Examining Whether AOSLO-Based Foveal Cone Metrics in Achromatopsia and Albinism Are Representative of Foveal Cone Structure

Genotype-Phenotype Correlation Model for the Spectrum of TYR-Associated Albinism

We present two children aged 3 and 5 years who share identical TYR genotype, yet exhibit contrasting phenotypic manifestations in terms of eye, skin, and hair coloration. The patients are heterozygous for TYR c.1A>G, p. (Met1?), which is pathogenic, and homozygous for TYR c.1205G>A, p. (Arg402Gln), which is classified as a risk factor. The children manifested diminished visual acuity, nystagmus, and foveal hypoplasia. The first patient presented with hypopigmentation of the skin, hair, and ocular tissues, while the second patient presented with hypopigmentation of the skin, hair, retinal pigment epithelium, and choroid with dark brown irises. Furthermore, the brown-eyed subject presented astigmatic refractive error and both global and local stereopsis capabilities, contrasting with the presentation of hypermetropia, strabismus, and the absence of stereopsis in the blue-eyed individual. Herein, we propose a genotype-phenotype correlation model to elucidate the diverse clinical presentations stemming from biallelic and triallelic pathogenic variants in TYR, establishing a link between the residual tyrosinase activity and resultant phenotypes. According to our proposed model, the severity of TYR variants correlates with distinct albino phenotypes. Our findings propose the potential association between reduced pigmentation levels in ocular tissues and binocular functions, suggesting pigmentation as a possible independent variable influencing the onset of strabismus-an association unreported until now in the existing literature.

Visual Field Deficits in Albinism in Comparison to Idiopathic Infantile Nystagmus

Purpose

This is the first systematic comparison of visual field (VF) deficits in people with albinism (PwA) and idiopathic infantile nystagmus (PwIIN) using static perimetry. We also compare best-corrected visual acuity (BCVA) and optical coherence tomography measures of the fovea, parafovea, and circumpapillary retinal nerve fiber layer in PwA.

Methods

VF testing was performed on 62 PwA and 36 PwIIN using a Humphrey Field Analyzer (SITA FAST 24-2). Mean detection thresholds for each eye were calculated, along with quadrants and central measures. Retinal layers were manually segmented in the macular region.

Results

Mean detection thresholds were significantly lower than normative values for PwA (-3.10 ± 1.67 dB, P << 0.0001) and PwIIN (-1.70 ± 1.54 dB, P < 0.0001). Mean detection thresholds were significantly lower in PwA compared to PwIIN (P < 0.0001) and significantly worse for left compared to right eyes in PwA (P = 0.0002) but not in PwIIN (P = 0.37). In PwA, the superior nasal VF was significantly worse than other quadrants (P < 0.05). PwIIN appeared to show a mild relative arcuate scotoma. In PwA, central detection thresholds were correlated with foveal changes in the inner and outer retina. VF was strongly correlated to BCVA in both groups.

Conclusions

Clear peripheral and central VF deficits exist in PwA and PwIIN, and static VF results need to be interpreted with caution clinically. Since PwA exhibit considerably lower detection thresholds compared to PwIIN, VF defects are unlikely to be due to nystagmus in PwA. In addition to horizontal VF asymmetry, PwA exhibit both vertical and interocular asymmetries, which needs further exploration.

Phenotypic Features Determining Visual Acuity in Albinism and the Role of Amblyogenic Factors

Albinism is a spectrum disorder causing foveal hypoplasia, nystagmus, and hypopigmentation of the iris and fundus along with other visual deficits, which can all impact vision. Albinism is also associated with amblyogenic factors which could affect monocular visual acuity. The foveal appearance in albinism can range from mild foveal hypoplasia to that which is indistinguishable from the peripheral retina. The appearance can be quickly and easily graded using the Leicester Grading System in the clinic. However, interquartile ranges of 0.3 logMAR for the grades associated with albinism limit the accuracy of the grading system in predicting vision. Here, we discuss the potential role of nystagmus presenting evidence that it may not be a major source of variability in the prediction of visual acuity. We also show that interocular differences in visual acuity are low in albinism despite high levels of amblyogenic factors indicating that active suppression of vision in one eye in albinism is uncommon.

Adaptive optics imaging in inherited retinal diseases: A scoping review of the clinical literature

Adaptive optics (AO) imaging enables direct, objective assessments of retinal cells. Applications of AO show great promise in advancing our understanding of the etiology of inherited retinal disease (IRDs) and discovering new imaging biomarkers. This scoping review systematically identifies and summarizes clinical studies evaluating AO imaging in IRDs. Ovid MEDLINE and EMBASE were searched on February 6, 2023. Studies describing AO imaging in monogenic IRDs were included. Study screening and data extraction were performed by 2 reviewers independently. This review presents (1) a broad overview of the dominant areas of research; (2) a summary of IRD characteristics revealed by AO imaging; and (3) a discussion of methodological considerations relating to AO imaging in IRDs. From 140 studies with AO outcomes, including 2 following subretinal gene therapy treatments, 75% included fewer than 10 participants with AO imaging data. Of 100 studies that included participants' genetic diagnoses, the most common IRD genes with AO outcomes are CNGA3, CNGB3, CHM, USH2A, and ABCA4. Confocal reflectance AO scanning laser ophthalmoscopy was the most reported imaging modality, followed by flood-illuminated AO and split-detector AO. The most common outcome was cone density, reported quantitatively in 56% of studies. Future research areas include guidelines to reduce variability in the reporting of AO methodology and a focus on functional AO techniques to guide the development of therapeutic interventions.

Comparison of the effects of psoriasis and vitiligo on retina pigment epithelium thickness

PURPOSE

The purpose of the study was to compare Retinal Pigment Epithelium (RPE) thickness in patients with Psoriasis and Vitiligo.

MATERIALS AND METHODS

The right eyes of 67 Psoriasis and 65 Vitiligo patients and 71 healthy individuals were included in the study. The RPE thicknesses were analyzed with the Spectral Domain Optical Coherence Tomography after routine ophthalmological examinations (SD-OCT).

RESULTS

No statistically significant differences were detected when Psoriasis and Vitiligo patients were compared in terms of RPE levels (p= 0.033). When compared with the control group, no significant differences were found with Psoriasis patients, but a significant difference was detected with Vitiligo patients (p=0.515, p=0.001, respectively).

CONCLUSION

Although no changes were detected in RPE in Psoriasis, the decreased RPE thickness in Vitiligo may be an indicator of the effect of melanin loss on the posterior segment of the eye in Vitiligo. For this reason, measurement of RPE thickness with OCT can help in detecting the damage in Vitiligo patients.

Structural, Microvascular, and Functional Findings Associated with Fovea Plana

PURPOSE

To analyse structural (OCT), microvascular (OCTA), and functional changes (BCVA, mfERG) associated with fovea plana and to compare it to healthy controls.

METHODS

A retrospective observational study was performed on 13 patients (26 eyes; aged 34.46 y ± 20.26) with a clinical picture of fovea plana and 15 controls (30 eyes; aged: 41.47 y ± 14.03).

RESULTS

In fovea plana, BCVA ranged from 0.25 to 1.0, with a spherical error of - 5.5 to + 18.0 dpt. Posterior segment changes included elevated papillomacular retinal fold, uveal effusion syndrome, crowded optic discs, and hypopigmented fundus. OCTA imaging of the superficial (FAZ-S), intermediate (FAZ-I), and deep foveal avascular zone (FAZ-D) confirmed absence of foveal avascular zone (FAZ-S in 13 eyes, FAZ-I in 21 eyes, and FAZ-D in 10 eyes). Fovea plana patients had a significantly smaller FAZ-S, FAZ-I, and FAZ-D than controls (p < 0.001). Within the fovea plana group, a smaller FAZ-S correlated with reduced BCVA (p = 0.004) and with reduced mfERGs in zones 1 and 2 (p = 0.001 and p = 0.017). Also, a smaller FAZ-D showed positive correlations with the mfERG, with statistically significant values in zones 1 and 2 (p = 0.003 and p = 0.017).

CONCLUSION

In conclusion, our results confirm an altered structural, microvascular, and functional pattern in patients with a clinical picture of fovea plana. As documented by the functional microvascular interactions in our study, the developmental arrest in foveation reflects the functional maturation by means of visual acuity and central retinal function.