DEVELOPMENT OF A STANDARDIZED EVALUATION SYSTEM FOR POSTERIOR SUBCAPSULAR CATARACTS IN RETINITIS-PIGMENTOSA

Introduction: Retinitis pigmentosa (RP) is associated with the formati on of a posterior subcapsular cataract (PSC), As only a small part of the crystalline lens is usually affected, it is sometimes difficult to determine to what extent the visual loss is caused by the PSC alone. Patients and methods: The methodology was developed in analogy to a sc oring system for posterior capsule opacification by Tetz et al. Follow ing dilation of the pupil, standardized photographs of the anterior se gments were obtained utilizing a Zeiss photoslitlamp model 40 SL/P. Th e PSC was scored by evaluating retroillummation photographs,The indivi dual PSC index was calculated by multiplying the density of the opacif ication (graded from 0 to 4) by the area involved in the central 4 mm zone of the pupil(calculated between 0 and 1). For testing the reliabi lity of the evaluation system in part 1 of this study, 11 RP patients with different grades of PSC were examined by three independent observ ers,ln part 2 of this study 37 eyes of 24 RP patients, aged 47.2+/-11. 8 years, were evaluated and the PSC index was correlated with differen t parameters (visual acuity, age, visual fields, eletroretinography). Results: Part 1,The cataract-density grades were between 1 and 4 in th e 11 patients. In relation to the central 4-mm pupillary zone between 13 and 100% of the area were opacified. Cataract indices (densityxarea ) were between 0.13 and 4.0 (Mean values: Examiner 1:1.41+/-1.49; Exam iner 2: 1.28+/-1.46; Examiner 3:1.22+/-1.44; differences not significa nt: P=0.77). Parr 2, After an average duration of RP of 23 years, the average cataract index of the 24 patients was 1.72+/-1.35, There was n o correlation between cataract index and ERG or Visual fields (r<0.2; P>0.4); however, there was a good correlation to visual acuity (r = -0 .72; P = 0.0001). Patients with early onset of RP (before 20(th) year of life) presented on average with an higher cataract index (2.06+/-1. 67) compared to patients with late manifestation (0.61+/-0.44), but: e quivalent duration of RP. Conclusions: The evaluation system offers a reliable and reproducible method for measuring PSC density and extensi on in RP patients. The method can serve as a useful tool for documenti ng PSC development and help to define the indications for cataract sur gery in RP.