between 20/20 and 20/30 without treatment, but an opposing study reported that in more severe nonischemic CRVO, only 4% of cases end with visual acuity of better than 20/100.47,77 Another study found that 50% of initially nonischemic CRVOs ended with visual acuity less than 20/200.112 This inconsistency may arise from the lack of agreement on deÞnitions of ischemic and nonischemic CRVO (see Chaps. 4 and 9). Poor visual acuity in nonischemic CRVO is associated with persistent macular edema, which is not the case in ischemic CRVO, where the problem instead is ganglion cell death in the inner retina.56

Inconsistency of results among different reports may also arise from differences in duration of nonischemic CRVO. For example, the sham arm of the CRUISE study provided natural history data on 130 eyes with mostly nonischemic CRVO.12 Duration of macular edema affected visual acuity outcome. Those eyes with duration less than 3 months experienced a mean gain of 1.1 lines of visual acuity at 6 months. Those eyes with duration greater than or equal to 3 months experienced a mean gain of 0.4 lines of vision.12

Apart from initial visual acuity, other baseline factors found to be independently predictive of Þnal visual prognosis in multiple regression analysis were male gender, a higher number of clinicalriskfactors(e.g.,hypertension,hyperlipidemia, diabetes, and primary open angle glaucoma), higher Þbrinogen level, and baseline severity of macular edema.23,39,56 A subnormal scotopic white ßash b wave amplitude and a scotopic white ßash b/a wave amplitude ratio less than 1.05 have been associated with poorer visual outcomes.39,97 Comorbidities of diabetes and stroke also increase the probability of visual acuity deterioration in patients with nonischemic CRVO and better initial visual acuity.56

For Þnal visual acuity outcome with follow-up of greater than or equal to 1 year, the implicit time for the ßicker fusion ERG, the initial visual acuity, and the presence of greater than 10 disc areas of capillary nonperfusion were all approximately equally strong predictors of a Þnal visual acuity less than 20/200 (kappas of 0.61, 0.60, and 0.58, respectively). Presence of optic disc edema has been reported to be a favorable prognostic

sign for visual acuity outcome in CRVO, but others have not conÞrmed its value.62

The annual risk of any vascular occlusion in the fellow eye of an eye with a CRVO is 0.9Ð5%.86,140 Vision-related quality of life is signiÞcantly lower in patients with CRVO than in a reference group of patients without ocular disease, roughly similar to those of patients with diabetic retinopathy, and does not correlate with the visual acuity in the eye with the CRVO. Instead the quality-of-life score correlates with the visual acuity in the better

of the two eyes which is usually the fellow eye.31

7.3Hemicentral Retinal Vein Occlusion

7.3.1 Clinical Signs

Hemispheric RVO is a synonym for HCRVO in some studies, but means a BRVO that involves half the retina in others, so care must be taken in reading the literature to distinguish the meanings. The fundus Þndings in the acute phase are the same in HCRVO as for CRVO, except that an uninvolved sector occurs in HCRVO that can vary in size from 25% to 66% of the fundus area depending on the region drained by the hemicentral retinal vein.52 Thus, for example, patchy ischemic retinal whitening occurs in HCRVO as it does in CRVO (Fig. 7.22). A branch retinal artery crosses over the hemicentral retinal vein in one-third of cases, evidence that HCRVO is unlike BRVO and like CRVO in pathogenesis.52 In a natural history study of 65 HCRVOs, 85% were nonischemic, a percentage similar to that in CRVO, and unlike the percentage in major BRVO, where the majority are ischemic.58 Macular edema deÞned by ßuorescein angiography is present in 75% of HCRVOs at the initial visit.52

The fundus Þndings in the chronic phase of HCRVO resemble those of CRVO with a few differences. Collateral vessels that develop in HCRVO and allow drainage of the involved hemiretinal venous system to the choroid, as in

Fig. 7.22 Images from a 66-year-old female with type 2 diabetes mellitus and hypertension who developed a paracentral scotoma inferior to Þxation in the right eye. Visual acuity was 20/25. (A) A superior hemicentral retinal vein occlusion is present with patchy ischemic retinal whitening (PIRW) (the black arrow). The zone of retinal transparency encroaches just past the superior edge of the horizontal raphe, presumably reßecting border oxygenation from the adjacent well-perfused inferior hemiretina. The amount of intraretinal hemorrhage does not parallel the distribution

of PIRW. In this case, the hemorrhages are densest in the peripapillary zone. (B) The early-phase ßuorescein angiogram shows delayed venous return in the superior hemiretina (vein at the yellow arrow, compare with vein at the red arrow) but good capillary perfusion. (C) The late-phase ßuorescein angiogram shows leakage of ßuorescein most prominent at the borders of the zone of PIRW (the green arrow). Fluorescein leakage is an inconsistent Þnding in PIRW and may be absent. (D) OCT shows a parafoveal cyst in the outer nuclear layer of the retina (the tan arrow)

CRVO, have been well described. But in HCRVO, collateral vessels also develop that drain venous blood from the obstructed venous circulation to the opposite unobstructed hemicentral retinal vein at the optic disc (Fig. 7.23).38,58 Retinal collateral vessels between involved and uninvolved sectors of the retina are seen, but some have claimed that these are less common in HCRVO than in major BRVO.48,52 In one study, development of disc collaterals did not correlate with resolution of macular edema.52

After HCRVO, neovascularization of the disc develops in 11Ð29% of cases, neovascularization of the retina in 9Ð14%, and ASNV in 9Ð36% over 12Ð21 months.52,121 The median time to NVE after HCRVO is greater than the time to NVD.52 Neovascular glaucoma develops in 3Ð7% of cases of HCRVO.52,121

In a study of 55 nonischemic HCRVOs followed for a median of 1.9 years, 9% developed an epiretinal membrane, 16% had foveal pigmentation, and 58% formed optic disc collaterals.58

Fig. 7.23 A 54-year-old male with treated hypertension and systemic lupus erythematosus developed an inferior HCRVO of the left eye. Visual acuity was 20/40. (A) Fundus photograph of the acute phase of the inferior hemicentral retinal vein occlusion. The inset shows a higher magniÞcation view of the optic disc. The inferior hemicentral vein is distended and does not communicate with the normal-caliber superior hemicentral retinal vein. (B) Frame from the mid-phase of the ßuorescein angiogram shows intact capillary perfusion in the posterior fundus. (C) Fundus photograph taken 1 year later. The hemorrhages have resolved and a large-caliber collateral vessel has developed between the inferior hemicentral and the superior hemicentral retinal vein (the yellow arrow, inset). This vessel was not present at presentation (com-

pare to panel A). An inspissated exudate remains (the black arrow). The inferior hemicentral retinal veins are no longer distended. (D) SD-OCT false-color map showing a broad area of thickened macula depicted as white (the brown arrow). (E) SD-OCT line scan showing from the OCT study of panel D showing macular cysts in the inner nuclear layer with thickening and more hyperreßective exudate with adjacent hyporeßective thickening of the outer nuclear layer. (F) Follow-up OCT false-color map 1 year after the scan of panel D shows resolution of the marked macular thickening but residual milder macular edema signiÞed by the red area. (G) Follow-up OCT line scan from the study of panel F showing resolution of the macular cysts but persistence of the inspissated exudate in the outer nuclear layer (the orange arrow)

7.3.2 Visual Acuity

Two independent studies of HCRVO comprising 147 patients reported similar distributions of visual acuity at the initial visit. The weighted average of the results showed that 33% of eyes had initial visual acuity of 20/40 or better, 46% had initial visual acuity of 20/50Ð20/200, and

21% had visual acuity of 20/200 or worse (Table 7.5).52,121 Initial visual acuity in patients with ischemic HCRVO is worse than in patients with nonischemic HCRVO (Table 7.5).52,121 In one study, there was a correlation of initial visual acuity with the percentage of affected retina judged to be nonperfused on ßuorescein angiography.52

The visual prognosis in untreated HCRVO was reported in a study of 39 cases followed on