Retinal sensitivity is a valuable complementary measurement to visual acuity--a microperimetry study in patients with maculopathies

Macular Sensitivity Endpoints in Geographic Atrophy: Exploratory Analysis of Chroma and Spectri Clinical Trials

Purpose

To assess different microperimetry (MP) macular sensitivity outcome measures capturing functional deterioration in eyes with geographic atrophy (GA) secondary to age-related macular degeneration (AMD).

Design

Patients were included from 2 identically designed, phase III, double-masked, randomized controlled clinical trials, Chroma (NCT02247479) and Spectri (NCT02247531).

Participants

Patients enrolled were aged ≥ 50 years with bilateral GA and no evidence of previous or active neovascular AMD.

Methods

Patients were randomized 2:1:2:1 to receive through 96 weeks intravitreal lampalizumab 10 mg every 4 weeks (LQ4W), every 6 weeks (LQ6W), or corresponding sham procedures. For this study, mesopic macular sensitivity of the central 20° was assessed using MP-1 microperimeter at selected sites.

Main Outcome Measures

Two exploratory endpoints were developed, namely perilesional sensitivity (average of points adjacent to absolute scotomatous points) and responding sensitivity (average of all nonscotomatous points; > 0 dB at baseline) by using customized masks for each patient. These were compared with conventional MP endpoints (mean macular sensitivity and number of absolute scotomatous points).

Results

Of 1881 Chroma and Spectri participants, 277 agreed to participate in the present study. Of these, 197 (LQ4W, n = 63; LQ6W, n = 68; pooled sham, n = 66) had reliable MP results. Enlargement of GA lesion area by approximately 2 mm2/year across treatment groups was accompanied by deterioration in all MP parameters. There was no difference in worsening of macular sensitivity or absolute scotomatous points among treatment groups. Perilesional and responding sensitivities showed greater decline over time than mean macular sensitivity. Change in GA lesion area at week 48 showed better correlation with perilesional sensitivity (r = -0.17) and responding sensitivity (r = -0.20) than mean macular sensitivity (r = -0.03), while the correlation was highest with the number of absolute scotomatous points (r = 0.37).

Conclusions

Perilesional or responding macular sensitivity measured by MP should be considered more sensitive endpoints than mean macular sensitivity for monitoring functional decline over time in GA. Although perilesional, responding, and mean macular sensitivity had weak correlation with GA lesion area, the number of absolute scotomatous points may provide additional information on the anatomic/functional correlation.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Investigating the Spatiotemporal Summation of Perimetric Stimuli in Dry Age-Related Macular Degeneration

Purpose

To measure achromatic spatial, temporal, and spatiotemporal summation in dry age-related macular degeneration (AMD) compared to healthy controls under conditions of photopic gaze-contingent perimetry.

Methods

Twenty participants with dry AMD (mean age, 74.6 years) and 20 healthy controls (mean age, 67.8 years) performed custom, gaze-contingent perimetry tests. An area-modulation test generated localized estimates of Ricco's area (RA) at 2.5° and 5° eccentricities along the 0°, 90°, 180°, and 270° meridians. Contrast thresholds were measured at the same test locations for stimuli of six durations (3.7-190.4 ms) with a Goldmann III stimulus (GIII, 0.43°) and RA-scaled stimuli. The upper limit (critical duration) of complete temporal summation (using the GIII stimulus) and spatiotemporal summation (using the RA stimuli) was estimated using iterative two-phase regression analysis.

Results

Median (interquartile range [IQR]) RA estimates were significantly larger in AMD participants (2.5°: 0.21 [0.09-0.41] deg2; 5°: 0.32 [0.15-0.65 deg2]) compared to healthy controls (2.5°: 0.08 [0.05-0.13] deg2; 5°: 0.15 [0.08-0.22] deg2) at all test locations (all P < 0.05). No significant difference in median critical duration was found in AMD participants with the GIII stimulus (19.6 [9.9-30.4] ms) and RA-scaled stimuli (22.9 [13.9-40.3] ms) compared to healthy controls (GIII: 17.0 [11.3-24.0] ms; RA-scaled: 22.4 [14.3-33.1] ms) at all test locations (all P > 0.05).

Conclusions

Spatial summation is altered in dry AMD, without commensurate changes in temporal summation.

Translational Relevance

The sensitivity of perimetry to AMD may be improved by utilizing stimuli that probe alterations in spatial summation in the disease.

Investigating the linkage between mesopic spatial summation and variations in retinal ganglion cell density across the central visual field

PURPOSE

The relationship between perimetric stimulus area and Ricco's area (RA) determines measured thresholds and the sensitivity of perimetry to retinal disease. The nature of this relationship, in addition to effect of retinal ganglion cell (RGC) number on this, is currently unknown for the adaptation conditions of mesopic microperimetry. In this study, achromatic mesopic spatial summation was measured across the central visual field to estimate RA with the number of RGCs underlying RA also being established.

METHODS

Achromatic luminance thresholds were measured for six incremental spot stimuli (0.009-2.07 deg2 ) and 190.4 ms duration, at four locations, each at 2.5°, 5° and 10° eccentricity in five healthy observers (mean age 61.4 years) under mesopic conditions (background 1.58 cd/m2 ). RA was estimated using two-phase regression analysis with the number of RGCs underlying RA being calculated using normative histological RGC counts.

RESULTS

Ricco's area exhibited a small but statistically insignificant increase between 2.5° and 10° eccentricity. Compared with photopic conditions, RA was larger, with the difference between RA and the Goldmann III stimulus (0.43°) being minimised. RGC number underlying RA was also higher than reported for photopic conditions (median 70 cells, IQR 36-93), with no significant difference being observed across test locations.

CONCLUSIONS

Ricco's area and the number of RGCs underlying RA do not vary significantly across the central visual field in mesopic conditions. However, RA is larger and more similar to the standard perimetric Goldmann III stimulus under mesopic compared with photopic adaptation conditions. Further work is required to determine if compensatory enlargements in RA occur in age-related macular degeneration, to establish the optimal stimulus parameters for AMD-specific microperimetry.

Lamellar Macular Holes: The Role of Microperimetry in Functional Assessment

Introduction

The aim of our observational cross-sectional study was to evaluate the association between visual function and anatomical characteristics of LMH, considering in particular different subtypes of LMH and their features.

Materials and Methods

This observational clinical study has been conducted in the Ophthalmology Clinic, ASST-Sette Laghi, University of Insubria of Varese-Como, Italy. Included patients underwent a complete ophthalmological examination, as well as MP1 microperimetry evaluation and optical coherence tomography (OCT). Two experienced masked observers evaluated OCT imaging in order to assess the integrity of the photoreceptor layer (interdigitation zone and ellipsoid zone: IZ/EZ) and the external limiting membrane (ELM).

Results

Twenty-five patients affected by an LMH were evaluated. Eighteen eyes of 18 patients met the study criteria and were included. Based on morphological and functional data, LMHs were divided into two subgroups: tractional (tLMH) and degenerative (dLMH). We identified 11 tLMHs and seven dLMHs. Functional parameters showed a significative difference in visual acuity and retinal sensitivity between the two groups, respectively: (sample median and the interquartile range) 0.0 (0.0; 0.09) LogMAR vs 0.15 (0.09; 0.52) LogMAR and 16.2 (14.2; 17.7) dB vs 10.0 (7.5; 11.8) dB (p < 0.05). Fixation was predominantly central in 90.9% of tLMH vs 71.4% of dLMH and stable in 81.8% tLMH vs 42.9% dLMH, but the differences were not statistically significant. Tractional and degenerative LMHs showed no significant differences in central foveal thickness. Conversely, LMH depth and horizontal diameters appeared different between the two groups. Tractional LMH showed a greater depth 257 (205; 278) μm vs 190 (169; 249) μm, whereas degenerative LMH showed a greater horizontal diameter 653 (455; 750) μm vs 429 (314; 620) μm (p < 0.05). IZ/EZ line was unaffected in 81.8% of tLMHs eyes versus 14.3% of dLMHs eyes (p < 0.05). Visual acuity and retinal sensitivity were higher in eyes with integrity of both IZ/EZ and ELM compared to those with a disruption of one or both layers (p < 0.05).

Conclusion

Two different subtypes of LMH showed peculiar functional aspects due to their morphological features. Tractional LMHs revealed higher visual acuity and retinal sensibility due to the relative preservation of the outer retinal layers compared to degenerative LMHs. Moreover, we underlined the importance of microperimetry to better identify functional defects in macular degenerative pathologies.

Microperimetry for geographic atrophy secondary to age-related macular degeneration

Geographic atrophy (GA) is a progressive, advanced form of age-related macular degeneration leading to visual function impairment and irreversible vision loss. Standard clinical tests to evaluate visual function in patients with GA provide poor anatomic-functional correlation, whereas fundus imaging does not assess the visual function deficit. Microperimetry is a psychophysical visual function test that spatially maps retinal sensitivity and allows for identification of correlation of anatomic features with visual function. In this review, we present an overview of mesopic microperimetry for GA, including commercially available microperimetry devices, strategies to capture a mesopic microperimetry test, and strategies to assess and interpret microperimetry data in patients with GA. We demonstrate the importance of microperimetry data for assessing GA progression and for evaluating visual function loss through anatomic-functional correlations. Although valuable, current microperimetry tests require an extensive time commitment from the patient and examiner, and the development of faster, more reproducible and accessible methods is important to enable broader use of microperimetry in both clinical and research settings.

Evaluation of the Effectiveness of Treatment with Dexamethasone Intravitreal Implant in Cystoid Macular Edema Secondary to Retinal Vein Occlusion

Purpose

To evaluate retinal functional improvement by means of visual acuity and retinal sensibility examination after intravitreal dexamethasone implant in patients affected by cystoid macular edema secondary to retinal vein occlusion.

Methods

Twenty-six consecutive patients affected by retinal vein occlusion complicated by cystoid macular edema were enrolled in this prospective interventional study. All patients underwent a baseline complete ophthalmological evaluation as well as retinal angiography, OCT examination, and microperimetry evaluation. Each patient was treated with intravitreal injection of a long-term steroid implant (Ozurdex, Allergan). Follow-up evaluations were performed at months 1, 3, and 6 and completed by OCT and MP1 examination. Clinical data underwent statistical analysis.

Results

Baseline functional evaluation showed mean visual acuity of 0,63±0,42 LogMAR and retinal sensitivity of 7,93±4,73 dB (mean±standard deviation); after treatment, at day 30 we found, respectively, 0,43±0,38 LogMAR (p<0.05, compared to baseline) and 10,15±4,410 dB (p<0.05); at day 90, we found 0,44±0,32 (p<0.05) and 9.61±4,29 dB (p<0.05); at day 180, we found 0,41±0,31 (p<0.05) and 9,95±3,79 dB (p<0.05). Fixation pattern improved significantly (p<0.05), showing a stable fixation in 30% of patients at baseline, increasing to 77% of patients at day 180. Baseline morphological evaluation showed a central retinal thickness (CRT) of 398,21±181,65 μm after treatment; we found a CRT of 222,64±95,21 μm at day 30 (p<0.05, compared to baseline), 307,50±120,25 μm (p<0.05) at day 90, and 294,93±135,86 μm (p<0.05) at day 180. About 15,3% patients showed already at month 3 a recurrence of macular edema. They underwent a retreatment before month 6 as for treatment guidelines.

Conclusion

Our detailed analysis showed the significative increase in retinal function in the early phases of the follow-up. Retinal sensibility showed a stronger correlation than VA in macular edema reabsorption, better underlying the progressive functional recovery and increase in quality of vision and life for the patients. This trial is registered with ClinicalTrials.gov NCT03559491.

Comparisons of Two Microperimeters: The Clinical Value of an Extended Stimulus Range

SIGNIFICANCE

Fundus-guided perimetry is a common clinical tool used to measure visual field sensitivities. Comparisons between perimeters are often made despite relative differences in hardware parameters. We directly compared two perimeters using Weber contrast, which allowed us to assess the clinical gain associated with the extended stimulus range of the macular integrity assessment (MAIA).

PURPOSE

The purpose of this study was to directly compare sensitivity thresholds for two microperimeters, the MAIA and Optos optical coherence tomography/scanning laser ophthalmoscope, using Weber contrast values. We also examined the clinical utility of the extended stimulus range of the MAIA.

METHODS

Six normally sighted adults with no visual field loss and 16 adults with low vision were recruited. Thresholds were measured on the MAIA and Optos using the same threshold algorithm and test points. To compare equivalent units, decibel thresholds were converted to light increments in apostilbs and then to delta increment intensities relative to each instrument's background luminance. Repeatability was assessed for normally sighted adults by testing both instruments on 3 separate days.

RESULTS

For normally sighted observers, mean thresholds were similar on both instruments, and repeatability within microperimeters was high. The MAIA has a 0.3-log lower contrast range and 1.37 higher contrast range. The lower contrast values did not result in lower thresholds for the normally sighted observers on the MAIA. There was a 25% increase in the number of measurable thresholds owing to the higher contrast values in low-vision observers.

CONCLUSIONS

The higher contrast range in the MAIA yielded only a small increase in detectable thresholds for participants with visual field loss.

Measuring Central Retinal Sensitivity Using Microperimetry

Microperimetry is an increasingly often used method of assessing the sensitivity of the central macula, analyzing fixation capabilities and loci, and accurately combining structural and functional information, even in the absence of stable fixation. Ongoing gene therapy trials have targeted the central retina, and utilized microperimetry as a main outcome measure for changes in retinal function. In retinal treatment planning, microperimetry has been used to assess the potential therapeutic window of opportunity. In the following pages, we briefly review the necessary steps to perform the Macular Integrity Assessment (MAIA) microperimetry.

Individual Test Point Fluctuations of Macular Sensitivity in Healthy Eyes and Eyes With Age-Related Macular Degeneration Measured With Microperimetry

Purpose

To establish fluctuation limits, it was considered that not only overall macular sensitivity but also fluctuations of individual test points in the macula might have clinical value.

Methods

Three repeated measurements of microperimetry were performed using the Standard Expert test of Macular Integrity Assessment (MAIA) in healthy subjects (N = 12, age = 23.8 ± 1.5 years old) and in patients with age-related macular degeneration (AMD) (N = 11, age = 68.5 ± 7.4 years old). A total of 37 macular points arranged in four concentric rings and in four quadrants were analyzed individually and in groups.

Results

The data show low fluctuation of macular sensitivity of individual test points in healthy subjects (average = 1.38 ± 0.28 dB) and AMD patients (average = 2.12 ± 0.60 dB). Lower sensitivity points are more related to higher fluctuation than to the distance from the central point. Fixation stability showed no effect on the sensitivity fluctuation. The 95th percentile of the standard deviations of healthy subjects was, on average, 2.7 dB, ranging from 1.2 to 4 dB, depending on the point tested.

Conclusion

Point analysis and regional analysis might be considered prior to evaluating macular sensitivity fluctuation in order to distinguish between normal variation and a clinical change.

Translational Relevance

Statistical methods were used to compare repeated microperimetry measurements and to establish fluctuation limits of the macular sensitivity. This analysis could add information regarding the integrity of different macular areas and provide new insights into fixation points prior to the biofeedback fixation training.

Intersession Test-Retest Variability of Microperimetry in Type 2 Macular Telangiectasia

Purpose

Microperimetry is used as an endpoint in type 2 macular telangiectasia (mactel) trials. The change required for defining disease progression depends on measurement error. We determined the threshold of test-retest variability (TRV) of microperimetry in mactel.

Methods

A prospective study was done of 24 patients with stable mactel enrolled in a tertiary eye clinic. Each patient underwent three sessions of microperimetry separated by a median of 28 days. An identical testing protocol was used: 4-2 staircase algorithm at 37 loci radial grid covering central 6°. Microperimetry variables were compared across three visits. TRV was quantified by calculating the coefficients of repeatability (CRs) for mean and median foveal sensitivity and the number of loci with dense scotoma (DS) or normal sensitivity (NS). The 95% confidence intervals (CIs) for CRs were calculated.

Results

Mean and median foveal sensitivity increased from first to second testing sessions. Test duration, visual acuity, number of loci with DS, and fixation stability remained stable through the three test sessions. The intersession CRs for mean and median foveal sensitivity were 2.6 (95% CI, 1.8-3.3) and 2.4 (95% CI, 1.7-3.1) dB, respectively. CRs for the number of DS and NS loci were 5 and 12 loci. CR for both logBCEA63 and logBCEA95 was 1.0 (95% CI, 0.8-1.2).

Conclusions

The first microperimetry examination should be discarded due to learning effects. TRV in foveal sensitivity may be as high as 3.3 and 3.1 dB (∼0.3 log unit; 2× change) for its mean and median.

Translational Relevance

Our results have implications for the design of clinical trials in mactel.

Intersession test-retest variability of conventional and novel parameters using the MP-1 microperimeter

Purpose

To investigate the intersession test–retest variability (TRV) of topography- and threshold-based parameters derived from the Nidek MP-1.

Design

Prospective observational study.

Methods

Sixteen participants with and without central scotoma underwent microperimetry in one eye over three sessions at 1-month intervals in a single institution. We calculated 95% coefficient of repeatability (CR) for the number of normal-suspect (NS) loci, relative scotoma (RS) and dense scotoma (DS), median macular sensitivity (MS), mean sensitivity of responding loci (RLS), perilesional loci (PLS), and extralesional loci (ELS). Topographical agreement score of mapping NS and DS loci (TAS_NS and TAS_DS) were also calculated for each patient.

Results

Mean (range) age was 50 (21–86) years. The CR (95% confidence intervals) for NS, RS, and DS were 9.9 (6.5–13.3), 9.5 (6.2–12.7), and 3.0 (1.1–4.1) respectively. CR (95% CIs) for median MS, mean RLS, PLS, and ELS were 3.4 (2.3–4.5), 1.6 (1.1–2.2), 1.8 (0.9–2.6), and 2.8 (1.5–4.0) dB. We found significant change in thresholds between Test 1, and Tests 2 and 3 (both P=0.03), but not between Tests 2 and 3 (P=0.8). Medians (range) TAS_NS and TAS_DS were 74% (39%–100%) and 77% (0%–97%), respectively, between Tests 2 and 3.

Conclusion

We recommend the use of four DS loci (upper limit of CR) as the limit of TRV for assessing change. There was large interindividual variability in NS or DS mapping agreement. We recommend discarding the first microperimetry test and caution the use of a change in spatial distribution to determine disease progression.