Keratokonus Evresi ile Retina Sinir Lifi Tabakası, Makula Kalınlığı, Gangliyon Hücre Tabakası Parametrelerindeki Değişikliklerin Optik Koherens Tomografi Kullanarak İncelenmesi

Abstract

Kazımova F. Evaluation of the Relationship Between Keratoconus Stage and Changes in Retinal Nerve Fiber Layer, Macular Thickness, and Ganglion Cell Layer Parameters Using Optical Coherence Tomography. Department of Ophthalmology, Hacettepe University Faculty of Medicine, Medical Specialty Thesis, Ankara, 2025. Introduction and Objectives: The aim of this study was to investigate the relationship between keratoconus stage and full-thickness foveal as well as individual retinal layer thicknesses using spectral-domain optical coherence tomography (SD-OCT) in patients diagnosed with keratoconus and staged according to disease severity. We also aimed to determine which retinal layers contribute to increases or decreases in thickness, to evaluate whether there is a difference in macular layer segmentation, to assess the presence of thinning in the retinal nerve fiber layer, to compare findings with a healthy control group, and to compare preoperative and postoperative measurements in the subgroup of patients who underwent corneal cross-linking. Materials and Methods: Demographic data, clinical examination findings, corneal topography, and spectral-domain OCT examinations of patients followed at the Hacettepe University Cornea Unit were evaluated by creating a dataset. A total of 282 eyes were included in the analyses comparing the patient and control groups. Of these, 202 eyes belonged to 101 patients in the keratoconus group, and 80 eyes belonged to 40 individuals in the control group. When the distribution of eyes in the patient group according to disease stage was examined, 22.8% were stage 1, 39.1% were stage 2, and 38.1% were stage 3. In the subgroup that underwent corneal cross-linking, analyses comparing pre- and postoperative measurements were performed on 33 patients with complete pre- and postoperative data. When the distribution of disease stages was examined, 8.0% of patients were stage 1, 34.0% were stage 2, and 58.0% were stage 3 in the preoperative period; postoperatively, these rates changed to 12.0%, 42.0%, and 46.0%, respectively. In this group, measurements were obtained from only one eye in 16 patients and from both eyes in 17 patients. Results: In the study, retinal layer thicknesses in the patient group differed according to disease stage when compared with the control group. In particular, statistically significant increases in inner retinal layers (NFL, GCL, IPL, INL, OPL, and IRL) were observed in stage 2 and stage 3 groups compared to the control group, while decreases were observed in outer retinal layers (RPE, ONL and ORL). In the corneal cross-linking group, no significant changes were observed in most retinal layers in the early period (1–3 months), whereas statistically significant changes emerged in certain retinal layers at 6 months and particularly at 12 months and beyond. Conclusions: The findings indicate that retinal layer thickness in keratoconus patients may vary in relation to both disease stage and follow-up duration after corneal cross-linking. As the disease stage progresses, more pronounced increases in inner retinal layers are observed, while decreases in outer retinal layers are noteworthy. The absence of significant changes in retinal layers in the early postoperative period suggests that the procedure does not have a marked short-term effect on retinal structure. However, significant changes observed in long-term follow-up (particularly ≥12 months) indicate that retinal measurements may change over time.