Straylight as an Indicator for Cataract Extraction in Patients with Retinal Dystrophy

PURPOSE: Straylight reduces retinal sensitivity, which is particularly relevant in conditions with retinal dysfunction, such as retinitis pigmentosa (RP). Retinitis pigmentosa is associated with posterior subcapsular cataract (PSC), a cataract type that is known to cause severe disability glare (i.e., straylight). Study purposes were (1) to determine the severity of disability glare before and after cataract extraction (CE) in subjects with retinal dystrophy; (2) to study possible aggravation of disability glare due to the combination of retinal degradation and increased straylight from PSC; and (3) to evaluate whether straylight can be used to support the possible benefit of (early) CE.

DESIGN: Prospective, comparative study.

PARTICIPANTS: Sixteen patients (25 eyes) with retinal dystrophy scheduled for CE participated.

METHODS: Cataract severity was graded according to the Lens Opacities Classification System (LOCS) III. Preoperatively and postoperatively, corrected distance visual acuity (CDVA), spatial contrast sensitivity with the Pelli-Robson chart, and straylight were tested. Retinal function was assessed with Goldmann visual field and temporal contrast sensitivity (TCS). Temporal contrast sensitivity is a flicker test to evaluate central retinal sensitivity isolated from the eye’s optical quality. Central retinal structure was assessed with spectral-domain OCT and fundus autofluorescence.

MAIN OUTCOME MEASURES: Preoperative and postoperative straylight were measured using the C-Quant (Oculus Optikgeräte GmbH, Wetzlar, Germany) and expressed as the logarithm of the straylight parameter s: log(s).

RESULTS: The average straylight value was 1.75 preoperatively and 1.45 postoperatively, 7.1 and 3.5 times higher than in a healthy young eye, respectively. Functionally significant improvement, defined as >0.20 log, was found in 72% of eyes for straylight and in 20% of eyes for CDVA. The CDVA and TCS were significantly correlated. Only straylight improvement was related to preoperative values; therefore, straylight was the only parameter that could be used to support postoperative improvement. In retinal dystrophy, eyes with cataract and a preoperative straylight value ≥1.66 log(s), a 50% chance of functionally significant log(s) improvement can be expected.

CONCLUSIONS: In patients with retinal dystrophy, straylight caused by cataract substantially aggravates visual disability, whereas CDVA is less affected. Therefore, straylight is a valuable (additional) indicator for beneficial CE in patients with retinal dystrophy and cataract.