Anomalies of binocular function in patients with longstanding asymmetric keratoconus

Aims-To study binocular function in patients with longstanding asymmetric k eratoconus. Methods-In 20 adult patients with longstanding asymmetric keratoconus manag ed with a scleral contact lens a full clinical and orthoptic assessment was performed with and without the scleral contact lens in the poorer eye. Results-All 20 patients had a corrected acuity of at least 6/9 in their bet ter eye. With the scleral lens in situ the acuity of the poorer eye ranged from 6/6 to 6/60 and without the lens from 6/18 to hand movements. Patients were aged from IS to 68 years and had worn a scleral contact lens for betw een 3 and 106 months. Without the contact lens in their poorer eye all pati ents had a small exotropia and all showed suppression, with the exception o f one patient who had a right hypertropia with diplopia. With the scleral l ens in situ 12 patients had an exophoria or esophoria, six a microexotropia , and two a manifest exotropia with suppression. Conclusions-Binocular function breaks down in some adult patients with long standing asymmetric keratoconus. This is probably caused by longstanding un ilateral visual deprivation. There are similarities to the breakdown of bin ocular function seen in some patients with a longstanding dense unilateral adult onset cataract who can develop intractable diplopia following catarac t surgery.