Prism Use in Adult Diplopia

Kammi B. Gunton; A'sha Brown


Curr Opin Ophthalmol. 2012;23(5):400-404. 

In This Article

Horizontal Deviations

There are a vast number of causes for horizontal diplopia. The results of prism in sixth nerve palsy, divergence insufficiency, decompensated childhood strabismus, and convergence insufficiency are reviewed in this section.

Sixth Nerve Palsies

In patients with horizontal deviations, such as sixth nerve palsies, fusional divergence can be utilized to allow for smaller prismatic correction to re-establish binocularity, but the lateral incomitance can be disabling. In one study, the average deviation in a group of patients with sixth nerve palsy was 13 prism diopters at distance.[1] The average prismatic correction was 9 prism diopters. The success rate with prismatic treatment in patients was not reported for this cohort specifically, but on average was 80% of all patients with diplopia from several causes in the study.[1] Four of 22 patients (18%) with partial recovery of their sixth nerve palsy had elimination of their diplopia with prisms in one study.[15]

Divergence Insufficiency

Another group of patients with horizontal deviations are patients with divergence insufficiency. This group has an esotropia greater in the distance than at near. The mean deviation was 9.8 prism diopters for this group in one study.[2] The average prismatic correction was 7.7 prism diopters. The success rate of prism was 100% in the 30 patients reported in the study. Other studies have suggested vergence exercises[16] or eye muscle surgery[17] to treat these patients.

Decompensated Childhood Strabismus

Patients with diplopia from decompensated childhood strabismus may also be managed with prisms.[18] Seventy-four percent of adult patients with strabismus have horizontal deviations, seventeen have vertical deviations, and combined horizontal and vertical deviations occur in 9%.[18] The mean horizontal deviation in a group of adults with decompensated strabismus was 18 prism diopters of exotropia and 15 prism diopters of esotropia.[2] The mean correction prescribed in prism was 11 prism diopters and 8 prism diopters, respectively. Prism successfully resolved diplopia in the primary position in 71% of this group of patients with decompensated esotropia and exotropia combined.[2] All but one of the patients in this group had greater than 10 prism diopters prescribed. The satisfaction rate did not differ significantly between patients who had esotropia compared to exotropia. Patients requiring both horizontal and vertical prism (i.e. oblique prism) had the least satisfaction, 57%.[2]

Convergence Insufficiency

Prism correction for convergence insufficiency presents several unique problems. In convergence insufficiency, diplopia occurs because of an exodeviation at near greater than in the distance or with no distance deviation. In Tamhankar et al.'s.[2] study, the mean deviation for patients with convergence insufficiency was 12 prism diopters, with 8 prism diopters prescribed in prismatic correction. Only 50% of patients had complete resolution of diplopia with prismatic correction. The authors speculated that need for prism only at near makes the prism harder to use for these patients. In children, base-in prism also did not prove successful in the treatment of convergence insufficiency.[19] Convergence exercises have been successful in the treatment of convergence insufficiency.[20] One study randomized presbyopic patients with convergence insufficiency to glasses with base-in prism correction or presbyopic correction alone. This study revealed a greater improvement in convergence insufficiency survey scores in patients with prism.[21]