Clinical Outcomes of a Randomized Trial with Contact Lenses for Astigmatic Myopia Management

Abstract

Significance:

There are limited treatment options for myopia management of patients with moderate to high astigmatism. This work directly compares toric orthokeratology and soft toric multifocal lenses to show differences in visual acuity and patient satisfaction that could impact clinical care. Toric orthokeratology caused reduced visual acuity but was preferred subjectively for vision and overall.

Purpose:

To quantify objective and subjective clinical differences between toric orthokeratology and soft toric multifocal contact lenses in the same cohort of myopic wearers with moderate to high astigmatism.

Methods:

Thirty adults with refractive myopia (plano to −5.00 D) and astigmatism (1.25 to 3.50 D) were fitted empirically with both toric orthokeratology and soft toric multifocal contact lenses. Participants wore lenses for 10 days in random order, separated by a 14-day washout period. High-contrast, low-contrast, and glare logMAR visual acuity were measured. Surveys ascertained subject preference for comfort, vision, handling, and cost. Friedman, Wilcoxon Signed Rank, and Chi-square tests were performed.

Results:

A subset of participants (n = 17) who achieved good vision with both lens types was analyzed. High-contrast and glare acuity with toric orthokeratology was reduced by 1 line compared to soft toric multifocal lenses (both 0.00 vs. −0.10, P ≤ .003). Participants preferred toric orthokeratology for vision (P ≤ .03), but soft toric multifocal lenses for handling (P ≤ .006). When forced to choose between lens types, participants preferred toric orthokeratology for vision and overall (both P ≤ .007).

Conclusions:

Participants who achieved good vision with both lens types preferred toric orthokeratology over soft toric multifocal lenses, despite reduced high-contrast and glare visual acuity. Further research is needed to understand the relationship between visual performance and patient satisfaction.

Current contact lens treatments for myopia management include orthokeratology and soft multifocal or dual-focus lenses.¹ Fewer toric lens options exist for patients with moderate to high astigmatism. In the United States, “toric” orthokeratology lenses utilize toric reverse and/or peripheral curves to improve centration, while maintaining spherical base curves. There is currently no orthokeratology lens with a toric base curve approved by the United States Food and Drug Administration. Two monthly replacement soft toric multifocal lenses with a center-distance design are commercially available in the United States, with custom designs available as annual or quarterly replacement. While toric multifocal lenses are commonly used off-label in practice, there is limited research available regarding pertinent clinical outcomes. The success of toric orthokeratology and soft toric multifocal contact lenses can be described by both objective and subjective outcomes.

Objective measures, such as high- and low-contrast visual acuity, are the gold standard for assessing refractive correction. Both orthokeratology and soft multifocal lens wearers have been shown to have similar high-contrast, but reduced low-contrast visual acuity, compared to single vision correction.^2,3 In a study of toric orthokeratology, low-contrast acuity in children was approximately three lines worse than high-contrast visual acuity, but there was no significant difference in low-contrast acuity between the orthokeratology and single vision spectacle group.⁴ Another study looking at the effect of soft multifocal add powers on low-contrast acuity showed a greater reduction with higher adds compared to lower add powers and single vision lenses.⁵ Glare has also been shown to further reduce visual acuity and contrast sensitivity with these lens designs.^6–8

Subjective patient-reported outcomes aim to capture information from the user’s perspective.⁹ If patient satisfaction is low, patients may elect to discontinue lens wear, which would negate any myopia management treatment effects. Many patient-reported outcome instruments have been developed to assess a specific type of refractive error correction. A recent review showed only two instruments have been used for both orthokeratology and soft contact lenses for myopia management⁹ – the National Eye Institute Refractive Error Quality of Life-42¹⁰ and the Orthokeratology and Contact Lens Quality of Life questionnaires.¹¹

The purpose of this study was to quantify objective and subjective clinical outcomes with toric orthokeratology and soft toric multifocal contact lenses in the same cohort of myopic wearers with moderate to high astigmatism.

METHODS

This research was reviewed by an independent ethical review board, conformed with the principles and applicable guidelines for the protection of human subjects in biomedical research, and was registered on ClinicalTrials.gov (NCT03728218). Informed consent was obtained prior to any data collection. The study was conducted at the University of Houston with a prospective, crossover design. Recruitment and data collection occurred from November 2018 to March 2020. Portions of this study were published previously, including the outcomes of peripheral refraction,¹² higher order aberrations,¹³ and microbiology of worn lenses.¹⁴

Participants

Thirty-four non-presbyopic adults (age 18 to 39 years) were recruited in order to obtain high-quality data throughout the numerous measurements at each visit. As well, the surveys were developed for use in adults. All participants had spherical refractive error at the corneal plane of plano to −5.00 D, refractive cylinder power of −1.25 to −3.50 D, and best corrected visual acuity of Snellen 20/25 or better in each eye. Participants were excluded if they had a history of ocular pathology or surgery, any clinically significant binocular vision disorder, or had worn gas permeable lenses in the month preceding their study enrollment.

Contact Lens Fitting

Corneal tomography was measured with the Pentacam (Oculus, Wetzlar, Germany). Lenses were empirically ordered based on the manifest refraction and topography following the manufacturer’s guidelines. The toric orthokeratology lenses were Dual Axis Corneal Refractive Therapy lenses (Paragon Vision Sciences, Gilbert, AZ), which have toric peripheral curves but a spherical base curve. The lens selection details have been published previously.¹⁵ The soft toric multifocal lenses were Proclear Multifocal Toric D lenses with a +2.50 add power (CooperVision, Pleasanton, CA), which have a center distance design. The distance lens power was based on the vertex-adjusted manifest refraction measured at the baseline visit. Following the manufacturer’s fitting guide, the 8.8 mm base curve was used if the participant’s flat keratometry was less than 43.50 D and then 8.4 mm base curve was used if it was greater than 43.50 D. Both lens designs were selected because they were the most commonly fitted lenses for astigmatic patients in our Myopia Management Service at the start of the study and Proclear Multifocal Toric lenses were the only disposable soft toric multifocal available in the United States. All participants were dispensed Clear Care Cleaning & Disinfecting Solution (Alcon, Fort Worth, TX) with written instructions for use with both lens types.

Study Visit Overview

The first visit was a baseline evaluation and both toric orthokeratology and soft toric multifocal lenses were ordered empirically using the data collected. Two pairs of lenses were ordered for each lens type to allow for fitting and dispensing to be done on separate days with new lenses. At Visit 2, both lens types were placed on eyes and the participant was allowed to continue only if the fit was adequate and they achieved Snellen 20/40 or better in each eye with both lens types. The soft contact lenses were fit first, followed by the orthokeratology lenses. Both were analyzed after at least 10 minutes of settling. One of the aims of the study was to determine the success rate of empirical ordering, so no changes to the lens fits were made, as there is no standard protocol for re-fitting astigmatic patients with toric orthokeratology. Additionally, soft toric multifocal lenses take several weeks to receive and no fitting set is available. If the fit of either lens was inadequate, the participant was exited from the study. The order of lens wear was randomized using a randomization table generated with blocks of five and was only accessed by the examiner during allocation. Lenses were each worn for 10 ± 2 days.^16,17 Due to diurnal fluctuations with toric orthokeratology, all outcome measures (Visits 3 and 5) were performed in the afternoon between 12–6 pm. Before wearing the second lens type, participants had a washout period of 14 ± 2 days, during which they returned to their habitual correction (single vision soft contact lenses or spectacles). Corneal tomography was repeated at Visit 4 to ensure proper washout and keratometry values had to be within 1 D of the baseline measures prior to dispensing a new, unopened pair of the second lens type.

Objective Outcomes

High-contrast, low-contrast (20% Michaelson), and glare monocular and binocular logMAR visual acuity were measured at four meters (Smart System 1, M&S Technologies, Niles, IL). The glare visual acuity was measured with the Glare Testing System which uses high-contrast letters and four high-intensity LED lights situated on both sides of the visual acuity chart.

The presence or absence of corneal staining with sodium fluorescein was observed at baseline and at each outcome visit. If present, the type and extent of corneal staining were graded on a scale of 1–4 following the Cornea and Contact Lens Research Unit grading scale.¹⁸

Subjective Patient-Reported Outcomes

Two surveys were used to assess patient satisfaction. To account for any learning curve, the surveys were explained to the participant at the baseline visit and they completed the survey based on their habitual correction. The Ranked Symptom Scale survey was used to assess comfort, vision, and handling.¹⁹ In each category, participants were asked to give an overall rating from 0–10 (0 being good, 10 being poor) and then could rank up to three symptoms that most contributed to their overall rating. The participants also completed seven questions from the Orthokeratology and Contact Lens Quality of Life questionnaire,¹¹ however the same 0–10 scale was used. The questions included asked how much trouble or how bothered the participant was with: seeing without lenses, routine care/cleaning of lenses, inserting lenses, removing lenses, vision changing/fluctuating throughout the day, vision in dim lighting, vision in bright lighting. At the final study visit, the participants completed a two-alternative forced choice survey, requiring them to state their lens preference for vision, comfort, handling, cost (based on our clinic pricing), and overall.

Statistical Analysis

Data were entered into Microsoft Office Excel (Microsoft Corporation, Redmond, WA). Statistical analyses were performed using SPSS software version 28 (IBM Corporation, Armonk, NY). Sample size calculations with ⍺ = 0.05, β = 0.20, and a standardized effect size of 0.70 would require a sample of 26 participants. The standardized effect size was calculated as a ratio of effect size to standard deviation. Due to the small sample sizes and non-normal distribution of some outcomes, median and interquartile ranges are presented. Friedman tests were used to compare between baseline, toric orthokeratology, and soft toric multifocal conditions, whereas Wilcoxon Signed Rank tests were performed to compare toric orthokeratology and soft toric multifocal lenses, as appropriate. A Bonferroni adjustment was made for multiple comparisons. Chi-square tests were used for forced choice responses. Due to both correlation within eyes of subjects and known differences in lens rotation and decentration, data from both eyes are presented separately and binocularly, since the subjective data would incorporate the visual experience with both eyes.

RESULTS

Participant Demographics and Empirical Fitting

Thirty-four participants were recruited for the study, and 30 completed the study (Figure 1). Seventeen achieved good vision, previously defined as logMAR visual acuity of +0.30 (Snellen 20/40) or better in each eye after 10 ± 2 days of wear.^12,13 This acuity threshold was selected based on the requirements for driving in the United States and determination of success for refractive surgeries.²⁰ Of the 13 excluded participants, more failed to achieve the visual threshold with toric orthokeratology lenses than soft toric multifocal lenses (12 vs. 3 participants), despite all lenses being clinically acceptable for dispense at the fitting visit. Soft toric multifocal lens rotation was measured after lens settling at the fitting visit (median [IQR], 18.5 [7 to 30] degrees) and was stable with adequate movement, centration, and coverage. All toric orthokeratology lenses had adequate centration, treatment and return zones, and edge lift. Because reduced vision may affect some outcomes, results are presented only for the cohort with good vision (N = 17, Table 1).

Figure 1.

Participant enrollment and completion.

Table 1.

Participant demographics and baseline refractive error.

	N = 17
Age (Mean ± SD, years)	26.35 ± 4.94
Sex
Male	5 (29%)
Female	12 (71%)
Race *
American Indian or Alaskan Native	1 (5%)
Asian	7 (37%)
Black	3 (16%)
Native Hawaiian or Pacific Islander	1 (5%)
White/Caucasian	6 (32%)
Other	1 (5%)
Ethnicity
Hispanic	4 (24%)
Non-Hispanic	13 (76%)
Baseline Sphere Power (median [IQR], D)
Right eye	−2.25 [−1.75 to −3.00]
Left eye	−2.00 [−1.25 to −2.75]
Between eyes	P = .09
Baseline Cylinder Power (median [IQR], D)
Right eye	−1.75 [−1.50 to −2.25]
Left eye	−2.00 [−1.50 to −2.50]
Between eyes	P = .32

^*Participants were allowed to select more than one race.

Baseline refractive error from manifest refraction was not different between the right and left eyes (all P > .09, Table 1).

The threshold of Snellen 20/40 or better after lens wear was achieved in 20 right eyes (66%) and 18 left eyes (60%) empirically fit with toric orthokeratology. Twenty-nine right eyes (97%) and 28 left eyes (93%) met the same visual threshold for empirical fitting with soft toric multifocal lenses. Overall, the first lens fit success rate for both eyes was 63% with toric orthokeratology and 95% with soft toric multifocal lenses.

Objective Outcomes

There were no adverse events causing disruption of study visits. No participants had corneal staining measured greater than Grade 2 on the Cornea and Contact Lens Research Unit grading scale.¹⁸

High-contrast visual acuity with toric orthokeratology (0.00 [−0.09 to 0.05]) was reduced about 1 line from best-corrected visual acuity (−0.12 [−0.18 to −0.08], P < .001, Figure 2). As expected, low-contrast visual acuity was reduced by 2–2.5 lines compared to the high-contrast visual acuity within each lens type. Glare acuity was similar to high-contrast visual acuity and showed a difference of 1 line between the lens types (0.00 [−0.10 to +0.05] vs. −0.10 [−0.18 to −0.06], P ≤ .003).

Figure 2.

Distance multifocal. Top bars indicate significant difference between groups (P < .05). Best-corrected visual acuity measured with manifest refraction at baseline visit.

Subjective Patient-Reported Outcomes

At baseline, the participants were generally satisfied with their comfort, vision, and handling of their habitual lenses (Figure 3). Overall they rated toric orthokeratology worse than baseline on the Ranked Symptoms Scale survey for comfort (5.0 vs. 2.0, P = .001), soft toric multifocal worse than toric orthokeratology and baseline for vision (5.0 vs. 3.0 vs. 1.0 respectively, both P ≤ .03) and toric orthokeratology worse than baseline and soft toric multifocal lenses for handling (1.0 vs. 0.0 vs. 0.0 respectively, both P ≤ .03).

Figure 3.

Overall multifocal in comfort, vision, and handling for baseline, toric orthokeratology, and soft toric multifocal conditions. The bars show comparisons that reached statistical significance (P < .05).

When comparing symptoms between toric orthokeratology and soft toric multifocal lenses, the most frequently ranked discomfort symptoms were lens awareness with toric orthokeratology (53%) and dryness with soft toric multifocal lenses (33%, Figure 4A). For vision, the participants ranked blurred distance vision (37%) and unstable vision (40%) with soft toric multifocal (Figure 4B). Lastly, difficulty with lens removal (27%) and time taken (17%) with toric orthokeratology were the most frequently ranked symptoms for handling (Figure 4C).

Figure 4.

Percentage of participants reporting symptoms of (A) discomfort, (B) vision, and (C) handling with toric orthokeratology versus soft toric multifocal lenses on the Ranked Symptoms Scale survey. The bubble size indicates the severity of the symptom and the 1:1 line shows where the symptoms would fall if the percentage between the lenses were the same.

On the Orthokeratology and Contact Lens Quality of Life questions, the participants reported improved ability to see without toric orthokeratology lenses and more difficulty removing toric orthokeratology lenses compared to the soft toric multifocal lenses (all P ≤ .01, Figure 5). Participants were bothered by fluctuating vision throughout the day with soft toric multifocal compared to baseline (P = .02). Vision in dim lighting was worse with soft toric multifocal and toric orthokeratology lenses compared to habitual (both P ≤ .02). There was no difference between habitual, toric orthokeratology, and soft toric multifocal lenses for any of the other questions.

Figure 5.

Orthokeratology and Contact Lens Quality of Life scores. The bars at the top of the figure indicate comparisons that reached statistical significance (P < .05).

At the end of the study, when forced to choose between toric orthokeratology and soft toric multifocal lenses, participants preferred toric orthokeratology for vision (88% vs. 12%, P < .001) and overall (82% vs. 18%, P = .007). There were no significant differences between the lens types for comfort or handling.

DISCUSSION

The purpose of this study was to evaluate both objective and subjective clinical outcomes with toric orthokeratology and soft toric multifocal lens wear in the same group of critical adult wearers. Objective measures showed differences in high-contrast and glare visual acuity. Subjectively, there were differences in overall ratings of the lenses in the areas of cost, vision, and overall.

Both lenses were able to be worn for 10 ± 2 days with no significant adverse findings during lens wear. Since lenses were ordered empirically and no refitting was performed, the number of eyes that had good vision (20/40 or better) with the initial lens were deemed successful. The first lens fit success rate was much greater with soft toric multifocal than toric orthokeratology (95% vs. 63%). A previous study reported a 95% first lens fit success rate with a different toric orthokeratology lens design, however they utilized a computerized software to calculate lens parameters from four topographic maps.²¹ Our toric orthokeratology lens selection was also based on corneal elevation, though we have found that there is a strong relationship between peripheral elevation and central keratometry.¹⁵ This difference in success rates highlights the need for ongoing effort to improve empirical fitting; however, one of the main drivers of decentration with orthokeratology lens wear is lid interaction, which cannot be accounted for with empirical fitting.

High-contrast, low-contrast, and glare acuity were all reduced with toric orthokeratology by approximately one line compared to soft toric multifocal lenses. As demonstrated by our previous work, toric orthokeratology induced more higher order root mean square, primary spherical aberration, and primary coma than soft toric multifocal lenses.¹³ This difference in higher-order aberrations would contribute to the difference in visual acuity. Chen, et al. also evaluated toric orthokeratology lenses and reported similar results to the full cohort of adults, with high-contrast visual acuity of +0.08 ± 0.11 logMAR (mean ± SD) and low-contrast visual acuity of +0.36 ± 0.15 logMAR in children after 24 months of wear.⁴ Another study used the same soft toric multifocal lens as in this study, but in a presbyopic sample, and found similar high-contrast visual acuity of −0.01 ± 0.03 logMAR, with a reduction in contrast sensitivity compared to a single vision toric lens.²²

Since the participants in this study were all adults, they were likely able to better discern their observations of visual quality based on their visual and lifestyle demands. These adults indicated a noticeable decrease in comfort, vision, and handling with toric orthokeratology lenses and a decrease in vision with soft toric multifocal lenses compared to their habitual single vision correction. Almost all the participants were habitual single vision toric soft lens wearers (N = 29), so they were likely more critical of the vision in soft toric multifocal lenses compared to their habitual and perhaps less critical of the handling since they were already familiar with care, application, and removal.

When forced to choose between the two lenses, adult participants preferred toric orthokeratology for vision and overall. This suggests that patients may prefer the more “stable” blur associated with orthokeratology correction to unstable blur associated with blinking with soft toric multifocal lenses.

One of the main limitations of this study was the smaller sample size for those who achieved good vision. Participants could be refit in future studies, but the empirical ordering results are very indicative of the first lens success rate clinically and the challenges that present when specifically fitting the toric version of these lenses. Further refitting would be expected to significantly increase the duration of the study and may also increase participant dropout or loss to follow-up. There are also several lens parameters that could contribute to lens decentration and overall success, so it is important to note that only one toric orthokeratology lens design was used in this study with a spherical base curve and toric peripheral curves. Additionally, the study was performed in adult participants due to the scope of testing and the length of visits. Future research should confirm that these findings are similar in children, as they may be prescribed these treatments for management of myopia. Lastly, there was no masked examiner in the study so there could have been examiner bias, as they were aware of what lenses were worn.

CONCLUSIONS

In a direct comparison of toric orthokeratology and soft toric multifocal lenses in the same group of adult wearers, the first lens fit success rate was 63% with toric orthokeratology and 95% with soft toric multifocal lenses. High-contrast and glare acuity were reduced with toric orthokeratology compared to soft toric multifocal lenses. Patient-reported outcomes for the cohort that achieved good vision showed a preference for toric orthokeratology for vision and overall. Future research should explore these clinical outcomes in children and how they may contribute to visual performance and patient satisfaction.

APPENDICES

The data from the full cohort of completed subjects (n=30) are included to compare with our previously published work. The overall results are similar to those of the group that saw well with both lens types (n=17).

Appendix Figure A1, available at http://links.lww.com/OPX/A585. Distance multifocal for full cohort (n=30). Top bars indicate significant difference between groups (P < .05). Best corrected visual acuity measured with manifest refraction at baseline visit.

Appendix Figure A2, available at http://links.lww.com/OPX/A585. Overall multifocal for full cohort (n=30) in comfort, vision, and handling for baseline, toric orthokeratology, and soft toric multifocal conditions. The bars show comparisons that reached statistical significance (P < .05).

Appendix Figure A3, available at http://links.lww.com/OPX/A585. Percentage of participants reporting symptoms of (A) discomfort, (B) vision, and (C) handling with toric orthokeratology versus soft toric multifocal lenses on the Ranked Symptoms Scale survey for full cohort (n=30). The bubble size indicates the severity of the symptom and the 1:1 line shows where the symptoms would fall if the percentage between the lenses were the same.

Appendix Figure A4, available at http://links.lww.com/OPX/A585. Orthokeratology and Contact Lens Quality of Life scores for full cohort (n=30). The bars at the top of the figure indicate comparisons that reached statistical significance (P < .05).

Appendix Figure A1.

Appendix Figure A2.

Appendix Figure A3.

Appendix Figure A4.