Clinical Phenotype and Course of PDE6A-Associated Retinitis Pigmentosa Disease, Characterized in Preparation for a Gene Supplementation Trial.

Importance: Treatment trials require sound knowledge on the natural course of disease. Objective: To assess clinical features, genetic findings, and genotype-phenotype correlations in patients with retinitis pigmentosa (RP) associated with biallelic sequence variations in the PDE6A gene in preparation for a gene supplementation trial. Design, Setting, and Participants: This prospective, longitudinal, observational cohort study was conducted from January 2001 to December 2019 in a single center (Centre for Ophthalmology of the University of Tübingen, Germany) with patients recruited multinationally from 12 collaborating European tertiary referral centers. Patients with retinitis pigmentosa, sequence variants in PDE6A, and the ability to provide informed consent were included. Exposures: Comprehensive ophthalmological examinations; validation of compound heterozygosity and biallelism by familial segregation analysis, allelic cloning, or assessment of next-generation sequencing-read data, where possible. Main Outcomes and Measures: Genetic findings and clinical features describing the entire cohort and comparing patients harboring the 2 most common disease-causing variants in a homozygous state (c.304C>A;p.(R102S) and c.998 + 1G>A;p.?). Results: Fifty-seven patients (32 female patients [56%]; mean [SD], 40 [14] years) from 44 families were included. All patients completed the study. Thirty patients were homozygous for disease-causing alleles. Twenty-seven patients were heterozygous for 2 different PDE6A variants each. The most frequently observed alleles were c.304C>A;p.(R102S), c.998 + 1G>A;p.?, and c.2053G>A;p.(V685M). The mean (SD) best-corrected visual acuity was 0.43 (0.48) logMAR (Snellen equivalent, 20/50). The median visual field area with object III4e was 660 square degrees (5th and 95th percentiles, 76 and 11 019 square degrees; 25th and 75th percentiles, 255 and 3923 square degrees). Dark-adapted and light-adapted full-field electroretinography showed no responses in 88 of 108 eyes (81.5%). Sixty-nine of 108 eyes (62.9%) showed additional findings on optical coherence tomography imaging (eg, cystoid macular edema or macular atrophy). The variant c.998 + 1G>A;p.? led to a more severe phenotype when compared with the variant c.304C>A;p.(R102S). Conclusions and Relevance: Seventeen of the PDE6A variants found in these patients appeared to be novel. Regarding the clinical findings, disease was highly symmetrical between the right and left eyes and visual impairment was mild or moderate in 90% of patients, providing a window of opportunity for gene therapy.

Influence of molecular weight on intracameral dextran movement to the posterior segment of the mouse eye.

PURPOSE: Uveoscleral outflow provides a potential pathway to the posterior segment for drug delivery. In this study, the influence of molecular weight on the intraocular distribution of dextran molecules after intracameral injection in the mouse eye was investigated. METHODS: The anterior chambers of the eyes of 64 anesthetized NIH Swiss mice were perfused with various fluorescent dextran solutions (10, 40, 70, and 500 kDa) at 500 nL/min for 10 minutes. At 10, 20, or 60 minutes after the initiation of the anterior chamber perfusion, the mice were killed and tissue obtained for evaluation by fluorescence microscopy. RESULTS: Each of the different molecular weight dextrans were visible in the anterior chamber of the mouse eye after the termination of the experiments. The 10-kDa dextran was observed in the supraciliary space and the supraciliary sclera after 10 minutes and in the anterior sclera after 60 minutes of perfusion. The 40-kDa dextran was detected in the supraciliary space and the anterior sclera after 10 minutes and in the anterior choroid and sclera after 20 and 60 minutes, but not in the posterior segment. The 70-kDa dextran was observed in the supraciliary space and anterior choroid after 10 minutes. After 20 minutes, it was visible in the equatorial choroid. After 60 minutes, it was observed in the posterior choroid. The 500-kDa dextran was observed in the supraciliary space and the anterior choroid after 10 minutes and in the supraciliary sclera at 20 minutes. At 60 minutes, 500-kDa dextran was observed in the equatorial choroid, but not farther toward the posterior. CONCLUSIONS: The influence of molecular weight on the redistribution of macromolecules from the anterior chamber to the posterior globe in the mouse eye appears to be similar to primate eyes. These similarities include passage of all size dextrans through the proximal uveoscleral pathway, the dependence of the extent of posterior movement on the size of the dextran, and the absence of large dextran entry into the distal uveoscleral pathway.

Fourier analysis of scanning laser polarimetry measurements with variable corneal compensation in glaucoma.

PURPOSE: To apply Fourier analysis to the retinal nerve fiber layer (RNFL) thickness measurements obtained with scanning laser polarimetry (SLP), by using variable corneal compensation, and to evaluate the ability of this method to discriminate glaucomatous from normal eyes. METHODS: The study included one eye each of 55 patients with glaucoma and 52 healthy subjects. RNFL thickness measurements were obtained with a modified commercial scanning laser polarimeter (GDx Nerve Fiber Analyzer; Laser Diagnostic Technologies, Inc., San Diego, CA) so that corneal birefringence could be corrected on a subject-specific variable basis. The shape of the RNFL thickness double-hump pattern was analyzed by Fourier analysis of polarimetry data. Fourier coefficients and GDx parameters were compared between the two groups. A linear discriminant function was developed to identify and combine the most useful Fourier coefficients to separate the two groups. Receiver operating characteristic (ROC) curves were obtained for each measurement, and sensitivity values (at fixed specificities) were calculated. RESULTS: The Fourier-based linear discriminant function (LDF Fourier) resulted in a sensitivity of 84% for a specificity set at 92%. For similar specificity, the GDx software-provided parameters had sensitivities ranging from 24% to 69%. The area under ROC curve for the LDF Fourier was 0.949, significantly larger than the ROC curve area for the single best GDx software-provided parameter, superior average (0.870). CONCLUSIONS: The combination of Fourier RNFL thickness measures in an LDF, obtained using SLP with variable corneal compensation, improved the ability to discriminate glaucomatous from healthy eyes, compared with the GDx software-provided parameters.

Visual function and perfusion of the optic nerve head after application of centrally acting calcium-channel blockers.

BACKGROUND: In a previous study it was shown that nimodipine 30 mg twice daily leads to an improvement in the visual field in a subgroup of normal-pressure glaucoma patients. To understand the mechanism of action of nimodipine on the visual system, the aim of this study was to examine the influence of nimodipine on different hemodynamic parameters and contrast sensitivity in healthy subjects. METHODS: Thirty-two healthy subjects (21-49 years old, mean age 28 years, 10 male, 22 female) received either nimodipine 30 mg twice a day or a placebo according to the same dosage regimen in a double-blind cross-over study design. The ocular blood flow was measured by means of the ocular blood flow system, the optic nerve head blood flow with the continuous laser Doppler flowmeter (Riva), and contrast sensitivity using the MCT 8000 Multivision Contrast Tester. Measurements were taken at baseline (1T0), 120 min after initial dose (1T3) and after 3 days (3T3) of therapy with 150 mg nimodipine or placebo in total. RESULTS: Contrast sensitivity improved significantly throughout almost all spatial frequencies in the nimodipine-treated subjects ( P=0.01), whereas there was no change in the placebo group. Ocular blood flow and optic nerve head blood flow increased slightly but not significantly in the nimodipine group (1T0: 706.6 microl/min, 9.33 AU; 3T3: 854.3 microl/min, 9.39 AU) and remained unchanged or were even lower in the placebo group ( P>0.05). CONCLUSION: The results showed a significant increase in contrast sensitivity during treatment with nimodipine in healthy subjects. This increase in visual function, however, was not correlated with an increase in ocular or optic nerve head blood flow. Therefore, another mechanism, e.g., a direct effect on the visual system, might be responsible for the improvement in visual function in healthy volunteers under nimodipine therapy.