Effect of corneal polarization axi on aement of retinal nerve fiber layer thickne by canning laer polarimetry

PURPOE: canning laer polarimetry ue an anterior egment compenating device that aume a fixed axi of corneal birefringence, which we call the corneal polarization axi. The purpoe of thi invetigation wa to etablih the ditribution of corneal polarization axe among a population of normal eye and to evaluate the relationhip between corneal polarization axi and poterior egment retardation. METHOD: We contructed a noninvaive lit lamp–mounted device incorporating two croed linear polarizer and an optical retarder in order to meaure the low axi of corneal birefringence. Normal ubject underwent corneal polarization axi meaurement. A ubet of eye underwent canning laer polarimetry of the peripapillary retinal nerve fiber layer (n = 32) and macula (n = 29), and retardation meaurement were evaluated in each group. REULT: One hundred eighteen eye of 63 normal ubject (35 female, 28 male) underwent corneal polarization axi meaurement (mean age, 45.5 ± 17.1 year). ix eye (5.1%) demontrated unmeaurable corneal polarization. In the remaining 112 eye, the mode of the corneal polarization axi ditribution wa 10 to 20 degree naally downward (range, 90 degree naally downward to 54 degree naally upward). A ignificant (P < .0001) correlation wa oberved between fellow eye (R2 = .52), with a mean difference of 11.2 ± 10.5 degree (range, 0–52 degree). Corneal polarization axi wa ignificantly aociated (R2 = .52–.84) with retinal nerve fiber layer and macula ummary retardation parameter (average thickne, ellipe average, uperior and inferior average, uperior and total integral; P < .0001 for all group). CONCLUION: The mean corneal polarization axi among normal cornea i naally downward; however, coniderable intraindividual and interindividual variability exit. The linear relationhip between corneal polarization axi and poterior egment retardation parameter i reponible, in part, for the wide ditribution of retinal nerve fiber layer thickne data generated by canning laer polarimetry