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   Table of Contents      
Year : 1984  |  Volume : 32  |  Issue : 6  |  Page : 522-524

Behaviour of cone of keratoconus under a well fitted hard contact lens

Dr. Rajendra Prasad Centre for Ophthalmic Sciences, AIIMS, New Delhi, India

Correspondence Address:
V K Dada
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, AIIMS, New Delhi
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Source of Support: None, Conflict of Interest: None

PMID: 6599896

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How to cite this article:
Dada V K, Acharjee S C, Kalra V K, Angra S K. Behaviour of cone of keratoconus under a well fitted hard contact lens. Indian J Ophthalmol 1984;32:522-4

How to cite this URL:
Dada V K, Acharjee S C, Kalra V K, Angra S K. Behaviour of cone of keratoconus under a well fitted hard contact lens. Indian J Ophthalmol [serial online] 1984 [cited 2022 Dec 6];32:522-4. Available from: https://www.ijo.in/text.asp?1984/32/6/522/30859

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Table 3

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Table 2

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Table 1

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Table 1

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Historically it has been said that contact lenses either stop or slow the progression of Keratoconus. Due to relatively limited number of patients, difficulty in early diagnos­is, lack of quantifying tests and the multiple fitting procedures, the corneal distortions caused by contact lens and the need of con­trol group, it is impossible to carry out a study to prove its effect or lack of its effect on the cone of keratoconus. In the present study an attempt has been made to analyse the keratoconus cases fitted with PMMA lenses for the last 10 years. [1],[2],[3],[4]

  Materials and methods Top

The study highlights 123 eyes of 74 successfully fitted patients of keratoconus who attended the contact lens clinic over the past 10 years.

Fitting Techniques

Contact lenses were chosen between the two keratometric readings or a steep trial lens was fitted over the irregular cornea. After stoppage of watering fluorescein pattern was observed. Multicurve apical lenses were fitted. Minimal apical clearance or 2 to 3 mm. apical touch was permitted, When former philosophy of clearance was not possible. Adequate tear exchange was estimated by fluorescein drainage. All physiological cons­traints were judged after 4 hour trial wear. After finalization of the base curve, over refraction was done through the same contact lens to determine the power. Patients with scarring, hydrops, advanced cones were not included in the study.

Post Fitting Care

Wearing time was increased very slowly half to one hour in four days. Total wearing time was divided in two shifts with 1-2 hours of rest without lenses. Cases were called for follow up once a week for 2 months, once a month for 6 months and then once every 6 months.

During the follow up visits wearing schedule, vision, refraction, lens corneal relationship, fluorescein pattern, corneal affection if any and keratometry reading along with patients complaints were record­ed. When apical touch became more than 4 mm the old lens was replaced by anew steeper lens.

  Observations Top

Contrary to the published literature, keratoconus was found more commonly in males (54.05%) as compared to females (45.94%). In 9.85% of the cases it was unilateral. 75.67% cases were between 21 to 40 years of age [Table - 1].

The visual improvement was 6/12 and better in 81.29% of eyes [Table - 2]. 43.90% had 6/6, 21.13% had 6/9 and 16.26% had 6/12 vision. Base curve varied between 42.00 D to 65.OOD (60% between 46& 5ID) and the power was between +3.5 to -22.00 D. Overall diameter ranged from 6 00 mm to 9.50 mm.

Regarding the behaviour of the cone after proper fitting of contact lens [Table - 3], 20 eyes (16.26%) out of 123 showed regression in base curve upto a maximum of 9 50D. Maximum reduction of power of contact lens was -5.50D. In seventeen eyes (13 82%) the cone progressed in spite of the contact lens, maximum steepening of base curve being 13.60 D. Myopia increased in those eyes upto 15 5D. Remaining 86 eyes (69.9%) showed no change during the follow up period. Three eyes were submitted for P.K.

Common complications were corneal oedema, 3-9 O'clock staining, congestion of the eye and swelling of the lids. Initially, few cases complained of displacement of the lens.

  Discussion Top

It has been said that contact lens either slows or stops the progression of the keratoconus. In the present study 69.91 eyes remained stationary. 16.26% showed regression and 13.82% showed progression of the cone under a well fitted PAMMA lens till the time of reporting. Three cases (2.43%) have been subjected to keratoplasty.

It is difficult to predict whether these eyes will behave in the same way or not in the years to come. Only further follow up can show the result. Due to the limited number of cases and lack of control group it is difficult to substantiate the effect of contact lens. As the lenses were fitted at an earlier stage in the younger age group (21-40 yrs) in 75 67% cases, we presume that this is the reason for the high incidence (69.91 %) of non progres­sion of the cone. Moreover, improvement of visual acuity ranging from 6/12 to 6/6 in 81.29% eyes alone makes contact lens an absolute optical indication, as this much vision is impossible to achieve by giving spectacles in a highly irregular astigmatic eye. We can conclude that there is no positive evidence at present that contact lenses are beneficial or detrimental to the progression of cone. The cone may have a variable course in patients who do not use even contact lenses and if such a patient wears contact lenses then one may attribute this to the use of contact lens. However, due to their tre­mendous optical advantage over other modes of correction in the absence of any evidence of adverse effects, patients should be strongly encouraged to wear them.

  References Top

Dada, V. K., 1983, Contact lenses, Text book for practitioners and students.  Back to cited text no. 1
Hales, R.H., 1982, Contact lenses-A clinical approach to fitting, Williams & Wilkins, London.  Back to cited text no. 2
Hartstein J., 1973, Questions & Answers in Contact lens.  Back to cited text no. 3
Stein H. A, & Slatt B.J., 1977, Fitting Guide for hard and soft contact lenses. The C. V. Mosby Company, Saint Luis.  Back to cited text no. 4


  [Table - 1], [Table - 2], [Table - 3]


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