Vision Screening in Adults Across the Life Span

Abstract

Objectives

The goal of this study was to determine if adults across the life span differ in responses to quick vision screening and how those responses relate to their use of specialized eye care.

Methods

Subjects were 363 community-dwelling, ambulatory adults, aged 21 to 95, tested while they wore their corrective lenses, during routine visits to a tertiary care facility. No subjects had known neurological impairments, age-related macular degeneration or other significant eye disease. A wall-mounted ETDRS chart was used.

Results

Older adults, aged 58+ had significantly worse scores than younger adults. Scores did not differ between subjects who had been tested within or prior to the last 10 months. Older subjects had had their vision tested significantly more recently than younger subjects.

Discussion

Seeking eye care, per se, does not indicate the quality of the patient’s vision. Patients may be unaware of how well or poorly they see with their prescription lenses.

Conclusion

Vision screening is quick, inexpensive, easily performed by ancillary staff, and may provide the physician with useful additional information for treatment planning.

Introduction

The value of vision screening for adults has been unclear. A recent review suggests that vision screening provides no value for future vision in asymptomatic patients over the age of 65 years (1) and thus provides no specific recommendation for vision screening in seniors. Other studies, however, have shown a relationship between poor vision and falling (2–4). A question about vision screening is included in a well-validated scale of falls risk, the Falls Risk of Older People in the Community scale (5). Many of the activities listed in another well-validated scale of falls risk, the Falls Efficacy Scale, require having functional vision (6). Therefore, although diagnosis of future visual problems may not be improved with routine vision screening during primary care visits, the physician may use that information when determining whether or not to refer the patient for rehabilitation services for fall prevention or balance therapy.

Several types of vision screening tools are available. In addition to the well-known Snellen charts, charts are available with just a single shape such as the Landolt C or the well-normed Early Treatment in Diabetic Retinopathy Study (ETDRS) chart (7, 8). In this study, we used an ETDRS chart, because its use of letters, rather than a single rotated shape, would be familiar to most people. In the context of a larger study of balance skills, we prescreened participants for visual acuity and asked them how long before the screening they had had their vision tested. The goal of the present analyses was to determine if older and younger adults differed in their vision screening scores, and if they differed in how recently they had had their vision checked by eye care professionals.

Methods

Subjects were 363 community-dwelling, ambulatory adults, mean age 56.24, SD 17.9, range 21 to 95, with at least 25 subjects per decade except the single subject in her 90’s. According to their self-reports subjects had no known neurological impairments or known significant visual impairments other than age-related changes requiring corrective lenses for distance, i.e., no subjects had observable nystagmus or disorders of ocular motility, glaucoma, age-related macular degeneration, or significant cataracts. Subjects recruited from the geriatric medicine clinic were prescreened by the geriatricians.

Potential subjects were excluded if the geriatrician determined that they did not have the cognitive capacity to participate, had neurological problems, or had known visual problems. Because this screening was part of a larger study on vestibular and balance disorders subjects were also excluded if they had significant hearing loss, surgery on one or both ears, current vertigo or a history of vertigo, or musculoskeletal or cardiovascular problems that precluded standing or walking unassisted.

All subjects gave informed consent prior to testing. This study was approved the Institutional Review Board.

Subjects were screened with an ETDRS chart (good-lite.com, # 50047). (Table 1 shows some possible scores on the ETDRS and the Snellen equivalent scores.) If they used corrective lenses, subjects were tested while wearing them, either prescription eyeglasses or contact lenses. Subjects were tested with both eyes open. Each subject sat in a standard-height arm chair in a well-lighted room. Per instructions on the chart, the chart was mounted on a wall, 3 m away at eye level. The subject was asked to read the letters on the chart starting with a large font line that the subject could read easily and going down in size until the subject could not read a line accurately. The test was not timed so the subject could take as long as necessary. After the test subjects were informed of their scores.

Table 1.

Relationship between Snellen scores and ETDRS scores used in this study. *** indicates the cut-off score for driving in Texas.

ETDRS score (logMar)	Snellen score equivalent
0.5	20/63
0.4	20/50
0.3 ***	20/40 ***
0.2	20/32
0.1	20/25
0.0	20/20
−0.1	20/16
−0.2	20/12

All variables were checked for normality. Descriptive variables were age, sex, and length of time (months) since the last vision check with an eye care professional, either an optometrist or ophthalmologist. The dependent measure of interest was the ETDRS vision scale (logMAR score) which was compared between males and females and patients younger or older than 58 years of age (median age) using Wilcoxon rank sum test, a non-parametric test used for non-normal data. We also compared length of time since last vision check by gender and age. P<.05 was considered statistically significant. All analyses were performed in SAS statistical software (version 9.4, Cary, NC).

Results

As shown in Table 2, no differences were found between males and females in either length of time since vision check, or in ETDRS scores. The ETDRS scores did not differ between subjects whose vision had been checked within the 10 months before this screening and subjects whose vision had been checked more than 10 months before this screening. Older subjects (aged 58 to 95) had had their vision tested significantly more recently than younger subjects (aged 21 to 57), p=0.005.

Table 2.

Description statistics, including medians, total ranges, and interquartile ranges (IQR), and medians and ranges, ages for time since last vision check (months)

	Time (months) since last vision check	ETDRS scores (logMAR)
Males, N=148	7 (range 1 to 249, IQR, 15.5)	0 (range −0.3 to +0.5, IQR, 0.1)
Females, N=215	11 (range 1 to 180, IQR, 10?)	0.1 (range −0.2 to 0.5, IQR, 0.2)
Younger (age 21 to 57 yrs), N=173	12.0 (range 1 day to > 10 years, IQR, 19.0)	0 (range −0.3 to +0.5, IQR, 0.2
Older (> 57 yrs), N=190	8.5 (range 1 day to > 10 years, IQR, 9.0)	0.1 (range −0.1 to +0.5, IQR, 0.2)

Younger and older subjects differed significantly on logMAR scores, p< 0.0001. Not surprisingly, older subjects had worse vision. See Figure 1.

Figure 1.

Discussion

In general, subjects whose vision screening scores were worse than 0.1 logMAR (20/25 on the Snellen scale) were unaware that even with their corrective lenses they did not see clearly, i.e., after the screening some people with vision worse than 0.1 logMAR expressed surprise at the result. More surprising is the finding that even subjects whose scores were very poor, e.g. 0.4 logMAR (20/50 on the Snellen scale) were unaware of how poorly they were seeing, as indicated by their comments to us. Perhaps they had become so used to the blur they experienced that it seemed normal.

Elderly subjects who were tested in the geriatric medicine clinic were approved for participation in the study by their geriatricians. The geriatricians assumed that a patient who had had a vision test within the past year and did not complain about a visual problem could see clearly with the current prescription for eyeglasses or contact lenses. The senior investigator made a similar assumption about other younger and older control subjects. Many of those people drive their cars locally, and often on the freeways. This assumption represents standard practice. In any primary care clinic, unless the patient complains of a problem the primary care physician has no reason to believe that the patient does not see clearly. Thus, this simple type of screening, which can be performed by a medical assistant in a brief period of time after taking the patient’s vital signs, would provide valuable information to the primary care physician and would augment the care being provided, but at no additional expense to the clinic.

The study had some limitations. Subjects had no known impairments, but they might have had impairments unknown to them or to the investigators, which might have influenced the outcome. The context of this study did not allow for in-depth study by ophthalmologists. Also, subjects were tested with both eyes open. We did not test acuity of individual eyes. A subject who had one eye with significantly better acuity than the other eye could have performed the test using only the better-seeing eye. This quick screening was not a substitute for more time-consuming, more careful screening of individual eyes. Instead, this quick screening test may have provided an indication of the type of functional visual acuity that people use when they move about the environment and view objects, signs, and people in the course of performing activities of daily living.

We did not account for potential effects of medications or ocular surgery, such as cataract surgery or laser-assisted in situ keratomileusis (LASIK) surgery, on vision. Prescription and nonprescription medications and surgery might all have affected vision. We were interested in how well people could see at that moment, regardless of their medication regimens or if they had had ocular surgery. If this type of screening is used in the primary care clinic, the physician will be aware of the patient’s medications or history of eye surgery and will be able to interpret the results of vision screening in that context. If a patient has impaired visual acuity while wearing corrective lenses and with both eyes open then that information may remind the physician to consider the side effects of medication and to determine whether or not the patient should be referred for in-depth visual testing by an eye care clinician.

People who had not had their vision tested in the past 10 months either had no interest in having their vision tested because they had not experienced any problems – usually younger subjects in their 20’s and 30’s, said that they planned to do it in the future, had forgotten to do it, or did not think it was necessary. For some seniors with limited financial resources, even though they had Medicare the expense of paying for an exam with an optometrist or ophthalmologist may have been beyond their means. Therefore, some subjects may have chosen not to have an annual vision check. We did not collect data on this point, but it might be a worthwhile question for study, particularly in the context of a geriatric medicine clinic.

Vision screening may be useful as one of the steps in determining fitness to drive, particularly with a patient who is resistant to change. The requirements for driving vary by state. In many states, such as Texas, people may drive without restrictions if they have visual acuity scores of 20/40 in both eyes on the Snellen scale, i.e., 0.3 logMAR, with or without corrective lenses. Otherwise, restrictions are imposed (9, 10). Therefore, if the patient fails vision screening then the physician has a basis for referring to eye care professionals for detailed assessment, or for advising the patient to stop driving.

Vision provides key information for maintaining balance and performing routine activities of daily living independently. Therefore, vision screening may also be an important step in determining the cause of decreased functional skill and in helping the patient to move toward improved independence. The American Optometric Association recommends a professional vision assessment by an optometrist every two years for people aged 18 to 60 years of age and annually for people aged 61 years and older (www.aoa.org). For healthy adults with no known visual problems, visual acuity screening in the primary care physician’s office should probably be performed in years when patients do not have professional vision examinations, or more frequently when a patient is being monitored for the effects of medications that may have visual side effects. Frail, elderly patients at risk for falls should probably be screened at every primary care visit and periodically throughout visits for rehabilitation services.

Vision screening can be easily performed by a medical assistant during the initial phase of a primary care visit, or by an occupational therapist if the patient is referred for rehabilitation. None of our subjects had difficulty understanding the instructions. The ETDRS chart has been normed and is easily interpreted. Therefore, we recommend its use for patients who have decreased independence in activities of daily living, for patients known to have had falls, and for all adults who drive cars or other motor vehicles and who have not had their vision checked within the past year. In situations where specialized eye care is not available, screening has the added benefit of giving the primary care provider information to justify recommending a visit to an eye care expert, despite the extra time, added expense and possible difficulty of traveling to such a visit.

We recommend visual acuity screening, of the type performed in this study, at the onset of each primary care visit, especially if the patient takes any medications that might cause blurred vision. If a chart is mounted at a standard place in each exam room then the medical assistant can perform acuity screening right after vital signs have been measured. The ability to see is so important that it might be considered a kind of vital sign.

Brief Description.

In adult primary care clinics patients may, or may not, be screened for visual acuity. This study examined visual acuity screening in younger and older adults and differences between subjects who had had vision checks within the 10 months or longer ago.

Key Points.

1. Older patients had consulted an eye care professional for vision checks more recently than younger patients.

2. Groups with more or less recent vision checks did not differ in vision screening scores.

3. Vision screening with a well-validated chart is quick and easy to perform and may give the primary care physician useful information for clinical decision-making, such as referral to eye care specialists or occupational therapy/certified driving rehabilitation specialists for assessment for driving fitness.