Contact Lenses

Leonardo da Vinci is thought to have first conceived the idea of what is known as contact lenses, but Sir John EW. Herschel, the royal astronomer, is usually credited with the honor of being the first to recommend its use. Thomas Young discovered astigmatism. Those connected with further advancement in the field of lenses were Rene Descartes, A. Eugene Flick and E. Kilt. The term corneal lens .appears to have been first used in 1889 by August Muller. However, in 1947, Kevin Touchy redeveloped and started manufacturing corneal lenses from clear plastic instead of glass. At that time the diameter of the lens was 10.8 to 12.5 mm. Thereafter, in 1952, Wilhelm Sohnges in Germany, in collaboration with John Neill and French Dickinson, introduced a small lens which came to be known as micro-corneal lens. The micro-corneal lens is widely used today. Apart from cosmetic reasons, contact lenses playa definite role in certain eye conditions.

In myopia, minus lenses are prescribed for its correction. This can be done by using spectacles, but the use of contact lenses has definite advantages, particularly in high errors. The advantages of contact lenses over spectacle lenses are as follows:

(a) Since contact lenses come in direct contact with the cornea, the cardinal points are least disturbed and, therefore, the extent of magnification of the retinal images as compared to spectacle correction is much less. In high myopia, spectacle correction will reduce the retinal image size to a considerable extent, thereby adversely affecting the visual acuity. However, with contact lenses the extent of magnification of retinal image size will be insignificant and will produce sharper images as compared to correctional spectacles.

(b) Contact lenses give a complete field of vision, more particularly in high numbers and the wearer is also free of prismatic effect, distortion and oblique aberration which he/she would face with conventional spectacles.

(c) It has been observed that patients in whom there is frequent change in refraction have stabilized after the regular use of contact lenses. It follows that contact lenses do have some arresting effect on the progress of myopia. It is also observed that patients who wear contact lenses need far fewer changes as compared to myopic spectacle-wearer. This may be attributed to the fact that contact lenses have restraining effect on the stretch of sclera and cornea.