Improving the Design of the Letter Contrast Sensitivity Test

Clinical vision sciences, 1988

I. A consideration of methods for assessing contrast sensitivity leads to the conclusion that, for a clinical test, letters are more suitable than gratings. 2. A letter chart is described in which letters decrease in contrast but not in size. The letters are arranged in groups of three; successive groups decrease in contrast by a factor of IfJ2 from a very high contrast down to a contrast below the threshold of normal observers. A subject's threshold is taken to be the lowest contrast for which at least two letters in a group are correctly reported. 3. A mathematical model of the observer and the chart-testing procedure has been used to predict how the accuracy and repeatability of the test score depend on the parameters of the chart and observer. This reveals that even a low probability of misreporting supra threshold letters will seriously bias the test score if the passing criterion is strict, requiring correct report of all letters in each group, but will have little effect if the passing criterion is less strict. This effect of the passing criterion may explain Rubin's [Clin. Vision Sci. 2, No. I (1987)] finding that the new test, which uses a lenient criterion, has excellent test-retest reliability, much higher than the Ginsburg [Am. J. Optom. Physiol. Opt. 61,403-407 (1984)] chart with its strict criterion.

Investigative Ophthalmology & Visual Science, 2006

PURPOSE: To compare the reliability, validity and responsiveness the Mars Letter Contrast Sensitivity (CS) Test to the Pelli-Robson CS Chart. METHODS: One eye of 47 normal control subjects, 27 open angle glaucoma patients, and 17 age-related macular degeneration (AMD) patients was tested twice with the Mars test and twice with the Pelli-Robson test, in random order, on separate days. Also, 17 patients undergoing cataract surgery were tested, once pre-surgery and once postsurgery. RESULTS: Mean Mars CS was 1.62 log CS (SD, 0.06 log CS) for normal subjects aged 22 to 77 years, with significantly lower values for glaucoma and AMD patients (P<0.001). Mars test-retest 95% limits of agreement (LOA) were 0.13, 0.19 and 0.24 log CS for normal, glaucoma and AMD subjects, respectively. In comparison, Pelli-Robson test-retest 95% LOA were 0.18, 0.19 and 0.33 log CS. The Spearman correlation between the Mars and Pelli-Robson tests was 0.83 (P<0.001). However, systematic differences were observed, particularly at the upper/normal end of the range, where Mars CS was less than Pelli-Robson CS. Following cataract surgery, Mars and Pelli-Robson effect size statistics were 0.92 and 0.88, respectively. CONCLUSIONS: The results indicate the Mars test has test-retest reliability equal to or better than the Pelli-Robson test and comparable responsiveness. The strong correlation between the tests provides evidence the Mars test is valid. However, systematic differences indicate normative values are likely to be different for each test.

Interprofessional Optometry, 2017

Introduction: Contrast sensitivity is a visual element used in optometric examinations to help assess visual capacity. This study compared two formats of contrast sensitivity tests, ETDRS Letters and Continuous Text. Methods: Contrast sensitivity was measured in 75 subjects, who met inclusion criteria, using the Adult Near Contrast Test. Patients' verbal readings provided data for the formats at five contrast levels. Results: Average visual acuity and number of lines/paragraphs read correctly decreased with decreasing contrast. ANOVAs showed significant differences by contrast level in total words and total letters (ps< 0.001) and a Pearson correlation gave high correlations between the contrast sensitivity readings of the two formats except at 100% contrast (ps< 0.05; p= 0.69). Conclusion: Analysis revealed that contrast sensitivity readings from the different formats were essentially the same for most contrast levels. These two test formats can both be used with success in measuring contrast sensitivity in a normally sighted population.

Optometry and Vision Science, 2014

Purpose. An iPad-based letter contrast sensitivity test was developed (ridgevue.com) consisting of two letters on each page of an iBook. The contrast decreases from 80% (logCS = 0.1) to 0.5% (logCS = 2.3) by 0.1 log units per page. The test was compared to the Pelli-Robson Test and the Freiburg Acuity and Contrast Test. Methods. Twenty normally sighted subjects and 20 low-vision subjects were tested monocularly at 1 m using each test wearing their habitual correction. After a 5-minute break, subjects were retested with each test in reverse order. Two different letter charts were used for both the Pelli-Robson and iPad tests, and the order of testing was varied systematically. For the Freiburg test, the target was a variable contrast Landolt C presented at eight possible orientations and used a 30-trial Best PEST procedure. Repeatability and agreement were assessed by determining the 95% limits of agreement (LoA) T1.96 SD of the differences between administrations or tests. Results. All three tests showed good repeatability in terms of the 95% LoA: iPad = T0.19, Pelli-Robson = T0.19, and Freiburg = T0.15. The iPad test showed good agreement with the Freiburg test with similar mean (TSD) logCS (iPad = 1.98 T 0.11, Freiburg = 1.96 T 0.06) and with narrow 95% LoA (T0.24), but the Pelli-Robson test gave significantly lower values (1.65 T 0.04). Low-vision subjects had slightly poorer repeatability (iPad = T0.24, Pelli-Robson = T0.23, Freiburg = T0.21). Agreement between the iPad and Freiburg tests was good (iPad = 1.45 T 0.40, Freiburg = 1.54 T 0.37), but the Pelli-Robson test gave significantly lower values (1.30 T 0.30). Conclusions. The iPad test showed similar repeatability and may be a rapid and convenient alternative to some existing measures. The Pelli-Robson test gave lower values than the other tests.

Ophthalmic and Physiological Optics, 2010

Aim: To determine the influence of surround luminance on the letter contrast sensitivity function. Method: The binocular contrast sensitivities of 31 young and ocularly healthy individuals were measured with letters of sizes calculated to obtain the targeted fundamental frequencies of 3, 10, 20, and 30 c deg )1 , respectively; with surround luminances from 1 to 1000 cd m )2 , always with a test chart background luminance of 200 cd m )2 . Results: The letter contrast sensitivity increased with surround luminance up to 100 cd m )2 and decreased when surround luminance increased from 100 to 1000 cd m )2 . These increments are larger for higher fundamental spatial frequencies, while decrements are similar for all frequencies. To analyse pupil size influence, results were compared with theoretical predictions obtained by combining different ocular MTFs with a typical neural function, where pupil size decrease leads to letter contrast sensitivity increments and veiling luminance causes the observed decrements. Other possible optical or neural factors that influence these values have also been considered. Conclusions: Letter contrast sensitivity function depends on surround luminance and this influence should be considered in future standardized directives.

Ophthalmology, 1993

In the evaluation of cataracts, contrast sensitivity testing attempts to determine the patient's ability to perceive objects of varying contrast. The purpose of this literature review was to determine whether contrast sensitivity testing provides valid and reliable information over and above the history and clinical examination regarding the patient's need for cataract surgery. The questions specified by the panel to be addressed in this review are detailed in the Results section. Method The National Library of Medicine conducted a literature search for abstracts of articles published from January 1, 1975, through December 31, 1990, on three topics (glare, contrast sensitivity, and potential vision testing). (Chapter 2 and Appendix A give a detailed description of the search strategy.) A printout of potentially relevant references was produced. Additional articles were identified by reviewers and other interested parties. After the abstracts and additional articles listed on the printout were screened, 204 were selected for further review because they appeared relevant to the topics covered. A review of the 204 articles for ophthalmologic content was conducted by a group of eight individuals selected by

International Congress Series, 2005

Contrast sensitivity is widely regarded as an important visual parameter. Yet, it is rarely measured in routine eye examinations, since busy practitioners do not take time for an extra test. A new test has been produced that reduces the time requirement to a minimum. An existing reading test with logarithmic progression and standardized sentence length was modified by alternating high-contrast (HC) sentences with low-contrast (LC, 10%) ones of the same size. Thus, the routine test bWhat is the smallest (black) line you can read?Q is simply extended with the question bWhat is the smallest gray line you can read?Q The difference (HCÀLC) is immediately obvious and can be expressed as a number of lines. We found this number to be independent of visual acuity. A 2-or 3-line difference is normal (even in patients with reduced acuity); in some patients, we have observed differences up to 9 or 10 lines. The card is also a good demonstration and education tool to demonstrate the importance of contrast and the beneficial effect of illumination to patients and to family members. The cards are available in several languages.

International Journal of Ophthalmology and Clinical Research, 2020

Contrast sensitivity (CS) expresses the quality of human vision. This article presents the main points for the interpretation of CS and what structures of the eye and brain contribute to achieving it. There is still information on the ways and types of CS clinical examination, factors and conditions affecting it, and the latest technological developments in its measurement.

Journal of Cataract & Refractive Surgery, 1989

Biomedical Journal of Scientific & Technical Research, 2020

Contrast sensitivity (CS) expresses the quality of human vision. This article presents the main points for the interpretation of CS and what structures of the eye and brain contribute to achieving it. There is still information on the ways and types of CS clinical examination, factors and conditions affecting it, and the latest technological developments in its measurement.