Assessment of Scotopic Function in Rod-Cone Inherited Retinal Degeneration With the Scotopic Macular Integrity Assessment

DRUSEN VOLUME AS CLINICAL OUTCOME MEASURE IN SUBJECTS WITH MALATTIA LEVENTINESE

PURPOSE

To assess if drusen volume can serve as structural clinical outcome marker in Malattia Leventinese, and to evaluate whether cones or rods are more affected by its progression, using multimodal imaging and mesopic and two-color scotopic microperimetry.

METHODS

This was a prospective monocentric cross-sectional cohort study of participants with genetically confirmed Malattia Leventinese. Participants were classified according to morphology. Mean drusen volume, calculated from spectral-domain optical coherence tomography, was compared with microperimetry parameters (mesopic retinal sensitivity, scotopic red and cyan function, difference between scotopic cyan-red function).

RESULTS

Fourteen participants (28 eyes) were enrolled. Mean drusen volume increased (bilaterally P = 0.028) and mesopic retinal sensitivity decreased with later stage (right eye: P = 0.028; left eye: P = 0.050). Scotopic microperimetry showed that scotopic cyan function was lower than scotopic red function in moderate stage. Scotopic red function decreased in severe stage. Mean drusen volume correlated to mesopic retinal sensitivity (right eye: P < 0.001; left eye: P = 0.007).

CONCLUSION

Retinal sensitivity diminishes with Malattia Leventinese progression. Rod function declines before cone function, whereas at late stages, cone loss predominates. Drusen accumulation, initially speckled around the macula and optic disc and confluent with disease progression, correlates well with visual function loss and impaired quality of life. Thus, therapeutically reducing drusen accumulation could be efficacious.

Assessment of CRB1-Associated Retinopathies Using the S-MAIA Fast Protocol and Spectral-Domain Optical Coherence Tomography

Background: A cross-sectional study was conducted at Moorfields Eye Hospital, UK, involving patients with CRB1-associated retinopathies: macular dystrophy (MD), cone-rod dystrophy (CORD), and early-onset severe retinal dystrophy/Leber congenital amaurosis (EOSRD/LCA). The study aimed to evaluate CRB1-associated retinopathies using microperimetry (macular integrity assessment (S-MAIA) fast protocol) and spectral domain optical coherence tomography (SD-OCT). Methods: Data quality and participant attrition were assessed in 18 patients (10 MD, 5 EOSRD/LCA, 3 CORD), aged 10-52 years, with a median best corrected visual acuity (BCVA) of 0.41 logMAR. Results: Microperimetry and SD-OCT data were obtained from 14 and 18 patients, respectively, but eccentric fixation hindered structure-function analysis. All participants showed overall abnormal sensitivity on the S-MAIA fast protocol. Parafoveal volume was significantly increased, while foveal thickness and volume were reduced compared to normative data (p < 0.01). Conclusions: This study highlights the challenges of participant attrition and the need for alternative functional metrics to complement traditional evaluations. It also reinforces previous findings of abnormal retinal architecture in CRB1-associated retinopathies, providing further insights into S-MAIA and SD-OCT assessments for this patient population.

THREE-DIMENSIONAL HILL OF VISION OF RETINAL SENSITIVITY IN PARTICIPANTS WITH X-LINKED RETINITIS PIGMENTOSA UNDER SCOTOPIC AND MESOPIC CONDITIONS

PURPOSE

To evaluate the utility of three-dimensional hill of vision (HOV) analysis in assessing retinal sensitivity in patients with X-linked retinitis pigmentosa (XLRP) under scotopic cyan, scotopic red, and mesopic microperimetry conditions.

METHODS

Baseline microperimetry data from 31 eyes of 16 patients with XLRP enrolled in the Horizon study were analyzed. HOVs were generated using thin plate spline interpolation. Grid volumes of the central 20° (V 20 ) were compared between lighting conditions using the Wilcoxon signed-rank test with Bonferroni correction. Central and global deficits were evaluated across age groups and genotypes.

RESULTS

The mesopic group showed the highest mean V 20 (1.3 dB-Sr), followed by scotopic red (0.6 dB-Sr) and scotopic cyan (0.5 dB-Sr). Significant differences were found between mesopic and scotopic conditions (P < 0.01), but not between scotopic conditions ( P = 0.26). Central and global deficits were more prevalent under scotopic conditions and increased with age.

CONCLUSION

HOV analysis provides a comprehensive assessment of retinal sensitivity in XLRP, enabling detection of localized changes and quantification of sensitivity gradients. This volumetric approach offers advantages over traditional methods for diagnosis, monitoring progression, and evaluating treatment response.

Standard automated perimetry for glaucoma and diseases of the retina and visual pathways: Current and future perspectives

Static automated perimetry (SAP) remains a mainstay of functional assessment of the visual field in diseases of the visual pathway, such as glaucoma and age-related macular degeneration. The fundamental psychophysical task of responding to stimuli of different levels of contrast has remained minimally changed since its inception in the 1980s, and this is potentially the root of several unresolved issues involving the technique. Enduring issues include the optimisation of SAP parameters for maximising defect detection, the influence of subjective behaviour on the response, structure-function discordance, and ageing- and disease-related changes of the visual pathway. Addressing these issues has been a focus of our research program and is the subject of this manuscript. We will review some of the basic psychophysical principles and methods that have contributed to the development of SAP and their contributions to its output measurements. Parameters that are interrogated include stimulus size and background luminance and their modification to improve defect defection in glaucoma and age-related macular degeneration. We propose frameworks for optimising testing parameters and leveraging the results for changing clinical care. In our pursuit of optimising the structure-function relationship in the eye, several areas of research have been developed and explored, including: the reconciliation of subjective responses in perimetry; by minimising sources of biases, such as Method of Limits we have been able to equate static and kinetic perimetry outputs in relation to underlying structural loci. This also formed the basis for our clustering framework, which groups together statistically similar structural and functional test locations to maximise structure-function concordance. Throughout the manuscript, we review the scientific underpinnings of clinical measurements, framing application into real-world patients to improve clinical practice.

Exploring Scotopic Microperimetry as an Outcome Measure in Choroideremia

Purpose

Choroideremia is an X-linked outer retinal degeneration. Early symptoms include nyctalopia and progressive visual field loss, but visual acuity is preserved until late disease stages. Dark-adapted two-color fundus-controlled perimetry (also known as scotopic microperimetry) has been developed to enable spatial assessment of rod and cone photoreceptor function. This study explores the use of scotopic microperimetry in patients with choroideremia.

Methods

Twenty patients with choroideremia and 21 age-matched healthy controls completed visual acuity and scotopic microperimetry testing, which used the Scotopic Macular Integrity Assessment (S-MAIA) microperimeter. A subset of participants completed repeat scotopic testing to enable Bland-Altman repeatability analyses. Test reliability was assessed using fixation stability, fixation losses, and assessment of the rod-free zones. Pointwise sensitivity, mean sensitivity, and volume sensitivity indices were analyzed.

Results

False positive responses were the main source of poor test reliability, indicated by stimuli responses in the physiological blind spot and lack of rod-free mapping. Scotopic cyan and red sensitivities were significantly reduced in choroideremia participants (n = 17) compared to healthy controls (n = 16) (P < 0.01, Mann-Whitney U test). Scotopic cyan sensitivity was statistically lower than scotopic red sensitivity in both healthy controls and choroideremia (P < 0.01, Wilcoxon signed rank test). Interpretation of scotopic cyan-red differences should be used with caution due to high test-retest variability.

Conclusions

Scotopic microperimetry could be a useful outcome measure in patients with early choroideremia. Careful selection of test grid design and sensitivity indices is required.

Translational Relevance

Scotopic microperimetry may be a useful outcome measure in clinical trials for patients with early stage choroideremia.

Establishing Fully-Automated Fundus-Controlled Dark Adaptometry: A Validation and Retest-Reliability Study

Purpose

The purpose of this study was to establish and validate a novel fundus-controlled dark-adaptometry method.

Methods

We developed a custom dark-adaptometry software for the S-MAIA device using the open-perimetry-interface. In the validation-substudy, participants underwent dark-adaptometry testing with a comparator device (MonCvONE, 59% rhodopsin bleach, cyan and red stimuli centered at 2 degrees, 4 degrees, and 6 degrees eccentricity). Following a brief break (approximately 5 minutes), the participants were bleached again and underwent dark-adaptometry testing with the S-MAIA device (same loci). In the retest reliability-substudy, participants were tested twice with the S-MAIA device (same loci as above). Nonlinear curve fitting was applied to extract dark-adaptation curve parameters. Validity and repeatability were summarized in terms of the mean bias and 95% limits of agreement (LoAs).

Results

In the validation-substudy (N = 20 participants, median age interquartile range [IQR] 31.5 years [IQR = 25.8, 62.0]), measures of rod-mediated dark-adaptation showed little to no between method differences for the cone-rod-break-time (bias 95% confidence interval [95% CI] of +0.1 minutes [95% CI = -0.6 to 0.8]), rod-intercept-time (-0.23 minutes [95% CI = -1.38 to 0.93]), and S2 slope (-0.01 LogUnits/minutes [95% CI = -0.02 to -0.01]). In the retest reliability-substudy (N = 10 participants, 32.0 years [95% CI = 27.0, 57.5]), the corresponding LoAs were (cone-rod-break-time) -3.94 to 2.78 minutes, (rod-intercept-time) -4.55 to 3.11 minutes, and (S2 slope [rate-limited component of rod recovery]) -0.03 to 0.03 LogUnits/minutes. The LoAs for the steady-state cone and rod thresholds were -0.28 to 0.33 LogUnits and -0.34 to 0.28 LogUnits.

Conclusions

The devised fundus-controlled dark-adaptometry method yields valid and reliable results.

Translational Relevance

Fundus-controlled dark-adaptometry solves the critical need for localized testing of the visual cycle and retinoid transfer in eyes with unstable fixation.