Assessment of OCT and Angio-OCT Parameters in Keratoconus Patients with and without Penetrating Keratoplasty.

Background/Objectives: Keratoconus (KC) is a bilateral eye disease characterized by corneal thinning and cone-like deformation, leading to visual impairment. This study evaluated the radial peripapillary capillaries (RPCs) in keratoconus patients with and without penetrating keratoplasty (PKP) using OCT and angio-OCT, comparing the results to a control group. Methods: This retrospective study included 149 eyes, 97 from patients who underwent PKP between January 2018 and February 2023 and 52 from patients who did not undergo PKP. The control group comprised 72 patients (144 eyes) who were healthy volunteers. Measurements included the best corrected visual acuity (BCVA), the intraocular pressure (IOP), slit-lamp biomicroscopy, a fundus examination, and corneal topography, as well as OCT and angio-OCT assessments of the RPCs, retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), and central retinal thickness (CRT). Statistical analyses were performed using Student's t -test and Pearson's correlation coefficient. Results: The RNFL was significantly thinner in KC eyes after PKP compared to control eyes ( p < 0.001), and the CRT was significantly thicker in KC eyes after PKP compared to control eyes ( p = 0.003). However, the GCC was similar across the groups ( p = 0.0885). Additionally, RPCs inside the disc were significantly reduced in KC eyes after PKP compared to control eyes ( p < 0.0001). A significant positive correlation was found between RPC whole vessel density and RNFL thickness as measured via angio-OCT (r = 0.308, p < 0.0001). Conclusions: This study found that the RPC density inside the disc is significantly reduced in keratoconus patients after penetrating keratoplasty, highlighting RPCs inside the disc as a potential diagnostic tool for further assessment of keratoconus.