Correlation Between CRA, Volume of SRF in NVAMD
A study shows CRA presence has a negative correlation with the volume of SRF.
Adel Ebraheem, MD, MS, post-doctorate research fellow, Doheny Eye Institute
Adel Ebraheem, MD, MS
A recent study demonstrated the relationship between the presence of a cilioretinal artery (CRA) and subretinal fluid (SRF) in eyes with treatment-naïve neovascular age-related macular degeneration (NVAMD).
Adel Ebraheem, MD, MS and the team from the Doheny Eye Institute in Los Angeles, Cali., and Department of Ophthalmology, David Geffen School of Medicine at UCLA, hypothesized that the presence of CRA could affect the extent of SRF by affecting the hemodynamics of blood flow supplying the choroidal neovascular membrane (CNV).
“Because the CRA redirects a percentage of blood volume from the outer retina to the inner retina, we hypothesize that the volume of SRF will be less in patients with a CRA than a control group,” Adel Ebraheem, MD, MS, post-doctorate research fellow, Doheny Eye Institute, told MD Magazine. “Age-related macular degeneration has several stages, 1 of them is the NVAMD stage in which subretinal fluid is a common finding.”
The CRA could potentially influence hemodynamics of flow to the macular choroid and the CNV. In some eyes, a CRA arises as a branch of the short ciliary artery and provides an additional blood supply to the macula.
“The cilioretinal artery is present in 20—35% of the total population, so we think it is very important to screen for the presence of this biomarker,” Ebraheem noted. “The most accurate method of diagnosing the presence of CRA is fluorescein angiography and since the patients who have CRA have less SRF volume, these patients should need a less number of anti-Vascular Endothelial Growth Factors (anti-VEGF) injections comparing to the control group.”
The study focused on 212 patients with treatment-naïve NVAMD in at least 1 eye from anonymized data available at the Doheny Eye Institute Reading Center.
Color fundus photos and fluorescein angiograms of the study eye were reviewed to identify eyes with CRA, or the cases, and eyes without CRA, the controls. Spectral-domain Optical Coherence Tomography (SD-OCT) data were evaluated by 2 masked graders to identify presence and volume of SRF.
The subtypes of CNV were identified, along with other OCT features that could affect SRF like the presence of subretinal hyperreflective material (SHRM), cystoid macular edema (CME) and pigment epithelial detachment (PED).
The non-parametric Mann-Whitney U test, univariate and multivariate analyses were performed to identify significant differences between cases and controls, evaluating the relationship between these factors and SRF volume.
Researchers identified 44 cases (subjects with CRA) and 168 controls (subjects without CRA) and among the 212 eyes studied, the mean SRF volume was significantly lower in cases when compared to controls.
A univariate regression analysis showed a weakly significant correlation between CRA presence and SRF volume while the multivariate analysis also demonstrated the presence of a CRA was correlated independently with the presence of SRF.
Even though the CRA presence was correlated negatively with the volume of SRF in eyes with nAMD, the findings may draw insights into the potential hemodynamic effect of CRA.
The researchers conducted another study finding that patients with a CRA had a larger area of macular atrophy (MA), less visual acuity and required fewer anti-VEGF injections compared to the control group. They think that patients fragile to the current anti-VEGF treatment protocol like monthly or PRN regimen and they need close monitoring and a special anti-VEGF injection regimen.
Recently, several clinical trials (CATT, IVAN, HARBOR), reported that MA can develop in a substantial number of eyes with NVAMD and treated with anti-VEGF injection. Interestingly in the trials, the presence of SRF was associated with a lower risk for the development of MA.
The study, “Relationship between the Presence of a Cilioretinal Artery and Subretinal Fluid in Neovascular Age-Related Macular Degeneration,” was published in Ophthalmology Retina.
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