Blue-on-yellow perimetry can predict the development of glaucomatous visual field loss

Retinotopy of the human retinal nerve fibre layer and optic nerve head

The organisation of the primate nerve fibre layer and optic nerve head with respect to eccentricity or the positioning of central and peripheral axons remains controversial. Crystals of the carbocyanine dyes DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate), or DiA (4-[4-didecylaminostryryl]-N-methylpridiniumiodide) were used to trace retinal ganglion cell axons within the nerve fibre layer, optic nerve head, and optic nerve. The present study demonstrated that peripheral retinal axons were scattered throughout the vitreal-scleral depth of the nerve fibre layer. This scattered distribution was maintained as the fibres passed through the optic nerve head and into the optic nerve. Axons of the arcuate bundles showed a bias towards the scleral portions of the nerve fibre layer and a variable degree of fibre scatter across the nerve fibre layer which was not as evident in labelling from other retinal regions. There was a rough topographic representation within the optic nerve head according to retinal circumference such that both peripheral and central fibres were mixed within a wedge extending from the periphery to the centre of the nerve. Foveal fibres occupied a large proportion of the temporal aspect of the optic nerve head and nerve, whereas fibres from areas temporal to the fovea appeared to be displaced to more superior and inferior regions. Consistent with the scleral bias seen in the retina, arcuate fibres maintained a peripheral position as they passed through the optic nerve head and occupied a more peripheral position in the nerve. The present results suggest that any degree of order present within the optic nerve is not an active process; optic axons are not instructed to establish a retinotopic order within the initial portions of the visual pathway.

Visual field loss in HIV-positive patients without infectious retinopathy

PURPOSE

To determine the extent of vision loss in a cross-sectional study of HIV-positive individuals who had no infectious retinopathy.

METHODS

Visual field loss was determined by computerized achromatic automated perimetry and short-wavelength automated perimetry in both eyes in 65 HIV-positive individuals without infectious retinopathy and in one randomly selected eye each in 57 age-matched normal controls. Results were analyzed using the global index of mean defect and the Glaucoma Hemifield Test, and significance was determined through analysis of variance, chi-square, and Tukey-Kramer tests.

RESULTS

We found that HIV-positive patients, compared with age-matched HIV-negative controls, demonstrated significant (at least P < .01) localized defects as well as an increased mean defect. The HIV-positive patients also had a significantly greater number of defective points, especially on short-wavelength automated perimetry, even while ophthalmoscopic examination and fundus photographs suggested that the retinas were normal.

CONCLUSIONS

There is a significant loss of visual function in HIV-positive individuals that is not the result of infectious retinopathies. The finding by short-wavelength perimetry of more severe defects suggests that the vision defects are not caused by attentional or other suprachiasmatic problems because the neurologic difficulty of both achromatic and short-wavelength perimetry is similar. The effects of this vision loss on the daily living and occupational tasks of this population require further study.

Color axis evaluation of the Farnsworth Munsell 100-hue test in primary open-angle glaucoma and normal-pressure glaucoma

BACKGROUND

It was the aim of the present study to analyze a separate color-axis evaluation of the Farnsworth Munsell 100-hue test (FM 100) in primary open-angle glaucoma (POAG) and normal pressure glaucoma (NPG).

PATIENTS AND METHODS

One eye of each of 112 individuals (age 35-65 years, visual acuity > 20/28, myopia < -7.5 D) was included. The groups consisted of 62 normal subjects and 50 glaucoma patients (33 POAG and 17 NPG). We evaluated the FM 100 overall error score and the error scores of the protan, deutan and tritan axes. The results were compared with perimetric (Octopus G1 mean defect) and morphometric data of the optic disc.

RESULTS

All error scores were significantly higher in the glaucoma group than in the normal group. In an age-related evaluation, differences were significant in age groups above 45 years. No significant differences were found between the POAG and NPG groups. The sensitivity of the overall score to identify glaucoma was 62% (specificity 80%). In the glaucoma group the overall score and the protan score increased significantly with the mean defect (r > 0.3, P < 0.01). Several scores increased slightly with decreasing neuroretinal rim area, but not on a significant level. Separate color-axis evaluations did not show any stronger correlations and did not reveal any differences between POAG eyes and NPG eyes. This was true even for the tritan axis error.

CONCLUSIONS

Although FM 100 error scores are higher in glaucoma eyes and increase with glaucomatous damage, they do not separate well. In the sample of this study, separate color-axis evaluation did not improve the diagnostic value. With the FM100 a different pattern of color vision defects in POAG and NPG eyes could not be detected.

Baseline alterations in blue-on-yellow normal perimetric sensitivity

BACKGROUND

the extent of any learning and fatigue effects in blue-on-yellow (B-Y) perimetry is unknown. The within- and between-eye changes in B-Y normal sensitivity at a single visit and between visits was investigated as a function of previous experience in white-on-white (W-W) perimetry and of subject age.

METHODS

Sixty-one normal subjects 22 young (range 20-34 years) and 39 elderly (range 51-80 years)-- assigned to one of four groups based upon perimetric experience and age underwent B-Y perimetry on four separate occasions using Program 30-2 of a modified Humphrey Field Analyser 640. Perimetry was performed for both eyes on three consecutive days and again one week later. Global, hemifield and annular mean sensitivities and global short-term fluctuation were calculated for each eye at each visit.

RESULTS

Mean sensitivity was higher in the first eye examined and increased over the 3 days. The increase in mean sensitivity was similar for each eye and was independent of perimetric experience and age. Short-term fluctuation decreased over the 3 days, regardless of eye and experience, but was more pronounced for the younger age group. The extent of all improvements varied considerably between subjects.

CONCLUSIONS

Improvements in B-Y perimetric performance occurred as the familiarity with the test increased, regardless of previous W-W experience. Failure to account for such improvement could reduce the efficiency of B-Y perimetry.

Random dot motion perimetry in patients with glaucoma and in normal subjects

PURPOSE

To determine whether patients with primary open-angle glaucoma have an increase in size thresholds, prolongation of reaction times, and greater localization errors to random dot motion stimuli than normal subjects.

METHODS

Motion perimetry, a computer graphics method of visual field testing, quantitates a subject's ability to detect a correlated shift in position of dots within a defined circular area against a background of fixed dots. We measured motion thresholds, the smallest detectable circular dot motion target, at the Humphrey 24-2 test loci. By using the subject's light-pen responses to the location of the targets, we computed motion size threshold, reaction times, and localization errors (number of pixels from where the subject touched the monitor to the target center). With motion perimetry and conventional automated perimetry, we tested one eye in each of 25 patients with primary open-angle glaucoma and 25 age-matched control subjects. We then generated total deviation pointwise probability plots for the patients with primary open-angle glaucoma.

RESULTS

Patients with primary open-angle glaucoma had increased mean motion size threshold (P < .001) and increased localization errors (P < .002), compared with the control subjects. With the probability plot analysis, there was good correlation of the visual field defects between the two perimetry tests. Additionally, motion perimetry identified nerve fiber bundle-like defects in 12 patients that were not detected with conventional automated perimetry.

CONCLUSIONS

Patients with primary open-angle glaucoma had abnormal motion perception with an increase in spatial localization error.

Quadrant analysis of peripheral colour contrast thresholds can be of significant value in the interpretation of minor visual field alterations in glaucoma suspects

Peripheral colour contrast thresholds were investigated in glaucoma suspects with no or minor visual field alterations, determining the average colour contrast threshold at 12.5 degrees off axis. The technique was introduced as a rapid screening test for pre-glaucomatous visual loss. Using this 'ring' test, all definite glaucoma patients in the initial study had elevated colour contrast thresholds. In our experience, however, a substantial proportion of early glaucoma patients were found to have normal thresholds. The peripheral colour contrast threshold determined by the ring test is an average threshold in the entire annular zone at 12.5 degrees eccentricity. We therefore modified the test procedure without a major increase in test duration. An arcade subtending 45 degrees at 12.5 degrees eccentricity was used to determine colour contrast thresholds in four quadrants of the visual field separately ('quadrant' test). We present here the first results of this novel procedure, investigating peripheral colour contrast thresholds in glaucomatous patients. The quadrant test is shown to be more sensitive than the ring test in the detection of functional loss.

Foveal adaptation abnormalities in early glaucoma

Foveal sensitivities were measured after onset of adapting background fields for each of the following four groups of subjects aged 40-70 years: (1) low-tension glaucoma subjects with minimal field loss in the test eye, (2) primary open-angle glaucoma subjects with minimal field loss in the test eye, (3) normal control subjects, and (4) subjects originally enrolled as control subjects but subsequently found, on the basis of masked clinical evaluation, to be suspect for glaucoma despite ostensibly normal intraocular pressures. We found that the desensitization of a short-wavelength-sensitive-cone-mediated response after onset of a 580-nm background field was diminished from that of normal observers for low-tension glaucoma subjects but not for primary open-angle glaucoma subjects. The desensitization was also diminished for a glaucoma-suspect subjects aged 60-70 years. In contrast, the flicker sensitivity instabilities that persisted after onset of a long-wavelength background field for the majority of subjects with primary open-angle glaucoma [J. Glaucoma Suppl. 3, S19 (1994)] occurred only infrequently among the other subject groups. These results imply that glaucoma often involves the fovea, probably by affecting retinal subtractive adaptation processes, although with different consequences for different types of glaucoma. The results also suggest that undiagnosed low-tension glaucoma may not be rare in the general aging population.

Newer visual function tests in the evaluation of glaucoma

Conventional visual field testing, with a uniform white-on-white stimulus, is used routinely to diagnose and follow patients with chronic open-angle glaucoma. Many investigators, however, believe that conventional perimetry may not detect the earliest visual dysfunction in patients with chronic open-angle glaucoma. Consequently, much research has been performed over the past decade to develop a visual function test which might diagnose chronic open-angle glaucoma earlier than conventional perimetry. This review discusses the mechanisms, clinical studies and the current usefulness of the most common new visual function techniques. These tests attempt to detect early glaucomatous visual loss, generally by placing the visual system under stress and by minimizing the influence of extensive functional redundancy in the retinal ganglion cell network due to widely overlapping receptive fields. Success of new visual function tests depends on the specificity and the sensitivity of the instrument, excellent patient acceptance, short test duration, standardization of techniques, and limited expense. In addition to searching for newer visual function tests to evaluate glaucoma, we should continue efforts to improve the diagnostic capability and shorten the test duration of conventional perimetry.

Peripheral cone contrast sensitivity in glaucoma

Colour vision tests for detection of glaucomatous damage frequently suffer from two problems: most tests are confined to foveal vision, whereas defects tend to appear first extrafoveally; and the modulation directions in colour space are not optimal. This paper deals with peripheral testing à la Yu, Falcao-Reis, Spileers and Arden [(1991) Investigative Ophthalmology and Visual Science, 32, 2779-2789], and investigates whether there are modulation directions that show preferential sensitivity reduction in glaucoma. In 14 eyes with early glaucoma, 17 risk eyes and 10 normals, 12 deg peripheral colour contrast thresholds were determined for L, M, S, L-M and L+M test directions. Threshold elevations were correlated in all test directions, with S modulation yielding the largest elevations.

The attenuation of blue-on-yellow perimetry by the macular pigment

PURPOSE

To determine the influence of macular pigment absorption on blue-on-yellow perimetry using a technique suitable for application with the Humphrey Field Analyzer.

METHODS

The sample comprised one eye from each of 46 healthy subjects (age range, 20-80 years). Macular pigment absorption was assessed by measuring medium-wavelength sensitive cone sensitivity for 460- and 570-nm narrowband stimuli at the fovea, at 5.5 degrees and at 8 degrees eccentricity. The differences in sensitivities recorded between the fovea and 8 degrees eccentricity and between 5.5 degrees and 8 degrees eccentricity for the 460-nm stimulus relative to a value of zero at 570 nm were attributed to absorption by the macular pigment. Blue-on-yellow perimetry was undertaken using a 460-nm narrowband blue Goldmann size V stimulus and a yellow 330-cdm-2 background.

RESULTS

Group macular pigment absorption (mean +/- standard error) was 0.40 +/- 0.03 log units foveally and 0.00 +/- 0.03 log units at 5.5 degrees eccentricity. The group mean foveal macular pigment absorption was significantly different from zero (P < 0.01). The coefficient of repeatability for the macular pigment absorption procedure (based on test-retest data for 16 subjects) was +/- 0.28 log units at the fovea and +/- 0.35 log units at 5.5 degrees eccentricity.

CONCLUSION

The net effect of ocular media and macular pigment absorption relative to 460 nm was to attenuate the blue-on-yellow visual field at the fovea by approximately 0.80 log units and elsewhere by 0.40 log units.

Ganglion cell death in glaucoma: pathology recapitulates ontogeny

I review some improvements in our knowledge about the death of retinal ganglion cells in glaucoma during the last 20 years. These include the realisation that glaucoma damage precedes its detection by perimetry, the fact that the lamina cribrosa is a major site of axonal injury to ganglion cells, and the association between regional structure of optic nerve head connective tissue and the pattern of glaucoma damage. The selective susceptibility of larger retinal ganglion cells and its functional significance are described. Apoptosis is the mode of cell death in at least some ganglion cells in experimental glaucoma. This supports a theory that retrograde axonal transport failure leads to loss of trophic factor influence on ganglion cells, causing them to initiate their own suicide. As a consequence of this theory, two therapeutic avenues are suggested for prevention of glaucoma injury and cell death: delivery of trophic factors and manipulation of ganglion cell genetic expression of controlling influences over programmed cell death.

Changes of color vision in ocular hypertension

Fifty-six ocular hypertension (OHT) patients were examined for 2-3 days in the Eye Clinic of Kuopio University Hospital. No glaucomatous changes were found. Twenty-seven of them were found to have several risk factors for developing glaucoma and medication was started. Twenty-nine of the patients did not show risk factors and had no medication. Color vision was examined with the Farnsworth-Munsell 100 (FM 100) hue test and Besançon anomalometer, later Color Vision Meter 712 at the beginning of the study and 3 years later. None of the 56 patients showed any glaucomatous changes after 3 years of the study. In the treatment group, the FM 100 test showed significantly (paired t-test, p = 0.004) improved error scores after 3 years. In the non-treatment group, 19 patients did not develop risk factors; they had no significant changes in the color vision results. In 10 patients of the non-treatment group, risk factors had developed with elevated intraocular pressure and medication was started for them after 3 years. Their color vision results in the blue anomalous quotient (AQ) of the anomalometer had significantly shifted to the blue part of the equation (paired t-test, p = 0.04). The other color vision results had not changed significantly. The significantly improved FM 100 scores in the treatment group could mean, that the treatment has a beneficial effect for the OHT eyes at risk for developing glaucoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Short-wavelength automated perimetry without lens density testing

Three experiments determined whether an estimate of localized short-wavelength visual field loss could provide enough specificity and sensitivity for glaucoma diagnosis, without correcting the fields for lens density. We used 100 normal, 53 glaucoma suspect, and 95 glaucoma eyes (or a subset of these, where noted). The first two experiments showed that lens density has a diffuse effect on the visual field, which is more linear than the effect of age. The third experiment showed that, with the glaucoma hemifield test, comparable results were obtained for short-wavelength fields either corrected or uncorrected for lens density (sensitivities of 81% and 76% and specificities of 82% and 90%, respectively). We conclude that it is possible to eliminate the lens density measurement with this approach, thereby reducing test time by 40 minutes. This should improve substantially the clinical utility of short-wavelength automated perimetry.

Flicker perimetry using a luminance threshold strategy at frequencies from 5-25 Hz in glaucoma, ocular hypertension and normal controls

A prototype automated flicker perimeter was used to investigate flicker luminance thresholds in glaucoma patients (n = 11), ocular hypertensives (high risk n = 10, low and intermediate risk n = 21) and normal controls (n = 10). Differential light sensitivity was measured for one eye of each subject using a flickering stimulus at frequencies of 5, 10, 15, 20 and 25 Hz at ten test locations of 1 degree in the arcuate and nasal regions of the central 50 degrees of the visual field using a 4-2 dB staircase. The glaucoma patients had significantly reduced sensitivities for all frequencies (p < 0.001) with minimum sensitivity at 15 Hz. The 'high risk' ocular hypertensives had significantly reduced sensitivities at 10 and 15 Hz (p < 0.02). At present the ocular hypertensive patients in this study show no abnormalities demonstrable by conventional automated static perimetry. These findings may represent the earliest of perimetric deficits in patients with glaucomatous optic neuropathy.

Longitudinal comparison of temporal-modulation perimetry with white-on-white and blue-on-yellow perimetry in ocular hypertension and early glaucoma

We obtained data over 3 years on temporal-modulation perimetry (TMP), standard automated [white-on-white (W/W)] perimetry, and short-wavelength-sensitive [blue-on-yellow (B/Y)] perimetry in ocular hypertensive (OH) patients and patients with early glaucomatous visual-field loss (EG). Evidence of visual-field defects was obtained with the use of both B/Y perimetry and TMP in the majority of OH and EG eyes that demonstrated progression on W/W perimetry as well as in all stable EG eyes. Using the nerve-fiber-bundle pattern to compare testing procedures, we determined that these defects were generally as extensive or more extensive than the concurrent W/W abnormalities. In terms of location over the 3 years of testing, TMP and B/Y defects were reasonably consistent in the EG eyes, somewhat less consistent in the OH eyes demonstrating progression, and both inconsistent and infrequent in the stable OH eyes. The greatest degree of overlap occurred between the location of defects obtained by use of the higher TMP frequencies (8 and 16 Hz) and that of defects obtained by use of B/Y perimetry. Since these two methods are thought to isolate different visual mechanisms subserved by different visual pathways, these results suggest that early glaucomatous visual-field damage as revealed by TMP and B/Y perimetry may not be specific to a single visual pathway.