Posterior Segment Distortion in Ultra-Widefield Imaging Compared to Conventional Modalities.

Background and Objectives: To describe posterior segment distortions in Optos ultra-widefield images (Optos 200TX; Optos, Dunfermline, United Kingdom) compared to Topcon retinal camera images (Topcon, Tokyo, Japan) using optic disc dimensions and exploring a proposed method for correcting these distortions.
Patients and Methods: Comparative image analysis study on 20 eyes with color fundus images from Optos and Topcon. A model eye with vertical and horizontal grids imaged with Optos in the conventional position and rotated 90° was analyzed.
Results: Mean vertical-to-horizontal disc diameter ratios were 0.956 [95% CI, 0.919-0.993] for Optos and 1.083 [95% CI, 1.045-1.121] for Topcon (P < .001). This was 0.910 in the conventional position and 1.072 with the object rotated 90° for the model eye with Optos and 1.008 and 0.999, respectively, using Topcon. The average of the measurements taken using both images from Optos yielded a ratio of 0.987.
Conclusion: Optos incorporates a consistent horizontal stretch to images. Combining images taken at right angles reduces the distortion. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:644-651.].
(Copyright 2016, SLACK Incorporated.)