Abstract
Abstract: :
Purpose: Despite considerable advancement in understanding of retinitis pigmentosa (RP), information about the natural course of the disease and changes in visual field, visual acuity, and especially contrast sensitivity over time is limited. Moreover, recent data may be contaminated by the use of nutritional supplements and experimental treatments, assuming such treatments have some efficacy. Methods: The records of 835 cases of RP who were visited in Lions Vision Center, the Wilmer Eye Institute, between June 1952 and February 2004 were reviewed retrospectively (more than 98% of visits were done between1972 and 1996). Typical cases of RP who were followed up for at least two years were included. Maximum likelihood random effects models and generalized estimation equation models were used to analyze the data. Results: The data from 329 cases (mean age at first visit 33.5 years, follow–up duration range: 2–22.4 years), who met the inclusion criteria, were analyzed. X–linked, autosomal recessive, and autosomal dominant modes of inheritance were observed in 6.7%, 62.6%, 23.4%, respectively. Data on visual acuity, contrast sensitivity, and visual field were available in 299, 39, and 305 cases, respectively. The mean visual acuity reduction was 3.1% of the baseline per year (p–value<0.001) and this rate remained the same after adjusting for age. Increases in age and visual field loss were significant predictors of the mean logMAR reduction (p–values: 0.017 and 0.045, respectively). The data on contrast sensitivity showed a 2.4% reduction in log CS in a year (p–value<0.001). Age was the most significant predictor of mean log CS (p–value: 0.009). However, in the model including both age and visual field, none of them showed significant association with mean log CS. Annual reduction rate in mean visual field area was 13.9 % (p–value<0.001). Older ages, longer periods of follow–up, and younger age at which visual filed loss started were significant predictors of mean visual field area (all p–values<0.001). The mode of inheritance and the age at which night vision loss started was not significant in any of the models and the age at which visual field loss started was significant only in the model for visual field. Conclusions: Visual acuity, contrast sensitivity, and visual filed of patients with RP are deteriorated with rates of 3.1%, 2.4%, and 13.9% of the baseline values in each year. This is important for clinicians to determine the natural course of disease and for researchers to set the prior beliefs in designing the studies on RP and analysis of data, particularly model building and hypothesis testing.
Keywords: retinitis • visual acuity • visual fields