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In evaluating posterior vitreous detachment (PVD), researchers suggest that the standard 6 mm optical coherence tomography (OCT) scan is approximately as useful as the wider 16.5 mm scan. In a study examining 157 eyes of retina clinic patients and 35 asymptomatic eyes, researchers were able to discern between complete vs partial PVDs with 91% sensitivity and 99% specificity based on standard 6 mm OCT scans — compared with reference scans taken with wider field 16.5 mm OCT.
Investigators who conducted this retrospective cross-sectional analysis found that, when using a staging classification system PVD stages were identically categorized using each sized scan in 138 eyes, indicating an 88% correlation in masked evaluation.
“When grading the scans, we assumed that if the posterior vitreous cortex was visible on the 6 mm scan, it was attached to the optic nerve just out of frame (stage 3),” the study authors explained. “This assumption was validated by our finding that all 16 eyes classified as stage 3 on 6 mm scans also were classified as stage 3 on 16.5 mm scans.”
Stage 4, or complete detachment, was inferred if both the posterior vitreous cortex and premacular bursa were absent in the image. Of 55 eyes identified in 6 mm scans as stage 4, 50 eyes were also categorized as stage 4 in 16.5 mm images.
Alternatively, stage 1 partial PVD was missed in 7 eyes. Investigators suggested that this is because PVD begins in the mid-periphery. They found no eyes displaying vitreoretinal separation in the macular region if the vitreous was attached at mid-periphery. Further, researchers analyzed 16.5 mm images of the unaffected eye of subjects with unilateral retinal conditions. All asymptomatic eyes with vitreoretinal separation at the macula also displayed some separation mid-periphery. Thus, 16.5 mm scans may be optimal to detect the earliest stage of PVD.
Participants in the comparative study were patients who visited the Froedtert & the Medical College of Wisconsin Eye Institute for routine monitoring — 36% with diabetic retinopathy, 45% with diverse retinal disorders, and 19% had no retinal disease. Their ages ranged from 10 years to 64 years, with a mean age of 50 years. Asymptomatic eyes examined included subjects from 9 years to 63 years old, mean age of 46 years. None of the subjects displayed stage 0 — no vitreoretinal separation in 16.5 mm scans. The results indicate that PVD may begin sooner than previously thought, as early as 11 years to 20 years of age in a retina clinic population.
Limitations of the study included that it did not compare OCT scans with ultrasound, and axial lengths were not measured.
“Our findings open the door for future retrospective investigations of PVD on databases of 6 mm scans to evaluate the correlation between PVD status and disease course in conditions such as diabetic retinopathy, retinal vein occlusion, and age-related macular degeneration,” researchers concluded.
Disclosure: Some of the study’s authors declared affiliations with the biotech and pharmaceutical industries. Please see the original reference for a full list of authors’ disclosures.
Reference
Kraker JA, Kim JE, Koller EC, George JC, Hwang ES. Standard 6-mm compared with widefield 16.5-mm oct for staging of posterior vitreous detachment. Ophthalmol Retina. 2020;4(11):1093-1102. doi: https://doi.org/10.1016/j.oret.2020.05.006.
