North Carolina macular dystrophy (MCDR1) caused by a novel tandem duplication of the PRDM13 gene.

PURPOSE: To identify the underlying cause of disease in a large family with North Carolina macular dystrophy (NCMD). METHODS: A large four-generation family (RFS355) with an autosomal dominant form of NCMD was ascertained. Family members underwent comprehensive visual function evaluations. Blood or saliva from six affected family members and three unaffected spouses was collected and DNA tested for linkage to the MCDR1 locus on chromosome 6q12. Three affected family members and two unaffected spouses underwent whole exome sequencing (WES) and subsequently, custom capture of the linkage region followed by next-generation sequencing (NGS). Standard PCR and dideoxy sequencing were used to further characterize the mutation. RESULTS: Of the 12 eyes examined in six affected individuals, all but two had Gass grade 3 macular degeneration features. Large central excavation of the retinal and choroid layers, referred to as a macular caldera, was seen in an age-independent manner in the grade 3 eyes. The calderas are unique to affected individuals with MCDR1. Genome-wide linkage mapping and haplotype analysis of markers from the chromosome 6q region were consistent with linkage to the MCDR1 locus. Whole exome sequencing and custom-capture NGS failed to reveal any rare coding variants segregating with the phenotype. Analysis of the custom-capture NGS sequencing data for copy number variants uncovered a tandem duplication of approximately 60 kb on chromosome 6q. This region contains two genes, CCNC and PRDM13. The duplication creates a partial copy of CCNC and a complete copy of PRDM13. The duplication was found in all affected members of the family and is not present in any unaffected members. The duplication was not seen in 200 ethnically matched normal chromosomes. CONCLUSIONS: The cause of disease in the original family with MCDR1 and several others has been recently reported to be dysregulation of the PRDM13 gene, caused by either single base substitutions in a DNase 1 hypersensitive site upstream of the CCNC and PRDM13 genes or a tandem duplication of the PRDM13 gene. The duplication found in the RFS355 family is distinct from the previously reported duplication and provides additional support that dysregulation of PRDM13, not CCNC, is the cause of NCMD mapped to the MCDR1 locus.

Worldwide Argus II implantation: recommendations to optimize patient outcomes.

BACKGROUND: A position paper based on the collective experiences of Argus II Retinal Prosthesis System investigators to review strategies to optimize outcomes in patients with retinitis pigmentosa undergoing retinal prosthesis implantation. METHODS: Retinal surgeons, device programmers, and rehabilitation specialists from Europe, Canada, Middle East, and the United States were convened to the first international Argus II Investigator Meeting held in Ann Arbor, MI in March 2015. The recommendations from the collective experiences were collected. Factors associated with successful outcomes were determined. RESULTS: Factors leading to successful outcomes begin with appropriate patient selection, expectation counseling, and preoperative retinal assessment. Challenges to surgical implantation include presence of staphyloma and inadequate Tenon's capsule or conjunctiva. Modified surgical technique may reduce risks of complications such as hypotony and conjunctival erosion. Rehabilitation efforts and correlation with validated outcome measures following implantation are critical. CONCLUSIONS: Bringing together Argus II investigators allowed the identification of strategies to optimize patient outcomes. Establishing an on-line collaborative network will foster coordinated research efforts to advance outcome assessment and rehabilitation strategies.

Rates of decline in regions of the visual field defined by frequency-domain optical coherence tomography in patients with RPGR-mediated X-linked retinitis pigmentosa.

PURPOSE: To determine whether annual decline in visual field sensitivity is greater in the transition zone at the edge of the frequency-domain optical coherence tomography (fdOCT) inner segment ellipsoid zone (EZ) than at other locations in the visual field. DESIGN: Prospective, longitudinal, observational study. PARTICIPANTS: Forty-four patients with X-linked retinitis pigmentosa (XLRP) resulting from a mutation in the RPGR gene. METHODS: Static perimetric fields (Humphrey 30-2; Carl Zeiss Meditec, Dublin, CA) were obtained annually for 4 years. Beginning with year 2, fdOCT scans were obtained annually with a Heidelberg Spectralis HRA + OCT (Heidelberg Engineering, Heidelberg, Germany). MAIN OUTCOME MEASURES: The rate of visual field decline at locations near the edge of the EZ compared with the rates for the macula and in the mid periphery. RESULTS: Sensitivity just inside and outside the edge of the EZ declined at rates of 0.84 and 0.92 dB/year, respectively. By comparison, average sensitivity in the macula and mid periphery declined by 0.38 and 0.61 dB/year, respectively. CONCLUSIONS: The edge of the EZ in each patient with XLRP indicates a transition zone between relatively healthy and relatively degenerate retina. The annual loss of sensitivity in the transition zone is more rapid than it is elsewhere in the retina.

ApoER2 function in the establishment and maintenance of retinal synaptic connectivity.

The cellular and molecular mechanisms responsible for the development of inner retinal circuitry are poorly understood. Reelin and apolipoprotein E (apoE), ligands of apoE receptor 2 (ApoER2), are involved in retinal development and degeneration, respectively. Here we describe the function of ApoER2 in the developing and adult retina. ApoER2 expression was highest during postnatal inner retinal synaptic development and was considerably lower in the mature retina. Both during development and in the adult, ApoER2 was expressed by A-II amacrine cells. ApoER2 knock-out (KO) mice had rod bipolar morphogenic defects, altered A-II amacrine dendritic development, and impaired rod-driven retinal responses. The presence of an intact ApoER2 NPxY motif, necessary for binding Disabled-1 and transducing the Reelin signal, was also necessary for development of the rod bipolar pathway, while the alternatively spliced exon 19 was not. Mice deficient in another Reelin receptor, very low-density lipoprotein receptor (VLDLR), had normal rod bipolar morphology but altered A-II amacrine dendritic development. VLDLR KO mice also had reductions in oscillatory potentials and delayed synaptic response intervals. Interestingly, age-related reductions in rod and cone function were observed in both ApoER2 and VLDLR KOs. These results support a pivotal role for ApoER2 in the establishment and maintenance of normal retinal synaptic connectivity.

Rod photoreceptor temporal properties in retinitis pigmentosa.

One of the characteristic signs of retinitis pigmentosa (RP) is the progressive loss of night vision. We have previously shown that the gain of rod photoreceptor activation is moderately reduced in some patients with RP, but this decrease in activation kinetics is not sufficient to account for the night blindness. Recently, single rod recording from animal models of RP showed rods under degeneration remain saturated for shorter periods than normal rods; i.e. are less able to sustain the rod photoresponse. Using paired-flash ERG, here we determine whether rod phototransduction inactivation parameters might also be abnormal in patients with RP. Inactivation parameters were derived from 13 subjects with normal vision, 16 patients with adRP, and 16 patients with autosomal recessive/isolate (rec/iso) RP. The adRP cases included 9 patients with rhodopsin mutations and 7 patients with peripherin/RDS mutations. The inactivation phase was derived using a double-flash paradigm, with a test flash of 2.7 log scot td-s followed at varying intervals by a 4.2 log scot td-s probe flash. Derived rod photoresponses to this just-saturating test flash in normal subjects exhibit a critical time to the initiation of recovery (T(sat)) of 525 ± 90 (SD) ms. The values of T(sat) were 336 ± 104 (SD) ms in patients with adRP (P < 0.001) and 271 ± 45 (SD) ms (P < 0.001) in patients with rec/iso RP. When T(sat) values were categorized by mutations, the values were 294 ± 91 (SD) ms (P < 0.001) for rhodopsin mutations, and 389 ± 100 (SD) ms (p = 0.01) for peripherin/RDS mutations. Overall, T(sat) in patients with RP was significantly correlated with the amplitude of ISCEV standard rod response (r = 0.56; P < 0.001) and the gain of the activation phase of phototransduction (r = 0.6, P < 0.001). T(sat) may be a useful marker for therapeutic efficacy in future clinical trials in RP.

Macular atrophy in birdshot retinochoroidopathy: an optical coherence tomography and multifocal electroretinography analysis.

PURPOSE: The purpose of this study was to evaluate macular atrophy by frequency-domain optical coherence tomography (OCT) in patients with birdshot retinochoroidopathy and to compare the resulting thickness measures with visual acuity and multifocal electroretinography (mfERG). METHODS: Measures were obtained from 14 eyes of 7 patients with birdshot retinochoroidopathy and 23 normal eyes. Optical coherence tomography-3 measures of macular thinning were related to visual acuity, mfERG response density, and time since diagnosis. Horizontal midline frequency-domain OCT scans identified which layers of the retina were primarily responsible for macular thinning. RESULTS: All eyes with a history of birdshot retinochoroidopathy for >10 years had abnormal mfERG response densities. Compared with those without anatomic thinning (n = 8), eyes with anatomic thinning (n = 6) had significantly lower visual acuity (P = 0.0006), foveal response density (P = 0.006), and overall mfERG response density (P = 0.009). Segmentation of retinal layers on frequency-domain OCT scans showed that anatomic thinning was as a result of reduction in the receptor 1 layer (REC+), the thickness of the segment extending from the proximal border of the outer plexiform layer to the Bruch membrane-choroid interface. CONCLUSION: Macular atrophy, as reflected in OCT evidence of macular thinning and mfERG evidence of macular function, occurs in patients with long-standing birdshot retinochoroidopathy. Measures of retinal layer thicknesses by frequency-domain OCT suggest that the atrophy occurs primarily in the outer retina.

Application of a Deep Machine Learning Model for Automatic Measurement of EZ Width in SD-OCT Images of RP.

Purpose: We applied a deep convolutional neural network model for automatic identification of ellipsoid zone (EZ) in spectral domain optical coherence tomography B-scans of retinitis pigmentosa (RP). Methods: Midline B-scans having visible EZ from 220 patients with RP and 20 normal subjects were manually segmented for inner limiting membrane, inner nuclear layer, EZ, retinal pigment epithelium, and Bruch's membrane. A total of 2.87 million labeled image patches (33 × 33 pixels) extracted from 480 B-scans were used for training a convolutional neural network model implemented in MATLAB. B-scans from a separate group of 80 patients with RP were used for testing the model. A local connected area searching algorithm was developed to process the model output for reconstructing layer boundaries. Correlation and Bland-Altman analyses were conducted to compare EZ width measured by the model to those by manual segmentation. Results: The accuracy of the trained model to identify inner limiting membrane, inner nuclear layer, EZ, retinal pigment epithelium, and Bruch's membrane patches in the test dataset was 98%, 89%, 91%, 94%, and 96%, respectively. The EZ width measured by the model was highly correlated with that by two graders (r = 0.97; P < 0.0001). Bland-Altman analysis revealed a mean EZ width difference of 0.30 mm (coefficient of repeatability = 0.9 mm) between the model and the graders, comparable to the mean difference of 0.34mm (coefficient of repeatability = 0.8 mm) between two graders. Conclusions: The results demonstrated the capability of a deep machine learning-based method for automatic identification of EZ in RP, suggesting that the method can be used to quantify structural deficits in RP for detecting disease progression and for evaluating treatment effect. Translational Relevance: A deep machine learning model has the potential to replace humans for grading spectral domain optical coherence tomography images in RP.

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

Purpose: Dark-adapted visual fields were obtained from patients with inherited retinal degeneration (IRD) and controls to evaluate the effect that age, retinal region, and disease had on scotopic sensitivity. Intra- and intersession test-retest repeatabilities for patients and controls were measured to establish significant change for longitudinal studies. Methods: A total of 41 patients with IRD and 30 controls had one eye dilated and dark-adapted for 40 minutes. Scotopic sensitivity was measured with a Medmont dark-adapted chromatic (DAC) perimeter (size V stimulus, 200-ms duration, background luminance < 0.0001 cd/m2, dynamic range 0-75 decibel [dB]). Mixed effects analysis was performed to analyze age, retinal eccentricity, and sensitivity. The intra-/intersession coefficients of repeatability (CR) were calculated for controls and patients with IRD. Results: Each additional year was associated with lower sensitivity (-0.22 dB) per year in normal controls over age 50 compared to younger controls (12-49 years). The superior field had lower sensitivity than the inferior, but the nasal field was not different compared to the temporal field in normal controls. The CR for intra- and intersession testing on mean sensitivity (MS)/pointwise sensitivity (PWS) were ±1.5/±8.5 and ±3.3/±9.8 dB, respectively, for patients with IRD. Control MS/PWS CR were ±1.5/±6.1 dB for intrasession and ±1.7/±6.8 dB for intersession DAC perimetry. Conclusions: The DAC perimeter is an important asset because it tests a wide field of scotopic vision. The CR are comparable to those of other perimetry devices. Effects of age and retinal region should be considered when assessing scotopic sensitivity measured with the DAC perimeter.

The very large G-protein-coupled receptor VLGR1: a component of the ankle link complex required for the normal development of auditory hair bundles.

Sensory hair bundles in the inner ear are composed of stereocilia that can be interconnected by a variety of different link types, including tip links, horizontal top connectors, shaft connectors, and ankle links. The ankle link antigen is an epitope specifically associated with ankle links and the calycal processes of photoreceptors in chicks. Mass spectrometry and immunoblotting were used to identify this antigen as the avian ortholog of the very large G-protein-coupled receptor VLGR1, the product of the Usher syndrome USH2C (Mass1) locus. Like ankle links, Vlgr1 is expressed transiently around the base of developing hair bundles in mice. Ankle links fail to form in the cochleae of mice carrying a targeted mutation in Vlgr1 (Vlgr1/del7TM), and the bundles become disorganized just after birth. FM1-43 [N-(3-triethylammonium)propyl)-4-(4-(dibutylamino)styryl) pyridinium dibromide] dye loading and whole-cell recordings indicate mechanotransduction is impaired in cochlear, but not vestibular, hair cells of early postnatal Vlgr1/del7TM mutant mice. Auditory brainstem recordings and distortion product measurements indicate that these mice are severely deaf by the third week of life. Hair cells from the basal half of the cochlea are lost in 2-month-old Vlgr1/del7TM mice, and retinal function is mildly abnormal in aged mutants. Our results indicate that Vlgr1 is required for formation of the ankle link complex and the normal development of cochlear hair bundles.

Dark-Adapted Chromatic Perimetry for Measuring Rod Visual Fields in Patients with Retinitis Pigmentosa.

PURPOSE: Although rod photoreceptors are initially affected in retinitis pigmentosa (RP), the full-field of rod vision is not routinely characterized due to the unavailability of commercial devices detecting rod sensitivity. The purpose of this study was to quantify rod-mediated vision in the peripheral field from patients with RP using a new commercially available perimeter. METHODS: Participants had one eye dilated and dark-adapted for 45 minutes. A dark-adapted chromatic (DAC) perimeter tested 80 loci 144° horizontally and 72° vertically with cyan stimuli. The number of rod-mediated loci (RML) were analyzed based on normal cone sensitivity (method 1) and associated with full-field electroretinography (ERG) responses by Pearson's r correlation and linear regression. In a second cohort of patients with RP, RML were identified by two-color perimetry (cyan and red; method 2). The two methods for ascribing rod function were compared by Bland-Altman analysis. RESULTS: Method 1 RML were correlated with responses to the 0.01 cd.s/m2 flash (P < 0.001), while total sensitivity to the cyan stimulus showed correlation with responses to the 3.0 cd.s/m2 flash (P < 0.0001). Method 2 detected a mean of 10 additional RML compared to method 1. CONCLUSIONS: Scotopic fields measured with the DAC detected rod sensitivity across the full visual field, even in some patients who had nondetectable rod ERGs. Two-color perimetry is warranted when sensitivity to the cyan stimulus is reduced to ≤20 dB to get a true estimation of rod function. TRANSLATIONAL RELEVANCE: Many genetic forms of retinitis pigmentosa (RP) are caused by mutations in rod-specific genes. However, treatment trials for patients with RP have relied primarily on photopic (cone-mediated) tests as outcome measures because there are a limited number of available testing methods designed to evaluate rod function. Thus, efficient methods for quantifying rod-mediated vision are needed for the rapidly increasing numbers of clinical trials.

Reliability of a Manual Procedure for Marking the EZ Endpoint Location in Patients with Retinitis Pigmentosa.

PURPOSE: We developed and evaluated a training procedure for marking the endpoints of the ellipsoid zone (EZ), also known as the inner segment/outer segment (IS/OS) border, on frequency domain optical coherence tomography (fdOCT) scans from patients with retinitis pigmentosa (RP). METHODS: A manual for marking EZ endpoints was developed and used to train 2 inexperienced graders. After training, an experienced grader and the 2 trained graders marked the endpoints on fdOCT horizontal line scans through the macula from 45 patients with RP. They marked the endpoints on these same scans again 1 month later. RESULTS: Intragrader agreement was excellent. The intraclass correlation coefficient (ICC) was 0.99, the average difference of endpoint locations (19.6 µm) was close to 0 µm, and the 95% limits were between -284 and 323 µm, approximately ±1.1°. Intergrader agreement also was excellent. The ICC values were 0.98 (time 1) and 0.97 (time 2), the average difference among graders was close to zero, and the 95% limits of these differences was less than 350 µm, approximately 1.2°, for both test times. CONCLUSIONS: While automated algorithms are becoming increasingly accurate, EZ endpoints still have to be verified manually and corrected when necessary. With training, the inter- and intragrader agreement of manually marked endpoints is excellent. TRANSLATIONAL RELEVANCE: For clinical studies, the EZ endpoints can be marked by hand if a training procedure, including a manual, is used. The endpoint confidence intervals, well under ±2.0°, are considerably smaller than the 6° spacing for the typically used static visual field.

Phenotypic characterization of a large family with RP10 autosomal-dominant retinitis pigmentosa: an Asp226Asn mutation in the IMPDH1 gene.

PURPOSE: To evaluate the clinical features associated with the RP10 form of autosomal-dominant retinitis pigmentosa in 11 affected members of various ages from one family with a defined IMPDH1 mutation (Asp226Asn). DESIGN: Prospective, observational case series. METHODS: Visual function assessment included visual acuity, color vision, visual field, dark adaptometry, full-field electroretinography (ffERG), and multifocal electroretinography (mfERG). Ophthalmologic examinations, fundus photography, and optical coherence tomographic scans were also performed. Blood samples were obtained to screen for basic immune function. RESULTS: Visual acuity was slightly reduced in the teenage years and substantially reduced in association with cystoid macular edema (CME) at all ages. Color defects were observed in three patients (one teen, two adults). Dark-adapted thresholds were elevated. Visual fields were markedly constricted by age 40 (

Docosahexaenoic Acid Slows Visual Field Progression in X-Linked Retinitis Pigmentosa: Ancillary Outcomes of the DHAX Trial.

PURPOSE: Docosahexaenoic acid (DHA) was supplemented in a single-site, placebo-controlled, randomized clinical trial designed to slow vision loss associated with X-linked retinitis pigmentosa (XLRP); the DHAX Trial. We previously reported no significant differences between supplemented and placebo groups in intent-to-treat analysis of primary ERG outcomes. Assessed herein are hypothesis-generating measures of ancillary visual function outcomes in participants fully adhering to trial protocol. METHODS: Male participants with XLRP (range, 7-31 years) received 30 mg DHA/kg/d (n = 29) or placebo (n = 22) for 4 years. Visual outcomes were measured annually and red blood cell (RBC) DHA determined every 6 months. RESULTS: Oral DHA supplementation increased mean RBC-DHA levels by 4-fold (P < 0.0001) over placebo. No group differences in progression were found for visual acuity (P = 0.11), shape discrimination (P = 0.18), or fundus appearance (P = 0.70). Optical coherence tomography (OCT) became available during year 2 of the trial; no group differences were seen in ellipsoid zone constriction (P = 0.87) over 2 years. Yearly rates of progression were reduced for dark-adapted thresholds (P = 0.06) and visual field sensitivity for foveal, macular, peripheral, total, and ellipsoid zone regions by DHA supplementation (P = 0.039, P = 0.031, P < 0.0001, P < 0.0001, and P = 0.033). Rates of visual field sensitivity decline were dependent on RBC-DHA (P = 0.046 to <0.0001). CONCLUSIONS: Supplementation of DHA significantly elevated blood DHA levels and reduced the rate of progression in final dark-adapted thresholds and visual field sensitivity. From the relationship between RBC-DHA and the rate of field sensitivity loss, we can extrapolate that an RBC-DHA level of 17% could minimize the decline in field sensitivity. (ClinicalTrials.gov number, NCT00100230.)

Shape discrimination in age-related macular degeneration.

PURPOSE: Recent studies suggest that a global shape-discrimination task is sensitive to neural undersampling and/or irregular sampling, but is not affected by normal aging. In this study, the ability of patients with age-related macular degeneration (AMD) to perform the shape-discrimination task was examined. METHODS: Twenty patients with AMD (age range, 66-81 years) were selected on the basis of Snellen visual acuity of 20/50 or better in at least one eye and prior clinical documentation. A control group consisted of 10 older subjects (age range, 61-93 years) with normal findings in a fundus examination. Radial frequency (RF) patterns were used as stimuli. A spatial paradigm and a temporal two-alternative, forced-choice (2AFC) staircase paradigm were used. In each trial, two RF patterns (one deformed and one undeformed) were presented, and patients were asked to identify the deformed pattern. The peak spatial frequency of RF patterns was 5 cyc/deg; the radial modulation frequency was 8 cyc/360 degrees; mean radii were 0.5 degrees, 1 degrees, 2.0 degrees, or 2.5 degrees; and stimulus contrast was 80%. Thresholds for detecting the deformation were estimated by a maximum-likelihood fitting procedure. RESULTS: Thirty-five of 40 eyes with AMD had 20/50 or better acuity. Among them, 29 eyes had early AMD (drusen, hyperpigmentation, hypopigmentation), 5 had extrafoveal geographic atrophy, and 1 had exudative AMD. With the spatial 2AFC, 91% (32/35) of eyes with AMD showed significant elevation of the threshold for detecting radial deformation of RF patterns when compared with normal control eyes. With the temporal 2AFC, 97% (31/32) of eyes with AMD showed significant threshold elevations, and the degree of the deficit in the shape discrimination did not correlate significantly with visual acuity loss (r = 0.3, P = 0.094). Comparison of the severity of AMD with shape-discrimination performance revealed that the average detection threshold of the eyes with extrafoveal geographic atrophy was significantly higher than that of the eyes with drusen only (P < 0.01), even though average acuity showed no significant difference. CONCLUSIONS: Patients with AMD had significant deficits in performing the global shape-discrimination task. The dissociation of shape discrimination with visual acuity suggests that the shape-discrimination task may provide distinguishable information about the integrity of the photoreceptor mosaic in AMD.

Cone and rod ERG phototransduction parameters in retinitis pigmentosa.

PURPOSE: To analyze cone and rod phototransduction parameters from ERG a-waves in patients with RP and to determine the relationships among these parameters, age, and mode of inheritance. METHODS: Sets of four white flashes (3.2-4.4 log scotopic troland [scot td-s]) were presented in the dark. The same stimuli were later presented against a rod-saturating background and the generated cone a-waves were subtracted from the dark-adapted responses to produce rod-only a-waves. The rod-only and cone a-waves were fit with computational models. RESULTS: Of 418 consecutive patients with retinitis pigmentosa (RP), cone a-waves were quantifiable in 136 (33%), whereas rod a-waves were quantifiable in 125 (30%). Cone R(max) (maximum response) and cone S (sensitivity) parameters were significantly below normal in all RP subgroups. Cone R(max) was lower in XlRP than in other forms of inheritance (P < 0.05). Cone S was abnormal in 77.9% of all patients with RP and in 96.8% of those with XlRP. More than 95% of the rod R(max) values were abnormal, whereas rod S was abnormal in 61.6% of these patients. CONCLUSIONS: The efficiency of cone phototransduction appears to be affected in all forms of RP, even in some patients in whom the sensitivity of rod phototransduction is normal. In this cross-sectional sample, there was no evidence that transduction efficiency decreased with increasing age of the patient. The X-linked mode of inheritance is associated with greater abnormalities in cone and rod photoreceptor function at a younger age compared with the other modes of inheritance.

Quantitative electroretinogram measures of phototransduction in cone and rod photoreceptors: normal aging, progression with disease, and test-retest variability.

OBJECTIVES: To determine (1) reference values for cone and rod phototransduction variables derived from the a-wave of the electroretinogram, (2) their dependence on age, (3) the progression in cone and rod variables in patients with X-linked retinitis pigmentosa (XLRP), and (4) the test-retest variability in these a-wave measures compared with the variability in cone and rod b-wave measures. PARTICIPANTS: One hundred control subjects aged 5 to 75 years and 24 patients with XLRP aged 5 to 38 years. METHODS: High-intensity stimuli were used to elicit electroretinograms in the dark and in the presence of a rod-saturating background. Computer averaging and computer subtraction of cone components from mixed rod-cone responses were used to derive rod-only and cone a-waves. Rod and cone phototransduction variables were derived by computer fitting physiologically based computational models to the leading edges of a-wave ensembles. RESULTS: Phototransduction efficiency, as indexed by the sensitivity variable (S), decreased with age for cone and rod-only responses, whereas maximum cone and rod photoresponses (Rm(P3)) remained constant. In patients with XLRP tested annually for 4 years, Rm(P3) for rods and, to a lesser extent, cones declined with disease progression, whereas S remained stable. The test-retest variability in the a-wave Rm(P3) is lower than previously reported measures of the variability in b-wave peak-to-peak amplitude. CONCLUSION: The leading edge of the a-wave of the electroretinogram can be related to rod and cone phototransduction variables through quantitative models. Rm(P3), rather than S, should be the outcome measure of choice when using the a-wave to follow photoreceptor function in prospective studies and treatment trials.

Biological safety assessment of docosahexaenoic acid supplementation in a randomized clinical trial for X-linked retinitis pigmentosa.

BACKGROUND: In a 4-year placebo-controlled trial to elevate blood docosahexaenoic acid levels in patients with X-linked retinitis pigmentosa (XLRP), the goal was to assess the potential benefit of docosahexaenoic acid supplementation in altering disease progression. However, docosahexaenoic acid (22:6omega3) is a highly unsaturated fatty acid and considered a target molecule for free-radical oxidative damage. Thus, nutritional provision of docosahexaenoic acid might lead to an increase in antioxidant stress. Additional concerns, such as decreased platelet aggregation, increased bleeding time, and alterations in lipoprotein cholesterol levels, have been reported in supplementation studies with long-chain polyunsaturates. OBJECTIVE: To assess the biological safety of long-term docosahexaenoic acid supplementation. DESIGN: Forty-four male patients (mean age, 16 years) enrolled in a randomized, double-masked, clinical trial and received docosahexaenoic acid, 400 mg/d, or placebo. Blood samples were collected every 6 months. Biological safety analysis included fatty acids, vitamin A and E concentrations, antioxidant capacity, platelet aggregation, alanine aminotransferase activity, and lipoprotein cholesterol and triglyceride profiles. RESULTS: Mean plasma docosahexaenoic acid levels were elevated 2.5-fold by supplementation compared with baseline. Patients receiving placebo capsules exhibited no change (P =.35) in plasma docosahexaenoic acid content. All adverse events reported were minor and equivalently distributed between groups. Plasma vitamin A concentrations remained unchanged during the trial. Mean plasma vitamin E concentrations were correlated with age (P =.005), such that as patients with XLRP matured, plasma vitamin E concentrations increased to approach normal values. There was a trend (P =.10) toward lower mean vitamin E concentrations in the docosahexaenoic acid-supplemented group after 4 years. Docosahexaenoic acid supplementation did not compromise plasma antioxidant capacity, platelet aggregation, liver function enzyme activity, or plasma lipoprotein lipid content in patients with XLRP. CONCLUSION: Long-term docosahexaenoic acid supplementation to patients with XLRP was associated with no identifiable safety risks in this 4-year clinical trial.

A randomized, placebo-controlled clinical trial of docosahexaenoic acid supplementation for X-linked retinitis pigmentosa.

PURPOSE: Low docosahexaenoic acid (DHA) in X-linked retinitis pigmentosa (XLRP) may influence retinal function. The goals of this study were to elevate blood DHA levels and determine the effect on the rate of disease progression. DESIGN: In a 4-year prospective randomized clinical trial, male patients with XLRP (mean age = 16 years; range = 4-38 years) received DHA (400 mg/d; n = 23; +DHA group) or placebo (n = 21) capsules. METHODS: Red blood cell (RBC)-DHA concentrations were assessed every 6 months. Full-field cone electroretinograms (ERGs; the primary outcome measure), visual acuity, dark-adaptation, visual fields, rod ERGs, and fundus photos were recorded annually. RESULTS: In the +DHA group, RBC-DHA increased 2.5-fold over placebo levels (70 vs 28 mg DHA/l). Repeated measures analysis of variance for cone ERG showed a significant main effect of year (P <.0001) but not of group (P =.16). Preservation of cone ERG function correlated with RBC-DHA (P =.018), and there was less change in fundus appearance in the +DHA group (P =.04). Neither visual acuity nor visual fields were changed. In subset analysis, DHA supplementation was beneficial in reducing rod ERG functional loss in patients aged <12 years (P =.040) and preserving cone ERG function in patients > or =12 years (P =.038). CONCLUSIONS: Although DHA-supplemented patients had significantly elevated mean RBC-DHA levels, the rate of cone ERG functional loss was not significantly different between groups. Supplemental analyses provided evidence for a DHA benefit and a direction for subsequent investigations.