[Keratoconus and contact lenses (author's transl)].

This work is a survey of 82 cases of keratoconus which have been followed up for 1 to 12 years. Among them only 66 were fitted with contact lenses. The contra-indications for them are: 1. a better visual acuity with spectacles than with contact lenses, 2. advanced cases (4th degree of Amsler) whose fitting is impossible, 3. unilateral keratoconus, 4. associated diseases such as trachomatous pannus, allergic kerato-conjunctivitis. Hard corneal lenses are now in use in most of the cases. Scleral lenses are much less used than they were 10 years ago, owing probably to the great improvement of the corneal lenses during this time. These hard corneal lenses have a short Ro (4 to 7 mm), an overall diameter between 8 and 11 mm, and an optic diameter of 5 mm. They are fitted under fluorescein control. The mobility must be good too. One case was fitted with soft lenses. The visual acuity is good and so is the tolerance: 80% of the patients wear their lenses 10 hours a day or more. Contact lenses do not affect the progression of keratoconus thus finally a keratoplasty must be performed in many cases. After the operation a contact lens is very often necessary, but its daily wearing time must be divided by two, to avoid corneal neo-vascularisation. Soft corneal lenses may be used in some cases of keratoconus. They are indicated when the hard lenses are no longer tolerated and before a keratoplasty. The base curves of these soft lenses are not related to the radii of the conic cornea. In most of the cases they are between 7.50 and 8.60 mm. The diameter is large: 14 or 15 mm. The lenses must not move too much: 1 mm up or down when the patient blinks. The edge of the lens must not depress the bulbar conjunctiva and there must be no air bubble under the lens. In many cases a cylindrical spectacle lens is necessary to obtain a good visual acuity. Some authors prefer to fit a hard corneal lens over the soft one: this is the "piggy back" method. Sometimes keratoconus has appeared in patients already fitted during several years to correct a myopic astigmatism. It is not clear whether these keratoconus have been produced or not be the contact lenses.