Characteristics of the normal central visual field measured with resolution perimetry

Topography of the frequency doubling perimetry visual field compared with that of short wavelength and achromatic automated perimetry visual fields

BACKGROUND

Traquair described the topography of visual field sensitivity as a "hill" or "island" of vision. Achromatic automated perimetry (AAP) demonstrates this shape of the visual field in photopic conditions. Techniques claimed to target the magnocellular pathway (frequency doubling perimetry, FDP) and those using a stimulus targeting the koniocellular pathway (short wavelength (or blue on yellow) automated perimetry, SWAP), might produce one that is different. The authors compared the visual field topography from FDP with those of SWAP and AAP, to investigate whether there were significant differences in their shape.

METHOD

A sample of 51 patients with previously confirmed normal perimetry were recruited; either low risk glaucoma suspects or normal controls. AAP, SWAP, and FDP perimetry was performed in random order on the same day. The topography of each field was analysed to determine its average shape and to compare results in the same individuals.

RESULTS

The topography of the visual field produced by each perimeter differed significantly. While all three had maximal sensitivity centrally, over the 24 degrees from the centre to the periphery, mean sensitivities decreased by 4.9 decibels (dB) for AAP and 7.3 dB for SWAP, while FDP sensitivities by just 1.8 dB over 20 degrees (the extent of the FDP field). FDP mean sensitivities decreased by approximately 0.3 dB with every 10 year increase in age, compared with 1 dB for AAP and 2 dB for SWAP.

CONCLUSION

While the topography of the SWAP (koniocellular) field is steeper than corresponding AAP fields, that of the FDP (magnocellular) visual field was considerably flatter. The difference in this shape may reflect retinotopic or cortical mechanisms, which are specific to the magnocellular pathways.

Visual Field of High-Pass Resolution Perimetry in Normal Subjects

PURPOSE

To investigate the properties of the visual field of high-pass resolution perimetry in normal subjects.

METHODS

Four centers collected normative data for high-pass resolution perimetry. In two of the centers the subjects were stratified by age. One eye was tested per subject using high-pass resolution perimetry (Ophthimus). We tested 640 normal subjects and describe their visual field results by test location. We also analyzed the data by concentric zone, age, and by testing center.

RESULTS

The individual test location averages confirmed a reduction in resolution with eccentricity. Resolution thresholds increased with age by 0.025 dB per year (P < 0.001). The mean ring size increased by about 1 dB from age 20 to 70. Among centers there were significant differences in the means and the change in threshold with age (P = 0.009).

CONCLUSION

The normal visual field of high-pass resolution perimetry is characterized by an increase in threshold with eccentricity. We found significant differences among the centers that were likely due to multiple factors including differences in subject selection criteria. Whether such differences occur with other perimetric techniques is unknown.

The value of high-pass resolution perimetry in glaucoma

High-pass resolution perimetry (HRP) is a perimetric technique that relies on low-contrast, high-spatial-frequency-filtered, ring-shaped test targets. It was devised as a quick and user-friendly technique that reflects the status of the retino-corneal pathway. Since its introduction in 1987, HRP has undergone substantial investigation, primarily in cross-sectional studies on patients with glaucoma, though it is also used in patients with neuro-ophthalmologic disorders. HRP has a shorter test time compared with conventional perimetry. Currently, evidence suggests that HRP is a viable test for the evaluation of the glaucomatous visual field.

A new scoring system for comparing the results of high-pass resolution perimetry and differential light sensitivity perimetry in glaucoma patients

Using a new standard, we compared the visual field defects detected by high-pass resolution perimetry (HRP) and differential light sensitivity (DLS) perimetry in 61 eyes of 61 open-angle glaucoma patients. Abnormal test points were determined using probability plot analysis of HRP and total deviation probability maps of the Humphrey Field Analyzer. To evaluate the agreement between the two tests, we developed a new scoring system. Thirty-three eyes, 23 eyes, and 5 eyes had good, fair, and poor agreement, respectively. In relation to Aulhorn's stage classification, the more advanced the glaucomatous stage, the more increased the percentages of good agreement. These results suggest that the distribution and severity of visual field defects demonstrated by HRP agree closely with those found using DLS perimetry in glaucomatous eyes, especially those with advanced visual field changes.

High-pass resolution perimetry and a Humphrey Field Analyzer as indicators of glaucomatous optic disc abnormalities. A comparative study

BACKGROUND

The "neural capacity (NC)" of high-pass resolution perimetry (HRP) may be correlated to the neuroretinal rim area of the optic disc. The authors compared HRP with conventional differential light sensitivity (DLS) perimetry in terms of correlation with glaucomatous optic disc changes.

METHODS

Thirty-seven eyes of 37 normal-tension glaucoma (NTG) patients were examined. The authors used an Ophthimus system for HRP and a Humphrey Field Analyzer (HFA) for DLS perimetry. The total rim area and the area of temporal, superior, nasal, and inferior quadrants were determined using a confocal laser tomographic scanner. Quadrant NC (QNC) was calculated using the resolution thresholds corresponding to a given quadrant. Quadrant mean deviation (QMD) was calculated from the total deviations of HFA.

RESULTS

In all eyes, NC and MD showed significant correlations with total rim area (Spearman rank correlation coefficient [rs] = 0.375, P < 0.05 for NC; rs = 0.336, P < 0.05 for MD). A significant correlation was observed in 21 eyes with early visual field changes (rs = 0.469, P < 0.05), but not in 16 eyes with advanced visual field changes. Both QNC and QMD showed significant correlations with inferior rim area (rs = 0.575, P < 0.01 for QNC; rs = 0.431, P < 0.01 for QMD). However, no significant correlations were found between QNC or QMD and superior rim area.

CONCLUSIONS

The NC may relate to glaucomatous optic disc changes better than does MD in NTG, especially in eyes with early-stage visual field changes.

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.

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.

Interpretation of high-pass resolution perimetry with a probability plot

BACKGROUND

The interpretation of high-pass resolution perimetry (HRP) fields can be difficult. An age-related probability plot was derived from a known data base to determine whether this improved specificity and sensitivity in early glaucoma detection.

METHODS

Forty glaucoma patients with minor field loss and 40 normals of equivalent age and sex underwent HRP. All had previous Humphrey field data available for comparison. The detection of previously confirmed field defects by HRP was examined using different parameters.

RESULTS

Using the age-corrected 95% confidence levels gave the best results, with sensitivity of 82.5% (33/40) and specificity of 85% (34/40). Using the contour plot yielded lower sensitivity (67.5%), while subjectively "eyeballing" the ring printout gave higher sensitivity (90%), but led to poor specificity (72.5%).

CONCLUSION

The use of a probability plot enhances the performance of HRP. A certain proportion of cases may be missed using one criterion alone, but combining the information with other indices can increase the yield.

High-pass resolution perimetry. A clinical review

Review of all available reports comparing high-pass resolution perimetry (HRP) and conventional perimetry in normals and in subjects with different visual disorders reveals closely comparable aspects of sensitivity, specificity, and reliability. HRP shows important advantages concerning variability, test duration, and subject preferences. Drawbacks seem largely limited to somewhat loose renditions of visual field defects of small area and large depth. Otherwise HRP's novel format of graphic result presentation may be better suited to visual evaluation than conventional gray-scale maps with their lumping of thresholds and extensive interpolations. Several examples are provided of visual field defects due to various lesions throughout the visual system.

High-pass resolution perimetry in eyes with ocular hypertension and primary open-angle glaucoma

We analyzed the results of high-pass resolution perimetry on normal eyes, eyes with ocular hypertension, and eyes with primary open-angle glaucoma. The subjects were matched for age and lens density. We controlled for refraction, visual acuity, pupil size, miotic medications, and learning effects. Under these conditions the glaucomatous eyes showed a significant reduction in overall resolution threshold compared to both normal (P less than or equal to .01) and hypertensive eyes (P less than .01). The hypertensive eyes were not significantly different from normal. Standard increment threshold fields and high-pass resolution visual fields had an agreement of abnormality of 67%. Resolution perimetry showed a 92% agreement with standard perimetry in the location of the defect, when the defect was apparent on both tests. These results indicated that resolution perimetry may be useful for diagnosis and management of primary open-angle glaucoma.