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Sodium hydroxide sterilzation of intraocular lenses.

Intraocular lenses of polymethylmethacrylate contaminated with various inocula of bacteria, spores, and fungi were sterilized by modifications of the Ridley method using sodium hydroxide. Positive cultures were obtained from iris-supported lenses contaminated with concentrations of approximately 1 x 10(6) organisms per milliliter after one hour in 10% NaOH. No positive cultures were obtained when lenses remained in 10% NaOH for three hours, a time corresponding to a 1 x 10(-6) probability of surviving organism. The NaOH method, when appropriately used, is an effective sterilization process for intraocular lenses.

Aspergillus niger

Extended-wear contact lenses and intraocular lenses for aphakic correction.

We evaluated extended-wear soft contact lens use in 128 aphakic eyes of 113 patients, 44 of whom had been unable to wear conventional contact lenses; 116 eyes (91%) have been successfully fitted and have worn the extended-wear lenses without significant complication. Eleven patients were unable to wear the lens or had to be discontinued for transient lens-related problems. In 103 eyes successfully fitted the lens is removed for cleaning less often than monthly. Ninety six of the 116 eyes fitted have visual acuity as good as, or better than, with aphakic correcting spectacles. The results obtained with the extended-wear soft contact lens are similar to those obtained with intraocular lenses, except for the recent high incidence of inflammation seen after intraocular lens insertion when using ethylene-oxide-sterilized lenses.

Adolescent

The optical quality of currently manufactured intraocular lenses.

We selected 95 intraocular lenses from ten lens manufacturers for a study of optical quality. Tremendous variation in resolution from a high of 313 line pairs per millimeter to a low of 40 line pairs per millimeter was seen. All of the lenses from eight manufacturers showed greater than 100 line pairs per millimeter resolution, the American National Standards Institute proposed minimum. Five of the 95 lenses had greater than 1.0 diopter error, whereas 79 of the 95 lenses had less than 0.5 diopter error from the stated power. With respect to toricity, there were 11 lenses with greater than 0.25 diopter (built-in astigmatism), however, no lenses showed more than 0.5 diopter astigmatism. Two lenses had a built-in double image, another clinically significant problem. We believe the optical quality of the lenses from some lens manufacturers cannot be guaranteed.

Lenses, Intraocular

On understanding the optics of intraocular lenses.

The optical considerations of intraocular lenses can be understood, using only the formulae and principles taught in a typical basic science course in ophthalmology. Some of the more common optical problems associated with intraocular lenses are presented and the methods for their solutions are illustrated and explained.

Humans

Dry coating of intraocular lenses with bovine submaxillary mucin.

Uncoated intraocular lenses caused extensive corneal endothelial cell damage after in vitro contact (mean, 30.9% cell loss), whereas lenses coated with bovine submaxillary mucin type 1 caused minimal cell loss (mean 4.3%). No observable in vivo toxicity in the eye occurred when 0.1 ml of 3, 6, or 9% solution was injected into the anterior chamber. Mucin-coated lenses can be sterilized by ethylene oxide with no measurable adsorbence into the coating. Scanning electron microscopy confirmed the results from vital staining.

Animals

The fate of eyes from which intraocular lenses have been removed.

The author removed 26 intraocular lenses in a series of 800 implantations (3.25%). The factors leading to lens removal and the clinical and visual end-results are analyzed and presented in tabular form. The most common factors leading to lens removal were: corneal edema, cystoid macular edema, uveitis, vitreitis, iris erosion/laceration, recurrent dislocation, updrawn pupil, glaucoma and blunt injury. Post-removal complications were: poor wound healing, high astigmatism, amblyopia, cystoid macular edema, retinal vascular occlusion, optic atrophy and phthisis bulbi. The average length of time between lens implantation and removal was 18 months. The vitreous loss rate was 35% during lens removal. On the average, an eye gained two Snellen lines of vision following removal of the offending lens; 69% had the same or better vision post-removal, and 64% of eyes with corneal edema/dystrophy improved.

Eye Diseases

[Ocular pathology related to intraocular lenses (author's transl)].

This study describes the ultramicroscopic alterations in several types of intraocular lenses removed from eyes with persistent ocular inflammation or elevated intraocular pressure. In some instances the alterations found in the lens material could have caused ocular disease. The corneal edema present in eyes with intraocular lenses sometimes is related to trauma at the trauma at the time of intraocular lens implantation. In most cases the alterations are similar to those found in Fuchs' dystrophy. The presence of warts in Descemet's membrane indicate previous corneal pathology, an obvious contraindication to the use of these devices.

Cornea

The dangers of metal-loop intraocular lenses.

The author implanted 500 intraocular lenses (IOLs) during intracapsular surgery. Data from the 60 lenses with metal posterior loops showed a markedly high incidence of complication compared to plastic loops: twice as many overall complications, three times the cystoid mascular edema, three times the rate for subsequent corrective surgical procedures, and 30 times more IOLs had to be removed. IOL manufacturers are advised to abandon metal loops for intracapsular implantation. Polypropylene is suggested as the apparent ideal loop material.

Alloys

Detection, removal, and effect of unpolymerized methylmethacrylate in intraocular lenses.

Gas-liquid chromatography, infrared spectroscopy, or Raman spectroscopy were used to determine the level of monomer in intraocular lenses and in the preforms used in each step of the manufacturing process. Heating, lathing, molding, and grinding caused an increase in monomer content, presumably the result of depolymerization. The tendency of methylmethacrylate to volatilize, repolymerize, or dissolve precludes high monomer contents from persisting in intraocular lenses. Vacuum ovens or water baths significantly reduced the monomer content to levels of 0.5% or less. Lenses with a monomer content higher than that found in currently available commercial lenses had no effect on rabbit kidney cell cultures. Lens fragments with a similarly elevated monomer content were indistinguishable from lenses with a low monomer content in rabbit eyes. According to these data, monomer does not appear to be a toxic agent in currently available intraocular lenses.

Animals