Key factors help clinician assess strabismus, diplopia

Oklahoma City-When patients with strabismus or diplopia present, ophthalmologists question if the condition is a congenital or an acquired neurologic disease and if imaging or any other tests are needed. R. Michael Siatkowski, MD, differentiated among the various possibilities.

"Five factors will assist the ophthalmologist to make these determinations: the temporal profile of the problem, the presence or absence of diplopia, the degree of binocular function, comitance, and associated findings," he stated. Dr. Siatkowski is professor of ophthalmology, University of Oklahoma, Dean A. McGee Eye Institute, Oklahoma City.

Temporal profileEstablishing a temporal profile means determining if the problem is new and acute, chronic and stable, or chronic and progressive.

In this case, he advised asking the patient about a history of eye muscle surgery, patching, or compensatory head tilting. Old photographs should be reviewed to discern a long-standing squint or ocular torticollis.

Another exception may be if the strabismus develops after ocular surgery or trauma, such as myotoxicity of the inferior rectus muscle from retrobulbar block or scleral buckle.

He also cautioned ophthalmologists to be aware of a switch in the fixating eye. This may happen in patients with strabismus who underwent cataract or refractive surgery, after which the nondominant eye may have the better visual acuity level. These patients then are forced to fixate with the nondominant eye and because of that have problems with spatial orientation accompanied by diplopia.

Chronic, stable problems, such as infantile esotropia or sensory exotropia, are least likely to be neurologic, Dr. Siatkowski pointed out. The exception is when the condition is chronic and stable when the doctor sees the patient, but the initial insult was not, for example, if the patient had a stroke in the remote past.

Chronic progressive conditions may or may not be neurologic in origin. If the eye movements are deteriorating, the deviation is building, and other signs and symptoms are present, the problem is likely to be neurologic; however, if there is long-standing strabismus with loss of fusion amplitudes, a neurologic origin is less likely.

"In general, if diplopia is present this increases the likelihood that the patient has neurologic disease. The exception is the presence of convergence and divergence insufficiencies in adults; in most cases this is related to senescence," he explained. "Vergence insufficiency in children, however, is more likely to be neurologic; convergence insufficiency is related to global development delays such as in cerebral palsy or attention deficit disorder and divergence insufficiency with brainstem problems or with Chiari malformations."

Binocular functionThe time of the onset of strabismus can be determined by measuring stereoacuity on the Titmus test. Stereoacuity of at least 7 of 9 circles means that the ocular alignment was good early in the patient's life and the current condition is not decompensated infantile squint.

"But this is not necessarily neurologic disease," he said. "It might be later-onset childhood strabismus, such as accommodative esotropia or intermittent exotropia."

Accurate stereoacuity measurements in patients with diplopia can be obtained by allowing the patient to use an anomalous head position or prisms in order to fuse. If the stereoacuity is poor or absent, the chances are increased that the patient has infantile squint, which can be confirmed by suppression on a red glass test or the Worth 4 dot test. An exception to this is patients who cannot fuse because of substantial torsion; testing in these patients will result in a falsely poor measure of stereoacuity potential.