Understanding Anterior Ocular Surface Shape
Pp. 68-87 (20)
Eef van der Worp, Gregory DeNaeyer and Patrick Caroline
Historically, there was little emphasis placed on the anterior shape of the
eye, apart from the corneal shape, but with the resurgence of scleral lenses, recent
interest in the anterior corneo-scleral junction has been examined, measured and
quantified. Interestingly, the corneo-scleral junction had been found to be
predominantly tangential. A variety of technology can be utilized to analyze the
anterior ocular surface shape. Instrumentation includes keratometry, Placido-based
topography, Scheimpflug topography, optical coherence tomography, and scleral
topography. Curvature and elevation data, symmetry or asymmetry are critical in
deciding whether a small diameter scleral lens, a large diameter scleral lens – or maybe
a toric scleral lens is indicated when fitting a patient. Different metrics and indices
define ocular surface shape. Consequences of inappropriate curvatures and parameters
of lenses placed on the ocular surface can result in lens misalignment, excessive
compression, impingement and/or edge lift that result in patient symptomatology. As
with any contact lens, the overall goal is to provide optimal vision, fit and comfort.
Therefore, it is crucial to understand the ocular surface shape to improve alignment and
centration of the optics for optimal vision. Improvements in alignment reduce ocular
signs and discomfort. A general understanding of ocular surface shape can lead to
enhanced designs and improved patient outcomes.
Anatomy, Anterior scleral shape, Conjunctival structures, Corneal
shape, Corneal structures, Corneo-Scleral Profile, Decentration, Episcleral, Eye
Dimensions, Eye muscle, OCT, Placido disc, Scheimpflug, Scleral Angles, Scleral
shape, Sectorial, Spiral of Tillaux, Tangential Shape, Tenon’s capsule, Toricity.
University of Maastricht, Maastricht, The Netherlands.