The effects of hard and soft contact lenses on the corneal endothelium.

We examined the morphologic characteristics of the corneal endothelium in three groups of contact lens wearers: those who had used daily-wear soft contact lenses for an average of 6.3 years, long-term (greater than 20 years) users of hard contact lenses, and former users of hard contact lenses who had worn them for an average of 9.6 years but who had discontinued them for an average of 4.3 years. When compared to age-matched controls, all groups had similar endothelial cell densities but demonstrated significant increases in variation of cellular size (polymegethism) and shape (pleomorphism). We found that daily-wear soft contact lenses can cause endothelial polymegethism and pleomorphism similar to those caused by hard contact lenses and that the endothelial changes induced by hard contact lenses are more profound with greater duration of wear and are apparently not completely reversible.

The corneal toxicity of presurgical skin antiseptics.

In a study of the corneal toxicity of some commonly used presurgical skin antiseptics, we used biomicroscopy, corneal pachymetry, healing studies, and electron microscopy to compare tincture of iodine (2% iodine, 2.35% sodium iodine, and 46% ethanol), Hibiclens (4% chlorhexidine and 4% isopropyl alcohol with detergent), pHisoHex (3% hexachlorophene and detergent), Lavacol (70% ethanol), 7.5% povidone iodine scrub (with a detergent), and 10% povidone iodine solution (without a detergent) in rabbits. Five minutes after application, moderate corneal epithelial edema was noted in all groups except the saline control group. After three hours there was marked corneal de-epithelialization, conjunctival chemosis, and anterior stromal edema in all groups except those treated with 10% povidone iodine solution and 0.9% sodium chloride. After one week all corneas had returned to normal. Accidental instillation of 7.5% povidone iodine scrub into the tear film of a 33-year-old man resulted in almost immediate chemical chemosis despite prompt irrigation, demonstrating the corneal toxicity of this substance. These results indicated that a 10% povidone iodine solution without detergent causes minimal corneal toxicity whereas the other presurgical skin antiseptics tested are toxic to the cornea.

The effect of radial keratotomy on the corneal endothelium.

Morphometric analysis of the corneal endothelium was performed on 11 eyes of patients who underwent anterior radial keratotomy with the contralateral eye serving as the controls. We analyzed cell density, variation in cell size (polymegethism), and cell shape (pleomorphism) by computer analysis of central and midperipheral specular micrograms one year after surgery. The central endothelial density decreased from 2,503 to 2,419 cells/mm2 (3.3% decrease). The coefficient of variation in cell size (polymegethism) was 0.290 preoperatively and 0.309 postoperatively centrally. Central hexagonality was reduced centrally from 61.4% preoperatively to 56.8% in the operated on eye. These differences were not statistically significant (P greater than .05). In a separate subgroup of six patients, midperipheral specular microscopy under and between incisions disclosed a similar pattern of mild cell density decrease and morphometric remodeling one year after surgery. No morphometric characteristic was significantly different from the central control values (P greater than .05), suggesting that the corneal endothelial monolayer had stabilized one year after radial keratotomy.

The effects of sodium hyaluronate, chondroitin sulfate, and methylcellulose on the corneal endothelium and intraocular pressure.

Sodium hyaluronate (Healon), chondroitin sulfate, and methylcellulose have been used to protect the corneal endothelium from intraocular lens trauma. A study of the efficacy and toxicity of these compounds showed that 1% sodium hyaluronate, 0.4% methylcellulose, and 20% chondroitin sulfate were nontoxic to the corneal endothelium, but that 20% chondroitin sulfate caused a marked decrease in corneal thickness because of its hypertonicity. Anterior chamber injection of these viscous substances resulted in an increase in intraocular pressure. Within one to four hours the maximum intraocular pressure with 1% sodium hyaluronate was 67 +/- 4.1 mm Hg and that with 20% chondroitin sulfate was 55 +/- 3.5 mm Hg. The intraocular pressure did not increase to these high levels with 10% chondroitin sulfate or 0.4% methylcellulose or when the test substances were washed out of the anterior chamber. The corneal endothelium was protected from injury with 1% sodium hyaluronate and 20% chondroitin sulfate, but 10% chondroitin sulfate and 0.4% methylcellulose provided only minimal protection.