Keratoscope

Keratoscope is a medical instrument used to examine the cornea, especially to detect the irregularities in its anterior surface. A keratoscope fitted with a video camera is videokeratoscope which is commonly employed in ophthalmic surgical procedures. Also called Placido's disk, keratoscope uses light to project rings on the cornea. It is a non invasive procedure. One can observe through a keratoscope, reflection of light from the cornea. An inspection of the shape and spacing of the rings which are concentric provides the viewer information about the degree of astigmatism. While in a regular shaped cornea there should be equally spaced symmetric reflections, in patients suffering from astigmatism, the rings will be distorted revealing corneal dystrophy.

In modern methods of sight correction including microsurgical operation of keratotomy and contact lens fitting, it becomes imperative to know the exact shape of the anterior surface of the cornea. For successful use of these methods, keratoscope is employed. Two new types of keratoscopes have evolved. One is the reflective type and the other transparent type. Transparent type of keratoscope is particularly useful in controlling corneal astigmatism during intra ocular surgery.

Such surgical keratometers enable the surgeons to monitor corneal astigmatism during wound closure and adjust suture tension accordingly. From the complex and expensive Terry Keratometer to the simple metal and plastic device of Karickoff, keratometers and scopes are varied, although these devices operate on the basic principle wherein the reflected image of a circular light source show an elliptical shape if significant astigmatism is present. Perhaps the most modern development of the keratoscope concept is corneal topography. Here, the analysis of the reflected image is passed on to a computer. The automated instrument is capable of producing color coded contour maps of the topology of the eye and even a three dimensional visualisation of its surface.