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Muneeswar Gupta Nittala, Zhihong Hu, Srinivas Sadda; Relationship between Dry Retinal Volume and Visual Acuity in Cystoid Macular Edema. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3628.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the relationship between a novel spectral domain optical coherence tomography (SD-OCT) parameter, the adjusted dry retinal volume, and visual acuity in subjects with cystoid macular edema (CME) associated with retinal vascular disease.
Ten eyes of 10 cases with CME associated with retinal vascular disease (either diabetic retinopathy or retinal vein occlusion), and 10 eyes of 10 normal controls were enrolled in this IRB-approved study. Cirrus SD-OCT volume scans (512x128) were obtained prior to and 6-12 months after anti-VEGF therapy. The borders of the neurosensory retina, nerve fiber layer (NFL), cystoid spaces was performed using previously-described grading software (3D-OCTOR). The NFL reflectivity was used to normalize the signal between all cases and controls. Summed normalized total retinal reflectivity was computed for all subjects. Using the normal eyes only, a ratio of retinal intensity per unit retinal thickness was generated. This ratio then used to compute corrected/adjusted dry retinal thickness and volume based on the total retinal intensity of the edematous eyes. The dry retinal thickness was correlated with visual acuity.
The mean ± SD age of the cohort was 66 ± 9.9 years and 30% were female. The mean best-corrected (log MAR) visual acuity at baseline was 0.53 ± 0.21 (Snellen ~ 20/60) and 0.44 ± 0.22 (Snellen ~ 20/50) at follow up. At baseline, the uncorrected (“wet”) total retinal volume was 12.22 ± 2.70 mm3 and the (FCS) thickness was 339.37 ± 74.92 µm. Although the reflectivity-adjusted “dry” total retinal volume (9.12 ± 1.59 mm3 ) and FCS thickness (372.72 ± 103.55 µm) were significantly smaller, it appeared they were still significantly higher than normal, suggesting that the adjustment was incomplete. Of note, hyperreflective features (lipid) were noted in the retina. Following treatment, both the uncorrected and dry retinal volumes decreased, though the uncorrected volume decreased by a greater magnitude (1.38 vs 0.96 mm3, p = <0.001). There was no significant correlation between uncorrected or dry retinal thickness/volume and visual acuity.
Adjustment of retinal thickness based on reflectivity equalization does not appear to fully correct for fluid infiltration of the neurosensory retina in the setting of edema. This is likely due to hyper-reflective confounders (lipid) which may have artificially increased the total reflectivity.
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