Abstract
Purpose :
The comparison of wide field eye fundus images (WFI) and functional tests is of great interest in a number of diseases of the retina. The purpose of this study was to evaluate a new technique for the comparison of WFI and wide field perimetry results (WFP).
Methods :
WFI and WFP are both projections on a plane surface of the retina which can be approximated to a spherical shape. However, the projection of a retinal scotoma is different in the stereographic projection used in WFI and in the azimuthal equidistant projection used for perimetry. This results in differences in the localization and quantification of scotoma.
In a first study, a simulation software was used to evaluate the errors produced by these two projection modes for the position, shape and surface area of a scotoma of circular shape and constant surface area on the retina.
In a second study, we evaluated on 7 clinical cases with peripheral alterations the benefit of converting the representation of the WFP to WFI coordinates to allow the comparison of Goldmann perimetry results obtained with the MonCvONE perimeter (Metrovision) with wide field eye fundus images imported from OPTOS. Superposition was obtained by matching the positions of the fovea and optic disk.
Results :
The following table summarizes the errors obtained with the two projection solutions.
When eccentricity to the fovea increases:
- measures of distances along meridians increase with WFI (+33% at 60d) and are constant with WFP,
- shapes of scotoma are preserved with WFI and become deformed with WFP (+21% at 60d)
- surface area is altered more significantly with WFI (+78%) than with WFP (+21%).
The following images show the results from a retinitis pigmentosa case with superposition of the eye fundus and Goldmann perimetry.
It shows that the discrepancy found with the WFP projection is corrected when using the WFI projection. The same is found for other cases when peripheral alterations are involved.
WFP projection WFI projection
Conclusions :
The new method allows the comparison of eye fundus images and perimetry results at large eccentricities (over 20 degrees) and this is important to avoid significant errors in the position and quantification of scotoma.
This is a 2021 ARVO Annual Meeting abstract.