Reaching for the Periphery
Here's how you can use ultra-widefield imaging to improve patient care.
BY SCOTT C. N. OLIVER, MD
When I see a patient with ablative peripheral and macular laser, I know they have very few options left (Figure 1). Sadly, untreated peripheral disease still may be causing vitreous hemorrhage or macular edema, but peripheral problem areas have remained undetected using conventional angiography.
Figure 1. Widefield angiography reveals ablative peripheral and macular laser.
There is an alternative to this scenario. Using ultra-widefield imaging, we can locate active retinal vascular disease and apply the laser in precisely the right location. Here, I will discuss how we are using the wide-angle approach to improve diagnosis and monitoring at UCLA.
WHY A WIDER VIEW?
Conventional angiography offers a view of only 30° of the retina.1 With widefield technology, we put a virtual focal point in the iris plane, allowing us to image 200° of the retina2 in a quarter-second (Figure 2).
Figure 2. With widefield technology, a virtual focal point is placed in the iris plane, allowing the capture of 200° of the retina in a quarter-second.
Using this device, our practice has examined 264 eyes in 143 diabetes patients. The images were graded for macular edema (focal, 31%; diffuse, 26%), neovascularization (posterior, 30%; anterior, 19%), nonperfusion (macular, 11%; peripheral, 54%) and late peripheral vessel leakage (41%) (Figure 3).
Figure 3. Peripheral vascular abnormalities are detected using widefield angiography in diabetic retinopathy.
Our analysis showed a strong statistical correlation between peripheral nonperfusion and neovascularization. This correlation held up for both anterior and posterior neovascularization and was consistent with past work by Shimizu and colleagues.3 Not surprisingly, we also found a very strong statistical correlation between macular ischemia and peripheral nonperfusion. Peripheral vessel leakage (PVL) also correlated strongly with neovascularization.
Macular edema is a bit more complicated than neovascularization, because endothelial cell damage, VEGF upregulation and traction all play a role. We hypothesized that active peripheral disease may drive macular edema.
A direct statistical correlation between peripheral nonperfusion or peripheral vessel leakage and macular edema was not present. However, in a subset of 186 nonproliferative patients without prior laser, there was a trend associating macular edema with peripheral nonperfusion.
Further, we noticed about 7% of patients with nonperfusion had no other disease activity, while less than 3% of patients with PVL had otherwise inactive disease. We thought PVL may be a stronger driver of macular edema than nonperfusion. We found that a strong statistical correlation exists between PVL with macular edema, when peripheral nonperfusion is excluded. That led us to consider using therapy to target PVL in the setting of macular edema.
GRADING RETINAL VEIN OCCLUSIONS
We also used ultra-widefield FA technology to grade 76 branch retinal vein occlusions (BRVO) and hemi-central retinal vein occlusions (HRVO) (Figure 4).
Figure 4. Ultra-widefield technology is used to grade branch retinal vein occlusions and hemi-central retinal vein occlusions.
A few interesting trends emerged. The first related to a challenge we all face — eyes that continue to bleed after heavy posterior laser treatment. Why do they continue to hemorrhage? Often, it is because of untreated nonperfusion in the periphery (Figure 5).
Figure 5. This widefield image reveals untreated peripheral nonperfusion in a branch retinal vein occlusion.
When we compared nonperfusion with neovascularization, we discovered a strong statistical correlation among BRVOs. Interestingly, the association between peripheral nonperfusion and cystoid macular edema for BRVOs was stronger than what we had seen previously in diabetes patients.4
Finally, we graded 44 central retinal vein occlusion (CRVO) patients. Very ischemic eyes also tended to have macular ischemia. Most significantly, peripheral vessel leakage in CRVOs strongly correlated with macular edema.
By using ultra-widefield fluorescein angiography, we can more effectively identify peripheral pathology in retinal vascular disease. At UCLA, we use this information to guide what we characterize as targeted retinal photocoagulation — TRP, instead of PRP. We try to spare healthy retinal tissue as much as possible. We find that we cannot target the diseased tissue unless we can obtain a precise view of it. The ultrawidefield technology provides the view we need to provide our patients with better care. RP
Dr. Oliver is an assistant professor in the department of ophthalmology at the Rocky Mountain Lions Eye Institute, University of Colorado Denver.