Assessment of Central Retinal Sensitivity Employing Two Types of Microperimetry Devices

Reliability of gaze-contingent perimetry

Standard automated perimetry, a psychophysical task performed routinely in eyecare clinics, requires observers to maintain fixation for several minutes at a time in order to measure visual field sensitivity. Detection of visual field damage is confounded by eye movements, making the technique unreliable in poorly attentive individuals and those with pathologically unstable fixation, such as nystagmus. Microperimetry, which utilizes 'partial gaze-contingency' (PGC), aims to counteract eye movements but only corrects for gaze position errors prior to each stimulus onset. Here, we present a novel method of visual field examination in which stimulus position is updated during presentation, which we refer to as 'continuous gaze-contingency' (CGC). In the first part of this study, we present three case examples that demonstrate the ability of CGC to measure the edges of the physiological blind spot in infantile nystagmus with greater accuracy than PGC and standard 'no gaze-contingency' (NoGC), as initial proof-of-concept for the utility of the paradigm in measurements of absolute scotomas in these individuals. The second part of this study focused on healthy observers, in which we demonstrate that CGC has the lowest stimulus positional error (gaze-contingent precision: CGC = ± 0.29°, PGC = ± 0.54°, NoGC = ± 0.81°). CGC test-retest variability was shown to be at least as good as both PGC and NoGC. Overall, CGC is supported as a reliable method of visual field examination in healthy observers. Preliminary findings demonstrate the spatially accurate estimation of visual field thresholds related to retinal structure using CGC in individuals with infantile nystagmus.

Inter and intradevice assessment of microperimetry testing in aging eyes

Microperimetry (MP) is a psychometric examination combining retinal imaging and functional sensitivity testing with an increasing importance due to its potential use as clinical study outcome. We investigated the repeatability of pointwise retinal sensitivity (PWS) on the most advanced commercially available MP devices under their standard setting in a healthy aging population. Two successive MP examinations on both MP-3 (NIDEK CO., Ltd., Gamagori, Japan) and MAIA (CenterVue S.p.A. (iCare), Padova, Italy) were performed on healthy aging subjects in a randomized order. PWS repeatability was analysed for different macular regions and age groups using Bland-Altmann coefficients of repeatability (CoR). A total of 3600 stimuli from 20 healthy individuals with a mean age of 70 (11) years were included. Mean CoR in dB were ±4.61 for MAIA and ±4.55 for MP-3 examinations. A lower repeatability (p=0.005) was detected in the central millimetre on MAIA examinations. Higher subject age was associated with a lower repeatability of PWS on both devices (both p=0.003). Intra-device correlation was good (MAIA: 0.79 [0.76-0.81]; MP-3: 0.72 [0.68-0.76]) whereas a moderate mean inter-device correlation (0.6 [0.55-0.65]) could be detected. In conclusion, older subjects and the foveal region are associated with a worse pointwise repeatability.

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.

Fotopic and scotopic retinal sensitivity and foveal fixation normal values using microperimetry in healthy population

PURPOSE

To determine normal values of fotopic and scotopic retinal sensitivity and foveal fixation obtained by microperimetry, using MP3-S microperimeter (Nidek, Gamagori, Japan), in a healthy population.

METHODS

Observational, crossectional, single centre study. Fotopic and scotopic microperimetry was performed using with a customized 13-point fovea-centered pattern in healthy volunteers without ocular pathology. A intraclass correlation coefficient (ICC) was performed to evaluate fotopic and scotopic microperimetry reliability.

RESULTS

We analyzed 102 eyes of 54 patients with a mean age of 49.8 +/- 15 years old. The fotopic and scotopic mean retinal sensitivity (MRS) was 28.55±3.3dB (95% CI=[27.87-29.23]) and 15.72±1.9dB (95% CI=[15.35-16.09]) respectively, showing a significant statistical difference (p<0.05). No differences were found when comparing SRM by gender group. However, when analyzing the SRM by age groups, statistically significant differences were found in both modalities of the test; SRM being higher in the group of subjects under 35 years of age with 30.3±1.7dB in the photopic and 16.3±1.3dB in the scotopic; and lower in the group of older than 65 years with 26.7±2.2dB in the photopic and 13.8±1.8dB in the scotopic with p=0.0001. The reliability analysis of both tests, revealed an excellent reliability of the fotopic microperimetry with a Crombach alpha of 0.958 and a good reliability of 0.841 in scotopic microperimetry.

CONCLUSIONS

Microperimetry is a test with good reliability both under photopic and scotopic conditions. SRM and fixation stability under photopic and scotopic conditions do not differ according to sex, but it does decrease with age. There is a positive correlation between photopic and scotopic SRM.

Calculation of test-retest variability in phase I/IIa clinical trials for Inherited Retinal Degenerations

Background: Several novel treatments of inherited retinal degenerations have undergone phase I/IIa clinical trials with limited sample size, yet investigators must still determine if toxicity or an efficacy signal occurred or if the change was due to test-retest variability (TRV) of the measurement tool.Materials and Methods: Synthetic datasets were used to compare three types of TRV estimators under different sample sizes, mean drift, skewness, and number of baseline measurements.Results: Mixed effects models underestimated the standard deviation of measurement error (SDEM); the unbiased change score estimator method (UBS) was more accurate. The fixed effect model had less bias and smaller standard deviation than UBS if >2 baseline measurements. The change score estimator had no bias; other estimators introduced bias for lower variability. With sample size <10, all estimators had high variance. With sample size ≥10, the differences between methods were often minimal. The pooled estimator model did not capture drift, whereas a fixed effect regression or mixed effects models accounted for drift while maintaining an accurate measure of variance. With small sample sizes, the bootstrap estimates of SDEM were severe underestimates, while the jackknife estimates were mildly low but much better. The jackknife was more accurate for the unbiased change score method than for the pooled estimator.Conclusions: The ideal phase I/IIa study has ≥20 subjects and uses UBS or its fixed effect model generalization if >2 baseline measurements. With non-ideal study parameters, investigators should at least quantify the error estimate present in their data analysis.

Clinical Perspectives and Trends: Microperimetry as a trial endpoint in retinal disease

Endpoint development trials are underway across the spectrum of retinal disease. New validated endpoints are urgently required for the assessment of emerging gene therapies and in preparation for the arrival of novel therapeutics targeting early stages of common sight-threatening conditions such as age-related macular degeneration. Visual function measures are likely to be key candidates in this search. Over the last two decades, microperimetry has been used extensively to characterize functional vision in a wide range of retinal conditions, detecting subtle defects in retinal sensitivity that precede visual acuity loss and tracking disease progression over relatively short periods. Given these appealing features, microperimetry has already been adopted as an endpoint in interventional studies, including multicenter trials, on a modest scale. A review of its use to date shows a concurrent lack of consensus in test strategy and a wealth of innovative disease and treatment-specific metrics which may show promise as clinical trial endpoints. There are practical issues to consider, but these have not held back its popularity and it remains a widely used psychophysical test in research. Endpoint development trials will undoubtedly be key in understanding the validity of microperimetry as a clinical trial endpoint, but existing signs are promising.

Structure-Function Analysis in Macular Drusen With Mesopic and Scotopic Microperimetry

Purpose

To investigate the structure–function relationship in eyes with drusen with mesopic and scotopic microperimetry.

Methods

We analyzed structural and functional data from 43 eyes with drusen. Functional data were acquired with mesopic and scotopic two-color (red and cyan) microperimetry. Normative values were calculated using data from 56 healthy eyes. Structural measurements were green autofluorescence and dense macular optical coherence tomography scans. The latter were used to calculate the retinal pigment epithelium elevation (RPE-E) and the photoreceptor reflectivity ratio (PRR). The pointwise structure–function relationship was measured with linear mixed models having the log-transformed structural parameters as predictors and the sensitivity loss (SL, deviation from normal) as the response variable.

Results

In the univariable analysis, the structural predictors were all significantly correlated (P < 0.05) with the SL in the mesopic and scotopic tests. In a multivariable model, mesopic microperimetry yielded the best structure–function relationship. All predictors were significant (P < 0.05), but the predictive power was weak (best R² = 0.09). The relationship was improved when analyzing locations with abnormal RPE-E (best R² = 0.18).

Conclusions

Mesopic microperimetry shows better structure–function relationship compared to scotopic microperimetry; the relationship is weak, likely due to the early functional damage and the small number of tested locations affected by drusen. The relationship is stronger when locations with drusen are isolated for the mesopic and scotopic cyan test.

Translational Relevance

These results could be useful to devise integrated structure–function methods to detect disease progression in intermediate age-related macular degeneration.

Fundus-controlled perimetry (microperimetry): Application as outcome measure in clinical trials

Fundus-controlled perimetry (FCP, also called 'microperimetry') allows for spatially-resolved mapping of visual sensitivity and measurement of fixation stability, both in clinical practice as well as research. The accurate spatial characterization of visual function enabled by FCP can provide insightful information about disease severity and progression not reflected by best-corrected visual acuity in a large range of disorders. This is especially important for monitoring of retinal diseases that initially spare the central retina in earlier disease stages. Improved intra- and inter-session retest-variability through fundus-tracking and precise point-wise follow-up examinations even in patients with unstable fixation represent key advantages of these technique. The design of disease-specific test patterns and protocols reduces the burden of extensive and time-consuming FCP testing, permitting a more meaningful and focused application. Recent developments also allow for photoreceptor-specific testing through implementation of dark-adapted chromatic and photopic testing. A detailed understanding of the variety of available devices and test settings is a key prerequisite for the design and optimization of FCP protocols in future natural history studies and clinical trials. Accordingly, this review describes the theoretical and technical background of FCP, its prior application in clinical and research settings, data that qualify the application of FCP as an outcome measure in clinical trials as well as ongoing and future developments.

The Effect of Attention on Fixation Stability During Dynamic Fixation Testing in Stargardt Disease

PURPOSE

Sensitive, reproducible visual function biomarkers are necessary to evaluate the efficacy of emerging treatments for Stargardt disease type 1 in clinical trials. We previously demonstrated that fixation stability may serve as a secondary outcome parameter for visual function loss. However, the test duration and protocol have an unknown effect on the assessment of fixation stability. Here, we hypothesize that separate fixation testing with a single target is different from combined fixation testing using the same target with simultaneous perimetry testing.

DESIGN

International, multicenter, prospective, cross-sectional study.

METHODS

Microperimetry data from the international, multicenter, prospective Progression of Atrophy Secondary to Stargardt Disease (ProgStar, NCT01977846) study were analyzed. Patients underwent various types of fixation testing including static testing and dynamic testing, and a duration-corrected dynamic test was generated (30sEpoch).

RESULTS

A total of 437 eyes from 235 patients were included (mean age, 33.8 ± 15.1 years; 55.3% female). The mean 1SD-BCEA (bivariate contour ellipse area), which is the smallest ellipse encompassing 1 standard deviation of all fixation events, was smaller for the static fixation test compared to the 30sEpoch (4.5 ± 6.9 deg² vs 5.3 ± 7.0 deg²; P = .02) and the number of points within both the 2-degree and 4-degree circles was larger (P < .0001).

CONCLUSIONS

Our results suggest that differences in static and dynamic assessment of fixation stability are dependent not only on different test durations but also on the testing protocol of a single fixation target vs fixation target plus simultaneous perimetry testing and provide information on the conduct of fixation testing for clinical trials.

Regional Variations and Intra-/Intersession Repeatability for Scotopic Sensitivity in Normal Controls and Patients With Inherited Retinal Degenerations

Purpose

Dark-adapted visual fields were obtained from patients with inherited retinal degeneration (IRD) and controls to evaluate the effect that age, retinal region, and disease had on scotopic sensitivity. Intra- and intersession test–retest repeatabilities for patients and controls were measured to establish significant change for longitudinal studies.

Methods

A total of 41 patients with IRD and 30 controls had one eye dilated and dark-adapted for 40 minutes. Scotopic sensitivity was measured with a Medmont dark-adapted chromatic (DAC) perimeter (size V stimulus, 200-ms duration, background luminance < 0.0001 cd/m², dynamic range 0–75 decibel [dB]). Mixed effects analysis was performed to analyze age, retinal eccentricity, and sensitivity. The intra-/intersession coefficients of repeatability (CR) were calculated for controls and patients with IRD.

Results

Each additional year was associated with lower sensitivity (−0.22 dB) per year in normal controls over age 50 compared to younger controls (12–49 years). The superior field had lower sensitivity than the inferior, but the nasal field was not different compared to the temporal field in normal controls. The CR for intra- and intersession testing on mean sensitivity (MS)/pointwise sensitivity (PWS) were ±1.5/±8.5 and ±3.3/±9.8 dB, respectively, for patients with IRD. Control MS/PWS CR were ±1.5/±6.1 dB for intrasession and ±1.7/±6.8 dB for intersession DAC perimetry.

Conclusions

The DAC perimeter is an important asset because it tests a wide field of scotopic vision. The CR are comparable to those of other perimetry devices. Effects of age and retinal region should be considered when assessing scotopic sensitivity measured with the DAC perimeter.

Microperimetry - A New Tool for Assessing Retinal Sensitivity in Macular Diseases

INTRODUCTION

Macular disease is the leading cause of low vision in the Western world. Drusen and pigmentary irregularities are common among the rural Northern Indian population. The disease process leads to loss of central vision, metamorphopsia, macropsia or micropsia and colour vision defect.

AIM

To study the retinal sensitivity changes in macular diseases using microperimetry.

MATERIALS AND METHODS

It was an observational study, conducted in the Department of Ophthalmology at a rural tertiary care hospital. This study was started from December 2014 until June 2016, in all patients with macular disease above the age of 20 years attending the outpatient department. Microperimetry was done for 84 eyes of 52 patients with macular disease. Mean retinal Sensitivity (MS) and fixation stability was evaluated. The statistical analysis of mean retinal sensitivity, central 2° and 4° fixation was done by calculating the mean and standard deviation using 95% confidence interval.

RESULTS

The range of age was between 20-81 years. Majority were 32 males (62%) and 20 females (38%). Out of the 84 eyes studied, majority of the macular disease were Age-Related Macular Degeneration (AMD) (50%). Rest 50% were other macular diseases. The mean retinal sensitivity (dB) shown by microperimetry was 10.83 in AMD, 9.12 in Cystoid Macular Oedema (CME), 10.34 in Epiretinal Membrane (ERM), 10.74 in Pigment Epithelial Detachment (PED), 8.96 in Central Serous Chorioretinopathy (CSCR), 6.43 in macular dystrophy, 7.15 in Lamellar Hole (LMH), 9.8 in Pseudomacular Hole (PMH), 3 in geographic atrophy, 11.1 in macular telangiectasia, 5.6 in Berlin oedema, 12.3 in macular scar and 15.2 in haemorrhage in macula. The study showed 64% of the eyes had stable 2° central fixation, 35% had relatively unstable fixation and 1% had unstable fixation. No significant correlation between retinal sensitivity and retinal thickness in AMD was found.

CONCLUSION

This study shows that microperimetry can be a useful tool for objective evaluation of macular function and progression of the disease.

Inter-device comparison of retinal sensitivity measurements: the CenterVue MAIA and the Nidek MP-1

BACKGROUND

Our aim is to compare retinal sensitivity measurements obtained on two microperimeters: the CenterVue MAIA and the Nidek MP-1.

DESIGN

A prospective study was conducted in a private ophthalmology clinic.

PARTICIPANTS

Seventeen individuals with a range of stable macular function were recruited as participants.

METHODS

Microperimetry in one eye with identical test strategy in both devices, with randomized testing order, is used.

MAIN OUTCOME MEASURES

The main outcome measures include differences in mean sensitivity (MS), point-wise sensitivity (PWS) and duration. Limits of agreement (LoA) in MS and pooled PWS were calculated. Concordance in scotoma assessment was analysed by kappa (κ) agreement of local defect classification (LDC), LoA in number of scotomatous loci detected and congruence in scotoma localization (CSL).

RESULTS

Median (interquartile range) MS of the MP-1 and MAIA was 13.3 (5.6-18.1) and 21.2 (14.5-27.0) dB, (P < 0.05). Mean difference in PWS was 7.3 dB (MAIA > MP-1). Median (interquartile range) duration for the MP-1 and MAIA was 10'28″ (7'17″-11'53″) and 8'46″ (8'30″-9'06″), (P = 0.21). LoA for MS and pooled PWS was 1.4 to 13.3 dB and -3.9 to 18.5 dB. There was moderate agreement between the devices for LDC (weighted κ = 0.55, P < 0.05). LoA in number of scotomatous loci detected was -13 to 18. CSL varied from 0 to 100% and correlated strongly with increasing scotoma size.

CONCLUSIONS

The large LoA and variation in scotoma mapping concordance suggest that the same microperimeter should be used for follow-up examination. We recommend caution in comparing results derived from different types of microperimeters.

Fixation Stability Measurement Using Two Types of Microperimetry Devices

PURPOSE

We compared the fixation stability measurements obtained with two microperimeters, the Micro Perimeter 1 (MP-1) and the Spectral OCT/SLO (OCT/SLO), in subjects with and without maculopathies.

METHODS

A total of 41 eyes with no known ocular diseases and 45 eyes with maculopathies were enrolled in the study. Both eyes of each participant had a 20-second fixation test using the MP-1 and OCT/SLO. The bivariate contour ellipse area (BCEA) was used for fixation stability evaluation.

RESULTS

In the normal group, BCEA was 2.93 ± 0.32 log minarc² on OCT/SLO and 2.89 ± 0.30 log minarc² on MP-1. In the maculopathy group, BCEA was 3.05 ± 0.41 log minarc² on OCT/SLO and 3.15 ± 0.46 log minarc² on MP-1. There was no statistically significant difference between the BCEA measured by OCT/SLO and by MP-1 in both groups. A moderate correlation was found between the two devices (r = 0.45, P < 0.001). The sample size during the fixation test was 535.5 ± 14.6 pairs of coordinates in the normal group and 530.7 ± 14.9 pairs in the maculopathy group with MP-1, while it was 72.3 ± 6.9 and 59.9 ± 10.1, respectively, with OCT/SLO. This was due to different tracking frequencies between the two microperimeters.

CONCLUSION

Fixation stability assessment yields similar results using the OCT/SLO and MP-1. A major difference in sampling rate between the two microperimeters does not significantly affect BCEA measurements.

TRANSLATIONAL RELEVANCE

Fixation stability assessments are comparable and interchangeable between the OCT/SLO and the MP-1.