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Cup-to-disc ratio, intraocular pressure, and primary open-angle glaucoma in retinal venous occlusion
1Eye & Vision Research Institute, Sydney, Australia.
Purpose:
To investigate the association of cup-to-disc ratio (CDR), intraocular pressure (IOP), and primary open-angle glaucoma (POAG) with the site of retinal venous occlusion (RVO) and optic nerve head swelling (ONHS).
Design:
Prospective observational case series.
Participants:
Four hundred fifty consecutive cases from a single tertiary referral center.
Methods:
Fundus photography of the retinopathy, 30 degrees stereo photography of the optic disc, and Goldmann applanation tonometry were the main parameters studied. The diagnosis of POAG was obtained from the referring ophthalmologist.
Main Outcome Measures:
The main outcome measures were the CDR, measured vertically through the center of the optic disc, and the site of RVO, identified as an arteriovenous (AV) crossing, optic cup, or optic nerve. Retinal venous occlusions occurring within the optic nerve were subdivided on the basis of the presence or absence of ONHS.
Results:
There were poor correlations between CDR and IOP (r = 0.18; P = 0.000209) and CDR and age (r = 0.21; P = 0.000012). There were 197 AV crossing-sited RVOs (AV-RVOs) (43.8%) and 46 optic cup (OC)-sited RVOs (10.2%). The remainder occurred within the optic nerve; the ONHS group had 80 cases (17.8%) and the nonoptic nerve head swelling group (NONHS) had 127 cases (28.2%). The OC-RVO group tended to be the oldest of the four groups, whereas the ONHS group was the youngest (P < 0.000001). The mean CDR was significantly higher in the OC-RVO (0.65) compared with the rest of the groups (0.45-0.48). The proportion of cases with CDR > or = 0.7 was significantly higher in the OC-RVO group (39.1%) compared with the rest of the groups (0-6.3%). There was a trend (P = 0.000012) for IOP in the OC-RVO group (19.0 mmHg) and NONHS group (17.6 mmHg); the proportion of cases with IOP more than 21 mmHg was also higher in these cases (P = 0.00033). The prevalence of POAG was highest (P < 0.000001) in the OC-RVO group (39.1%) followed by the NONHS group (18.1%), ONHS group (8.8%), and AV-RVO (4.1%) group, respectively.
Conclusions:
Optic cup and optic nerve-sited RVO without ONHS are associated with raised IOP and may share a common management strategy aimed at controlling ocular pressure. Glaucomatous optic disc cupping, in contrast, seems to be important in the OC-sited RVO group only. Intraocular pressure, POAG, and glaucomatous optic disc cupping do not significantly seem to contribute to the development of RVO at an AV crossing or when the occlusion occurs within the optic nerve in association with ONHS.