Effect of Corneal Collagen Cross Linkage on Intra-Ocular Pressure Measurement in Iraqi Patients with Keratoconus

Abstract

Keratoconus (KC) is increasingly recognized as a complex, multifactorial, and heterogeneous disease that may arise from multiple independent metabolic and biochemical factors.

Corneal collagen cross-linking (CXL) using riboflavin (vitamin B2) with ultraviolet A (UVA) irradiation has recently been introduced as a new therapeutic option. This study aimed to evaluate intraocular pressure (IOP) changes after CXL in a sample of Iraqi patients with keratoconus. This prospective study included 28 patients with bilateral keratoconus (56 eyes) who underwent CXL with riboflavin and UVA irradiation in both eyes. IOP measurements were performed with a Tonopen, and optical coherence tomography (OCT) was used to evaluate corneal thickness immediately before treatment and at 3- and 6-month post-treatment.

Intraocular pressure (IOP) was significantly increased (P<0.001) after 3 and 6 months compared to baseline. The IOP rise remained significant (P<0.001) after correcting IOP measurements for corneal thickness decrease (from 475.1 μm to 447.5 μm after 3 months and from 475.1 μm to 470.1 μm after 6 months). The percentage increases in IOP after three months were 11.2% and 27.1% before and after IOP correction, respectively. The percentage increases in IOP after six months were 16.8% and 20.1% before and after IOP correction, respectively.

In conclusion, in patients with keratoconus, CXL with riboflavin and UVA irradiation resulted in a significant increase in IOP as measured with the Tonopen, even after correction for corneal thickness changes. This finding may have been due to increased corneal rigidity rather than a true increase.