Selective laser trabeculoplasty induced changes in the thickness of ciliary body and iris evaluated by ultrasound biomicroscopy

Selective laser trabeculoplasty (SLT) is widely used for the treatment of glaucoma. The main target tissue of this treatment modality is trabecular meshwork. We aimed to detect the SLT-induced changes in the thickness of ciliary body (CBT) and iris (IT), quantitatively.

Thirty-one patients treated by SLT were examined by ultrasound biomicroscopy (UBM) at different locations of ciliary body and iris at four quadrants, before and after (3rd, 7th, and 30th days) SLT. The IT was measured at various locations; 500 μm anterior to the scleral spur (IT(1)), 2 mm from the iris root (IT(2)) and near the pupillary edge where the iris thickness was maximum (IT(3)) at four quadrants. The CBT at positions 1 and 2 mm posterior to the scleral spur were measured (CBT(1-2)). Additionally, intraocular pressure (IOP) levels were measured in all visits and post-laser 1 h.

There were statistically significant higher CBT values at 3rd and 7th-day measurements in the study compared to pre-treatment levels (p < 0.0001, p < 0.0001, respectively). CBT(2) values at day 30 were similar compared to pre-treatment values (overall p = 0.140), but CBT(1) values at day 30 were not exactly similar compared to pre-treatment values in superior and nasal quadrants (overall p = 0.027). IT values obtained in the 3rd and 7th days were significantly higher in all quadrants and regions when compared to the pre-treatment values (p < 0.0001, p < 0.0001, respectively). There were no statistically significant differences in any of the IT values at the 30th day in comparison to the pre-treatment values (p = 0.45).

The results suggest that SLT induces prominent increases in CBT and IT returning to baseline thickness in a month, which may be caused by inflammation, vascular engorgement, or mechanical muscular contraction.