The Relationship Between Keratoconus Stage and the Thickness of the Retinal Layers

Abstract

Objectives: To examine the relationship between keratoconus (KC) stage and the thickness of the retinal layers. Materials and Methods: Retinal layer thicknesses were compared between 85 eyes of 85 KC patients and 40 eyes of 40 controls similar in age, sex, and axial length. KC patients were staged as stage 1, 2, or 3 according to the Amsler-Krumeich staging system, and segmentation of the retinal layers was performed with spectral domain optical coherence tomography automatic segmentation program. The thickness of the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), and retinal pigment epithelium (RPE) in the central 1 mm Early Treatment Diabetic Retinopathy Study subfield was analyzed. Results: There was no significant difference between the control and KC groups in the segmentation of the RNFL, GCL, IPL, or OPL (p=0.306; p=0.661; p=0.893, p=0.664, respectively). The INL differed significantly between control and stage 2 KC, control and stage 3 KC, stage 1 and 2 KC, and stage 2 and 3 KC, increasing in thickness with higher stage (p=0.004; p=0.005: p=0.001; p=0.002, respectively). The RPE also differed significantly between control and stage 2 KC, control and stage 3 KC, stage 1 and 2 KC, and stage 2 and 3 KC, showing decreased thickness with higher stage (p=0.03; p=0.001; p=0.001; p<0.001, respectively). The ONL also thinned as stage increased, but the results were not statistically significant (p=0.051). Conclusion: More advanced KC stage was associated with increased thickness of the INL layer, where the neuroglial cell bodies are located, and decreased thickness in the outer retinal layers, especially the RPE.

The link between Keratoconus and posterior segment parameters: An updated, comprehensive review

“…Few studies have investigated the retinal pigment epithelium (RPE) layer changes accompanied by KCN. Özsaygılı et al by comparing KCN patients with different severities and non-KCN subjects found a significantly decreasing trend in RPE layer thickness along with increasing KCN severity [59]. They proposed that elevated ROS levels and reduced antioxidant activities of the tissue in keratoconic eyes could result in cellular injuries at the photoreceptor level and the RPE layer due to cellular apoptosis [64].…”

Letter to the Editor Re: “The Relationship Between Keratoconus Stage and the Thickness of the Retinal Layers”

“…The more progression in myopia, the more changes in the profile of the retinal layers. Although Özsaygılı et al 1 measured the refractive state of their patients with manifest refraction, they did not clearly state the range and mean values of the refractive errors of their study subjects. Furthermore, other influential factors on retinal thickness including diurnal variations, segmentation errors, gender, and body mass index were not considered as confounding factors.…”

“…We read with interest the recent study conducted by Özsaygılı et al 1 regarding the relationship between the keratoconus (KC) stages and the thickness of the retinal layers. The authors concluded that patients with more advanced KC had a thicker inner nuclear layer (INL) and thinner retinal pigment epithelium (RPE) layer.…”

“…In the study by Özsaygılı et al 1 , patients with myopia lower than -6.00 D were included. However, the authors attributed the significant changes in the INL and RPE to the different biochemical, oxidative, genetic, and cellular mechanisms in a KC eye.…”

Reply to Letter to the Editor re: “The Relationship Between Keratoconus Stage and the Thickness of the Retinal Layers”

“…We would like to thank the authors for their comments and evaluation of our study. 1 As mentioned in the study, patients with myopia above 6 diopters and axial length greater than 26 mm were excluded in order to prevent the potential confounding effect of the optical defocus that might be caused by high myopia and the stretching effect on retinal layers. Liu et al found that there was a difference in the thickness of the retinal layers in the peripheral macular region of eyes with high myopia compared to the emmetropic control group.…”