Quantitative comparisons of ultra-widefield images of model eye obtained with Optos ® 200Tx and Optos ® California

Abstract

Background: To compare the quality of the ultra-widefield images acquired by Optos® 200Tx to those acquired by Optos® California. Methods: Images of the posterior surface of a Gullstrand's model eye obtained by Optos® 200Tx were compared to those obtained by Optos® California in terms of the angular field of view and the symmetry of the image, i.e., vertical and horizontal aspect ratios at the center (0°) and at the periphery (40° and 80°) in each direction. In addition, we compared the enlargement of the image on the posterior surface as the square ratio, and the differences in the contrasts. Results: No significant differences were detected in the angular field of view between the two instruments. The aspect ratios showed that the Optos® California had more symmetrical images than the Optos® 200Tx at the center (0.98 vs 0.89, P < 0.01) and at the 40° periphery (0.93-1.04, Δ0.11 vs 0.79-1.01, Δ0.22) and 80° periphery (0.81-1.25, Δ0.44 vs 0.42-1.12, Δ0.70) in each direction. The amplitude of the square ratio of the Optos® California was smaller at 40° periphery (1.16-1.28, Δ0.12 vs 1.06-1.37, Δ0.31) and 80° periphery (2.12-2.46, Δ0.34 vs 1.14-3.29, Δ2.15). The contrast of the Optos® California images was significantly higher in the posterior pole (0.09 vs 0.12, P < 0.01), upper (0.07 vs 0.03, P < 0.01), and right (0.12 vs 0.07, P < 0.01) peripheries. Conclusion: Optos® California can record equal angular widefield images to Optos® 200Tx and more symmetrical images with higher contrast in the posterior pole, upper and right peripheries.