Effect of Media Opacity on Retinal Nerve Fiber Layer Thickness Measurements by Optical Coherence Tomography

Purpose: to assess the effect of ocular media opacity on retinal nerve fiber layer(rnfl) thickness measurements by optical coherence tomography (oct).methods: in this prospective, non-randomized clinical study, ocular examinationsand oct measurements were performed on 77 cataract patients, 80 laser refractivesurgery patients and 90 patients whose signal strength on oct was different on twoconsecutive measurements. none of the eyes had preexisting retinal or optic nervepathology, including glaucoma. cataracts were classified according to the lensopacity classification system iii (locs iii). all eyes were scanned with the stratusoct using the fast rnfl program before and three months after surgery. internalfixation was used during scanning and all eyes underwent circular scans around theoptic disc with a diameter of 3.4 mm.results: average rnfl thickness, quadrant thickness and signal strength significantlyincreased after cataract surgery (p<0.05). cortical and posterior subcapsular cataracts,but not nuclear cataracts, had a significant influence on rnfl thickness measurements(p<0.05). there was no significant difference between oct parameters before andafter laser refractive surgery. in eyes for which different signal strengths wereobserved, significantly larger rnfl thickness values were obtained on scans withhigher signal strengths.conclusion: oct parameters are affected by ocular media opacity because of changesin signal strength; cortical cataracts have the most significant effect followed byposterior subcapsular opacities. laser refractive procedures do not seem to affectoct parameters significantly.