Brightness discrimination and contrast sensitivity in chronic glaucoma--a clinical study

Visual function tests for glaucoma practice - What is relevant?

Glaucoma represents one of the most important ocular diseases causing irreversible ganglion cell death. It is one of the most common causes of visual impairment and morbidity in the elderly population. There are various tests for measuring visual function in glaucoma. While visual field remains the undisputed method for screening, diagnosis, and monitoring disease progression, other tests have been studied for their utility in glaucoma practice. This review discusses some of the commonly used tests of visual function that can be routinely used in clinics for glaucoma management. Among the various modalities of testing visual function in glaucoma, this review highlights the tests that are most clinically relevant.

A Comparative Analysis of the Fear of Falling Between Glaucoma and Age-Related Macular Degeneration Patients From a Developing Country

PURPOSE

Falls are very prevalent in the older population. Visually impaired elderly patients are prone to falls as the result of visual loss and ageing. The purpose of the study was to compare the fear of falling (FoF) between primary open angle glaucoma (POAG) and age-related macular degeneration (ARMD) patients who live in a developing country.

METHODS

This was a cross-sectional observational study. After a complete eye examination including measurement of best-corrected visual acuity, ophthalmoscopy, and automated visual field, all subjects completed the Fall Efficacy Scale International Brazil (FES-I-Brazil) questionnaire.

RESULTS

The sample comprised 64 patients with POAG, 48 with ARMD, and 52 controls. All groups were matched for age, sex, comorbidity, and ethnic distribution. The FES-I score was 24.6 ± 8.7, 25.3 ± 6.3, and 24.2 ± 7.7 for glaucoma, ARMD, and controls, respectively (P = 0.894). A post hoc analysis comparing all subjects with advanced visual field defect (mean deviation [MD] < -12 dB) revealed a higher FES-I score in ARMD patients as compared to POAG ones (46.2 ± 16.8 and 24.0 ± 7.7 for ARMD and POAG, respectively, P < 0.001).

CONCLUSION

In this cohort of elderly subjects with eye diseases, the FoF was similar among groups; however, ARMD patients with more compromised visual field had higher FoF as compared to POAG patients and controls.

TRANSLATIONAL RELEVANCE

A high rate of fear of falling exists in ARMD patients with compromised visual field. This finding may be useful in developing multidimensional strategies to decrease fear of falling and improve quality of life in older persons living in a developing country.

Evaluation of Contrast Sensitivity, Chromatic Vision, and Reading Ability in Patients with Primary Open Angle Glaucoma

Purpose. To compare contrast sensitivity, acquired color vision deficiency, and reading ability in patients with glaucoma at different stages of the disease and to establish correlations between visual field parameters and visual function scores. Methods. This prospective cross-sectional study included 121 glaucoma patients. Subjects with a diagnosis of chronic open angle glaucoma were recruited and classified according to Hodapp-Parrish-Anderson criteria. Patients with severe visual field defects were excluded because they were older, which could bias the interpretation of visual function tests. Contrast sensitivity was measured using the Pelli-Robson Chart and the CSV1000E test. Chromatic vision was evaluated using the Farnsworth-panel D15 and the L'Anthony D15 tests of Vision Color Recorder software. Reading ability was measured using Radner-Vissum test. Results. Contrast sensitivity (with photopic and mesopic luminance with glare) differed significantly between patients with early and moderate visual field defects (p < 0.05). Reading ability scores and results of the chromatic vision tests did not differ significantly between the two groups. Significant and moderate Spearman correlations between visual field indexes and contrast sensitivity tests were detected. Conclusions. Contrast sensitivity was significantly worse in patients with moderate glaucoma compared to those with early-stage glaucoma. Evaluation of visual function in clinical practice provides important information to address a glaucoma patient's vision complaints.

FACT contrast sensitivity as a diagnostic tool in glaucoma: FACT contrast sensitivity in glaucoma

PURPOSE

To investigate spatial-contrast sensitivity (CS) assessment as a tool for diagnosis of early glaucoma in patients with good visual acuity.

METHODS

In this prospective cross-sectional study we evaluated one eye of 50 patients with primary open angle or normotensive glaucoma who were newly diagnosed. All met the 0.6, or better, vision requirement. CS was measured at 1.5, 3, 6, 12, and 18 cycles per degree (cpd) spatial frequencies for one luminance level (85 cd/m2) using the functional acuity contrast test (FACT). Visual fields were evaluated using the Humphrey 750i field analyzer and the 30-2 standard full threshold program. The results from the visual acuity and CS assessments were compared with results for 20 age-matched control subjects.

RESULTS

CS scores were significantly lower at all spatial frequencies for the glaucoma patients than for the control subjects. The sensitivity of CS measurements was generally around 50%. Specificity ranged between 68 and 100%. FACT CS scores of less than 22 at 12 cpd spatial frequency provided sensitivity and specificity values concomitantly exceeding 60%.

CONCLUSIONS

Both the presence of a significant difference between the CS of glaucoma patients and control subjects and a high specificity of contrast sensitivity suggests that the FACT test may be used as a tool for diagnosis of patients with glaucoma, besides other methods such as short-wavelength automated perimetry (SWAP).

Relationship between visual field loss and contrast threshold elevation in glaucoma

BACKGROUND

There is a considerable body of literature which indicates that contrast thresholds for the detection of sinusoidal grating patterns are abnormally high in glaucoma, though just how these elevations are related to the location of visual field loss remains unknown. Our aim, therefore, has been to determine the relationship between contrast threshold elevation and visual field loss in corresponding regions of the peripheral visual field in glaucoma patients.

METHODS

Contrast thresholds were measured in arcuate regions of the superior, inferior, nasal and temporal visual field in response to laser interference fringes presented in the Maxwellian view. The display consisted of vertical green stationary laser interference fringes of spatial frequency 1.0 c deg(-1) which appeared in a rotatable viewing area in the form of a truncated quadrant extending from 10 to 20 degrees from fixation which was marked with a central fixation light. Results were obtained from 36 normal control subjects in order to provide a normal reference for 21 glaucoma patients and 5 OHT (ocular hypertensive) patients for whom full clinical data, including Friedmann visual fields, had been obtained.

RESULTS

Abnormally high contrast thresholds were identified in 20 out of 21 glaucoma patients and in 2 out of 5 OHT patients when compared with the 95% upper prediction limit for normal values from one eye of the 36 normal age-matched control subjects. Additionally, inter-ocular differences in contrast threshold were also abnormally high in 18 out of 20 glaucoma patients who had vision in both eyes compared with the 95% upper prediction limit. Correspondence between abnormally high contrast thresholds and visual field loss in the truncated quadrants was significant in 5 patients, borderline in 4 patients and absent in 9 patients.

CONCLUSION

While the glaucoma patients tested in our study invariably had abnormally high contrast thresholds in one or more of the truncated quadrants in at least one eye, reasonable correspondence with the location of the visual field loss only occurred in half the patients studied. Hence, while contrast threshold elevations are indicative of glaucomatous damage to vision, they are providing a different assessment of visual function from conventional visual field tests.

Temporal contrast sensitivity with peripheral and central stimulation in glaucoma diagnosis

AIMS

To evaluate temporal contrast sensitivity with full field, peripheral, and central stimulation and to determine the most sensitive corresponding retinal area for glaucoma damage.

METHODS

Temporal contrast sensitivity was determined either with a full field, a peripheral annular area from 30 degrees to 90 degrees, or a central area from 0 degree to 30 degrees at a frequency of 37.1 Hz. 232 eyes of 232 subjects were included. They were classified into four groups: eyes with ocular hypertension (OHT, n = 54), "preperimetric" glaucomas (n = 73) with glaucomatous optic disc abnormalities but no visual field loss, "perimetric" glaucomas (n = 53) with visual field loss, and 52 normals.

RESULTS

In all four groups, temporal contrast sensitivity was almost equal with full field and peripheral, but significantly higher than with central stimulation (p < 0.001). With regard to the diagnostic power of the three different stimulus areas, OHTs and glaucomas were found to be best discriminated from normals by peripheral stimulation.

CONCLUSIONS

According to these results, temporal contrast sensitivity seems to be determined by peripheral retinal areas. As the diagnostic power of the three different stimulus areas was best with the peripheral stimulation, this condition should be used for early glaucoma diagnosis.

Motion coherence perimetry in glaucoma and suspected glaucoma

Motion direction sensitivity in glaucoma patients, glaucoma suspects and controls was assessed perimetrically at 22 visual field locations using small random dot kinematograms and a motion coherence task. For foveal stimulus presentations, mean motion coherence sensitivity was normal in both patient groups. However, nearly all glaucoma patients and about half of glaucoma suspects (all with normal visual fields as assessed with static perimetry) had some deficit of motion sensitivity. These were most pronounced and most prevalent in the superior field at 15 and 21 deg eccentricity. Glaucoma appears to produce a reduction in the normal integrative visual function necessary for the perception of global motion in textured displays and this disruption is non-uniformly distributed across the visual field.

Correlation of spatial contrast sensitivity and visual fields in glaucoma

Perimetry is the standard examination in glaucoma, whereas contrast sensitivity is often proposed as a complementary test. This study investigates the extent to which the outcomes of the two tests correlate. One eye each of 44 glaucoma patients and 16 glaucoma suspects was tested with the Haag-Streit Visometer and the Octopus 201 perimeter (program G1). Contrast sensitivities correlated highest with the center of the visual field (Spearman's rho = 0.76; P < 0.001) and slightly less with the mean sensitivity of the entire visual field (rho = 0.63; P < 0.001). Mean contrast sensitivity correlated weakly with the square root of corrected loss variance (rho = -0.45; P < 0.001) and short-term fluctuation (rho = -0.34; P < 0.007). The two tests differed considerably only in very few patients. We recommend careful evaluation of the central area of glaucomatous visual fields whenever contrast sensitivity testing is not available.

Isolating the effects of primary open-angle glaucoma on the contrast sensitivity function

We evaluated spatial contrast sensitivity functions in age-matched and lens density-matched healthy eyes, eyes with primary open-angle glaucoma, and eyes with ocular hypertension. We also controlled for refraction, visual acuity, pupil size, and previous ocular history. We found an overall reduction in contrast sensitivity for the glaucomatous eyes with a significant difference at 12 cycles per degree (P less than .012). Eyes with ocular hypertension were not significantly different from normal eyes. Significant differences were noted at several spatial frequencies with less careful controls for age and lens effects. We concluded that spatial contrast sensitivity may be a useful adjunctive diagnostic test for glaucoma, but interpreting the results without other clinical data may lead to errors in diagnosis.