Donald G. Pitts

Wavelength dependency of cataracts in albino mice following chronic exposure

Albino mice exposed to 1 X 10(-4) W cm-2 of UV radiation in the range 290-400 nm for 12 hr per day developed anterior lens opacities within 1-2 months after onset of the exposure. Histological changes demonstrated marked derangement of the lens epithelium. When the radiation was filtered with glass, eliminating radiation shorter than 320 nm, these opacities did not develop and the histology of the lenses was normal. We conclude that following chronic exposure, UV-B (290-320 nm) radiation is cataractogenic and acts via a mechanism involving the lens epithelium. UV-A (320-400 nm) does not appear to be cataractogenic, even with chronic exposure.

Glenn A. Fry Award Lecture, 1977. The ocular effects of ultraviolet radiation

The author reviews the previous known effects of UV radiation on the eye together with results obtained on human and animal eyes in his laboratory during the past 11 years. Damage to the cornea and lens is assessed, classified, and discussed. Methods of calculating safe UV exposures and establishing characteristics of protective devices are presented.

Ultrastructural analysis of corneal exposure to UV radiation

Abstract. The primate cornea was exposed to 300 nm UVR with five levels of radiant exposure from 0.08 to 0.6 Jcm−2. All cellular layers of the cornea were damaged at the 0.08 Jcm−2 exposure, and damage became more severe as the exposure level was increased. The corneal cells showed variable response in that essentially normal cells were found among damaged cells. Eight days post‐exposure using the 0.6 Jcm−2 level, the epithelium had regained its normal thickness and was populated largely by normal appearing cells; however, the stroma showed damaged keratocytes and the loss of keratocytes. The corneal basement membranes (the epithelial basement membrane and the posterior limiting lamina) and the anterior limiting lamina were not damaged at any exposure level except for an isolated area along the epithelial basement membrane in one cornea. Therefore, one is lead to conclude that basement membranes are unaffected by UVR. The endothelium continued to demonstrate the loss of mitochondria, endoplasmic reticulum and some vacuoles at 8 days after exposure. However, the endothelium appeared to have resumed its physiological function as demonstrated by the reduced stromal oedema. This research gives the first complete description of UV‐B induced corneal damage and repair of the full, in‐depth cornea of the primate using the EM.

Determination of infrared radiation levels for acute ocular cataractogenesis.

One hundred pigmented rabbit eyes and ten primate eyes were exposed to infrared (IR) radiation in the 715 to 1,400 nm wavelength range and to the full spectrum output from a 5,000 W Xenon high-pressure source. The ocular exposures were evaluated independently with a slitlamp by two researchers and classified for ocular damage. The primary ocular lesions resulting from exposure to IR radiation were corneal, iritic, and lenticular. Corneal damage varied from epithelial haze to epithelial erosion but no endothelial damage was found. The iris showed stromal haze and swelling. Lenticular changes showed small white dots that, occur at the level of the anterior cortex. All lens damage depended on iris involvement. Ocular damage was related to the rate of delivery of the IR radiation since the data show that as the irradiance level increases, the radiant exposure threshold decreases. Exposures for the full spectrum were found to be additive for irradiance levels at 4 W-cm−2 and above. The threshold radiant exposures for the full spectrum of 750 J · cm−2 for the cornea, 1,000 J · cm−2 for the iris, and 2,000 J · cm−2 for the lens were essentially identical to the IR exposure thresholds for the same irradiance levels. The primate threshold radiant exposure was a factor of six above the respective rabbit thresholds.

The efficacy of a UV‐blocking soft contact lens in protecting cornea against UV radiation

Abstract. Recently, it has been shown that UV keratitis is more serious than previously thought because it is not limited to the corneal epithelium but also involves the stroma and the endothelium. It is, therefore, very important to avoid ultraviolet radiation (UVR) damage, and the purpose of the present study was to examine the ability of a UV absorbing hydrogel lens to filter such wavelengths. Ultrastructural observations of rabbit corneas showed that a regular soft (Vistamarc normal) contact lens offered no protection, and since wearing one adds stress to the cornea it seems possible that the cornea may be more vulnerable to UVR trauma. A UV absorbing soft contact lens (Vistakon UV‐BLOC) provided complete protection to all corneal layers. Subepithelial nerve fibres in the traumatized corneas were mostly of normal morphology and may explain why UV keratitis is a very painful experience. It was concluded that a UV absorbing soft contact lenses with acceptable clinical performance may be prescribed on a routine basis.

Effects of Ultraviolet Radiation on the Eye

In humans, the eye has evolved into an incredibly sophisticated organ whose neurophysiologic responses to photons in a certain portion of the electromagnetic spectrum provide a constant detailed map of our immediate environment. The action spectrum for this response lies primarily within the 400–700 nm wavelength range, which has therefore been labeled the visible spectrum, or “light” The maximum of the eye’s spectral response corresponds roughly to the maximum of solar spectral irradiance. Because solar UV radiation is present during most of the daylight hours, the eye may be exposed daily to some amount of solar ultraviolet radiation throughout life.

Ocular effects of near ultraviolet radiation: literature review.

&NA; The literature related to the effects on the eye of ultraviolet radiation in the wavelength range 300 to 400 nm is reviewed. Insufficient data are available to establish criteria for ocular protection. Exposure of the eye to sufficient quantities of near ultraviolet radiation can interfere with synthesis of crystalline lens protein, catalyze lens proteins, produce chromatic changes in the lens, and enhance formation of cataract.

Sunlight as an ultraviolet source

An understanding of the spectral composition of sunlight is necessary if the effects of human exposure and protection criteria are to be meaningful. Also provided is a brief review of data for the ultraviolet UV solar spectrum in space and on earth that have been related to ocular damage. In addition, the effects of increases and decreases in the levels of ozone on the amount of ultraviolet radiation (UVR) reaching earth are presented. It is shown that enough UVR is encountered on earth to cause ocular damage and the damage will increase significantly as the levels of ozone decrease.

Ultraviolet-Absorbing Spectacle Lenses, Contact Lenses, and Intraocular Lenses

Optical materials that are available to the practitioner for protection of the eye against hazardous exposure to ultraviolet radiation (UVR) are discussed. Principles of protection, procedures for calculating safe ocular exposure duration, and transmittance curves of commonly prescribed spectacle lenses, contact lenses, and intraocular lenses are discussed. Suggestions are made to assist the practitioner in providing adequate protection for the patient.

Acanthamoeba culbertsoni and Contact Lens Disinfection Systems

Acanthamoeba culbertsoni was used in this study inasmuch as its susceptibility to disinfection has not been examined. Although heat was found to be the most effective means of disinfection some cysts survived this procedure. Chlorhexidine exhibited a dose-response kill curve but the most effective concentrations are also corneo-toxic. Polyaminopropylbiguanide (0.00005%) has good effectiveness against the cyst but was not completely cidal at the dose tested. Thimerosal (0.002%) and hydrogen peroxide (3%) were found to be without effect. These findings should give contact lens practitioners guidelines for selecting a disinfection system for their patients.