Vitreous fluorophotometry in carriers of choroideremia and X-linked retinitis pigmentosa

Anatomical and functional correlates of cystic macular edema in retinitis pigmentosa

Cystoid macular edema (CME) is a major cause of central visual deterioration in retinitis pigmentosa. The exact reason for CME and its prognostic significance in this patient population is unknown. We seek to find clues to answer these questions by examining the anatomical correlations between retinal cysts and retinal morphometric parameters in a cohort of patients with retinitis pigmentosa and CME. For this reason, 103 patients (196 eyes) with untreated cystoid macular edema (CME) were identified from a pool of 578 genotyped patients with retinitis pigmentosa. Image analyses were conducted using three central horizontal OCT scans of these patients to calculate cross-sectional areas of the retinal nerve fiber layer, outer retinal, inner retinal, cysts, and total retinal areas. Lengths of the ellipsoid zone and outer limiting membrane were also measured. Best-fit curves were derived for analyzing the factors playing a role in the size of the retinal cysts and the patients’ visual acuity. Generalized Estimating Equation and multivariate linear regression analyses were conducted to determine the correlations between visual acuity, morphometric and clinical data, and the significant cyst size and visual acuity determinants. Twenty-five percent of the screened patients (103/578) had CME. Patients with autosomal dominant retinitis pigmentosa had the highest incidence of CME (43.6%, p<0.001) but also had the best visual acuity (20/34±20/30, p = 0.02). The total cyst area was 0.14±0.18 mm². Outer retinal area (B = 0.214; p = 0.008), age (B = -0.003; p<0.001) and retinal nerve fiber area (B = 0.411; p = 0.005) were main determinants of the (r = 0.44; p<0.001) cyst size. Cysts resolved with progressing retinal degeneration. Length of the intact ellipsoid zone (B = -5.16E-5; p<0.001), the inheritance pattern (B = 0.04; p = 0.028) and retinal nerve fiber area (B = 0.751; p<0.001) were the main determinants of visual acuity. In patients with retinitis pigmentosa and cystoid macular edema, retinal nerve fiber layer thickness is associated with decreasing visual acuity and cyst size. This finding suggests that intraretinal cysts may compress retinal axons and cause subsequent visual loss in retinitis pigmentosa.

Choroideremia: effect of age on visual acuity in patients and female carriers

BACKGROUND/AIMS

The extent and time course of vision loss in Choroideremia (CHM) is still unclear. We undertook this study to quantitate the change in visual acuity (VA) over time in order to gain a better understanding of the natural course of this retinal disorder.

METHODS

Corrected VA of 120 males with CHM and 53 female carriers were collected from 24 studies and/or case reports published between 1981 and 2010, as well as from data on 15 patients examined at the Cole Eye Institute (Cleveland Clinic). Cross-sectional and longitudinal analyses were used to investigate the relationship between VA and age, as well as the progression rate of VA with age, respectively. Age grouping effects were investigated using ANOVA.

RESULTS

The mean age of affected males was 36.6 ± 17.7 years. The mean logMAR VA was 0.35 ± 0.53. There was a significant 0.0072 decrease in logMAR VA per year (p = 1.22 × 10(-4)). There was a significant difference between VA of patients <50 years of age and those >50 years (0.27 ± 0.39 vs. 0.61 ± 0.81, p = 2.90 × 10(-5)). When we compared the rate of VA loss for patients <50 years vs. those >50 years, we also found a significant difference (0.01 ± 0.04 vs. 0.06 ± 0.08, p = 1.23 × 10(-2)). The average age of female carriers was 36.4 ± 17.7 years, with an average logMAR VA of 0.36 ± 0.6. There was no significant correlation between VA of female carriers and age (p = 0.12) with 46% of female carriers having a VA better than 20/20 at an average age of 33 years compared to 25% of affected males at 30 years.

CONCLUSION

In affected males with CHM, VA decreases very slowly until subjects reach 50 years of age, at which time the rate and extent of vision loss become significantly higher. Additionally, VA decreases more rapidly as individuals get older. In contradistinction to affected males, VA loss in female carriers is much milder.

Non-cell-autonomous photoreceptor degeneration in rds mutant mice mosaic for expression of a rescue transgene

The inherited retinal dystrophies represent a large and heterogenous group of hereditary neurodegenerations, for many of which, the molecular defect has been defined. However, the mechanism of cell death has not been determined for any form of retinal degeneration. The retinal degeneration slow (rds-/-) mutation of mice is associated with nondevelopment of photoreceptor outer segments and gradual death of photoreceptor cell bodies, attributed to the absence of the outer segment protein rds/peripherin. Here, we examined the effects of a transgene encoding normal rds/peripherin that had integrated into the X-chromosome in male and female rds-/- mutant retinas. In 2-month-old transgenic males and homozygous-transgenic females on rds-/-, we observed virtually complete rescue of both the outer segment nondevelopment and photoreceptor degeneration. In contrast, hemizygous-transgenic rds-/- female littermates showed patchy distributions of the transgene mRNA, by in situ hybridization analysis, and of photoreceptor cells that contain outer segments. This pattern is consistent with random inactivation of the X-chromosome and mosaic expression of the transgene. Surprisingly, we observed significant photoreceptor cell loss in both transgene-expressing and nonexpressing patches in hemizygous female retinas. These observations were supported by nuclease protection analysis, which showed notably lower than predicted levels of transgene mRNA in retinas from hemizygous females compared with male and homozygous female littermates. This phenotype suggests an important component of non-cell-autonomous photoreceptor death in rds-/- mutant mice. These results have significance to both the etiology and potential treatment of human inherited retinal degenerations.

Reduction of macular oedema by acetazolamide in patients with chronic iridocyclitis: a randomised prospective crossover study

Thirty patients with cystoid macular oedema secondary to chronic iridocyclitis were enrolled in a two period, prospective, randomised, double masked, crossover study that compared sustained release acetazolamide (500 mg twice a day) with a placebo to measure the effects on the reduction of cystoid macular oedema and improvement of visual acuity. All patients were treated for 1 month with either acetazolamide or placebo, received no treatment for 1 month, and were then treated for 1 month with the other medication. Statistically significant improvement in visual acuity was seen at 14 and 28 days in the treated patients. No improvement was seen when patients received placebo. Improved visual acuity was not associated with race or sex. However, younger patients (under age 55 years) were more likely to benefit from treatment. Results of vitreous fluorophotometry, obtained at baseline and 4 weeks, demonstrated an improvement in posterior vitreous penetration ratios and mid vitreous penetration ratios after treatment with acetazolamide but not with placebo.