Comparisons of Effective Fields of Two Ultra-Widefield Ophthalmoscopes, Optos 200Tx and Clarus 500

Abstract

Purpose: To compare the effective fields of the Optos 200Tx® and Clarus 500™, two ultra-widefield ophthalmoscopes, based on their ability to image branches of retinal vessel in the four retinal quadrants.

Methods: Ninety retinal images from 90 patients with various eye diseases were studied. All patients had undergone 200° retinal imaging to obtain a single image of Optos (O) and the montage of two images of the Clarus (C). The highest number of traceable vessel branches in the four retinal quadrants was determined by two masked raters. An image was classified as "O > C" when the number of identifiable branch was greater in the Optos than the Clarus, as "O = C" when the number was equal and as "O < C" when the number was fewer in the Optos than the Clarus.

Results: The appearance probability of "O > C" was significantly higher at the upper temporal quadrant than "O < C" (p < 0.01 for both raters). In contrast, the appearance probability of "O < C" was significantly higher at the lower nasal quadrant than "O > C" (p < 0.01 for both raters). There were no significant differences in the appearance probability between "O > C" and "O < C" at the other two retinal quadrants (p > 0.50 for both raters).

Conclusions: These results demonstrate that the effective field of views was different between the two devices at different retina quadrants. Further studies are needed to clarify possible factors such as artifacts by the eyelashes, differences in the depth of focus, motion of the device, and different locations of the images on the effective field of views.

Conflict of interest statement

The authors declare that they have no conflicts of interest.

Copyright © 2019 Yoshitsugu Matsui et al.

Figures

Figure 1

Representative retinal images recorded with a viewing angle of 200° in the horizontal plane by the Optos 200Tx and Clarus 500; two ultra-widefield ophthalmoscopes, from the same patient (normal subject, 40-year-old man). A single image obtained by the Optos (a) and a montage image created by the two images of the Clarus (b) are shown. Magnified views of the area outlined by a dashed white line are shown in the right panels. We noted that the blood vessels of the peripheral retina appear to be more blurred in the Clarus image than the Optos image. Black arrows also indicate the center of the image.

Figure 2

An example of comparing the number of the highest identifiable vessel branches in the upper temporal quadrant, which was performed by Rater 1. The vessel branches are sequentially numbered starting from the optic disc. In this quadrant, the 16th branch of the vessel was the highest number of branches identified in the Optos image (a) whereas the 15th branch of the vessel was the highest number of branch in the Clarus image (b). At this upper temporal quadrant, this image was classified as “O > C” by Rater 1 because the highest number of vessel branches was larger in the Optos image than in the Clarus image.

Figure 3

Fundus images obtained by the Optos and Clarus devices of a 42-year-old man with Coats' disease that was evaluated by Rater 2. White arrows indicate the positions of the most peripheral branch identified on both devices. The asterisks indicate the branching positions more peripheral to the arrow in one device. In addition, the numbers indicate the branches identified beyond the most peripheral branch by the other device. In this case, three additional branches were identified in the upper temporal quadrant and an additional branch in the lower temporal quadrant pn the Optos image than the Clarus image. In contrast, when compared with the Optos image, an additional branch was identified in the upper nasal quadrant and two additional branches in the lower nasal quadrant in the Clarus image. Therefore, the upper temporal and lower temporal quadrants were classified as “O > C” and the superior nasal and inferior nasal quadrants as “O