Fundus-driven perimetry (microperimetry) compared to conventional static automated perimetry: similarities, differences, and clinical applications

ATXN7-Related Cone-Rod Dystrophy: The Integrated Functional Evaluation of the Cerebellum (CERMOI) Study

Importance

Reliable biomarkers with diagnostic and prognostic values are needed for upcoming gene therapy trials for spinocerebellar ataxias.

Objective

To identify ophthalmological biomarkers in a sample of spinocerebellar ataxia type 7 (SCA7) carriers.

Design, Setting, and Participants

This article presents baseline data from a cross-sectional natural history study conducted in Paris, France, reference centers for rare diseases from May 2020 to April 2021. Data were analyzed from September to December 2022. Fifteen adult ATXN7 pathogenic expansion carriers (9 with preataxia and 6 with ataxia) were included, all with a Scale for the Assessment and Rating of Ataxia (SARA) score of 15 of 40 or lower. Patients were recruited at the Paris Brain Institute, and all contacted patients accepted to participate in the study.

Main Outcomes and Measures

Three visits (baseline, 6 months, and 12 months) were planned, including neurological examination (SARA and Composite Cerebellar Functional Severity Score), ophthalmological examination (best-corrected visual acuity, microperimetry, full-field electroretinogram, optical coherence tomography, and fundus autofluorescence imaging), and neurofilament light chain (NfL) measurements. Here we report the baseline ophthalmic data from the cohort and determine whether there is a correlation between disease scores and ophthalmic results.

Results

Among the 15 included SCA7 carriers (median [range] age, 38 [18-60] years; 8 women and 7 men), 12 displayed cone or cone-rod dystrophy, with the number of CAG repeats correlating with disease severity (ρ, 0.73, 95% CI, 0.34 to 0.90; P < .001). Two patients with cone-rod dystrophy exhibited higher repeat numbers and greater ataxia scores (median [range] SARA score, 9 [7-15]) compared to those with only cone dystrophy (median [range] SARA score, 2 [0-5]). A correlation emerged for outer nuclear layer thickness with SARA score (ρ, -0.88; 95% CI, -0.96 to -0.59; P < .001) and NfL levels (ρ, -0.87; 95% CI, -0.86 to 0.96; P < .001). Moreover, ataxia severity was correlated with visual acuity (ρ: 0.89; 95% CI, 0.68 to 0.96; P < .001) and retinal sensitivity (ρ, -0.88; 95% CI, -0.96 to 0.59; P < .001).

Conclusions and Relevance

In this cross-sectional study, retinal abnormalities were found at preataxic stages of the disease. Most of the carriers presented with cone dystrophy and preserved rod function. The outer nuclear layer thickness correlated with SARA score and plasma NfL levels suggesting nuclear layer thickness to be a biomarker of disease severity. These findings contribute to understanding the dynamics of SCA7-related retinal dystrophy and may help lay the groundwork for future therapeutic intervention monitoring and clinical trials.

Trial Registration

ClinicalTrials.gov Identifier: NCT04288128.

Retinal sensitivity changes in early/intermediate AMD: a systematic review and meta-analysis of visual field testing under mesopic and scotopic lighting

Visual fields under mesopic and scotopic lighting are increasingly being used for macular functional assessment. This review evaluates its statistical significance and clinical relevance, and the optimal testing protocol for early/intermediate age-related macular degeneration (AMD). PubMed and Embase were searched from inception to 14/05/2022. All quality assessments were performed according to GRADE guidelines. The primary outcome was global mean sensitivity (MS), further meta-analysed by: AMD classification scheme, device, test pattern, mesopic/scotopic lighting, stimuli size/chromaticity, pupil dilation, testing radius (area), background luminance, adaptation time, AMD severity, reticular pseudodrusen presence, and follow-up visit. From 1489 studies screened, 42 observational study results contributed to the primary meta-analysis. Supported by moderate GRADE certainty of the evidence, global MS was significantly reduced across all devices under mesopic and scotopic lighting with large effect size (-0.9 [-1.04, -0.75] Hedge's g, P < 0.0001). The device (P < 0.01) and lighting (P < 0.05) used were the only modifiable factors affecting global MS, whereby the mesopic MP-1 and MAIA produced the largest effect sizes and exceeded test-retest variabilities. Global MS was significantly affected by AMD severity (intermediate versus early AMD; -0.58 [-0.88, -0.29] Hedge's g or -2.55 [3.62, -1.47] MAIA-dB) and at follow-up visit (versus baseline; -0.62 [-0.84, -0.41] Hedge's g or -1.61[-2.69, -0.54] MAIA-dB). Magnitudes of retinal sensitivity changes in early/intermediate AMD are clinically relevant for the MP-1 and MAIA devices under mesopic lighting within the central 10° radius. Other factors including pupil dilation and dark adaptation did not significantly affect global MS in early/intermediate AMD.

Optical coherence tomography angiography in diabetic retinopathy

There remain many unanswered questions on how to assess and treat the pathology and complications that arise from diabetic retinopathy (DR). Optical coherence tomography angiography (OCTA) is a novel and non-invasive three-dimensional imaging method that can visualize capillaries in all retinal layers. Numerous studies have confirmed that OCTA can identify early evidence of microvascular changes and provide quantitative assessment of the extent of diseases such as DR and its complications. A number of informative OCTA metrics could be used to assess DR in clinical trials, including measurements of the foveal avascular zone (FAZ; area, acircularity, 3D para-FAZ vessel density), vessel density, extrafoveal avascular zones, and neovascularization. Assessing patients with DR using a full-retinal slab OCTA image can limit segmentation errors and confounding factors such as those related to center-involved diabetic macular edema. Given emerging data suggesting the importance of the peripheral retinal vasculature in assessing and predicting DR progression, wide-field OCTA imaging should also be used. Finally, the use of automated methods and algorithms for OCTA image analysis, such as those that can distinguish between areas of true and false signals, reconstruct images, and produce quantitative metrics, such as FAZ area, will greatly improve the efficiency and standardization of results between studies. Most importantly, clinical trial protocols should account for the relatively high frequency of poor-quality data related to sub-optimal imaging conditions in DR and should incorporate time for assessing OCTA image quality and re-imaging patients where necessary.

Spatial Cluster Patterns of Retinal Sensitivity Loss in Intermediate Age-Related Macular Degeneration Features

Purpose

To examine spatial patterns of retinal sensitivity loss in the three key features of intermediate age-related macular degeneration (iAMD).

Methods

One-hundred individuals (53 iAMD, 47 normal) underwent 10-2 mesopic microperimetry testing in one eye. Pointwise sensitivities (dB) were corrected for age, sex, iAMD status, and co-presence of co-localized key iAMD features: drusen load, pigmentary abnormalities, and reticular pseudodrusen (RPD). Clusters (labeled by ranks of magnitude C-2, C-1, C0) were derived from pointwise sensitivities and then assessed by quadrants and eccentricity/rings.

Results

Two clusters of decreased sensitivities were evident in iAMD versus normal: C-2, -1.67 dB (95% CI (confidence intervals), -2.36 to -0.98; P < 0.0001); C-1, -0.93 dB (95% CI, -1.5 to -0.36; P < 0.01). One cluster of decreased sensitivity was independently associated each with increased drusen load (13.57 µm increase per -1 dB; P < 0.0001), pigmentary abnormalities (C-1: -2.23 dB; 95% CI, -3.36 to -1.1; P < 0.01), and RPD (C-1: -1.07 dB; 95% CI, -2 to -0.14; P < 0.01). Sensitivity loss in iAMD was biased toward the superior and central macula (P = 0.16 to <0.0001), aligning with structural distributions of features. However, sensitivity loss associated with drusen load also extended to the peripheral macula (P < 0.0001) with paracentral sparing, which was discordant with the central distribution of drusen.

Conclusions

Drusen load, pigmentary abnormalities, and RPD are associated with patterns of retinal sensitivity loss commonly demonstrating superior and central bias. Results highlighted that a clinical focus on these three key iAMD features using structural measures alone does not capture the complex, spatial extent of vision-related functional impairment in iAMD.

Translational Relevance

Defining the spatial patterns of retinal sensitivity loss in iAMD can facilitate a targeted visual field protocol for iAMD assessment.

Female carriers of X-linked inherited retinal diseases - Genetics, diagnosis, and potential therapies

Inherited retinal diseases (IRDs) are a group of heterogeneous conditions that cause progressive vision loss, typically due to monogenic mutations. Female carriers of X-linked IRDs have a single copy of the disease-causing gene, and therefore, may exhibit variable clinical signs that vary from near normal retina to severe disease and vision loss. The relationships between individual genetic mutations and disease severity in X-linked carriers requires further study. This review summarises the current literature surrounding the spectrum of disease seen in female carriers of choroideremia and X-linked retinitis pigmentosa. Various classification systems are contrasted to accurately grade retinal disease. Furthermore, genetic mechanisms at the early embryonic stage are explored to potentially explain the variability of disease seen in female carriers. Future research in this area will provide insight into the association between genotype and retinal phenotypes of female carriers, which will guide in the management of these patients. This review acknowledges the importance of identifying which patients may be at high risk of developing severe symptoms, and therefore should be considered for emerging treatments, such as retinal gene therapy.

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.

Overcoming the Challenges to Clinical Development of X-Linked Retinitis Pigmentosa Therapies: Proceedings of an Expert Panel

X-linked retinitis pigmentosa (XLRP) is a rare inherited retinal disease manifesting as impaired night vision and peripheral vision loss that progresses to legal blindness. Although several trials of ocular gene therapy for XLRP have been conducted or are in progress, there is currently no approved treatment. In July 2022, the Foundation Fighting Blindness convened an expert panel to examine relevant research and make recommendations for overcoming the challenges and capitalizing on the opportunities in conducting clinical trials of RPGR-targeted therapy for XLRP. Data presented concerned RPGR structure and mutation types known to cause XLRP, RPGR mutation-associated retinal phenotype diversity, patterns in genotype/phenotype relationships, disease onset and progression from natural history studies, and the various functional and structural tests used to monitor disease progression. Panel recommendations include considerations, such as genetic screening and other factors that can impact clinical trial inclusion criteria, the influence of age on defining and stratifying participant cohorts, the importance of conducting natural history studies early in clinical development programs, and the merits and drawbacks of available tests for measuring treatment outcomes. We recognize the need to work with regulators to adopt clinically meaningful end points that would best determine the efficacy of a trial. Given the promise of RPGR-targeted gene therapy for XLRP and the difficulties encountered in phase III clinical trials to date, we hope these recommendations will help speed progress to finding a cure.

Translational Relevance

Examination of relevant data and recommendations for the successful clinical development of gene therapies for RPGR-associated XLRP.

The Comparison of Foveal Sensitivity Between Diabetic and Non-diabetic Patients by Using Standard Automated Perimetry 10-2 Protocol: A Cross-Sectional Study

Purpose The purpose of the study is to assess whether standard automated perimetry (SAP) was capable of detecting early neuroretinal changes by comparing foveal sensitivity in diabetic and non-diabetic subjects. Settings and design This is an observational and cross-sectional study that compared foveal sensitivity between a case group of 47 subjects with no or mild-to-moderate diabetic retinopathy (DR) without maculopathy and a control group of 43 healthy subjects. Materials and Methods After a thorough ocular examination, all patients were put through tests using a Humphrey visual field analyzer with the Swedish interactive threshold algorithm (SITA) standard system (10-2 software). The primary indicator of success was the age-adjusted foveal awareness-esteem difference. Mean deviation (MD) and pattern standard deviation (PSD) readings were the supplementary performance indicators. Results The mean age of the case and control group was 50.76 ± 13.20 years and 49.90 ± 12.20 years, respectively. The probability of cataract development was higher in the case group (p < 0.0001). In the control group, 95.3% had best-corrected visual acuity (BCVA) in the category of good visual acuity (VA) (p < 0.0001). The mean foveal sensitivity in the case group was 28.57 ± 7.54 and 32.16 ± 7.09 for the control group, and the difference was statistically significant (p < 0.023). The mean of MD in the case group was -6.05 ± 7.93, whereas in the control group, it was -3.28 ± 1.70, which was found significant (p = 0.027). There was no difference in PSD between the study groups. Conclusions Foveal sensitivity decreased in diabetics, even without maculopathy, so SAP helps identify a patient at risk of future vision loss.

Functional Correlates of Outer Retina Remodeling in Intermediate Age-Related Macular Degeneration Using Microperimetry

Purpose

To assess the effect of drusen morphometric changes and choroidal vascular modifications on retinal sensitivity (RS) evaluated through microperimetry in intermediate age-related macular degeneration (iAMD).

Methods

A retrospective review of 18 iAMD patients (18 eyes) with a 12-month follow-up was performed. Eye-tracked spectral-domain optical coherence tomography was obtained, with automatic segmentation of the outer retinal layer (ORL) delineating the drusen area from the external limiting membrane to Bruch's membrane and outer nuclear layer (ONL) thickness maps adjusted manually, as needed. Advanced retinal pigment epithelium analysis was also performed with a ZEISS PLEX Elite 900. Microperimetry obtained under mesopic conditions was overlaid with the corresponding thickness maps with Fiji software. The choroidal vascularity index (CVI) was calculated in the subfoveal b-scan and volumetric in the central 1-mm subfield.

Results

A reduced central ONL thickness was strongly associated with RS decline at the same region (r = 0.69, P = 0.002) and globally (r = 0.80, P < 0.001) at baseline, but also at 1 year in the central subfield (central: r = 0.70, P = 0.001). One-year subfoveal CVI variation, differently from volumetric CVI, directly influenced the central (r = 0.64, P = 0.004) and global RS (r = 0.59, P = 0.009), indicating that a CVI reduction negatively affected RS. A greater volumetric CVI within central 1-mm was associated with ORL thickening at 1 year (r = 0.61, P = 0.008).

Conclusions

Progressive degeneration of the ONL is related to irreversible photoreceptor dysfunction in iAMD. Likewise, choroidal vascular modifications are associated with a significant functional decline in the central region and diffusely.

Retinoblastoma and vision

The assessment of vision has a growing importance in the management of retinoblastoma in the era of globe-conserving therapy, both prior to and after treatment. As survival rates approach 98-99% and globe salvage rates reach ever-higher levels, it is important to provide families with information regarding the visual outcomes of different treatments. We present an overview of the role of vision in determining the treatment given and the impact of complications of treatment. We also discuss screening and treatment strategies that can be used to maximise vision.

Investigating the discrepancy between MAIA and MP-1 microperimetry results

PURPOSE

Previous work has suggested that sensitivities measured on the iCare MAIA and Nidek MP-1 microperimeters differ systematically, although it is unclear whether one or both devices are inaccurate. Here, we assess the discrepancy between these two instruments as well as with a rigorous reference standard.

METHODS

Fifteen healthy participants underwent visual field testing on the MAIA and MP-1 microperimeters. Results were compared to a reference measure of increment thresholds on a laboratory-based, calibrated computer monitor system using the same background luminance and target size. Discrepancies were assessed as a function of eccentricity along the vertical meridian. Differences in decibels (dB) due to differences in the maximum stimulus luminance between devices were accounted for mathematically.

RESULTS

The mean sensitivity measured with the MAIA was <1 dB lower than laboratory-based measures, which was statistically significant but of limited clinical importance. In contrast, the mean sensitivity measured with the MP-1 was >8 dB lower than the laboratory measures. The difference was greater for an eccentric superior retinal location, in contrast to what would be predicted if the discrepancy was due to a ceiling effect caused by the MP-1's limited dynamic range.

CONCLUSIONS

While MAIA measurements showed low bias compared with our rigorously determined reference standard, the MP-1 showed large discrepancies that could not be explained purely by the limited dynamic range of the instrument. MAIA and MP-1 sensitivity values cannot be compared directly, and caution is advised when assessing absolute sensitivities or eccentricity effects in the extensive MP-1 literature.

Fixation stability after surgical treatment of strabismus and biofeedback fixation training in amblyopic eyes

Background

Visual fixation may be affected in amblyopic patients and, moreover, its stability may be associated with the effects of amblyopic treatments on visual performance in patients with strabismus. Therefore, fixation stability is a relevant biomarker that might predict the recurrence of amblyopia after a therapeutic intervention. Microperimetric biofeedback fixation training (BFT) can stabilize visual fixation in adult patients with central vision loss. It was the purpose of the present study to evaluate the effects of BFT on fixation stability in adult amblyopic patients after surgical intervention to treat strabismus.

Methods

Participants were 12 patients with strabismus (mean age = 29.6 ± 8.5 years; 6 females) and 12 healthy volunteers (mean age = 23.8 ± 1.5 years; 9 females). The protocol included ophthalmological and microperimetric follow-ups to measure fixation stability and macular sensitivity. BFT was applied monocularly to four amblyopic eyes either on the spontaneous preferential retinal locus or to a fixation area closer to the anatomical fovea after surgical treatment of strabismus.

Results

Baseline measurements showed significantly altered microperimetric average threshold in amblyopic eyes compared to fellow eyes (p = 0.024) and compared to control eyes (p < 0.001). Fixation was unstable in amblyopic eyes compared to control eyes (p < 0.001). Fixation stability did not significantly change after surgical alignment of strabismus (p = 0.805). BFT applied to operated eyes resulted in a more stable fixation with improvements of about 50% after three months of training.

Conclusions

Fixation stability improvements following BFT highlight its potential use in adult amblyopic eyes after the surgical alignment of the strabismus. Future investigations may also consider applying this method in combination with standard treatments to improve vision in amblyopic patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-02020-3.

Looking Ahead: Visual and Anatomical Endpoints in Future Trials of Diabetic Macular Ischemia

Diabetic macular ischemia (DMI) is a common complication of diabetic retinopathy that can lead to progressive and irreversible visual loss. Despite substantial clinical burden, there are no treatments for DMI, no validated clinical trial endpoints, and few clinical trials focusing on DMI. Therefore, generating consensus on validated endpoints that can be used in DMI for the development of effective interventions is vital. In this review, we discuss potential endpoints appropriate for use in clinical trials of DMI, and consider the data required to establish acceptable and meaningful endpoints. A combination of anatomical, functional, and patient-reported outcome measures will provide the most complete picture of changes that occur during the progression of DMI. Potential endpoint measures include change in size of the foveal avascular zone measured by optical coherence tomography angiography and change over time in best-corrected visual acuity. However, these endpoints must be supported by further research. We also recommend studies to investigate the natural history and progression of DMI. In addition to improving understanding of how patient demographics and comorbidities such as diabetic macular edema affect clinical trial endpoints, these studies would help to build the consensus definition of DMI that is currently missing from clinical practice and research.

Effect of Background Brightness on Preferred Retinal Loci in Patients With Macular Disease

Purpose

To evaluate the effect of background brightness on the preferred retinal locus (PRL) in patients with macular disease.

Methods

The study included 27 eyes (27 patients) with macular disease. Microperimetry (MP) was performed to evaluate the PRL and retinal sensitivity (RS) at 10 cd/m². A prototypical device was used to evaluate the PRL at 650 cd/m². Patients were divided into two groups: central fixation (CF) and eccentric fixation (EF).

Results

The PRLs under different brightness levels differed significantly (P < 0.001) in 15 of 27 eyes (two of 13 eyes in the CF group and 13 of 14 eyes in the EF group). The best-corrected visual acuities (BCVAs) in eyes with different PRLs were significantly worse (P = 0.019) than in eyes with one PRL, although the foveal RS did not differ significantly. In patients with BCVAs over 0.1, the PRLs differed in four of 13 eyes in the CF group and in three of four eyes in the EF group (P > 0.05); in patients with BCVAs of 0.1 or lower, the PRLs differed in one of four eyes and 10 of 10 eyes, respectively (P = 0.011).

Conclusions

In patients with macular disease, PRLs can change depending on the surrounding brightness. It may be beneficial to evaluate PRLs under brighter background conditions (e.g., in ambient light) when performing visual rehabilitation for these patients.

Translational Relevance

This study provides important information for visual rehabilitation of patients with macular disease.

Comparison and Correlation of Retinal Sensitivity Between Microperimetry and Standard Automated Perimetry in Low-tension Glaucoma

PRéCIS:: Our study demonstrated that in low-tension glaucoma (LTG) patients, Microperimeter-3 (MP-3)-derived and Humphrey Field Analyzer (HFA)-derived retinal sensitivities were similar and strongly correlated, allowing the respective data to be interrelated.

PURPOSE

To compare and correlate retinal sensitivities obtained by Nidek MP-3 with those obtained from the HFA in eyes with LTG.

MATERIALS AND METHODS

In this prospective comparative study, 45 eyes of 24 LTG patients underwent retinal sensitivity assessments using the MP-3 (Nidek Technologies) and the HFA (Carl Zeiss Meditec) at the UCLA-Doheny Eye Center. Global and pointwise retinal sensitivity measurements were compared and correlated between the 2 devices.

RESULTS

No statistically significant differences (P=0.85) were noted between the mean retinal sensitivities determined by each device (MP-3: 26.33±4.31 dB; range, 13.05 to 31.60 vs. HFA: 26.42±3.98 dB; range, 17.17 to 30.96), and a strong correlation (r=0.66, P<0.001) was noted for retinal sensitivity measurements. In addition, moderate to strong correlations were observed between the mean retinal sensitivity derived by MP-3 versus HFA-derived mean deviation (r=0.57, P<0.001), as well as, the pattern standard deviation (r=0.67, P<0.001). The intraclass correlation coefficient was excellent (ICC=0.80, 95% confidence interval, 0.63-0.89), while the Bland-Altman analysis showed good agreement between the 2 devices with respect to retinal sensitivity.

CONCLUSION

Retinal sensitivity measurements obtained by the MP-3 microperimetry instrument and the standard automated HFA perimeter were similar and highly correlated in patients with LTG. Given the potential benefits of microperimetry technology such as auto-eye-tracking and potentially more precise structure-function correlations, the use of microperimetry to monitor visual function in glaucoma management warrants further consideration.

Clinical spectrum, genetic complexity and therapeutic approaches for retinal disease caused by ABCA4 mutations

The ABCA4 protein (then called a “rim protein”) was first identified in 1978 in the rims and incisures of rod photoreceptors. The corresponding gene, ABCA4, was cloned in 1997, and variants were identified as the cause of autosomal recessive Stargardt disease (STGD1). Over the next two decades, variation in ABCA4 has been attributed to phenotypes other than the classically defined STGD1 or fundus flavimaculatus, ranging from early onset and fast progressing cone-rod dystrophy and retinitis pigmentosa-like phenotypes to very late onset cases of mostly mild disease sometimes resembling, and confused with, age-related macular degeneration. Similarly, analysis of the ABCA4 locus uncovered a trove of genetic information, including >1200 disease-causing mutations of varying severity, and of all types – missense, nonsense, small deletions/insertions, and splicing affecting variants, of which many are located deep-intronic. Altogether, this has greatly expanded our understanding of complexity not only of the diseases caused by ABCA4 mutations, but of all Mendelian diseases in general. This review provides an in depth assessment of the cumulative knowledge of ABCA4-associated retinopathy – clinical manifestations, genetic complexity, pathophysiology as well as current and proposed therapeutic approaches.

THE OASIS MP-1 SUBSTUDY: Characterization of the Effect of Ocriplasmin on Microperimetry Parameters

The MP-1 substudy of the OASIS trial evaluated the effects of ocriplasmin and symptomatic VMA resolution on visual fixation and macular sensitivity using microperimetry, identifying parameters that were distinct between patients with and without VMA resolution.

Purpose:

To evaluate the effects of ocriplasmin and symptomatic vitreomacular adhesion resolution on visual fixation and macular sensitivity using microperimetry.

Methods:

MP-1 parameters were analyzed from 3 OASIS sites after the use of standardized instruments and testing procedures over 24 months.

Results:

A total of 27 patients (19 ocriplasmin, 8 sham) were evaluated. Mean distance of the preferred fixation locus to the anatomical center was farther in the sham group at baseline and farther in the sham versus ocriplasmin group throughout the study. Retinal sensitivity values were consistently higher in the ocriplasmin versus sham group after Month 3. Fewer patients in the ocriplasmin group had predominantly eccentric fixation at study end compared with the sham group, which also had an increased number of patients with unstable fixation. Patients with vitreomacular adhesion resolution had lower bivariate contour area, fewer relative scotomas, and higher retinal sensitivity parameters at baseline than those with unresolved vitreomacular adhesion.

Conclusion:

Substudy results suggest that fixation and sensitivity parameters tended to be better in the ocriplasmin group than in the sham group over time. The substudy identified parameters that were distinct between patients with and without vitreomacular adhesion resolution, suggesting that microperimetry warrants further study as a relevant biomarker for visual function.

Retinal Microperimetry: A Useful Tool for Detecting Insulin Resistance-Related Cognitive Impairment in Morbid Obesity

Background: There is clear association between type 2 diabetes (T2D) and cognitive decline. Retinal microperimetry is a useful tool for detecting cognitive impairment in T2D. Morbid obesity (MO) has been associated with cognitive impairment. Insulin resistance (IR) seems a major determinant, but the data are unclear. The aim of this study was to evaluate the cognitive impairment in MO as well as the utility of retinal microperimetry in identifying these alterations. Methods: In total, 50 consecutive patients with MO were matched by age and gender with 30 healthy controls. All patients underwent cognitive evaluation (Montreal Cognitive Assessment Test-MoCA) and retinal microperimetry, using MAIA microperimeter 3rd generation. Retinal sensitivity and gaze fixation parameters were used for the evaluation of the analysis. Results: MO patients showed a significantly lower neurocognitive performance than the controls: MoCA score 24.94 ± 2.74 vs. 28.95 ± 1.05, p < 0.001. Cognitive function inversely correlated with the HOMA-IR (r = −0.402, p = 0.007). The AUROC for cognitive impairment using microperimetry was 0.807, CI 95% (0.592–0.947), p = 0.017. Conclusions: (1) Systemic insulin resistance is a major underlying mechanism accounting for the higher prevalence of cognitive impairment detected in young MO subjects. (2) Retinal microperimetry is a useful tool for identifying MO patients with cognitive impairment.

Evaluation of retinal function improvement in neovascular age-related macular degeneration after intravitreal aflibercept injections with the use of the assessment of retinal sensitivity: The use of the assessment of retinal sensitivity in anti-VEGF treatment - a STROBE-compliant observational study

This study compares 2 methods of macular function evaluation: the microperimetric examination (mean central retinal sensitivity and fixation stability) and the distance best-corrected visual acuity (BCVA) examination, which is the most frequently used method of assessing macular function in patients with newly diagnosed wet age-related macular degeneration (AMD) who have been treated with anti-vascular endothelial growth factor (VEGF) drug (aflibercept).Prospective analysis was conducted on 44 eyes of 44 patients treated with intravitreal injection of anti-VEGF (aflibercept) because of newly diagnosed neovascular AMD. According to the research protocol, all patients had a 6-month follow-up. The response to treatment was monitored functionallybyMP-1 microperimetry, fixation, and distance BCVA assessment after injection. Improvement of retinal sensitivity and BCVA was found under aflibercept treatment. There was statistically significant improvement in retinal sensitivity in the MP-1 study 3 and 6 months from the beginning of anti-VEGF therapy. Moreover, a significant improvement in retinal sensitivity between 3 and 6 months of observation was demonstrated. At the same time, up to 3 months from the beginning of treatment, BCVA improved significantly compared to the baseline value. In the 6th month of the study BCVA remained stable without further significant improvement.Microperimetric examination with medium sensitivity and fixation stability assessment is a very valuable test determining the retinal function. It is clear that examining the macular morphology itself in modern diagnostics is not enough to assess retinal function. Microperimetry technique is a valuable tool for functional long-term evaluation of retinal function (also for a period of more than 3 months).

Comparison of Fundus-Guided Microperimetry and Multifocal Electroretinography for Evaluating Hydroxychloroquine Maculopathy

Purpose

To compare retinal function by using fundus-guided microperimetry (MP) and multifocal electroretinography (mfERG) for detecting hydroxychloroquine (HCQ) maculopathy.

Methods

Forty-six eyes of 25 patients referred to our clinical practice for HCQ maculopathy assessment and 3 groups of normal control subjects were evaluated by mfERG and MP. Macular structure was assessed using spectral-domain optical coherence tomography (SD-OCT). Ring ratios from the three innermost mERG rings were compared with average sensitivity of each MP ring at approximately equivalent distances from the fovea. HCQ toxicity was defined as an mfERG ring ratio or mean MP ring sensitivity >2 standard deviations below the normal mean. The sensitivity and specificity of MP to detect HCQ toxicity relative to mfERG were evaluated.

Results

MP rings MR2 and MR3 were positively correlated with corresponding mfERG ring ratios (r = 0.52, P = 0.002 and r = 0.56, P < 0.001 respectively). Ring 2 and ring 3 measures of MP and mfERG were significantly worse in HCQ eyes than controls (P < 0.001). The sensitivity of MP to detect toxicity for MR1 through MR3 ranged from 33% to 88%, whereas specificity ranged from 72% to 85%. Through rings 1 to 3, the frequency of abnormal function ranged from 20% to 48% for MP, 11% to 35% for mfERG, and 41% to 45% for SD-OCT.

Conclusions

The frequency of detection of HCQ toxicity with MP was greater than with mfERG. MP showed an overall good sensitivity and moderate specificity in detecting HCQ-induced functional deficits.

Translational Relevance

Results from this study may allow clinicians to improve screening accuracy for HCQ toxicity by using the alternative modality of MP.

PREOPERATIVE AND POSTOPERATIVE MACULAR SENSITIVITY ASSESSMENT USING MICROPERIMETRY IN EYES UNDERGOING SILICONE OIL REMOVAL

PURPOSE

To evaluate the functional changes on the macula, before and after silicone oil removal (SOR) using microperimetry (MP3) in patients originally operated for macula-off rhegmatogenous retinal detachments.

METHODS

Prospective interventional study, N = 20. All cases underwent complete ophthalmic examination, including determination of Snellen best-corrected visual acuity, indirect ophthalmoscopy, and MP3 for measuring retinal sensitivity. Primary outcome measure was to describe the alterations in the retinal sensitivity on the macula after SOR.

RESULTS

Mean retinal sensitivity increased in 100% patients (20/20) after SOR with a mean value of 97.44 dB. Best-corrected visual acuity after SOR remained unchanged in 90% (18/20) and improved by 2 lines in only 10% patients (2/20). Median retinal sensitivity of central 6° of the macula was 766.95 ± 173.29 dB before SOR and 863.8 ± 181.08 dB after SOR, P < 0.0001. Mean best-corrected visual acuity was 20/40 before SOR (range, 20/30-20/60) (logarithm of the minimum angle of resolution 0.314 ± 0.169) and 20/40 after SOR (range 20/30-20/80) (logarithm of the minimum angle of resolution 0.315 ± 0.159), P = 0.1628.

CONCLUSION

MP3 was found to be a highly sensitive tool in detecting increased retinal sensitivity after SOR, particularly in central 6° of the macula without significant change in best-corrected visual acuity. Hence, MP3 is an important qualitative indicator of visual function.

HbA1c and retinal sensitivity in diabetics using microperimetry

PURPOSE

The purpose of this study was to determine the relationship between HbA1c values and retinal sensitivity at central 10° using the MP-1 microperimeter.

METHODS

A prospective study was carried out on 32 healthy subjects (control group) and 60 diabetic patients. The diabetic patients were divided into 2 groups. Group 1 comprised of 30 patients without diabetic retinopathy (DR) and group 2 had 30 patients with mild non-proliferative DR. A full-threshold microperimetry of the central 10° of retina (the macula) was performed on all subjects, utilizing 32 points with the MP-1. The relationship between light sensitivity and HbA1c value was calculated using linear regression analysis.

RESULTS

Total mean sensitivity at 10° for group 1 without DR, group 2 with mild NPDR and control group were 18.67±0.83, 17.98±1.42 and 19.45±0.34 (dB), respectively. There was a significant difference in total mean retinal sensitivity at 10° between the 3 groups (F(2,89)=18.14, p=0.001). A simple linear regression was calculated to predict HbA1c based on retinal sensitivity. A significant regression equation was found (F(1,90)=107.61, p=0.0001, with an R² of 0.545). The linear regression analysis revealed that there was a 0.64dB decline in mean retinal sensitivity within the central 10° diameter with an increase of 1mmHg of HbA1c.

CONCLUSION

Retinal sensitivity at the central 10° of the macula is affected by changes in HbA1c values.

Microperimetry and swept-source optical coherence tomography in the assessment of the preferred retinal locus in a child with macular retinoblastoma in the remaining eye

Assessing the visual capabilities that remain to children affected with bilateral retinoblastoma has relied on psychophysical tests based on recognition visual acuity. We report a case in which fundus-driven perimetry and swept-source optical coherence tomography was performed in a patient with a macular tumor in the remaining eye as a novel way of further assessing fixation after oncological disease and treatment.

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.

Correlation of optical coherence tomography angiography and microperimetry (MP3) features in wet age-related macular degeneration

PURPOSE

To evaluate and correlate the functional treatment response using microperimetry (MP3) with the morphological findings on optical coherence tomography angiography (OCTA) in wet AMD pre- and post-treatment with anti-vascular endothelial growth factor (VEGF). This was a single-centre prospective, interventional study.

METHODS

Patients with wet AMD were treated with 3 injections of intravitreal anti-VEGF at monthly intervals for 3 months and followed at 1, 2, 3, and 6 months postinjection. Using "overlay" features, morphologic characteristics of OCTA at the site of choroidal neovascular membrane (CNVM) lesion were analyzed and correlated functionally with MP3. Data were collected including visual acuity at presentation and follow-up with multimodal imaging features, treatment details, complications (if any), and treatment given for that complication. Descriptive observational analysis and paired t-test was used to compare the appearance of the neovascular network on OCTA imaging with retinal sensitivity on MP3.

RESULTS

OCTA in the pretreatment phase revealed CNVM as an abnormal vascular network arising from the choroid and invading the subretinal space. On MP3, decreased retinal sensitivity was observed corresponding to the area of CNVM. Post-treatment, OCTA revealed reduction in abnormal vascular network in 51 (91.07%) eyes that correlated with increased retinal sensitivity at the corresponding area on MP3. Statistical analysis showed baseline mean retinal sensitivity at the site of CNVM as 320.07 dB, which improved to 521.53 and 730.20 dB at 1 and 3 months postinjection follow-up, respectively.

CONCLUSION

Combining the findings of OCTA and MP3 using "overlay" features gives us precise information of structure-function correlation at presentation and also in response to treatment. It also helps to improve patient's compliance, confidence to treatment, and their understanding of the disease process as well.

THE NATURAL HISTORY OF FULL-FIELD STIMULUS THRESHOLD DECLINE IN CHOROIDEREMIA

PURPOSE

To evaluate full-field sensitivity thresholds (FSTs) across a wide range of choroideremia (CHM) disease stages and to determine their applicability as functional endpoints for CHM clinical trials.

METHODS

Thirty CHM subjects (60 eyes) and 50 healthy controls (50 eyes) underwent FST testing under dark-adapted conditions to determine rod- and cone-mediated FSTs. Central retinal structure and function were assessed using fundus autofluorescence and microperimetry. Correlation and regression analyses were performed to compare FST responses with the residual area of retinal pigment epithelium in the peri- and parafoveal regions, as well as the mean and highest macular microperimetry sensitivity.

RESULTS

All patients with CHM had a baseline of 18 dB elevation in dark-adapted rod FSTs, including the least affected individuals. Further FST sensitivity loss was exponentially associated with decrease in the area of residual peri- and parafoveal retinal pigment epithelium, with precipitous loss of sensitivity noted for fundus autofluorescence areas less than 5 mm. Cone FSTs were comparable with controls, except for advanced stages of CHM. Full-field sensitivity threshold responses showed high correlation with both mean and highest macular microperimetry thresholds (P < 0.001). In some cases of absent macular fundus autofluorescence, the peripheral retina could contribute to detectable rod FST responses but with severely diminished cone-driven responses.

CONCLUSION

Full-field sensitivity threshold testing demonstrated a baseline level of rod dysfunction in CHM present in all rod photoreceptors. Further decline in FST responses correlated strongly with the extent of central retina structural and functional loss. Full-field sensitivity threshold allowed quantification of residual rod function in peripheral islands of vision, which cannot be reliably achieved with other conventional tests. As such, the FST can serve as a complimentary tool to guide patient selection and expand the eligibility criteria for current and future CHM clinical trials.

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.

Potential Utility of Retinal Imaging for Alzheimer's Disease: A Review

The ensuing upward shift in demographic distribution due to the increase in life expectancy has resulted in a rising prevalence of Alzheimer's disease (AD). The heavy public burden of AD, along with the urgent to prevent and treat the disease before the irreversible damage to the brain, calls for a sensitive and specific screening technology to identify high-risk individuals before cognitive symptoms arise. Even though current modalities, such as positron emission tomography (PET) and cerebrospinal fluid (CSF) biomarker, showed their potential clinical uses in early detection of AD, the high cost, narrow isotope availability of PET probes and invasive characteristics of CSF biomarker limited their broad utility. Therefore, additional tools for detection of AD are needed. As a projection of the central nervous system (CNS), the retina has been described as a "window to the brain" and a novel marker for AD. Low cost, easy accessibility and non-invasive features make retina tests suitable for large-scale population screening and investigations of preclinical AD. Furthermore, a number of novel approaches in retina imaging, such as optical coherence tomography (OCT), have been developed and made it possible to visualize changes in the retina at a very fine resolution. In this review, we outline the background for AD to accelerate the adoption of retina imaging for the diagnosis and management of AD in clinical practice. Then, we focus on recent findings on the application of retina imaging to investigate AD and provide suggestions for future research directions.

Test-Retest Reproducibility of the Microperimeter MP3 With Fundus Image Tracking in Healthy Subjects and Patients With Macular Disease

Purpose

To evaluate the test–retest reproducibility of a novel microperimeter with fundus image tracking (MP3, Nidek Co, Japan) in healthy subjects and patients with macular disease.

Methods

Ten healthy subjects and 20 patients suffering from range of macular diseases were included. After training measurements, two additional microperimetry measurements were scheduled. Test–retest reproducibility was assessed for mean retinal sensitivity, pointwise sensitivity, and deep scotoma size using the coefficient of repeatability and Bland-Altman diagrams. In addition, in a subgroup of patients microperimetry was compared with conventional perimetry.

Results

Average differences in mean retinal sensitivity between the two study measurements were 0.26 ± 1.7 dB (median 0 dB; interquartile range [IQR] −1 to 1) for the healthy and 0.36 ± 2.5 dB (median 0 dB; IQR −1 to 2) for the macular patient group. Coefficients of repeatability for mean retinal sensitivity and pointwise retinal sensitivity were 1.2 and 3.3 dB for the healthy subjects and 1.6 and 5.0 dB for the macular disease patients, respectively. Absolute agreement in deep scotoma size between both study days was found in 79.9% of the test loci.

Conclusion

The microperimeter MP3 shows an adequate test–retest reproducibility for mean retinal sensitivity, pointwise retinal sensitivity, and deep scotoma size in healthy subjects and patients suffering from macular disease. Furthermore, reproducibility of microperimetry is higher than conventional perimetry.

Translational Relevance

Reproducibility is an important measure for each diagnostic device. Especially in a clinical setting high reproducibility set the basis to achieve reliable results using the specific device. Therefore, assessment of the reproducibility is of eminent importance to interpret the findings of future studies.

Retinal Microperimetry: A New Tool for Identifying Patients With Type 2 Diabetes at Risk for Developing Alzheimer Disease

Type 2 diabetes is associated with a high risk of cognitive impairment and dementia. Therefore, strategies are needed to identify patients who are at risk for dementia. Given that the retina is a brain-derived tissue, it may provide a noninvasive way to examine brain pathology. The aims of this study were to evaluate whether retinal sensitivity 1) correlates with the specific parameters of brain imaging related to cognitive impairment and 2) discriminates patients with diabetes with mild cognitive impairment (MCI) from those with normal cognition and those with Alzheimer disease (AD). For this purpose, a prospective, nested case-control study was performed and included 35 patients with type 2 diabetes without cognitive impairment, 35 with MCI, and 35 with AD. Retinal sensitivity was assessed by Macular Integrity Assessment microperimetry, and a neuropsychological evaluation was performed. Brain neurodegeneration was assessed by MRI and fludeoxyglucose-18 positron emission tomography (¹⁸FDG-PET). A significant correlation was found between retinal sensitivity and the MRI and ¹⁸FDG-PET parameters related to brain neurodegeneration. Retinal sensitivity was related to cognitive status (normocognitive > MCI > AD; P < 0.0001). Our results suggest that retinal sensitivity assessed by microperimetry is related to brain neurodegeneration and could be a useful biomarker for identifying patients with type 2 diabetes who are at risk for developing AD.

Management of diplopia with visual-field defects

PURPOSE:

The management of diplopia can be challenging in patients with a concurrent visual-field (VF) defect. We conducted a retrospective chart review to analyze and compare treatment outcomes for different types of VF defects.

METHODS:

A retrospective chart review.

RESULTS:

Seven patients with diplopia and VF defects were identified during the study. Four had bitemporal hemianopia, one had homonymous hemianopia, and two had a constricted central VF. A favorable or satisfactory outcome was achieved in all but two patients with bitemporal hemianopia.

CONCLUSIONS:

The hemifield-slide diplopia may develop in patients with bitemporal hemianopia or heteronymous altitudinal visual defects. Sensory abnormalities usually persist, even after elimination of ocular misalignment.

The use of microperimetry in assessing visual function in age-related macular degeneration

Microperimetry is a novel technique for assessing visual function that appears particularly suitable for age-related macular degeneration (AMD). Compared with standard automated perimetry, microperimetry offers several unique features. It simultaneously images the fundus, incorporates an eye-tracking system to correct the stimulus location for fixation loss, and identifies any preferred retinal loci. We identified 52 articles that met the inclusion criteria for a systematic review of microperimetry in the assessment of visual function in AMD. We discuss microperimetry and AMD in relation to disease severity, structural imaging outcomes, other measures of visual function, and evaluation of the efficacy of surgical and/or medical therapies in clinical trials. The evidence for the use of microperimetry in the functional assessment of AMD is encouraging. Disruptions of the ellipsoid zone band and retinal pigment epithelium are clearly associated with reduced differential light sensitivity despite the maintenance of good visual acuity. Reduced differential light sensitivity is also associated with outer segment thinning and retinal pigment epithelium thickening in early AMD and with both a thickening and a thinning of the whole retina in choroidal neovascularization. Microperimetry, however, lacks the robust diffuse and focal loss age-corrected probability analyses associated with standard automated perimetry, and the technique is currently limited by this omission.

Interdevice comparison of retinal sensitivity assessments in a healthy population: the CenterVue MAIA and the Nidek MP-3 microperimeters

Background

To compare and correlate the retinal sensitivity measurements obtained with Nidek Microperimetry-3 (MP-3) and the CenterVue Macular Integrity Assessment (MAIA) microperimeters among healthy subjects.

Methods

In this prospective comparative study, 31 eyes of 23 subjects underwent complete ophthalmological examination including retinal sensitivity assessments using two microperimeters, the MP-3 (Nidek Technologies) and the MAIA (CenterVue). The mean retinal sensitivity (dB) and its corresponding luminance (asb) and contrast (log units) were analysed between the two instruments. The interdevice reproducibility and level of agreement between the sensitivity values of the devices were assessed.

Results

The mean retinal sensitivity (dB) measured by the MP-3 (25.02±1.06 dB, range: 20.90–26.70) was significantly (p<0.0001) lower compared with the MAIA (30.68±0.74 dB, range: 28–31.84). The luminosity levels were significantly (p<0.0001) higher with the MP3 (7.75±1.31 asb, range: 6.44–9.06) compared with the MAIA (0.92±0.14 asb, range: 0.78–1.06). The contrast sensitivity was significantly higher for the MP-3 (0.94±0.33 log units, range: 0.61–1.27) compared with the MAIA (0.23±0.03 log units, range: 0.20–0.26). Despite these absolute differences, the intraclass coefficient was 0.85 (95% CI 0.70 to 0.92) between the two devices after applying a standard correction factor to each data point (MAIA sensitivity=MP-3 sensitivity+5.65) with a mean difference between MAIA and MP-3 of 0.01.

Conclusion

Retinal sensitivity measures higher, but luminance and contrast sensitivity measure lower for MAIA-generated values compared with the MP-3. The relationships, however, appeared fairly consistent, and application of a standard correction factor allowed the data to be inter-related, at least for normal eyes.

Self-reported optometric practise patterns in age-related macular degeneration

BACKGROUND

The use of advanced imaging in clinical practice is emerging and the use of this technology by optometrists in assessing patients with age-related macular degeneration is of interest. Therefore, this study explored contemporary, self-reported patterns of practice regarding age-related macular degeneration diagnosis and management using a cross-sectional survey of optometrists in Australia and New Zealand.

METHODS

Practising optometrists were surveyed on four key areas, namely, demographics, clinical skills and experience, assessment and management of age-related macular degeneration. Questions pertaining to self-rated competency, knowledge and attitudes used a five-point Likert scale.

RESULTS

Completed responses were received from 127 and 87 practising optometrists in Australia and New Zealand, respectively. Advanced imaging showed greater variation in service delivery than traditional techniques (such as slitlamp funduscopy) and trended toward optical coherence tomography, which was routinely performed in age-related macular degeneration by 49 per cent of respondents. Optical coherence tomography was also associated with higher self-rated competency, knowledge and perceived relevance to practice than other modalities. Most respondents (93 per cent) indicated that they regularly applied patient symptoms, case history, visual function results and signs from traditional testing, when queried about their management of patients with age-related macular degeneration. Over half (63 per cent) also considered advanced imaging, while 31 per cent additionally considered all of these as well as the disease stage and clinical guidelines. Contrary to the evidence base, 68 and 34 per cent rated nutritional supplements as highly relevant or relevant in early age-related macular degeneration and normal aging changes, respectively.

CONCLUSIONS

These results highlight the emergence of multimodal and advanced imaging (especially optical coherence tomography) in the assessment of age-related macular degeneration by optometrists. Clinically significant variations in self-rated test competency and the understanding regarding nutritional supplements for different stages of age-related macular degeneration suggest that further work to up-skill optometrists may be required.

Effects of pupil dilation on MAIA microperimetry

BACKGROUND

Macular Integrity Assessment microperimetry assesses macular sensitivity to projected point light sources and maps eye movements to assess fixation stability. Although microperimetry is gaining prominence as an assessment tool in clinical and research settings, there is no consensus on whether it should be performed before or after pupil dilation. No studies to date have examined the effect of pupil dilation on results. The aim of this project was to elucidate the effect of pupil dilation on microperimetry outcomes.

DESIGN

Prospective audit.

PARTICIPANTS

Twenty healthy patients from postoperative cataract clinic and 10 patients with choroideremia to simulate a disease with peripheral visual field loss.

METHODS

Subjects underwent 10-2 68-point field testing using the Macular Integrity Assessment microperimeter on each eye. Subjects then underwent randomized dilation of one eye, and the test was repeated in both eyes.

MAIN OUTCOME MEASURES

We compared changes in threshold sensitivity and fixation stability pre-pupil and post-pupil dilation. The undilated eye was analysed for any learning or fatigue effect caused by test repetition.

RESULTS

Dilation produced no significant effect on threshold sensitivity (dilation effect: -0.29 decibels, P = 0.23) or fixation stability in healthy controls or in choroideremia patients (dilation effect: +0.08log bivariate contour ellipse area, P = 0.14). There was also no significant learning effect seen in the undilated eye, with no improvement in threshold sensitivity (order of eye testing: +0.03log bivariate contour ellipse area, P = 0.71).

CONCLUSIONS

In the clinical setting, patients may be tested for 10 degree microperimetry with or without pupil dilation, as both scenarios yield consistent and interchangeable results.

Selective Automated Perimetry Under Photopic, Mesopic, and Scotopic Conditions: Detection Mechanisms and Testing Strategies

PURPOSE

Automated scotopic, mesopic, and photopic perimetry are likely to be important paradigms in the assessment of emerging treatments of retinal diseases, yet our knowledge of the photoreceptor mechanisms detecting targets under these conditions remains largely dependent on simian data. We therefore aimed to establish the photoreceptor/postreceptoral mechanisms detecting perimetric targets in humans under photopic, mesopic, and scotopic conditions and to make recommendations for suitable clinical testing strategies for selective perimetry.

METHODS

Perimetric sensitivities within 30° of fixation were determined for eight wavelengths (410, 440, 480, 520, 560, 600, 640, and 680 nm) under scotopic, mesopic (1.3 cd.m^-2) and photopic (10 cd.m^-2) conditions. Data were fitted with vector combinations of rod, S-cone, nonopponent M+L-cone mechanism, and opponent M- versus L-cone mechanism templates.

RESULTS

Scotopicperimetric sensitivity was determined by rods peripherally and by a combination of rods and cones at, and immediately around, fixation. Mesopic perimetric sensitivity was mediated by M+L-cones and S-cones centrally and by M+L-cones and rods more peripherally. Photopic perimetric sensitivity was determined by an opponent M- versus L-cone, a nonopponent M+L-cone, and an S-cone mechanism centrally and by a combination of an S-cone and an M+L-cone mechanism peripherally.

CONCLUSIONS

Under scotopic conditions, a 480-nm stimulus provides adequate isolation (≥28 dB) of the rod mechanism. Several mechanisms contribute to mesopic sensitivity: this redundancy in detection may cause both insensitivity to broadband white targets and ambiguity in determining which mechanism is being probed with short-wavelength stimuli. M- and L-cone-derived mechanisms are well isolated at 10 cd.m^-2: these may be selectively probed by a stimulus at 640 nm (≥ 20 dB isolation).

TRANSLATION RELEVANCE

In human observers, multiple mechanisms contribute to the detection of Goldmann size III and size V perimetric targets under scotopic, mesopic, and photopic conditions. The relative contribution of these mechanisms appears to differ from those found previously for macaques. Our results furthermore suggest that caution must be exercised when using microperimetric techniques, which are typically conducted under mesopic conditions and which are likely to be important in the assessment of emerging treatments for retinal disease. This is because mesopic background conditions maximize the redundancy of target detection. Furthermore, our results demonstrate that spectral manipulation of the stimulus alone cannot be used to reliably separate rod from cone responses under these conditions.

Pathogenic mechanisms and the prospect of gene therapy for choroideremia

INTRODUCTION

Choroideremia is a rare, X-linked disorder recognized by its specific ocular phenotype as a progressive degenerative retinopathy resulting in blindness. New therapeutic approaches, primarily based on genetic mechanisms, have emerged that aim to prevent the progressive vision loss.

AREAS COVERED

This article will review the research that has progressed incrementally over the past two decades from mapping to gene discovery, uncovering the presumed mechanisms triggering the retinopathy to preclinical testing of potential therapies.

EXPERT OPINION

While still in an evaluative phase, the introduction of gene replacement as a potential therapy has been greeted with great enthusiasm by patients, advocacy groups and the medical community.

Correlation of structure and function of the macula in patients with retinitis pigmentosa

PURPOSE

To correlate the structure of the macula, as measured by spectral-domain optical coherence tomography (SD-OCT) and function, as measured by microperimetry (MAIA) in patients with retinitis pigmentosa (RP) and relatively good visual acuity.

DESIGN

Prospective, cross-sectional, non-intervention study.

SUBJECTS

Patients with RP.

METHODS

Thirty patients with RP and good central visual acuity were identified. Each patient underwent SD-OCT of the macula and microperimetry. The images were overlaid using the custom-designed software. The retinal sensitivity by microperimetry was correlated with corresponding retinal thickness, as measured by the SD-OCT. ELM, COST, and IS/OS junction were scored as intact, disrupted, or absent.

MAIN OUTCOME MEASURES

Comparing the retinal sensitivity on the MAIA with various measurements on the SD-OCT.

RESULTS

The retinal sensitivity on the MAIA showed a significant correlation with total retinal thickness and outer retinal thickness on the SD-OCT. There was no association with either the inner retinal thickness or the choroidal thickness. ORT showed a statistically significant correlation with the anatomical classification of ELM (r=-0.76, P<0.001), IS/OS (r=-0.800, P<0.001), and COST (r=-0.733, P<0.001).

CONCLUSION

This study determined that there was a high correlation of the structure and function of the central macula in patients with RP. These studies are important to establish surrogate markers that can be used as end points for various tests in future therapeutic clinical trials.

Reliability and Intersession Agreement of Microperimetric and Fixation Measurements Obtained with a New Microperimeter in Normal Eyes

PURPOSE

To evaluate the reliability and intersession agreement of measurements of retinal sensitivity as well as of the fixation pattern obtained in healthy eyes with a microperimeter integrating the mechanism of the scanning laser ophthalmoscope (SLO) with the static perimetry.

METHODS

This study included a sample of 44 healthy eyes of 44 subjects of a mean age of 27.0 ± 8.5 years. In all cases, microperimetric exams with the MAIA system (Centervue, Padova, Italy) were performed in three different sessions to evaluate the intersession repeatability. The consistency of measurements was analyzed by using the Friedman test and by analyzing the correlation between consecutive measurements. Agreement between the first and third sessions was assessed by using the Passing-Bablok regression analysis. The following parameters were analyzed: average threshold (AT), macular integrity (MI) index, fixation indexes P1 and P2, bivariate contour ellipse area (BCEA), major and minor axes of the ellipse and high preferred retinal locus position (PRLh).

RESULTS

Not statistically significant differences were found in the evaluated parameters between the three sessions (p ≥ 0.193). The correlation between consecutive measurements was moderate to strong for all parameters evaluated (r ≥ 0.49, p < 0.01), except for the MI and the position of the PRLh (r ≤ 0.305, p ≥ 0.05). The Passing-Bablok regression analysis showed a good agreement between the first and third measurement for all parameters, except for the MI and the position of the PRLh.

CONCLUSION

MAIA MP system is able to provide consistent measurements of AT and fixation in normal subjects. MI and the position of PRLh seem to be the least reliable parameters in this group of patients.