Benefit of Stimulus Size V Perimetry for Patients With a Dense Central Scotoma From Leber's Hereditary Optic Neuropathy

Interpretation of the Visual Field in Neuro-ophthalmic Disorders

PURPOSE OF REVIEW

In this review, we will describe current methods for visual field testing in neuro-ophthalmic clinical practice and research, develop terminology that accurately describes patterns of field deficits, and discuss recent advances such as augmented or virtual reality-based perimetry and the use of artificial intelligence in visual field interpretation.

RECENT FINDINGS

New testing strategies that reduce testing times, improve patient comfort, and increase sensitivity for detecting small central or paracentral scotomas have been developed for static automated perimetry. Various forms of machine learning-based tools such as archetypal analysis are being tested to quantitatively depict and monitor visual field abnormalities in optic neuropathies. Studies show that the combined use of optical coherence tomography and standard automated perimetry to determine the structure-function relationship improves clinical care in neuro-ophthalmic disorders. Visual field assessment must be performed in all patients with neuro-ophthalmic disorders affecting the afferent visual pathway. Quantitative visual field analysis using standard automated perimetry is critical in initial diagnosis, monitoring disease progression, and guidance of therapeutic plans. Visual field defects can adversely impact activities of daily living such as reading, navigation, and driving and thus impact quality of life. Visual field testing can direct appropriate occupational low vision rehabilitation in affected individuals.

Correlation Between Visual Acuity and Foveal Threshold by Automated Perimetry With Size V Stimulus

BACKGROUND

Visual acuity has been shown to correlate with foveal threshold as determined by automated perimetry. Although automated perimetry with size V stimulus is commonly used in neuro-ophthalmology practice, the relationship between the visual acuity and the foveal threshold with this larger stimulus is not well known.

METHODS

Retrospective study of patients who had undergone neuro-ophthalmology evaluation and visual field testing with automated perimetry using size V stimulus. Healthy controls were also recruited. Using visual acuity and foveal threshold, Pearson correlation coefficients were calculated, and basic foveal threshold statistics were stratified by visual acuity. Prediction intervals for visual acuities by various foveal threshold were also calculated.

RESULTS

A total of 106 unique eyes were included. The final Pearson correlation coefficient between visual acuities was -0.795 for the right eye and -0.578 for the left eye, with a pooled correlation coefficient of -0.751 (P < 0.001). A foveal threshold of at least 34 dB was present in 94.4% of eyes with 20/20 visual acuity, and a foveal threshold of greater than 35 dB was not observed in eyes with visual acuity of 20/40 or worse.

CONCLUSIONS

Foveal threshold as determined by automated perimetry using size V stimulus has moderate-to-strong correlation with visual acuity in patients undergoing neuro-ophthalmology evaluation.

The Value of Static Perimetry in the Diagnosis and Follow-up of Negative Dysphotopsia

SIGNIFICANCE

There is a clinical need for a quantitative test to objectively diagnose negative dysphotopsia, especially because the diagnosis is generally assessed using patients' subjective descriptions. In the search of a clinical test to objectify the shadow experienced in negative dysphotopsia, this study excludes static perimetry as suitable evaluation method.

PURPOSE

This study aimed to evaluate the value of static perimetry in the objective assessment and follow-up of negative dysphotopsia.

METHODS

Peripheral 60-4 full-threshold visual field tests were performed in 27 patients with negative dysphotopsia and 33 pseudophakic controls. In addition, 11 patients with negative dysphotopsia repeated the test after an intraocular lens exchange. Both the total peripheral visual field and the averaged peripheral visual field from 50 to 60° eccentricity were compared between patients and controls, and pre-operatively and post-operatively in patients who had an intraocular lens exchange.

RESULTS

The peripheral visual fields from 30 to 60° did not show significant differences between patients with negative dysphotopsia and pseudophakic controls. Analysis of the peripheral visual field from 50 to 60° showed a median [Q1, Q3] of 20.0 [17.1, 22.5] dB in the negative dysphotopsia group compared with 20.1 [15.5, 21.3] dB in the control group (P = .43). Although 82% of patients treated with an intraocular lens exchange subjectively reported improvement of their negative dysphotopsia complaints post-operatively, there were no significant differences in their total peripheral visual field or averaged peripheral visual field from 50 to 60° (P = .92).

CONCLUSIONS

Full-threshold static perimetry with a Goldmann size III stimulus up to 60° eccentricity does not show significant differences between patients with negative dysphotopsia and pseudophakic controls or between measurements before and after intraocular lens exchange. Therefore, this type of static perimetry cannot be used as a quantitative objective test for diagnosis or follow-up of patients with negative dysphotopsia.

Long- and Short-Term Variability of Perimetry in Glaucoma

Purpose

Test–retest variability in perimetry consists of short-term and long-term components, both of which impede assessment of progression. By minimizing and quantifying the algorithm-dependent short-term variability, we can quantify the algorithm-independent long-term variability that reflects true fluctuations in sensitivity between visits. We do this at locations with sensitivity both < 28 dB (when the stimulus is smaller than Ricco's area and complete spatial summation can be assumed) and > 28 dB (when partial summation occurs).

Methods

Frequency-of-seeing curves were measured at four locations of 35 participants with glaucoma. The standard deviation of cumulative Gaussian fits to those curves was modeled for a given sensitivity and used to simulate the expected short-term variability of a 30-presentation algorithm. A separate group of 137 participants was tested twice with that algorithm, 6 months apart. Long-term variance at different sensitivities was calculated as the LOESS fit of observed test–retest variance minus the LOESS fit of simulated short-term variance.

Results

Below 28 dB, short-term variability increased approximately linearly with increasing loss. Long-term variability also increased with damage below this point, attaining a maximum standard deviation of 2.4 dB at sensitivity 21 dB, before decreasing due to the floor effect of the algorithm. Above 30 dB, the observed test–retest variance was slightly smaller than the simulated short-term variance.

Conclusions

Long-term and short-term variability both increase with damage for perimetric stimuli smaller than Ricco's area. Above 28 dB, long-term variability constitutes a negligible proportion of test–retest variability.

Translational Relevance

Fluctuations in true sensitivity increase in glaucoma, even after accounting for increased short-term variability. This long-term variability cannot be reduced by altering testing algorithms alone.