Transient Alterations Of Schlemm’S Canal And Anterior Chamber Angle During Scleral Contact Lens Wear In Keratoconus Eyes

To investigate the short-term effects of scleral contact lens (SCL) wear on anterior chamber angle configuration and Schlemm’s canal cross-sectional area in eyes with keratoconus (KC), and to compare intraocular pressure (IOP) measurements obtained before lens wear and one hour after lens removal

Observational repeated-measures study

19 eyes of 19 patients diagnosed with KC were evaluated. Anterior segment measurements were obtained at three predefined time points: at baseline without lens wear, during SCL at 16.50 mm diameter wear following at least 4 hours of continuous use, and 1 hour after lens removal.

IOP was measured using applanation tonometry at baseline and one hour after lens removal. Anterior segment optical coherence tomography (AS-OCT) was performed to assess anterior chamber angles (ACA), as well as Schlemm’s canal cross-sectional area in four quadrants (nasal, temporal, superior, and inferior). Paired statistical comparisons were conducted, and a p value < 0.05 was considered statistically significant.

During SCL wear, significant narrowing of the nasal (32.30 ± 2.90 vs 25.76 ± 3.75; p < 0.001) and superior (35.21 ± 4.13 vs 21.34 ± 5.63; p < 0.001) anterior chamber angle (ACA) was observed, with no significant change in the temporal or inferior quadrants (p > 0.05). Schlemm’s canal cross-sectional area decreased significantly in the nasal (8399 ± 1300 vs 6891 ± 1319 µm²; p < 0.001), superior (8452 ± 1271 vs 6899 ± 1051 µm²; p < 0.001), and inferior quadrants (8429 ± 1264 vs 6806 ± 1229 µm²; p < 0.001), while remaining unchanged temporally (p = 0.388). Following lens removal, both ACA and Schlemm’s canal measurements returned to baseline in all quadrants (all p > 0.05), and IOP showed no significant difference from baseline (p > 0.05).

Short-term SCL wear in KC eyes results in transient narrowing of the anterior chamber angle, sparing the temporal quadrant, along with a reduction in Schlemm’s canal area. The regional pattern of these changes supports a localized mechanical effect of the scleral contact lens landing zone on aqueous outflow structures. Notably, all structural alterations were reversible after lens removal and were not associated with sustained IOP elevation. Further longitudinal studies are warranted, particularly in eyes with potential susceptibility to glaucoma.