Antonio R. Gasset

Thermokeratoplasty in the Treatment of Keratoconus

Of 59 keratoconus eyes treated with the thermokeratoplasty procedure and followed for as long as two years visual acuity improved to better than 20/30 in most. Despite the varied procedures, temperatures, sites and duration of application, sizes and shapes of the probe, as well as follow-up periods, the results were satisfactory and compared favorably with the results of penetrating keratoplasty. Thermokeratoplasty did not preclude later penetrating keratoplasty. The disadvantages of the thermokeratoplasty procedure were: (1) a transitory corneal haziness; (2) production of corneal scarring if not properly done; and (3) the fact that further studies are necessary for better standardization of the technique. Despite these disadvantages, less than 5% of the patients who underwent thermokeratoplasty required further penetrating keratoplasty.

Hard Contact Lens Wear as an Environmental Risk in Keratoconus

We studied 162 keratoconus patients in an attempt to clarify the role of hard contact lens wear in the development of keratoconus. Forty-three (26.5%) of these 162 patients developed keratoconus while wearing hard contact lenses. In a group of 1,248 controls who were fitted for soft contact lenses and observed by us from one year to six years, only one patient developed keratoconus. We demonstrated a circumstantial association between hard contact lens wear and the development of keratoconus, but no cause-effect relationship can be drawn from the existing data. However, we concluded that hard contact lenses do not retard or halt progression of the cone. Hard contact lens wear could not be ruled out as the specific environmental risk factor triggering keratoconus in 26.5% of the patients. If we identify the genetic risk present in this subpopulation, eliminating environmental risks would be an effective means of preventing keratoconus in those predisposed individuals.

Benzalkonium chloride toxicity to the human cornea.

A 36-year-old woman fitted with a soft contact lens after an uneventful extracapsular cataract extraction was wearing her aphakic lens successfully until she switched her lens-soaking solution to an isotonic solution of boric acid, potassium chloride, and sodium carbonate preserved with benzalkonium chloride and edetic acid. After three days her eye became inflamed and vision decreased. No endothelial damage was apparent and the anterior chamber showed 2+ cell and flare reaction. Three weeks after removal of the lens and fitting with an aphakic lens visual acuity was 6/9 (20/30). Study of the preservative by a semiquantitative dilution method together with the clinical evidence in this case proved the cytotoxic effect of benzolkonium chloride when used to sterilize soft contact lenses.

Permanent wear of soft contact lenses in aphakic eyes.

In a five-year study, permanent wear of soft contact lenses was achieved by selecting patients and lenses properly, and offered a viable and probably safer alternative to intraocular lenses. Twenty-five of these 49 patients wore their initial lens or a similar lens continuously for over three years. A visual acuity of 6/12 (20/40) or better was obtained in 45 (91.8%) patients. Four (8%) had ocular problems not related to contact lenses that precluded the same improvement in central vision. The most common complications were reversible epithelial edema, superficial vascularization, and conjunctivitis. There was a strong correlation between edema and superficial vascularization in eyes fitted with lenses having a poorly made inside bevel. Calcium deposits were the most frequently found spot on permanent-wear soft contact lenses (nine eyes, 18%).