MTE Journal, Vol 1 No 4, September 1941 - Medical Training Establishment

M. T.E. JOURNAL SEPTEMBER 1941 CONTACT GLASSES Wing Commander KEITH LYLE M.A. M.D. M.Chir.(Cantab.) M.R.C.P.(Lond.) F.R.C.S.(Eng.). CONTACT Glasses are glass lenses which are worn inside the eyelids indirect contact with the eye­ball itself. They have the great advantage of being almost invisible to ordinary observation. H ISTO RY.—As long ago as 1827 J .F. Herschel, a brother of the famous astronomer first suggested the use of a glass shell to cover the front of the eye-ball to protect it from a diseased eye-lid. Little is known of the results of this experiment but exactly 60 years later Muller in Germany made a “blown ”contact lens for the same reason and the patient wore the lens for several years. The first use of a contact glass to improve the vision was made by Fick in German}' in 1880 in a case of conical cornea a condition in which the clear transparent part of the eye takes 0 1 the shape of the small end of a pear instead of the normal shape of a ball. Persons suffering from this condition are usually only helped but little by the use of ordinary spectacles. Fick conceived the idea that the crude protective lenses used by Muller might be adapted to give these patients good vision if a fluid were placed between the lens and the front surface of the cornea. Where the cornea is irregular the contact lens filled with saline solution to form a homogeneous connection between the glass and the eye establishes the effect of a perfect sphere and gives normal vision. In 1929 Heine suggested and demon­strated the practical application of contact lenses for correcting near-sightedness (myopia) far-sightedness (hypermetropia) and irregularity of the surface of the cornea (corneal astigmatism) by grinding the centre of the surface of the contact glass as a correcting lens. This involved using a chemically resistant glass as introduced by Stock in 1920. (The Muller type of lenses were blown from glass, such as is used in the manufacture of glass eyes and on account of the nature of the glass employed Fig. I they soon became roughened which necessitated renewal after a few months.) Thus Contact Glasses were brought to the aid of the average person with the usual forms of defective vision due to errors of refraction. It was soon found, however that whereas quite a number of persons could wear the glasses for along period of time others were unable to do so. This was due to the fact that so many people do not possess a stock size type of eye. A further important instep the production of contact glasses was made in 1936 by an Hungarian eye specialist Dr. Dallos of Budapest (he is now working at the Contact Lens Centre in London) who reported that he had been able to take a cast of the human eye and from that he could make a moulded contact lens which with a certain amount of adjust­ment was wearable with comfort. The modern properly fitting contact glasses are capable of being worn all daylong although most people take time to get used to them and as one would expect this “accustoming ”period varies considerably with different individuals. It should be mentioned that at the present time in order to produce really com­fortable lenses several fittings are usually required and it is this fact which to some extent main­tains the high price of these lenses. anOn average the price of a pair of Contact Glasses ‘‘made to measure ’including the fitting charge is from 30 to 40. In some cases stock sizes can be used which cost only about 5 per pair. THE CONTACT LEN S.—The Contact Lens is about to 1 millimetre thick and has two segments a central domed portion which lies next to the cornea itself and a peripheral portion adjacent to the curvature of the sclera. Fig. 1 shows an ordinary pair of glasses for the correction of myopia compared with a pair of contact lenses for the same case.
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