The retinal thickness analyzer (RTA) is a device in which a green 540-nm helium-neon laser slit is projected onto the retina and viewed at an angle through a slit lamp. The separation of reßections from the vitreoretinal interface and the chorioretinal interface is used to measure the retinal thickness. The laser is scanned to generate 10 optical cross sections 200 mm apart covering a 2 × 2-mm areas of the macula in 400 ms. The data are analyzed by a proprietary software algorithm. The RTA was used in cases of BRVO and CRVO to demonstrate areas of retinal thickening, cystoid spaces, and retinal hemorrhages and improvement in edema after interventions.24,30,66,90 Variability in Þxation with this machine in cases of severe macular edema was a problem that prevented quantitative longitudinal data collection.66 OCT accomplishes the same objectives with better resolution and reproducibility and has been adopted more widely.

8.4 Visual Field Testing

Visual Þeld testing using a Goldmann perimeter reveals defects in 100% of ischemic CRVOs and smaller percentages in nonischemic CRVOs depending on the size of the test object.39 Inability to see the I2e test object is reported to have 94Ð100% sensitivity and 67Ð78% speciÞcity to detect ischemic CRVO.39 Although over 35 years Hayreh has argued for the importance of visual Þeld testing in CRVO both for classifying it as ischemic or nonischemic and for assessing visual handicap, the test has not been adopted.40 The methods of grading Goldmann perimetry in CRVO are subjective and have not been replicated by others.38 Visual Þeld testing in BRVO shows arcuate scotomas, central scotomas, paracentral scotomas, and segmental peripheral constriction.8

Static perimetry has been used to demonstrate that krypton red grid laser treatment of macular edema associated with BRVO reduces retinal thresholds in concert with reductions in macular edema.58 Similarly, capillary nonperfusion correlates with decreased visual sensitivity, as assessed by static perimetry.6 Areas of capillary nonperfu-

sion in more recent-onset BRVO (average duration 11 months) correlated with relative scotomata on visual Þeld testing. However, in chronic BRVO (average duration 24 months), nonperfused areas correlated with absolute scotomata.59 Perimetry using the Humphrey 10Ð2 program has been performed in nonischemic BRVO with macular edema. Retinal sensitivity correlated with OCT-measured macular thickness at the fovea (r=−0.629) and 3¡ eccentric to the fovea (r=−0.885).45

Neither Goldmann nor static perimetry is routinely obtained in clinical care of patients with RVO. However, many patients with RVO have concomitant primary open-angle glaucoma for which serial visual Þelds are regularly obtained. The scotomata associated with the RVO can confound the interpretation of the visual Þeld and make it difÞcult to judge progression of glaucomatous damage.

Scanning laser perimetry identiÞes the functional threshold at identiÞable positions within the area of a retinal vein occlusion.5 An investigation of scotomata before and after grid laser for macular edema in BRVO showed variable results. In one-third of cases, the scotoma was closer to the fovea after grid laser than it was before; in onethird, its location was unchanged; and in one-third, the scotoma was located further from the fovea than before grid laser.5 Likewise, scotoma size was variably affected with 25% unchanged in size, 25% smaller, and 50% larger after grid laser.5

Microperimetry is a technique incorporating automatic perimetry and a fundus tracking system that allows presentation of the stimulus at a speciÞed fundus position.72 A fundus camera is part of the instrument, and the stimuli can be recorded on a photograph. Microperimetry is used as a method to assess Þxation location and stability, characteristics of visual function not assessed by checking visual acuity. It has been used to show that ME associated with BRVO is associated with elevated perimetric thresholds and that successful reduction in edema improves the thresholds.105 Retinal thickness and retinal volume are more closely correlated with retinal sensitivity in BRVO than with best corrected visual acuity (BCVA).72 Microperimetry documented absolute scotomata in 34.7%, relative scotomata in 53.1%, and minimal, insigniÞcant defects in 12.2% of eyes with macular BRVO.5 In one study of