A formula to predict spectral-domain OCT retinal nerve fiber layer measurements based on time-domain OCT measurements

Purpose To establish and validate a formula to predict spectral-domain optical coherence tomography (SD-OCT) retinal nerve fiber layer (RNFL) thickness from time-domain (TD)-OCT RNFL measurements and other factors. Methods From healthy participants and patients with glaucoma, SD-OCT and TD-OCT scans were obtained on the same day. Univariate and multivariate linear regression relationships were analyzed to convert Stratus TD-OCT measurements to Cirrus SD-OCT measurements. Other baseline characteristics included were age, gender, intraocular pressure, central corneal thickness, spherical equivalent, anterior chamber depth, optic disc area, visual field mean deviation, and pattern standard deviation. The formula was generated using a training set of 220 patients and then evaluated on a validation dataset of 105 patients. Results Univariate analysis determined that TD-OCT RNFL thickness, age, optic disc area, visual field mean deviation, and pattern standard deviation were significantly associated with SD-OCT RNFL thickness. Multivariate stepwise regression analysis using available variables yielded the following equation: SD-OCT RNFL = 0.746 × TD-OCT RNFL + 17.104 (R2 = 0.879). In the validation sample, the multiple regression model explained 85.6% of the variance in the SD-OCT RNFL thickness. Conclusion This formula based on TD-OCT RNFL thickness may be useful in predicting SD-OCT RNFL thickness. Other factors associated with SD-OCT RNFL thickness, such as age, disc area, and mean deviation, did not contribute to the accuracy of the final equation.