Differences in contributory factors among hemicentral, central, and branch retinal vein occlusions.
Hemicentral retinal vein occlusion (HRVO) is an anatomic variant of central retinal vein occlusion (CRVO) and thus different from branch retinal vein occlusion (BRVO). Therefore, the risk factors for HRVO should be similar to those of CRVO and different from those of BRVO. To test this, the authors compared 15 demographic and clinical variables of 28 HRVO patients with those of 117 CRVO and 214 BRVO patients. Mean age of onset and sex ratio were not significantly different among the groups. Elevated erythrocyte sedimentation rate (ESR) (P = 0.019) and elevated intraocular pressure (IOP) (P = 0.025) were significantly more prevalent in the HRVO than the BRVO group. In addition, when the authors compared CRVO with BRVO, elevated ESR (P = 0.003), elevated IOP (P = 0.015), and positive purified protein derivative (PPD) (P = 0.003) were significantly more prevalent in the CRVO than the BRVO group, whereas hypertension (P = 0.03) and hyperopia (P = 0.008) were significantly more prevalent in the BRVO group. However, of the variables tested between HRVO and CRVO patients, no significant differences were found.