Means to Measure Corneal Thickness
The cornea is the outermost clear layer of the eye that helps focus light onto the lens located behind it. The thickness of the cornea plays a major role in the diagnosis of certain conditions such as oedema (corneal swelling) and ectasia (bulging), determining eye pressure and progress of glaucoma (increased eye pressure), and also in planning corneal surgery. Some of the instruments used to measure corneal thickness include:
- Ultrasound pachymetry is a standard technique that places a probe in direct contact with the eye to determine corneal thickness by passing ultrasound waves, which reflect off the cornea.
- Specular microscopy is a photographic technique that determines corneal thickness and evaluates the cells of the cornea. It projects light onto the cornea, analyses the reflected image and expresses its results on a highly magnified digital image.
- Confocal microscopy is a technique that advances a special microscope close to the eye to produce real-time corneal images at high magnification.
Other techniques of measuring corneal thickness include ultrasound biomicroscopy, spectral optical coherence tomography (SOCT) and the Scheimpflug system.