Efficacy of Morpho-Geometrical Analysis of the Corneal Surfaces in Keratoconus Disease According to Moderate Visual Limitation

Abstract

The cornea is a complex hemispheric structure, made of collagen fibres that provide it a homogenous and stable geometry. During keratoconus disease, a loss of tenacity takes place in the collagen fibres that form the corneal structure, producing an alteration of its geometry, this is, a change of its curvature, and therefore, a loss of visual quality of patients. The geometric characterization of the hemispheric structure by means of biometric parameters is a very solid technique of diagnosis, based in a virtual 3D model, which has already been validated for several degrees of severity of keratoconus pathology. In this prospective comparative study, 93 corneas (50 healthy subjects and 43 patients with keratoconus with moderate visual limitation) were geometrically modelled. The results obtained in this work suggest that the best predictive biometric parameters are anterior corneal surface area and posterior apex deviation, and that the strongest correlation is produced between sagittal plane apex area in minimum thickness point and sagittal plane apex area. The studied biometric parameters have shown significant differences between groups. Therefore, the analysis of the biometric parameters that register the geometric decompensation that locally appear in a corneal region, as a response to the asymmetry produced during the development of keratoconus disease with a moderate visual impairment, is a new approach that may lead to a better understanding of the disease with this degree of optical limitation.

Evidence of a Down Syndrome Keratopathy: A Three-Dimensional (3-D) Morphogeometric and Volumetric Analysis

“…With this configuration, a point cloud was generated for the zone that started in the cornea’s geometric centre (r = 0 mm) and reached the mid-peripheral area (r = 4 mm). This area of study typically includes most of the biometrical information of the cornea, not only for healthy eyes, but also for diseased ones [ 16 , 17 , 19 , 20 , 21 ].…”

“…By means of this software, the 3D custom model representing the corneal biometry was generated, and the following morphogeometric parameters could be calculated: anterior/posterior apex deviation from the geometrical axis (D apexant /D apexpost ); anterior/posterior minimum thickness points deviation from the geometrical axis (D mctant /D mctpost ); anterior corneal surface (ACS) area (A ant ); posterior corneal surface (PCS) area (A post ); total corneal surface area (A tot ); area of the cornea within the sagittal plane passing through the Z axis and the anterior apex/posterior apex/posterior minimum thickness point (A apexant /A apexpost /A mctpost ); centre of mass coordinates X,Y and Z (C x , C y , C z ); total corneal volume (V total ); volume between the solid corneal model and a cylinder with radius “x” (from 0.1 to 1.5 mm) and axis defined by the perpendicular line to the plane that is tangent to the anterior/posterior corneal surface at the apex (VOL AAP /VOL PAP ); and volume between the solid corneal model and a cylinder with radius “x” (from 0.1 to 1.5 mm) and axis defined by the line joining points of minimum corneal thickness of both ACS and PCS (VOL MCT ). All these indices have already been exhaustively described and used in precedent research from our group [ 16 , 17 , 19 , 20 , 21 , 22 ].…”