Abstract
Purpose: :
Several factors contributing to irreversible vision loss after radiation for uveal melanoma have been identified. These have included tumor size, presence of subretinal fluid, radiation dose to the optic nerve or macula and pre-existing vascular disease, specifically diabetes mellitus. In this study we evaluated whether retinal vessel caliber was associated with vision loss following radiation.
Methods: :
Database searches identified patients with uveal melanomas located within three millimeters of the optic disk or fovea and at least three years follow-up. Patients were then grouped into those who maintained 20/40 vision or better at least three years following treatment and those whose vision became 20/200 or worse. Patient data was collected from records and fundus photos of adequate quality for retinal vessel analysis were identified. Digital images were enhanced in Adobe Photoshop Elements software followed by manual vessel measurements in the NIH Imagej analysis software. Using the revised Parr-Hubbard formula, central retinal arteriolar(CRAE) and venular equivalents (CRVE) were calculated for each patient at several time points including pre-treatment, 3 years, and last visit. Means for each group were then compared. Patient visits with fundus images insufficient for vessel measurements were excluded.
Results: :
The mean CRAE and CRVE were 139±33 and 216±55 (n=23), 125±31 and 185 ±43 (n=21), and 115±24 and 181 ±43 microns (n=17) at pre-treatment, 3 year, and final follow-up visits in those with better than 20/40 vision. Mean follow-up was 120 months. In those with worse than 20/200 vision, the mean CRAE and CRVE were 124±18 and 199±21 (n=19), 104±18 and 160±28 (n=14), and 99±14 and 162±23 microns (n=9) at pre-treatment, 3 year, and final follow-up visits. Mean follow-up was 58 months. Between the pre-treatment and final visits, the mean CRAE and CRVE declined by 17.3% and 15.9% in the good vision group and 20.4% and 18.4% in the poor vision group. Confounding factors included tumors being closer to the disc and fovea and a higher mean radiation dose to the fovea in the poor vision group.
Conclusions: :
Retinal vessel analysis showed a decline in vessel caliber including CRAE and CRVE following radiation. Despite the mean age and rates of hypertension, diabetes, and ischemic vascular diseases being similar between groups, patients in the poor vision group showed smaller caliber vessels pre-treatment possibly offering a prognostic measure of post-treatment vision although numbers were small and further study may be warranted.
Keywords: tumors • melanoma • radiation therapy