Study: pigmentary dispersion may be affected by anterior segment architecture

VANCOUVER, British Columbia — The architecture of the anterior segment may influence the development of pigmentary glaucoma, a new study suggests. In the study, patients with pigmentary dispersion syndrome were found to have flatter corneas than normal patients matched for age and myopia.

Pigmentary dispersion syndrome (PDS) and pigmentary glaucoma (PG) are characterized by loss of pigment from the posterior surface of the iris due to reverse pupillary block. The position of the globe within the orbit, the axial length of the globe and the corneal curvature in PG patients may have an anomalous relationship that affects the progression of the syndrome.

Researchers here and in Thailand recorded anterior segment and exophthalmometry measurements, age and refractive error in 13 patients with PDS or PG and 17 myopic controls.

There was no statistically significant difference between groups in refraction (sphere, cylinder, axis and spherical equivalent), anterior chamber depth or lens thickness. However, the PDS group had flatter keratometry by about 2 D in both the steeper and flatter keratometry axes. No differences were detected in the axis between the two groups.

The flatter corneas in the PDS and PG patients may be a factor in inducing reverse pupillary block, the authors suggest. "It may be that for a given refractive error and axial length, a flatter cornea predisposes a patient to the development of reverse pupil block during a blink. Alternatively, the flatter cornea may be a noncausal but significantly related anatomic characteristic in these patients," the researchers write in the October issue of the Journal of Glaucoma.