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

Area of Science:

• Ophthalmology
• Medical Imaging
• Retinal Imaging Analysis

Background:

• Optos ultra-widefield imaging (Optos 200TX) and Topcon retinal cameras are used for posterior segment imaging.
• Posterior segment distortions in Optos images require characterization compared to Topcon images.

Purpose of the Study:

• To describe and quantify posterior segment distortions in Optos ultra-widefield images.
• To compare these distortions with Topcon retinal camera images using optic disc dimensions.
• To explore a method for correcting Optos image distortions.

Main Methods:

• A comparative image analysis of 20 eyes using color fundus images from Optos and Topcon retinal cameras.
• Analysis of a model eye with grids imaged using Optos in conventional and rotated positions.
• Calculation of vertical-to-horizontal optic disc diameter ratios.

Main Results:

• Optos images exhibited a mean vertical-to-horizontal disc diameter ratio of 0.956, significantly different from Topcon's 1.083 (P < .001).
• A model eye imaged with Optos showed ratios of 0.910 (conventional) and 1.072 (rotated 90°).
• The average ratio from combined Optos images (conventional and rotated) was 0.987.

Conclusions:

• Optos ultra-widefield images demonstrate a consistent horizontal stretch distortion.
• Combining Optos images acquired at right angles effectively reduces these observed distortions.
• This method offers a way to correct for posterior segment distortions in Optos imaging.