Revista nº 814

López-Jiménez A, et al. | Choroidal thickness analysis in keratoconus patients 253 Actual Med. 2021; 106(814): 252- 259 Keratoconus (KC) is an ectatic corneal disease. It has been traditionally defined as non-inflammatory (1), although recent studies (2) (3) reject this hypothesis. It is characterized by a progressive thinning of the corneal thickness, with a consequent alteration of corneal biomechanics, generating an irregular astigmatism. KC is a complex pathology, based on the interaction of genetics and environmental factors. It also represents one of the main causes of keratoplasty today( 4). Recent studies show increased levels of inflammatory cytokines and proteolytic enzymes including interleukin 1 and 6 (5), Intercellular Adhesion Molecule (ICAM-1), tumoral necrotic factor-alpha (TNF-α) and vascular cell adhesion protein one (VCAM-1) (6). These inflammatory mediators activate an enzymatic cascade that increases the level of metalloproteases(7), triggering ectasia on the corneal matrix. These inflammatory alterations in the anterior segment could be related to an enhanced vascular flow in adjacent tissues such as the choroid, all which leads to a thicker choroid in KC patients. Our purpose was to evaluate the choroidal thickness (CT) in keratoconus patients and compare it to healthy controls. Study design This is a cross-sectional, comparative study between groups, to evaluate the choroidal thickness of patients with KC. 26 eyes of 26 patients without ocular pathologies different from KC were included and assessed by corneal tomography analysis (Pentacam® HR, OCULUS, Optikgeräte GmbH, Wetzlar, Germany) and EDI SD-OCT using Spectralis® Heildelberg® (Germany). The results were compared to 26 healthy eyes of 26 patients (control group). This study was approved by the ethics committee of Hospital Universitario Reina Sofia de Murcia, and is adhered to the tenets of the Declaration of Helsinki. Scanning Participants underwent a complete ophthalmological examination including: refraction, best corrected visual acuity (BCVA), Perkins applanation tonometry, slit lamp biomicroscopy, fundoscopy under tropicamide dilation, spectral domain optical coherence tomography (SD-OCT) with enhanced deep imaging (EDI) Spectralis® (Heidelberg Engineering, Germany) and corneal topographic examination with Pentacam HR® (Oculus Optikgeräte GmbH, Germany). Inclusion and exclusion criteria The inclusion criteria were both clinical and topographic diagnosis of KC. One eye was randomly selected in case of bilateral disease. Patients with history of previous eye trauma, glaucoma, infectious or inflammatory eye disease, systemic disease or previous intraocular surgery were excluded from the study. Those who had undergone corneal cross-linking less than twelve months prior to the study were also excluded Patients without ocular or systemic pathology, with BCVA of 20/20, were randomly selected as controls. As myopia is related to thinner choroidal thickness, individuals with ± 2 D of spherical equivalent were excluded from the control group. Instruments Topographic and pachymetric criteria of normality were checked in healthy controls with Oculus Pentacam (®HR, Germany). In the KC group, keratometry, pachymetry, corneal asphericity index, keratoconus index (KI), vertical asymmetry index (VIA), degree of keratoconus (TKC) and location of the corneal apex (central, inferior-nasal, inferior-temporal or upper) was also analyzed. Choroidal thickness (CT) measurements were performed with the Enhanced Depth Imaging (EDI) EDI-OCT Spectralis® from Heidelberg, Germany. It was carried out by the same expert manually using the tomograph’s Caliper function and the 1:1 µm ratio. Manual measurement is reliable and has a very high interobserver and intersystem agreement(8). The evaluations were always performed in the afternoon (12:00 to 15:00) to minimize circadian variation. The subfoveal CT (M) was obtained measuring perpendicularly the distance between the posterior limit of the retinal pigment epithelium (RPE) and the choroid-scleral junction just below the fovea. Twelve further CT measurements were assessed every 500 µm; six temporal and six nasal to the fovea (Fig. 1). INTRODUCTION MATERIAL AND METHODS Figure 1. Subfoveal CT (M) was obtained measuring manually the perpendicular distance between the posterior limit of the retinal pigment epithelium (RPE) and the choroid-scleral junction just below the fovea. Twelve further CT measurements were performed every 500 µm; six temporal (T1-T6) and six nasal (N1-N6) to the fovea.