Abstract
Abstract: :
Purpose: To study the effect of lens opacities on the measurement of retinal nerve fibre layer thickness (RNFL) using optical coherence tomography (OCT) – 3. Methods: Design: Prospective non randomised observational study. Study population: 22 eyes of 22 patients undergoing planned phacoemulsification cataract surgery and meeting the following criteria: absence of any pre existing retinal or optic nerve pathology which can influence the RNFL thickness, absence of any other media opacities and uneventful surgical outcome. Procedure: The classification and grading of cataract was done using Lens Opacities Classification System III (LOCS III). The eye was scanned before the cataract surgery with OCT using Fast RNFL programme. All eyes had circular scans around optic disc with a diameter of 3.4 mm. The OCT scan was again repeated 4 weeks after surgery when the patients returned for post operative check. Main outcome measures: Mean RNFL thickness and signal:noise ratio (SNR) with respect to the type of cataract. Results: The mean pre operative RNFL thickness was 86.8+13.7. The post operative mean RNFL thickness was 96.0+12.5. The pre and post operative SNR was 33.3 and 38.8 respectively. The difference between pre and post operative values of mean RNFL and SNR are statistically significant (P<0.001). The change in mean RNFL thickness was significant in nuclear and posterior subcapsular cataract category. Conclusions: The results indicate that lens opacities influence the RNFL thickness measurement using OCT. The OCT tends to underestimate the RNFL thickness in the presence of lens opacities.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • cataract • nerve fiber layer