The prognostic utility of the Silicone Study Classification System. Silicone Study Report 9. Silicone Study Group
J. Lean, S. P. Azen, P. F. Lopez, D. Qian, M. Y. Lai and B. McCuen
Doheny Eye Institute, University of Southern California, Los Angeles, USA.
OBJECTIVE: To evaluate the reproducibility and the prognostic utility of
the Retina Society and Silicone Study Classification Systems in eyes after
surgery for severe proliferative vitreoretinopathy (PVR). DESIGN: Subgroup
analysis of the Silicone Study--a randomized, multicentered, surgical
trial. SETTING: Community and university-based ophthalmology clinics.
MATERIALS: Three hundred forty eyes with preoperative and intraoperative
evaluations using both systems of grading PVR (reproducibility study), and
287 eyes with preoperative and intraoperative evaluations using both
systems of grading PVR and with a 24-month follow-up examination (prognosis
study). INTERVENTIONS: Vitrectomy for PVR with long-acting perfluoropropane
gas or silicone oil as the intraocular tamponade. OUTCOME MEASURES: Retinal
reattachment, visual acuity ( > or = 5/200), intraocular pressure,
corneal clarity, and the need for reoperation. RESULTS: The reproducibility
of the Silicone Study Classification System was 64% (type of contraction),
77% (number of clock hours), 67% (posterior PVR), 88% anterior and
posterior PVR), and 94% (anterior, posterior, and subretinal PVR). The
reproducibility of the Retina Society Classification System was 99%. Using
the Silicone Study Classification System, location of PVR predicted visual
acuity (P=.004, chi 2 test for trend) and hypotony (P=.03, chi 2 test for
trend). Using the Retina Society Classification System, the grade of PVR
predicted only visual acuity (P=.01, chi 2 test for trend). For eyes with
anterior and posterior PVR, there was a decreasing trend in successful
visual acuity outcome with increasing severity of PVR (from C-3 to D-3,
P=.02, chi 2 test for trend). CONCLUSIONS: Although the classification of
PVR using the Silicone Study classification System was not reproducible for
the type of contraction or for posterior PVR, identification of the
anteroposterior extent of the PVR was prognostic of visual acuity and
hypotony at 24 months. The joint knowledge of the location of PVR (using
the Silicone Study Classification System) and the tightness of the funnel
for retinas with 9 to 12 clock hours involved by fixed folds (using the
Retina Society Classification System) has prognostic utility for eyes with
anterior and posterior PVR.
