Evaluation of Retinal Layer Thicknesses in Patients with Keratoconus Using Retinal Layer Segmentation Analysis

Area of Science:

• Ophthalmology
• Retinal Imaging
• Corneal Diseases

Background:

• Keratoconus (KC) is a progressive corneal disorder causing irregular astigmatism.
• Astigmatism can influence retinal structure, but its specific effects in KC are not fully understood.
• Spectral-domain optical coherence tomography (SD-OCT) allows detailed analysis of retinal layers.

Purpose of the Study:

• To evaluate the impact of irregular astigmatism in keratoconus (KC) on retinal nerve fiber layer (RNFL) and macular thickness (MT).
• To assess changes in specific retinal layers using SD-OCT in KC patients.
• To compare retinal layer thickness in KC patients, astigmatism patients, and healthy controls.

Main Methods:

• SD-OCT was used to analyze RNFL and MT maps in 255 eyes (72 KC, 70 astigmatism, 113 controls).
• Measurements included RNFL, inner and outer plexiform layers (IPL, OPL), inner and outer nuclear layers (INL, ONL), ganglion cell layer, and retinal pigment epithelium (RPE).
• Automated segmentation using Spectralis software was performed within a 6-mm ETDRS grid.

Main Results:

• KC eyes exhibited significantly reduced global, temporal, superotemporal, and inferotemporal RNFL thickness compared to controls and astigmatic eyes.
• KC group showed significantly decreased central MT, except in the inferior outer sector.
• Segmentation analysis revealed significantly lower IPL, ONL, RPE, and outer retinal layer (ORL) thickness in KC eyes.

Conclusions:

• Patients with keratoconus demonstrate thinner RNFL and MT compared to those with astigmatism and healthy controls.
• Outer retinal layers, specifically the outer nuclear layer (ONL) and retinal pigment epithelium (RPE), are the most compromised macular components in KC.
• These findings highlight structural retinal changes associated with irregular astigmatism in keratoconus.