An assessive model for corneal endothelium morphometry by diffraction

Abstract

Abstract Purpose Most in vivo measurements on the corneal endothelium morphology are done by specular microscopy. This is a time consuming process, due to the need of operator involvement. To assess alternative methods, an experimental optical setup for corneal endothelium morphometry by diffraction has been created. Methods A phantom Polymethyl methacrylate (PMMA) cornea was created, having dimensions of a real cornea. The posterior surface of the phantom cornea was grated to allow for identification of a reflected far field (Fraunhofer) diffraction. The grating was manually etched under a microscope and consisted of a quadratic mesh with a periodicity of approximately 80 µm. The phantom cornea was fitted to a phantom anterior chamber. Because of differences in refractive indices, the phantom anterior chamber was filled with a water/sugar solution (61%) to fully emulate the relative reflection of the cornea‐aqueous humor interface. Light from a He‐Ne laser at 632.8 nm was modulated with achromatic lenses towards the phantom cornea at an incident angle of 45 degrees. The light reflected from the phantom cornea‐aqueous humour interface was collected at the opposite 45 degree angle. The Fraunhofer diffraction pattern was recorded with a CCD chip. Results Experiments showed that a diffraction pattern of the periodicities of the emulated corneal endothelium could be recorded. Conclusion A simple optical setup was created and a grated emulated cornea was used to assess the possibilities of corneal endothelium morphometry using diffraction. Even with the low reflective power of the emulated cornea‐aqueous humor interface, clear diffraction patterns could be recorded. The result is encouraging for further development of an optical system for in vivo morphometry on the corneal endothelium.