Management of strabismus with hemianopic visual field defects.

BACKGROUND: Hemianopia and strabismus leads to severe disturbance of visual orientation and diplopia under binocular conditions if the deviated eye has a normal retinal localization. SUBJECTS AND METHODS: Four cases with homonymous (two) and bitemporal (two) hemianopia and strabismus will be described with respect to binocular visual field and diplopia/confusion. All of them were recommended for strabismus surgery. Preoperatively, prism adaptation test was carried out to analyze functional results and fusional competence. In three of the four cases, strabismus surgery was successfully performed to avoid diplopia/confusion. All three patients revealed normal retinal correspondence. Furthermore, in two cases surgery led to an extension of binocular visual field; in one case with a bitemporal hemianopia and hemifield-slide phenomenon, blurred central vision and reading problems reduced significantly postoperatively. In one patient with anomalous retinal correspondence due to early childhood trauma exotropia led to an extension of the binocular visual field. In this case, strabismus surgery would have been unfavourable.
RESULTS: Case 1 showed a homonymous hemianopia to the left and acquired exotropia of the right eye, leading to binocular diplopia. Case 2 with homonymous hemianopia to the right and exotropia of right eye revealed anomalous retinal correspondence after history of perinatal brain injury, resulting in absence of diplopia and enlargement of visual field to the right. Cases 3 and 4 with bitemporal hemianopia suffered from sensory disturbances caused by additional acquired strabismus. The exodeviation of the right eye in case 3 led to a restriction of binocular visual field with overlap of the nasal parts causing diplopia, whereas the esodeviation of case 4 resulted in a "gap" between the nasal parts (blind area).
CONCLUSION: Depending on the extent of visual field defects and on retinal correspondence, functional consequences for binocular vision and binocular visual field should be considered prior to surgery. In normal retinal correspondence, strabismus surgery will be indicated in most cases because of diplopia. However, surgery might result in a reduction of binocular visual field. Preoperatively, it is important to map monocular and binocular visual fields, to examine retinal correspondence, and to undertake prism adaptation test to imitate the postoperative functional result and risk of double vision.