Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study One Year After Surgery

David B. Elliott* and Mark A. Bullimore\Purpose. To gather information regardin the reliabilityg , discriminative ability an,d validit oyfdisability glare tests.Methods. The following glare tests were evaluated the Miller-Nadler: , Vistech MCT8000 Ber, -keley, van den Berg Straylightmeter, and the Brightness Acuity Tester used with the Pelli-Rob-son and Regan charts. Three test evaluation criteria wer (1e used) repeatability—comparin: gtest score osn two visits (2; ) discriminative ability—the tests' abilit to differentiaty e betweenyoung and old subjects and between old normal and cataract subjects; (3) validity—comparingcataract test scores wit thhe reference standar odf the van den Berg Straylightmeter. Threesubject groups were evaluated: young normals (n = 24, mean age 24.3 ± 3.3 yr), older normals(n = 22, mean age 66.0 ± 6.2 yr), and early cataract ( n = 33, mean age 70.6 ±8.1 yr).Results and Conclusions. Data indicate that contrast sensitivit or loyw contrast acuity measuredin the presence of glare are superior to disability glare scores in assessing cataract patients withnormal neural function. Under glare conditions, contras and lot sensitivitw contrast acuity yscores from the Pelli-Robson, Regan, and Berkeley tests provide similarly reliable, discrimina-tive, and valid measure osf visual assessmen it n cataract. The Miller-Nadler glare tester poorlydetects and measures subtle change ins the ocular media, such as early cataract, becaus ofe itslarge step sizes at low contrast thresholds. The poor reliabilit of they Vistech MCT8000 limitsits usefulness Th. e study suggests that unless good chart an desigd psychophysicn s are used,the geometry and intensit oyf the glare source are of little importance. Invest Ophthalmol VisSci. 1993;34:108-119.v>«ontrast sensitivity (CS) and glare tests are beingused more frequently to clinically evaluate patientswith media opacities, such as after refractive surgeryand in patients with corneal edema, cataract, and cap-sular opacification. In some cases, they also are used to

Assessing the reliability, discriminative ability, and validity of disability glare tests.

Efforts to assess visual deterioration with increasing age, coupled with new mechanisms proposed to limit the exposure of visually impaired drivers to driving risks, have emerged in response to the increase in older drivers. Visual functions discussed in this context include static acuity (photopic, mesopic, and in the presence of glare), dynamic visual acuity, visual field, contrast sensitivity, and motion perception. Exposure control mechanisms discussed include alternative periodic vision testing strategies, visual training, and environmental and vehicular modifications to accommodate the older driver. Finally, relevant research needs are addressed.

Visual requirements for safety and mobility of older drivers.

Intraocular light scattering was studied in 34 controls and 65 patients with cortical, nuclear, or posterior subcapsular cataracts by measuring forward scatter and backscatter. Forward scatter was measured by the psychophysical direct compensation method. Backscatter was determined with the Lens Opacity Meter of Interzeag. Contrast sensitivity loss caused by forward scatter was assessed with a glare tester (Vistech MCT 8000). Mean forward scatter was in the upper range for subcapsular cataracts compared to nuclear and cortical cataracts. Experimental results of the glare test (the contrast loss) deviated systematically from expected results based on measured forward scatter. Mean backscatter was largest for nuclear, intermediate for posterior subcapsular, and almost zero for cortical cataracts. Thus, each cataract has a characteristic mean ratio between forward scatter and backscatter. However, this ratio varied considerably among individuals, especially for cortical and posterior subcapsular cataracts. As a rule, forward scatter cannot be derived from backscatter (or the slit-lamp image).

/pdf/intraocular-light-scattering-in-age-related-cataracts-2b373jxd3i.pdf

Intraocular light scattering in age-related cataracts.

For healthy eyes intraocular light scatter was investigated several decades ago. For pathological eyes, however, little is known. As clinical test several techniques have been proposed but none has gained general acceptance. A disadvantage of these tests was that quantities were estimated that related only indirectly to the amount of light scatter. We propose a method that gives a direct estimate of the light scatter. We studied patients with cataract, corneal dystrophy, iris and fundus hypopigmentation, etc. A remarkable finding was that visual acuity correlates rather weakly with the amount of scatter. Since, however, the amount of scatter causes a considerable loss of visual function, the results show that for these patients the visual acuity test gives a rather limited impression of their visual handicap. More attention to the problems associated with intraocular light scatter is needed.

Importance of pathological intraocular light scatter for visual disability.

A simple, inexpensive, readily available, easy-to-service clinical glare tester combines an audioviewer able-top projector with a series of specially made slides. Each slide supplies a constant glare source and a variable-contrast, central target. The device was evaluated on 161 normal subjects, 144 patients with cataracts, and 110 aphakic patients whose visual acuity was corrected with spectacles or intraocular lenses. Results showed that aphakic patients, irrespective of the mode of correction, were statistically more glare sensitive than normal phakic patients. Further results confirmed earlier studies that demonstrated that glare sensitivity also increased with age in normal eyes. Broad potential exists for using this method of glare testing in industry, transportation media, and medicolegal and and clinical ophthalmologic studies.

A New Glare Tester for Clinical Testing: Results Comparing Normal Subjects and Variously Corrected Aphakic Patients

Glare and Contrast Sensitivity for Clinicians

• A glare tester was described previously and was found, in the presence of cataracts, to be almost twice as predictive as was Snellen measurement for determining visual acuity outdoors. The current study tests the reproducibility of glare test scores and the influence of refractive error and contrast sensitivity on such scores when used in a clinical environment. Although the effects of visual acuity and impaired contrast sensitivity were found to be statistically significant components of glare test scores, the magnitudes of their effects were found to be clinically insignificant. Sequential retesting of physiologically stable eyes or, in the case of progressive cataracts, within intervals short enough to preclude discernible lenticular changes indicated that, for the most part, reproducibility of glare testing was comparable to that of visual acuity testing.

https://jamanetwork.com/journals/jamaophthalmology/articlepdf/635290/archopht_102_11_017.pdf

Clinical performance of a disability glare tester.

In the body, collagen bundles, interstitial fluids, and cellular elements all combine to make tendons white, dura opaque, and epidermis translucent.

Light Scattering: Its Relationship to Glare and Contrast in Patients and Normal Subjects

An apparatus for testing glare susceptibility of a subject. A planar member having an opaque target is surrounded by a contrasting surface which is surrounded by a translucent surface. Light is directed to one side of the planar member and the subject's ability to see the target against the contrasting surface against a glare of light through the translucent surface determines the glare susceptibility of the subject.

M. Princeton Nadler

Papers

A New Glare Tester for Clinical Testing: Results Comparing Normal Subjects and Variously Corrected Aphakic Patients

Glare and Contrast Sensitivity for Clinicians

Clinical performance of a disability glare tester.

Light Scattering: Its Relationship to Glare and Contrast in Patients and Normal Subjects

Glare susceptibility tester