Monovision should be induced cautiously in patients with strabismus history

The authors present a series of patients who were diagnosed with strabismus for the first time or experienced a recurrence of an earlier strabismus after the production of monovision. Strabismus occurred two months to two years after the procedure that induced monovision, elucidating that a successful trial of monovision with a contact lens prior to surgery is not a guarantee that a patient can tolerate monovision. In patients with a previous history of strabismus or those with significant phorias, the authors say caution should be used in recommending monovision. They conclude that keeping anisometropia at the lowest functional level will help reduce the loss of stereopsis and possibly aid in lowering the incidence of decompensated strabismus after monovision surgery.

They reviewed the clinical records of 12 patients from the private practice of the corresponding author. Patients obtaining monovision via contact lenses, LASIK and cataract surgery with posterior chamber IOLs were studied if their monovision produced a new strabismus or was related to the recurrence of a previous strabismus. The majority of patients developed strabismus after two years of monovision. The authors say these patients most likely had a phoria that had been held in check by fusion for a long time prior to the onset of monovision.

The patients were first treated by converting the monofixing near eye to distance vision and then using reading glasses for near work. Seven patients regained fusion by doing away with monovision, recovering their ability to fuse within three to four months. The authors decided that after four months, patients who were still symptomatic and nonfunctional with their diplopia and/or strabismus would be treated with surgery. After undergoing surgery to reestablish motor or sensory control, the remaining patients obtained excellent alignment but one did not regain sensory fusion.

The authors conclude that patients with a history of strabismus should be advised that the use of monovision to treat presbyopia might precipitate a recurrence of previous strabismus or asthenopic symptoms, and patients diagnosed with a significant exophoria or esophoria should be informed that monovision might cause strabismus. If monovision is elected, they recommend keeping anisometropia to small levels, such as 1.25 to 1.50 D, which may lessen the chance of strabismus.

In patients with strabismus who desire monovision correction via LASIK, they say that a trial with a contact lens or glasses to simulate monovision should be tried first. If diplopia occurs, then there is a very high risk for postoperative double vision. However, the authors say that the absence of diplopia does not guarantee that postoperative diplopia will not develop, as it could present several months or years after the surgical inducement of monovision. They note that they have seen fusional or motor complications occur after several years of monovision, even in nonstrabismic patients.