|Year : 1982 | Volume
| Issue : 6 | Page : 519-520
Study of 'Follow-up Keratometry' in contact lens practice
Sankara Nethralava Medical Research Foundation, Madras, India
Sankara Nethralya, 18 College Road, Madras. 600 006. (T.N.)
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Anandakannan K. Study of 'Follow-up Keratometry' in contact lens practice. Indian J Ophthalmol 1982;30:519-20
Corneal contact lens can cause alterations in corneal curvature in one or both meridions in over 70% of patients. Methods of fitting contact lens by not using keratometer are being practised nowadays. It is the purpose of this study to correlate the keratometer findings with the comfort of the patient and proper fitting of contact lens and its value in making a few alterations so as to make the patient a successful wearer of the contact lens.
It will be out of place to give either a description of the keratometer or the method of using this instrument.
| Materials and methods and observations|| |
50 eyes that were fitted corneal contact lens during the period of 6 months from July to December 1979 were taken up for this study. They were followed up for a period of 3 to 6 months at regular intervals.
A. routine ocular examination, keratometry and breakup time (BUT) of tear film were done in all cases before fitting the lenses. Fluorescein pattern was used as the confirmative test before ordering for lenses. Based on the keratometer reading
33 eyes were fittted "steeper than K"
15 eyes were fitted "flatter than K"
2 eyes were fitted "on K"
Before fitting the contact lens there were with the rule-44 eyes, against the rule-4 eyes, spherical error-2 eyes
Post contact lens keratometry showed
Astigmatism `with the rule' in 42 eyes; Astigmatism `against the rule' in 6 eyes.
A change of more than 0.50 D in keratometric reading was seen in 29 eyes (58%) during the first week. In 17 eyes lenses were fitted steeper than K, in 8 flatter than K and one was fitted on K.
In this group central corneal clouding was noted in 25 eyes. Of these > 5 showed persistent corneal odema and changes in the keratometer reading during subsequent visits also. There was punctate corneal staining and the patients were uncomfortable due to photophobia ^and watering. 3 lenses which showed a steep fluorescein pattern were ordered to reduce the diameter so as to make them flatter; two lenses showing a flat fluorescein pattern were changed. These lenses were worn comfortably after the change. Rest of the lens belonging to this group were tolerated well by the patients and the signs and symptoms came down gradually after the adaptation period.
21 eyes showed change in keratometric reading of less than 0.513. They were by and large happy and comfortable with their lenses and wearing the lenses for more than 10 hours a day. It is also worthy to mention that in general, lenses fitted `steeper than K' were tolerated much better than the fit on K' or flatter than K'.
| Discussion|| |
One of the criteria for a well fitted contact lens after adaptation is that the keratometer reading do not show a significant change after wearing the lens. Corneal anoxia and the retention of metabolites within the tissue lead to corneal oedema which causes change in the thickness of the cornea and the surface shape changing the refractive status of the eyes.
The significance of these induced refractive changes of the cornea can be utilized to modify the lenses so as to improve the tear flow beneath the lens or a new fitting assessment is to be undertaken only after the cornea has regained its prefitting status. When the other signs of corneal changes are also present refit with new lenses is further emphasized.
| Summary|| |
Measurement of the corneal curvature during the course of adaptation is an important test to determine whether the adaptation is progressing favourably. Marked change in the corneal curvature may indicate an ill fit and this is used as a parameter for refitting the lenses.