Bradley E. Dougherty

An Evaluation of the Mars Letter Contrast Sensitivity Test

Purpose. The Mars Letter Contrast Sensitivity Test (initially known as the Lighthouse Letter Contrast Sensitivity Test) is similar in design to the Pelli-Robson Test but may offer several advantages. This study evaluates the repeatability of the Mars test and its agreement with the Pelli-Robson test in normal and low-vision subjects. Methods. Fifty-four subjects were tested (age 22–86 years), including 20 normally sighted young adults, 17 normally sighted older adults, and 17 adults with low vision (20/16 to 20/250). Subjects were tested with both contrast sensitivity tests and with the ETDRS visual acuity chart. After a short break, subjects were retested with an alternate form of each contrast sensitivity test. The chart forms used (two Pelli-Robson and three Mars) and the order of testing were varied systematically. Testing was monocular with habitual correction and, for subjects over 40 years of age, included appropriate near add. Letter-by-letter scoring was used for both tests. Repeatability and agreement were assessed by determining the 95% limits of agreement (LoA): ± 1.96 standard deviations of the differences between administrations or tests. Results. The Mars test showed excellent agreement with the Pelli-Robson test, with 95% LoA of ± 0.21 log units for all subjects. The Mars test was similarly repeatable (95% LoA = ±0.20 log units) to the Pelli-Robson test (95% LoA = ±0.20 log units) among all subjects. Conclusion. The new Mars Letter Contrast Sensitivity Test shows excellent agreement with the Pelli-Robson test and has similar repeatability. There are subtle differences in the actual contrast levels on different forms of the Mars test, and adjusting for these differences leads to superior repeatability of the Mars test. Thus, the Mars test may be a useful alternative to the Pelli-Robson test offering several advantages, including smaller size, improved durability, and ease of use.

Rasch Analysis of the Ocular Surface Disease Index (OSDI)

PURPOSE The Ocular Surface Disease Index (OSDI) is a 12-item scale for the assessment of symptoms related to dry eye disease and their effect on vision. Its reliability and validity have been investigated within the classical test theory framework and, more recently, using Rasch analysis. The purpose of the present analysis was to more completely investigate the functioning of its response category structure, the validity of its three subscales, and the unidimensionality of the latent construct it is intended to assess. METHODS Responses to the OSDI from 172 females participating in the Dry Eye in Postmenopause (DEiM) study who had previously been diagnosed with dry eye or reported significant ocular irritation and dryness were analyzed. Response category structure and item fit statistics were evaluated for assessment of model fit. Person separation statistics were used to examine the validity of the subscales. Unidimensionality was assessed by principal component analysis (PCA) of model residuals. RESULTS The recommended five-category response structure resulted in disordered response thresholds. A four-category structure resulted in ordered thresholds. Item infit statistics were acceptable for all 12 items. Person separation with this category structure was adequate, with a person separation index of 2.16. None of the three subscales demonstrated adequate person separation. PCA showed one other significant factor onto which the three environmental items loaded significantly. CONCLUSIONS All items demonstrated acceptable fit to the model after collapsing categories to order the response thresholds. The original subscales did not prove valid, and there is some evidence of multidimensionality and poor targeting.

Development of a battery of functional tests for low vision.

Purpose. We describe the development and evaluation of a battery of tests of functional visual performance of everyday tasks intended to be suitable for assessment of low vision patients. Methods. The functional test battery comprises—Reading rate: reading aloud 20 unrelated words for each of four print sizes (8, 4, 2, & 1 M); Telephone book: finding a name and reading the telephone number; Medicine bottle label: reading the name and dosing; Utility bill: reading the due date and amount due; Cooking instructions: reading cooking time on a food package; Coin sorting: making a specified amount from coins placed on a table; Playing card recognition: identifying denomination and suit; and Face recognition: identifying expressions of printed, life-size faces at 1 and 3 m. All tests were timed except face and playing card recognition. Fourteen normally sighted and 24 low vision subjects were assessed with the functional test battery. Visual acuity, contrast sensitivity, and quality of life (National Eye Institute Visual Function Questionnaire 25 [NEI-VFQ 25]) were measured and the functional tests repeated. Subsequently, 23 low vision patients participated in a pilot randomized clinical trial with half receiving low vision rehabilitation and half a delayed intervention. The functional tests were administered at enrollment and 3 months later. Results. Normally sighted subjects could perform all tasks but the proportion of trials performed correctly by the low vision subjects ranged from 35% for face recognition at 3 m, to 95% for the playing card identification. On average, low vision subjects performed three times slower than the normally sighted subjects. Timed tasks with a visual search component showed poorer repeatability. In the pilot clinical trial, low vision rehabilitation produced the greatest improvement for the medicine bottle and cooking instruction tasks. Conclusions. Performance of patients on these functional tests has been assessed. Some appear responsive to low vision rehabilitation.

Abandonment of low-vision devices in an outpatient population.

Purpose. To investigate abandonment rate of prescribed low-vision devices for near tasks and factors associated with abandonment in a U.S. outpatient population. Methods. A telephone survey was administered to 88 patients with low vision from four clinical sites about 1 year after examination and prescription of devices. Patients were surveyed on timing and frequency of use and reasons for abandonment of devices. The main outcome measure (abandonment) was defined as patient report of no use of prescribed device in the previous 3 months. Multivariate logistic regression was used to investigate significant vision and demographic factors related to abandonment. Results. Of 119 prescribed devices, 19% (95% CI, 12 to 26) had not been used within the previous 3 months. Mean (±SD) better eye visual acuity at examination was 0.61 ± 0.29 logMAR, and mean age was 77 ± 17 years. Mean time between device prescription and survey was 11 ± 3 months. Device abandonment was not associated with age (p = 0.863), time since prescription (p = 0.125), visual acuity (p = 0.804), or category of magnification device (spectacle, handheld, stand, or video) (p = 0.412). There was a significant association between documented non-central visual field loss and abandonment of magnification device (p = 0.046). Repeat administration of the survey resulted in the same abandonment classification in 15 of 15 patients (100%). Conclusions. Abandonment rate was similar for this outpatient population to those previously reported in the U.S. veteran inpatient population and in other countries. Patients with visual field loss may be more likely to abandon prescribed devices.

Comparison of scoring approaches for the NEI VFQ-25 in low vision.

Purpose. The aim of this study was to evaluate different approaches to scoring the National Eye Institute Visual Functioning Questionnaire-25 (NEI VFQ-25) in patients with low vision including scoring by the standard method, by Rasch analysis, and by use of an algorithm created by Massof to approximate Rasch person measure. Subscale validity and use of a 7-item short form instrument proposed by Ryan et al. were also investigated. Methods. NEI VFQ-25 data from 50 patients with low vision were analyzed using the standard method of summing Likert-type scores and calculating an overall average, Rasch analysis using Winsteps software, and the Massof algorithm in Excel. Correlations between scores were calculated. Rasch person separation reliability and other indicators were calculated to determine the validity of the subscales and of the 7-item instrument. Results. Scores calculated using all three methods were highly correlated, but evidence of floor and ceiling effects was found with the standard scoring method. None of the subscales investigated proved valid. The 7-item instrument showed acceptable person separation reliability and good targeting and item performance. Conclusions. Although standard scores and Rasch scores are highly correlated, Rasch analysis has the advantages of eliminating floor and ceiling effects and producing interval-scaled data. The Massof algorithm for approximation of the Rasch person measure performed well in this group of low-vision patients. The validity of the subscales VFQ-25 should be reconsidered.

Vision, training hours, and road testing results in bioptic drivers

Purpose Bioptic telescopic spectacles can be used by people with central visual acuity that does not meet the state standards to obtain an unrestricted driver’s license. The purpose of this study was to examine the relationships among visual and demographic factors, training hours, and the results of road testing for bioptic drivers. Methods A retrospective study of patients who received an initial daylight bioptic examination at the Ohio State University and subsequently received a bioptic license was conducted. Data were collected on vision including visual acuity, contrast sensitivity, and visual field. Hours of driver training and results of Highway Patrol road testing were extracted from records. Relationships among vision, training hours, and road testing were analyzed. Results Ninety-seven patients who completed a vision examination between 2004 and 2008 and received daylight licensure with bioptic telescopic spectacles were included. Results of the first Highway Patrol road test were available for 74 patients. The median (interquartile range) hours of training before road testing was 21 (17) hours (range, 9 to 75 hours). Candidates without previous licensure were younger (p < 0.001) and had more documented training (p < 0.001). Lack of previous licensure and more training were significantly associated with having failed a portion of the Highway Patrol test and points deducted on the road test. Conclusions New bioptic drivers without previous nonbioptic driving experience required more training and performed more poorly on road testing for licensure than those who had previous nonbioptic licensure. No visual factor was predictive of road testing results after adjustment for previous experience. The hours of training received remained predictive of road testing outcome even with adjustment for previous experience. These results suggest that previous experience and trainer assessments should be investigated as potential predictors of road safety in bioptic drivers in future studies.

Previous driving experience, but not vision, is associated with motor vehicle collision rate in bioptic drivers

PURPOSE Bioptic telescopic spectacles (BTS) consist of a small telescope (or telescopes) mounted high in a pair of spectacle lenses. More than 40 states allow for some form of bioptic driving licensure for people with decreased central vision. The purpose of this study was to determine significant associations among previous driving experience, vision, and motor vehicle collisions (MVCs) for bioptic drivers in Ohio. METHODS We conducted a retrospective study of patients who received a vision examination and subsequently obtained bioptic licensure. We obtained driving records from the Ohio Bureau of Motor Vehicles in order to determine MVC involvement. Relationships among vision measures, age, sex, previous experience, and MVCs were investigated using time-to-event analysis and the Cox proportional hazards regression model. RESULTS We identified 237 bioptic drivers (65% male). Age at initial exam ranged from 16 to 81 years, and mean visual acuity was approximately 20/120. The number of MVCs per driver ranged from 0 to 11, with 124 (52%) drivers having had at least one MVC. Visual acuity and contrast sensitivity were not significant predictors of MVC. Drivers without previous driving experience were significantly more likely to have been involved in an MVC (P < 0.001), and this association remained significant after adjusting for age and sex (P = 0.01). The rate of MVC per year decreased steadily over a 10-year period for drivers without previous experience. CONCLUSIONS Previous nonbioptic driving experience, but not visual acuity or contrast sensitivity, was associated with yearly MVC rate in bioptic drivers.

Psychometric Analysis of the SPEED Questionnaire and CLDEQ-8

Purpose This study reports on the ability of the Standard Patient Evaluation of Eye Dryness (SPEED) questionnaire to detect dry eye (DE) symptoms in contact lens (CL) and non-CL wearers. Methods The SPEED questionnaire was administered to all subjects while the Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8) was only administered to CL wearers. Tear meniscus heights (TMH) were measured, and the phenol red thread (PRT) test was conducted. These tests along with self-reported DE were used to identify subjects with dry eye disease (DED). Rasch analysis was performed to evaluate the questionnaires for measurement precision and unidimensionality, and the scores from these Rasch analyses were used to understand their ability to predict measures of DED. Results We enrolled 284 subjects (150 CL and 134 non-CL wearers). Mean subject age was 39.4 ± 14.2 years. Rasch analysis yielded a multidimensional short form of the SPEED questionnaire (8-items) and a unidimensional short form of the CLDEQ-8 (4-item). Scores from both questionnaires were significantly associated with self-reported DE in CL and non-CL wearers. Scores of the 8-item SPEED questionnaire were associated with DED status in non-CL wearers but not in CL wearers while 4-item CLDEQ scores were associated with DED status in CL wearers. TMH or PRT were not associated with either questionnaire in CL or non-CL wearers. Conclusions The 8-item SPEED questionnaire demonstrated adequate measurement precision with evidence of quantifying multiple symptoms categories while the 4-item CLDEQ-8 primarily quantified DE symptoms. Questionnaire scores were associated with self-reported DE, which suggests that they may have utility in both populations analyzed.