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CLAPIKS utilises the topical instillation of a nonsteroidal anti-inflammatory drug, ketorolac tromethamine 0.5% (Acular), to induce stromal thickening, combined with continuous wear of a tight-fitting, corrective contact lens which remolds the cornea while providing vision correction and patient satisfaction in the interim. Dr McDonald reported that his use of this technique in a series of 14 eyes of 12 patients resulted in a >0.5 D decrease in consecutive hyperopia in 11 (78.6%) eyes, with a mean dioptric change of 1.05 D. All but two of the eyes achieved a greater than one line increase in near or distance UCVA, with an average gain of three lines in Snellen or Jaeger testing.
The mean time to onset of an effect was 1.71 weeks and the mean number of weeks to achieve the desired endpoint was 8.29. During follow-up, ranging from approximately eight months to over two years, both the refractive change and improvements in vision have remained stable. The time to initiation of CLAPIKS in Dr McDonald’s series ranged from as early as one week after laser vision correction surgery to as long as 36 weeks. Patients returned weekly for slit-lamp examination, refraction and contact lens exchange, with a change in power as needed. Patients whose MRSE or visual acuity remained unchanged after three weeks were instructed to increase ketorolac dosing to six times a day. If there is still no change after two more weeks, CLAPIKS is discontinued. Responders continue NSAID use for two weeks after the desired refraction is reached while wearing a retainer contact lens. Based on his relatively small series, Dr McDonald observed the onset of response seemed to occur earlier when treating overcorrected myopia, compared to undercorrected hyperopia. Efficacy of the treatment appeared unrelated to the delay between its initiation and the laser surgery. The greatest amount of corneal steepening occurred among patients who had myopic PRK (average 2.25 D), while patients who were post-myopic or hyperopic LASIK achieved an average change of about 0.75 D. In addition, some patients achieved improved visual acuity without a change in MRSE. "Perhaps those latter cases could be attributed to corneal surface smoothing and secondary elimination of higher order optical aberrations as a result of the CLAPIKS treatment, although confirmation of that hypothesis would require aberrometry studies," Dr McDonald said. No complications were encountered and while the use of artificial tears or rewetting drops were allowed to alleviate discomfort from contact lens wears, most patients discontinued those agents within 48 hours. "CLAPIKS is an easy technique to correct hyperopia present after PRK or LASIK and can spare about three-quarters of patients the need for further surgery. Meanwhile, patients are generally happy to receive active intervention and enjoy good vision from contact lens wear. "I believe the minority of patients who eventually need surgery are more accepting of a secondary procedure than they might have been initially," Dr McDonald said. Dr McDonald credited Tal Raviv MD with giving him the idea for CLAPIKS. At the annual ASCRS meeting in 1999, Dr Raviv, a New York ophthalmologist, reported on his use of topical ketorolac to treat 14 patients with hyperopia from overcorrected myopia. Not all patients responded, but the average regression achieved was 1.1 D and the change was observed to be long-lasting in some eyes. A scientific basis for using the topical NSAID as a corneal steepening modality was suggested by studies conducted by Hank Edelhauser PhD, which showed that it induced stromal thickening. Evaluating both animal and human corneas, Dr Edelhauser noted that stromal thickness could be increased by 50 to 70 microns, but only if the epithelium was not intact. Dr McDonald’s protocol of adding the tight-fitting contact lens to NSAID instillation not only aims to mould the cornea and provide vision correction, but also serves to disrupt the epithelial barrier to improve NSAID penetration into the cornea. Patients with severe dry eye and/or collagen vascular disease complex should be treated very cautiously or not at all due to the increased risk of corneal melt reported with NSAID. Whether the contour change results from epithelial thickening or actual stromal change can be elucidated hopefully with high frequency ultrasound. "We expected patients might be bothered with irritation and dryness by the tight-fitting contact lens, but they were actually quite comfortable, probably because of the anti-inflammatory effect of the ketorolac," Dr McDonald observed. Jay
McDonald MD
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