Table 2.
Silicone Study Classification (1989). This classification scheme included proliferative membranes in the preequatorial region and on the vitreous base (anterior PVR). Attention was paid to the quantitative assessment of PVR (number of clock hours of the retina involved by membranes). Minimal (grade A) and moderate (grade B) classifications remained unchanged, but grades C and D were replaced by grades P and A (posterior and anterior forms). Moreover, grades P and A were further defined by the presence of “types” of contraction. The extension of each grade was assessed by the number of clock hours of the involved retina. Modified from [10].
| Silicone Study Classification (1989) | |
|---|---|
| Grade and type | Clinical signs |
| A | Vitreous haze and pigment clumps |
|
| |
| B | Surface retinal wrinkling, rolled edges of the retinal, retinal stiffness, and vessel tortuosity |
|
| |
| P P1: 1 quadrant (1–3 clock hours) P2: 2 quadrants (4–6 clock hours) P3: 3 quadrants (7–9 clock hours) P4: 4 quadrants (10–12 clock hours) (i) Type 1 (focal) (ii) Type 2 (diffuse) (iii) Type 3 (subretinal) |
Starfolds and/or diffuse Contraction in posterior retina and/or subretinal membrane in posterior retina (i) Starfold (ii) Confluent irregular retinal folds in posterior retina; remainder of retina drawn posterior; optic disc that may not be visible (iii) “Napkin ring” around disc or “clothesline” elevation of retina |
|
| |
| A A1: 1 quadrant (1–3 clock hours) A2: 2 quadrants (4–6 clock hours) A3: 3 quadrants (7–9 clock hours) A4: 4 quadrants (10–12 clock hours) (i) Type 4 (circumferential) (ii) Type 5 (perpendicular) (iii) Type 6 (anterior) |
Circumferential and/or perpendicular and/or anterior traction in anterior retina (i) Irregular retinal folds in the anterior retina; series of radial folds more posteriorly; peripheral retina within vitreous base stretched inward (ii) Smooth circumferential fold of retina at insertion of posterior hyaloids (iii) Circumferential fold of retina at insertion of posterior hyaloids pulled forward; trough of peripheral retina anteriorly; ciliary processes stretched with possible hypotony; iris retracted |
Quadrants refer to the circumferential area of retina directly involved in contraction. One quadrant, 1–3 clock hours; two quadrants, 4–6 clock hours; three quadrants, 7–9 clock hours; and four quadrants, 10–12 clock hours. Clock hours need not necessarily be contiguous.