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PURPOSE To better understand the effects of retinitis pigmentosa (RP) on post-receptor anatomy, the thicknesses of the receptor, inner nuclear, retinal ganglion cell (RGC), and retinal nerve fiber layers (RNFL) were measured with frequency-domain optical coherence tomography (fdOCT). METHODS FdOCT scans were obtained from the horizontal midline in 30 patients with RP and 23 control subjects of comparable age. Raw images were exported and the thicknesses of photoreceptor/RPE, inner nuclear, RGC plus inner plexiform, and nerve fiber layers were measured with a manual segmentation procedure aided by a computer program. The RNFL thickness was also measured in 20 controls and 25 patients using circular peripapillary fdOCT scans. RESULTS Results from controls were consistent with known anatomy. In patients with RP, the pattern of photoreceptor loss with eccentricity was consistent with the field constriction characteristic of RP. INL and RGC layer measures were comparable to normal subjects, although some patients showed slightly thicker RGC layers. However, RNFL layer thickness was significantly greater than normal; a majority of patients showed a thicker RFNL on both horizontal midline scans and peripapillary scans. CONCLUSIONS To make optimal use of OCT RNFL thickness as a measure of the integrity of RGCs in patients with RP, a better understanding of the causes of the thickening seen in the majority of the patients is needed. As the RGC layer thickness can be measured with fdOCT, RGC layer thickness may turn out to be a more direct and valid indicator of the presence of RGCs in patients with RP.

IMPORTANCE Determining the annual rate of change in the width of the inner segment ellipsoid zone (EZ; ie, inner/outer segment border) in the context of short-term variability should allow us to better understand the value of this measure for future treatment trials in X-linked retinitis pigmentosa (XLRP).OBJECTIVES To identify the width of the central region showing an EZ and to determine the short-term repeat variability and the annual rate of change in the width of the EZ from spectral-domain optical coherence tomography (SD-OCT) measures in RP. DESIGN Patients with recessive or simplex RP (age range, 8-65 years; mean age, 40.5 years) underwent scanning twice on the same day to evaluate test-retest variability. Patients with XLRP (age range, 8-27 years; mean age, 15.2 years) from a larger group participating in an ongoing double-blind treatment trial (docosahexaenoic acid vs placebo; clinicaltrials.gov NCT00100230) underwent spectral-domain optical coherence tomography line scanning across the horizontal meridian at 3 yearly intervals. SETTING Research center specializing in medical retina. PARTICIPANTS Forty-eight patients with RP, including 20 with recessive or simplex RP and 28 with XLRP, and 23 healthy control subjects. MAIN OUTCOME AND MEASURE Widths of the EZ calculated and compared among the 3 annual visits.RESULTS Test-retest differences were normally distributed, and the magnitude of the difference was independent of mean EZ width. The mean (SD) for test-retest differences in EZ width was 0.08°(0.22°) (range, −0.30°to 0.60°). Thus, 95% of all test-retest differences fall within ±0.43°(124 μm). Of the 28 patients with XLRP, 27 showed a significant decrease in EZ width after 2 years. Patients with XLRP showed a mean annual decrease in EZ width of 0.86°(248 μm, or 7%). CONCLUSIONS AND RELEVANCEThe mean rate of decline in EZ width (7%) translates into a mean rate of change of 13% for the equivalent area of functioning retina. This rate of change is consistent with that reported for visual fields and full-field electroretinograms. Unlike visual fields and electroretinograms, however, the repeat variability is less than the annual rate of change. These results support the validity of EZ width as an outcome measure in prospective clinical trials in RP.

Macular degeneration is a heterogeneous group of disorders characterized by photoreceptor degeneration and atrophy of the retinal pigment epithelium (RPE) in the central retina. An autosomal dominant form of Stargardt macular degeneration (STGD) is caused by mutations in ELOVL4, which is predicted to encode an enzyme involved in the elongation of long-chain fatty acids. We generated transgenic mice expressing a mutant form of human ELOVL4 that causes STGD. In these mice, we show that accumulation by the RPE of undigested phagosomes and lipofuscin, including the fluorophore, 2-[2,6-dimethyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)-1E,3E,5E,7E-octatetraenyl]-1-(2-hyydroxyethyl)-4-[4-methyl-6-(2,6,6,-trimethyl-1-cyclohexen-1-yl)-1E,3E,5E-hexatrienyl]-pyridinium (A2E) is followed by RPE atrophy. Subsequently, photoreceptor degeneration occurs in the central retina in a pattern closely resembling that of human STGD and age-related macular degeneration. The ELOVL4 transgenic mice thus provide a good model for both STGD and dry age-related macular degeneration, and represent a valuable tool for studies on therapeutic intervention in these forms of blindness.phagosome ͉ Stargardt disease ͉ photoreceptor ͉ retinal pigment epithelium M acular degeneration involves the death of photoreceptor cells in the central retina, which is responsible for fine-detail vision. Age-related macular degeneration (AMD) affects Ϸ30% of people over the age of 75 (1, 2), and is becoming a greater health problem with the rapidly growing elderly population of developed countries. There is no treatment to halt or reverse the disease for the dry form, which comprises Ϸ90% of AMD cases. Moreover, there is a lack of suitable animal models for experimentation on therapies for dry AMD. Stargardt macular dystrophy (STGD) shares pathological features with AMD, except that it occurs at a young age. Both AMD and STGD are characterized by the accumulation of high levels of lipofuscin in the retinal pigment epithelium (RPE), which precedes degeneration of the photoreceptors in the macula and RPE atrophy.The gene responsible for an autosomal dominant form of STGD, STDG3, was identified recently as ELOVL4 (3, 4). It is predicted to encode an enzyme involved in the elongation of very long-chain fatty acids (hence the name, ELOVL), and is highly expressed in rod and cone photoreceptor cells (5, 6). Sequence analysis of human ELOVL4 cDNA predicts a protein of 314 aa that shares homology with members of the yeast Elo (elongation of long chain fatty acid) family and the human ELO1 homolog (HELO1) (3). HELO1 and the ELO family members possess biochemical features that suggest their participation in reduction reactions occurring during fatty acid elongation (7,8). Mutational analysis of the ELOVL4 gene in five large STGD-like macular dystrophy pedigrees revealed a 5-bp deletion, resulting in a frame-shift and the introduction of a stop codon, 51 codons from the end of the coding region (3). Subsequently, two 1-bp deletions, 789delT and 794delT, in ELOVL4 were identifi...