O. Hockwin

Glutathione peroxidase, glutathione reductase and superoxide dismutase in the aging lens

Glutathione reductase (GR) and glutathione peroxidase (GPx) show in bovine lenses a decrease in specific activity; furthermore, the heat lability of both enzymes increases with age monitoring structural changes of the molecules. GR activity was correlated with type of cataract in human lenses. Its decrease is significantly connected with cortical opacities. Superoxide dismutase activity declines in aging and cataractous lenses. These results support the assumption that in old lens tissue the capacity of the antioxidative scavanger system is diminished.

Investigations on lens transparency and its disturbances by microdensitometric analyses of Scheimpflug photographs

During the aging process, the lens is subjected to changes of its pertinent properties which condition the transmission of light of different wavelengths. Between the second and the third decade, for instance, wavelengths below 400 nm are almost completely absorbed. The increase in lens thickness, effected by the appositional growth during life, might be considered responsible for this phenomenon, if the newly developing lens fibers in the outer periphery would synthesize proteins which, with respect to light transmission, differ from those formed during the embryonic phase. For such a phenomenon, however, no indication was found either by clinical observations or biochemical research. -Microdensitometric analysis of Scheimpflug-photographs of the anterior eye segment allows measurements of lens transparency in the single lens which directly depend on the respective wavelengths used in the photographic procedure. Investigations performed with this method on a normal age-grouped population, show that the changes in light transmission are most evident in two of the lens segments. The lens nucleus shows a continuous increase in light scatter during aging. Also the anterior cortex - particularly in the deeper layers - shows changes in light transmission. With advancing age (beginning between 30 and 40 years of age), increased lens fluorescence is found in the region of the deeper anterior cortex, which can be excited by UV wavelengths of 330-380 nm. This phenomenon is not found in the lens nucleus. The localization of the changes within the lens clearly shows that they are due to age-related modifications of the protein properties earlier designated as posttranslational or postsynthetic molecular modifications.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-Related Changes in Water and Crystallin Content of the Fetal and Adult Human Lens, Demonstrated by a Microsectioning Technique

By means of a microsectioning technique, human fetal and adult lenses were divided into 8-16 fractions. The dry weight (DW), the water content, and the amounts of water-soluble (WS) crystallins and water-insoluble (WI) lens fraction were determined in each layer or fraction. Within the lens, the changes of these parameters are gradual and continuous. The lens nucleus contains the highest amounts of DW and WI fraction, and the lowest amounts of water and WS crystallins. There is a relative dehydration of the lens during development and ageing, most pronounced in the lens nucleus.

Ultraviolet-visible slit lamp densitography of the human eye

A new slit lamp densitographic apparatus (based on the Scheimpflug principle) capable of accurately and reproducibly recording visible changes in lens density as it ages was recently introduced. We have modified this apparatus to utilize u.v. radiation (300–400 nm) to measure and quantitate the age related fluorescence levels in the normal lens in vivo and correlate them with our in vitro data reported in previous communications. These studies demonstrate the feasibility of obtaining in vivo lens fluorescence data which are objective, reproducible and can be quantified. Several laboratories have demonstrated that u.v. radiation (longer than 300 nm) can play a role in the generation and enhancement of non-tryptophan fluorescence of lens proteins. Furthermore, we have previously reported that 8-methoxypsoralen, a known u.v. photosensitizer (used in treating psoriasis) can become photobound to nucleic acids and proteins within the lens resulting in its accumulation and the enhancement of lenticular fluoresence and phosphorescence. Thus, u.v. slit lamp densitography can be used to monitor objectively one parameter of lens aging (fluorescence) as well as photosensitized lens damage at a molecular level years before visible opacities become manifest by conventional slit lamp examination.

Photographic Documentation of Disturbances of the Lens Transparency during Ageing with a Scheimpflug Camera System

Due to its limited depth of focus, the conventional slitlamp photography is not suitable for the documentation of a total lens section which depends on a sufficient depth of focus. By applying the Scheimpflug principle it is, however, possible to demonstrate the optical section through the lens as a slit image which is nearly undistorted and shows sufficient depth of focus. An integrated instrument based on the Scheimpflug principle has been developed, and the present paper demonstrates its importance for clinical and experimental use. After densitometric evaluation, these photos enable to obtain hard data on normal and pathologically changed lenses. Different densitometric methods may be employed for the evaluation. Experiences with the equipment from running clinical test series are reported.

Improved Biometry of the Anterior Eye Segment

In this paper, a method is presented to evaluate the true values of several optical parameters of the anterior eye segment. These are: the thicknesses of the cornea and lens, the depth of the anterior chamber and the anterior and posterior curvatures of the cornea and lens. First, a photo is taken of each patients eye with a Topcon SL-45 Scheimpflug camera. There are two effects distorting the photo. As the film plane and the object plane are perpendicular to each other, the imaging scale is not constant over the photo, a phenomenon which is called the camera distortion. As the light passes through different refractive media on its way from the inner structures of the eye to the camera, the rays of light are refracted, which is called the refractive distortion of the eye. Following these distortions, the proportions on the photo do not correspond to those in the human eye. The intention of this paper is to calculate the true optical parameters of the anterior eye segment. The seeming optical parameters are taken from the photo and the path of light from a point in the film plane through the camera and the refracting surfaces into the eye is constructed by ray tracing. A set of representative points calculated according to ray tracing provides a basis to evaluate the true optical parameters. This work is done using a Basic program, that accepts the seeming parameters from the photo as input values and provides the true values as output. The adjectives seeming and true added to the optical parameters indicate a value correlating with a distorted photo and a value that was corrected by the theory. The two terms were chosen by mnemonic reasons, although another pair of adjectives such as distorted and corrected might have been of higher precision. For an average adult human eye the optical parameters from the photo were compared with the calculated ones. A phantom eye with well-known optical parameters was constructed and photos were taken from this eye to verify the calculations.

Biometry of the Anterior Eye Segment by Scheimpflug Photography

Scheimpflug photos of 262 cataract patients, classified according to various forms of opacifications characteristic for senile cataracts were evaluated by biometric methods. The measured values on cornea thickness, depth of anterior chamber, lens thickness, and radii of curvatures of cornea and anterior lens surface show that a correlation between some of the parameters and certain forms of opacities must be assumed.

Superoxide dismutase (SOD) in normal and cataractous human lenses.

Normal human lenses removed from eye bank eyes and cataractous lenses were assayed for superoxide dismutase (SOD) activity. In normal whole human lenses, SOD shows no marked difference in activity during aging. When comparing the activity in the nucleus with that in the equator, one finds that the activity in both lens parts has decreased with increasing age. The mean values of SOD are significantly lower in human lenses with mature cataract than in clear lenses. Interestingly, no residual activity could be proved in mature cataracts, whereas the activity in posterior subcapsular cataracts lay within normal limits.

Cataract and Health Status: A Case-Control Study

Data from 97 cataract patients and 105 normal controls with ages less than 67 years were collected with respect to sex, age, disease status, drug intake, and blood chemistries. The statistical method of fitting log-linear models was used to determine the association between the case-control indicator variable and the other variables. The following variables were shown to be important and to associate independently with the risk of developing cataracts: age, allergy, diabetes, hypotension, hypertension, use of analgesics and coronary disease.

Photo-Cell Device for Slit-Beam Adjustment to the Optical Axis of the Eye in Scheimpflug Photography

In the photographic documentation of lens findings according to Scheim-pflug’s principle, a good reproducibility of the camera adjustment to the patient’s eye is prerequisite for quantitative densitom