A recent study examined the visual outcomes and vascular changes associated with macular capillary nonperfusion in eyes with stable laser-treated proliferative diabetic retinopathy. According to the findings, vascular density and foveal avascular zone enlargement may have a role in guiding future trials aimed at preventing further vision loss from diabetic macular ischemia or macular capillary nonperfusion.
This prospective cohort study was conducted in the United Kingdom and included 63 participants (88 eyes) with stable proliferative diabetic retinopathy (PDR) treated with panretinal photocoagulation (PRP).
PRP is currently the most common treatment approach for PDR, the researchers explained in their JAMA Ophthalmology article. Clinical trials comparing intravitreal anti-vascular endothelial growth factor injections with PRP for PDR showed visual acuity stabilization in PRP arms up to 5 years. However, in real-world clinical settings, patients experienced a median decline of 9 letters on the Early Treatment Diabetic Retinopathy Study (ETDRS) chart 3 years after PRP. The study followed patients for 12 months to evaluate changes in visual function and vascular parameters.
Participants exhibited macular capillary nonperfusion (CNP) as detected by optical coherence tomography angiography (OCTA) and maintained best-corrected visual acuity (BCVA) of at least 54 ETDRS letters. Mean BCVA improved slightly from 77.52 letters at baseline to 78.76 letters at 12 months. Low-luminance visual acuity (LLVA) remained stable, increasing from 68.33 letters at baseline to 70.20 letters at 12 months. Seven participants (9.3%) lost five or more letters of BCVA over 12 months, suggesting vision loss was uncommon but clinically significant for a subset of patients. Eyes with baseline superficial vascular density (SVD) below 33.5% in the 3 × 3 mm scan were more likely to lose 5 or more letters compared to those with higher SVD. No significant changes were observed in deep vascular density or other OCTA metrics over the study period.
Foveal avascular zone (FAZ) area progressively increased over the study period, from 1.80% at six months to 2.26% at 12 months. This progressive enlargement indicated that FAZ area may be a sensitive measure for monitoring diabetic macular ischemia.
The researchers proposed FAZ area and SVD as reliable, objective endpoints for clinical trials aimed at understanding and managing macular CNP. Specifically, the square root transformation of FAZ area was recommended for analysis due to its independence from baseline FAZ size. However, BCVA was a better predictor of functional decline in macular CNP compared with LLVA, and vascular density metrics provided a more actionable measure for predicting visual function decline than FAZ changes alone. While BCVA and LLVA remained stable over 12 months in eyes with stable laser-treated PDR, a subset of patients may experience significant vision loss associated with decreased baseline vascular density for which FAZ enlargement may be a suitable objective measure to improve management strategies for diabetic macular ischemia.
The study’s multiethnic cohort enhanced the generalizability of findings, but applicability to advanced cases was limited because the investigators excluded participants with severe visual impairment. The researchers were also “unable to perform a multivariable analysis to assess the association between baseline OCTA metrics and vision loss.”
Still, the lower BCVA limit ensured that “included eyes had a potential to lose vision over the study period. As a result, approximately 85% had a BCVA letter score of 70 or higher, highlighting that a substantial proportion of patients with stable-treated PDR and macular CNP may still qualify to meet the driving requirements in most countries if their visual fields are not affected by PRP.”
“This study found that FAZ area continued to deteriorate overtime although both BCVA and LLVA remained relatively stable over 12 months,” the researchers concluded. Longer trials may be needed to observe changes of 5 letters or more.
A full list of author disclosures can be found in the published research