Abstract
Purpose :
We showed (Transl Vis Sci Technol. 2020;9(8):27), in a 3-decade follow-up of a patient with Retinitis Pigmentosa (RP), that while the Retinal Blood Vessel Arborization (RBVA) seemed immutable at the optic nerve head (ONH), there were suggestions of vessel movements more peripherally, as the disease progressed. We aimed at further documenting this claim.
Methods :
Fundus photographs of patients (N=10) affected with a well-defined retinal degeneration were selected from our ERG databank. To be included, patients had to have at least 3 follow-up visits over a 5-year span at least. Fundus pictures were digitized (Epson Perfection v600 Photo Scanner) and processed (Adobe Photoshop) to extract the arterial and venous RBVAs. These RBVAs were compared intra-individually by overlapping the RBVAs of the 1st visit to next ones using retinal landmarks (i.e., ONH & fovea-macula). Movements were quantified using vessel overlap percentages and angular measurements of displacement at predetermined eccentricities. Results where then correlated with clinical tests such as: visual acuity (VA), visual fields (VFs) and electroretinography (ERG). Standardization of the RBVA method was tested on 18 normal subjects.
Results :
The control group had a mean RBVA-overlap value (measures repeated at a 5-week interval) of 96.5±1.1%. In patients, the overlap % at each follow-up visits were always significantly smaller than normal (p<.05) and the overlap gradually decreased as the retinal degeneration progressed. As a rule, angular displacements (direction and speed of displacement) were not significantly different between arteries and veins (p>.05). Comparing the displacement of the RBVA (overlap % and angular displacement) with other signs of disease progression we noticed a strong correlation with the VF changes (mostly constriction) and ERG measurements [rod and cone b-waves amplitude and Hölder exponent (a Time-Frequency Domain descriptor of the ERG)]. No correlations could be obtained with the VA.
Conclusions :
Our study clearly demonstrates that movements of the RBVA is a measurable clinical sign of a progression in retinal degenerative disorders similar to visual field constrictions and ERG attenuations. It remains to be determined if this new diagnostic sign could detect the onset of a retinal degenerative process at an earlier time, a finding that could be helpful in pedigree studies and genetic counseling.
This is a 2021 ARVO Annual Meeting abstract.