Author: Nishaant Bhambra (Canada)
Co-authors: Carolina Francisconi, Samara Marafon, Natalia Figueiredo, Verena Juncal, Roxane Hilier, Rajeev Muni
To determine the frequency and significance of retinal displacement in patients after treatment by pneumatic retinopexy (PnR) and pars plana vitrectomy (PPV) using fundus autofluorescence images (FAFs).
83 FAFs from PnR patients and 74 FAF images from PPV patients were included from St. Michaels' Hospital (Toronto, Canada), Newcastle Eye Center (Newcastle, UK), and Hamilton Regional Eye Institute (Hamilton, Canada).
For each image, the location of the optic disk and fovea were determined using a machine learning model from Optos. From these values, we determined the location of Zone 1, a circle drawn from the optic disk, using the fovea as the center of the circle. Two graders then located points on retinal vasculature that matched retinal vessel printings (RVPs) on the FAFs within this Zone 1 region. These corresponding pairs of points were then drawn on the image and projected to a 3D using machine learning tools. From these coordinates on the 3D projection, we determined the horizontal, vertical, and diagonal displacements of the RVP to vessel in each FAF across the curvature of the eye. This provided us with a measurement of displacement of the retina after PPV or PnR that accounted for the three-dimensional curvature of the retina.
Patients treated by PPV (n=74) had significantly greater displacement within Zone 1 than those treated by PnR (n=83). 50% of PPV patients showed retinal displacement compared to 25.3% of PnR patients (p = 0.001). Among eyes with retinal displacement (n=58) there was a moderate correlation between the amplitude of maximum displacement across the 3D projection and aniseikonia (r=0.402; p=0.003), vertical metamorphopsia scores (r=0.313; p=0.02) and logMAR BCVA (r=0.376; p=0.004). Similarly, we found that there was a moderate correlation between the amplitude of displacement in Zone 1 and the following outcomes: aniseikonia (r=0.314; p=0.03) and BCVA (r=0.373; p=0.007). There was a weak correlation between amplitude of displacement in Zone 1 and vertical metamorphopsia (r=0.291; p=0.04).
This study developed a robust methodology to determine displacement across the three-dimensional curvature of the retina using RVPs from two-dimensional FAF images. Furthermore, our results using this methodology show a correlation between displacement of the retina and increased aniseikonia, increased vertical metamorphopsia, and decreased visual acuity.