.75 D. Study results of the economic evaluation showed that astigmatic patients performed vision-related tasks slower (1.00 D, 9% slower; 2.00 D, 29% slower) and made more errors (1.00 D, 38% more errors; 2.00 D, 370% more errors) compared with fully corrected individuals.²³

Quality Appraisal Summary

Overall, the quality of included economic studies and systematic review/meta-analysis in the present systematic review was found to be fair to good as assessed by the respective standard checklists of quality appraisal (Appendix Tables A5 to A6, available at http://links.lww.com/OPX/A589). The majority of randomized controlled trials that were included in the present review for evidence synthesis were assessed to be at risk of bias because of nonreporting of methods of allocation concealment or randomization by the authors (Appendix Tables A7, available at http://links.lww.com/OPX/A589). The quality of majority of the observational and cross-sectional studies was found to be fair, as assessed by the standard checklists of quality appraisal (Appendix Tables A8 to A10, available at http://links.lww.com/OPX/A589).

DISCUSSION

Prolonged vision impairment can lead to eyestrain and headaches for patients with increased difficulties in performing day-to-day activities.⁸ Timely intervention and increased awareness could help reduce patients' difficulties and prevent further deterioration of the condition. Astigmatism is a type of refractive error that affects both young and aged population.⁸ Although the exact cause of astigmatism is still not known, it is a pervasive condition with high prevalence reported both regionally and with respect to the global population.¹

The present study focused on identifying the published literature on astigmatism's epidemiology, patient, and economic burden through a systematic review. In addition, the unmet needs of astigmatic patients with coexisting ocular conditions (cataract, glaucoma, dry eye, presbyopia, or macular degeneration) and the risks associated with untreated astigmatism were also reviewed. There are multiple systematic reviews in the literature that have independently reviewed the published evidence related to astigmatism epidemiology and burden.^1,13,27–30 To the best of our knowledge, our systematic review is the first to attempt a comprehensive assessment of astigmatism-related outcomes. Hence, comparison with the existing literature is challenging. The present review is an extension of the work performed by Anderson et al.¹³ and adds a review of the identified studies related to epidemiology and astigmatism burden (search period, 1996 to 2021) in the general adult population (including patients suffering from cataract and other concomitant eye diseases).

Among the countries/regions, the highest astigmatism prevalence was reported in China (62%).⁴⁴ A huge variation in the astigmatism prevalence was noted across studies conducted in China with rates as low as 8% reported in the rural population.⁴¹ The variation in prevalence across studies could be due to different age groups, differences in examination techniques, variation in study sample size, differences in environmental conditions as well as genetic reasons, and residential status of the study population (urban vs. rural).⁴¹

It is apparent from the literature that astigmatism prevalence is age dependent.^{41,42,46,47,49,53–55} Generally, the prevalence of with-the-rule astigmatism was higher in the younger population (40 years or younger), whereas rates of against-the-rule and oblique astigmatism increased with age.^{41,42,46,49,50,53,54} The reasons for the age-dependent change in axis could be due to changes in upper eyelid tension, intraocular pressures, and changes to the corneal structure.^56,71,79,86 Although against-the-rule astigmatism was more frequently reported in males and with-the-rule astigmatism was more common in females,^{50,53,85,127,128} sex-related differences may be attributed to differences in sex hormones.⁷¹ In adult astigmatic patients, prevalence of mild astigmatism is more compared with moderate/significant astigmatism.^35,57,68

None of the retrieved studies reported the incidence of astigmatism during adulthood. Thus, there is a need for robust studies to better understand the onset in adults to provide better vision care to patients, inform treatment guidelines, and assist in policy decisions related to ophthalmic care.

Uncorrected astigmatism significantly affected patients' vision-related quality of life (visual disturbances and spectacle independence) and overall well-being.^18–21 Astigmatism patients suffered from increased glare,^18,100 haloes,^101,102 night-time driving difficulties,¹⁰¹ and risk of falls (particularly with oblique astigmatism),²² all leading to decreased quality of life. These findings highlight the increased burden on patients because of astigmatism, and in some cases, patients might require family or caregiver assistance to perform their day-to-day activities.⁸

Astigmatism correction with toric contact lenses provided better quality of life as compared with spherical contact lenses, and most subjects preferred toric contact lenses over spherical contact lenses. The toric lenses showed stability and ease in fitting.¹¹² Similarly, toric intraocular lens implantation resulted in better quality-of-life scores as compared with spherical intraocular lens among astigmatic patients, primarily owing to better objective optical quality and retinal image quality obtained with toric intraocular lens implantation.¹²⁹ Implantation with multifocal intraocular lenses resulted in better quality of life and increased patient satisfaction rates compared with monofocal intraocular lenses.²¹ In cataract patients with pre-existing astigmatism, implantation of advanced technology intraocular lenses (trifocal/presbyopia-correcting/toric intraocular lenses) led to reduced post-operative spectacle dependency compared with conventional intraocular lenses (monofocal intraocular lenses).^18,19,29

In terms of severity of disease, mild astigmatism (<1.50 D) is most commonly reported, accounting for as much as 82%.⁷⁰ However, it has been demonstrated that correcting even the milder forms of astigmatism resulted in increased quality-of-life benefits compared with uncorrected individuals.^18,20

A limited number of studies showed that the economic burden of astigmatism in cataract patients was driven mainly by post-operative vision correction costs with spectacles, optometrist/ophthalmologist visits, transportation costs, and time spent caring for visual acuity.^24–26 Uncorrected astigmatic patients were found to perform vision-related tasks slower and made more errors than fully corrected individuals.²³ In cataract patients with pre-existing astigmatism and undergoing surgery, mean per-patient productivity losses ranged from €55 ($77) to €84 ($117), and mean per-patient informal care costs ranged from €30 ($42) to €55 ($77) with a mean of 2.3 to 4.1 hours spent on informal care.²⁴ In developing and developed countries, vision care services are usually borne by patients and their families.¹³⁰ Economically underprivileged patients might not opt for vision correction at an early stage of disease progression, which could further lead to a decrement in quality of vision and put further strain on their overall quality of life. Thus, there is a need for generating more robust and extensive evidence to assess the full economic impact (including productivity losses) of astigmatism on patients and their families and spread awareness among the affected individuals on the necessity of timely correction.

This article is the first systematic review that has comprehensively assessed and reported the scientific published evidence on the epidemiology, patient burden, and economic burden associated with astigmatism in the general population (in association with other ocular conditions). A robust search strategy was developed to identify the published evidence from the medical literature database. In addition, key eye congresses and gray literature sources were searched to retrieve relevant evidence not captured in database searching.

Despite the strengths of this systematic review, there are a few limitations with the identified evidence. From a methodology perspective, non-English publications were excluded. Second, not all countries were included. To ensure a manageable scope, the review excluded studies from several countries with smaller populations and sample sizes, various study designs, or clinical standards. Within the Europe, this review only included data from major economies. Even though not all countries were included, the geographical distribution of studies was broad. In addition, preliminary searching identified too many publications with different populations and clinical outcomes. Therefore, to manage the scope of this review, adult patients (18 years or older) were included, and within clinical outcomes, this review was restricted to glare and haloes (patient burden due to disturbances in visual acuity). Nonetheless, clinical outcomes of high importance were not included in this review. Moderate to high astigmatism can often cause amblyopia in children. Vision correction to prevent the development of amblyopia is often initiated before age 7 or 8 years, making it ineligible for inclusion in our review.³³ The potential impact of astigmatism on myopia progression was also out of the scope of this systematic literature review. These fields are of huge clinical importance, and future review should focus on this perspective and pediatric population (younger than 18 years). Furthermore, this review identified studies evaluating risk of falls and driving difficulties in cataract patients with pre-existing astigmatism; however, no study evaluated these outcomes in astigmatism population, thus highlighting a need for further research.

CONCLUSIONS

The present study findings highlight the epidemiological, patient, and economic burden of astigmatism. Across studies, the prevalence of astigmatism was usually high, with age being a significant risk factor. Patients with uncorrected astigmatism suffered from decreased vision-related quality of life, had difficulty performing daily activities, and were slower and made more errors at work than corrected individuals. With its significant prevalence in the global population, timely screening of astigmatism is necessary to detect and correct astigmatism at an early stage even in adults. In addition, robust primary research studies are needed to determine the full economic impact of astigmatism on patients.