Low intraocular pressure resulting from ciliary body detachment in patients with myotonic dystrophy.

PURPOSE: To investigate why myotonic dystrophy type 1 (DM1) patients have low intraocular pressure (IOP).

DESIGN

Prospective, comparative case series.

PARTICIPANTS

One hundred two eyes of 51 patients with DM1 (age range, 21-64 years) and 44 eyes of 22 healthy subjects of similar age (21-64 years).

METHODS

All participants underwent IOP measurement with Goldmann applanation tonometry and an in vivo examination of the ciliary body with a 35-MHz high-resolution B-scan. The findings were compared between the 2 groups. In both groups, only patients with no history of ocular trauma or surgery were included. The differences were evaluated using the unpaired Student t test.

MAIN OUTCOME MEASUREMENTS: Intraocular pressure, central corneal thickness (CCT), and echographic evidence of ciliary body detachment.

RESULTS

The mean ± standard deviation (SD) IOP in patients with DM1 was 10.9 ± 3.1 mmHg and that in the control patients was 15.4 ± 2.2 mmHg, a difference that reached significance (P<0.01). The mean ± SD CCT (measured at the pupillary center) was 574.4 ± 37.9 μm in the patients with DM1 and 557.8 ± 39.2 μm in the controls (P = 0.02). Detachment of the ciliary body was identified in all DM1 subjects. Size was variable and the detachment involved 1 or more quadrants. The number of quadrants affected by the detachment was not correlated with the IOP (R(2) = 0.088) or the size of the CTG expansion. No detachments were found in the healthy controls.

CONCLUSIONS

Detachment of the ciliary body may explain the low IOP values in patients with DM1. The finding of a ciliary body detachment in an individual who has not had recent eye surgery or trauma raises the possibility of a DM1 diagnosis.