A clinical review of non-age-related cataracts.

BACKGROUND: A cataract is any opacity or partial loss of transparency of the lens, whether the absence of transparency is small or complete. Pupil dilation affords a view of a legion of internal variations and abnormalities of the human crystalline lens which often tell us about its events and insults, as well as when in the patient's life these might have occurred. METHODS: In this article, we review the major non-age-related association of cataractogenesis with respect to metabolic, environmental, ocular-specific, infectious, dermatologic, retinal, and toxic etiologies. The data are presented from the clinical perspective of incidence for a given condition and cataract type. RESULTS: Two simplified summary reference sheets are provided: (1) frequency of occurrence vs. etiology and (2) cataract type vs. etiology (color-coded). The busy clinician can refer to both tools chair-side. CONCLUSIONS: The human body has numerous methods of signaling insults and abnormalities. As the crystalline lens is an important gauge of overall health, an argument can be made for routine dilation of all patients. This information is also essential for future neutraceutical and pharmaceutical therapeutic intervention.

Water soluble antioxidants in mammalian aqueous humor: interaction with UV B and hydrogen peroxide.

HPLC/electrochemical detection was used to identify five major low MW water soluble electrochemically active molecules from the aqueous humor of three species of mammals: New Zealand White rabbits and humans (diurnal) and Sprague-Dawley rats (nocturnal). These molecules are L-cysteine (CYS), L-ascorbic acid (AA), glutathione (GSH), uric acid (UA) and L-tyrosine (TYR); all of these molecules have known antioxidant properties. Nocturnal rat aqueous humor is concentrated in two thiols: GSH (125 microM; n = 24 pooled eyes) and CYS (63 microM), in contradistinction to diurnal species which have high concentrations of AA. No deterioration of any of these antioxidants occurs in a synthetic aqueous humor mixture irradiated with a physiologically relevant spectral UV B dose of 30 mJ/cm2/h (5.5 UV equivalent sunlight hours). The same result occurred with addition of the endogenous aqueous humor UV B photosensitizer L-tryptophan. In a second set of experiments, human synthetic aqueous humor was subjected to hydrogen peroxide induced oxidant stress. The decay of antioxidants was CYS > GSH > AA > UA > TYR. The second highest concentrated antioxidant in human aqueous humor is TYR. Yet TYR failed to protect AA against H2O2-induced free radical damage in a synthetic aqueous humor model system (P = 0.10; ANOVA). The existence of multiple electrochemically active constituents and their thermodynamic interactions must be recognized when choosing animal models to evaluate human aqueous humor antioxidant defense.

Ocular oxidants and antioxidant protection.

Oxidative damage and antioxidant protection in ocular tissues has not been reviewed recently. Metabolism in the eye is of increasing interest because the organ is highly susceptible to damage by sunlight, oxygen, various chemicals, and pollutants. Interest is expected to increase because of an aging Western world population and a continued depletion of stratospheric ozone. Hydrogen peroxide is discussed because it is both a byproduct and a source of free radical reactions and is normally present in the aqueous humor. The metabolism of reactive oxygen species by enzymes, nutrients, pigments, and low molecular weight scavengers is evaluated. Ascorbic acid, because of its high concentration in the eye, is thought to be a primary substrate in ocular protection; progress in determining the mechanisms by which it is recycled and maintained in the useful, reduced state is discussed. Recent information is included about antioxidants not previously known to be present in the eye, and some importance is placed on the properties of the vitreous humor and tear fluid because of the previous lack of emphasis on these.

Tear fluid content of electrochemically active components including water soluble antioxidants.

PURPOSE: To describe the content of water-soluble antioxidants in tear fluid. METHODS: We collected tear fluid from healthy subjects, either into borosilicate glass tubing or by absorption onto Schirmer strips. High pressure liquid chromatography with electrochemical detection provided data on several components in a single assay. The system was sufficiently sensitive to provide reliable values for components present in tear fluid collected at normal (basal) or stimulated rates of secretion. RESULTS: Tear fluid at basal secretion was found to contain four compounds often considered to function in biology as antioxidants. Ascorbic acid (AA) is found at 665 microM, tyrosine at 45 microM and glutathione (GSH) at 107 microM. Cysteine (48 microM) and uric acid (328 microM) are reported for the first time; the latter is somewhat controversial as a physiologically active antioxidant. One peak on the chromatogram was consistently present but has not been identified. During stimulation of flow by brief inhalation of ammonium hydroxide fumes, the concentration of each compound was lower. CONCLUSION: This work demonstrates the presence of electro-chemically active components that might function as antioxidants at the anterior surface of the cornea against potential damage from radiation, oxygen toxicity, abrasion and environmental chemicals.

Properties of electrochemically active components in mammalian vitreous humor.

Antioxidants are considered to have important roles in protecting the eye against radiation, oxygen toxicity and other threats. Several water-soluble electrochemically-active compounds that might function as antioxidants in vitreous humor of rabbit, rat and bovine eyes were identified and quantitated. In that the rat is a nocturnal animal species and the other two are diurnal, the results allow a tentative evaluation on the comparative physiology of light-dark behavior patterns that influence this ocular fluid. All analyses were performed by HPLC with electrochemical detection. The utility of this approach is that components of vitreous humor can be identified by their retention time and by their characteristic response when the voltages of the two sensing electrodes are progressively brought together. Four compounds regarded as functional antioxidants in the animal kingdom were identified and quantitated. Other antioxidants known to be present in several biological fluids are not present at detectable or significant levels in vitreous humor; metabolites or precursors of these might be present in trace quantities.

An apparatus for ultraviolet B irradiation of small volumes of biological fluid under controlled oxygen tension.

BACKGROUND: The design, construction, and calibration of a unique apparatus for ultraviolet (UV) B irradiation of small volumes of biological fluid under temperature-controlled open atmospheric or closed cell conditions of defined Po2 is described. METHODS: The apparatus consists of a custom designed UV transmissible quartz silica 3 port spectrophotometric cuvette coupled to a deuterium UV B source by UV transmissible fiber optics. Fluid movement, temperature regulation, dosimetry, and miniaturized biosensors for oxygen, pH, and temperature are described along with a preliminary experiment. RESULTS: The apparatus produces a known photochemical effect using an endogenous aqueous humor UV B photosensitizer-L tryptophan. UV B radiation is contained, thus protecting laboratory personnel. The system provides a continuous spectral UV B dose of 30 mJ/cm2/hr, which is equivalent to approximately 5.5 UV sunlight hours reaching an aliquot of mammalian aqueous humor. CONCLUSIONS: This biophysical apparatus can be used to investigate antioxidant protective systems in ocular fluid (aqueous/vitreous humors and tears), and is also applicable to evaluating the interaction of radiation with ocular and nonocular tissue cell homogenate.

Is there a prevention and treatment strategy for macular degeneration?

BACKGROUND: Reduced antioxidant defense of the retina secondary to poor nutrition and smoking combined with increased life expectancy and exposure to solar radiation can provide a triple assault on the aging retina. If left untreated, without prophylactic measures, 7.5 million American adults will suffer vision loss from ARM by the year 2020. METHODS: Better known pathobiologic interrelationships between ARM, nutritional/antioxidant status and UV/blue visible solar exposure risk based on animal research and recent epidemiologic studies is presented, along with an overview of ocular free radical biochemistry. RESULTS: Because ARM begins parafoveally, and confounding ocular lens changes often occur, there have been practical clinical/research difficulties in early diagnosis, and assessing improvement/loss from nutritional intervention. Threshold Amsler grid testing, contrast sensitivity and more recently red foveal flicker fusion frequency testing are presented as promising tests for discerning subtle pathologic and functional changes in vision. CONCLUSIONS: A conservative prevention/treatment strategy is presented involving identification of at-risk patients, solar radiation protection, nutritional counseling based on the new USDA Food Pyramid concept and vitamin/mineral supplementation if necessary for non-compliant high risk patients. Excessive vitamin intake of particular micronutrients has some drawbacks, and the optometrist should be aware of the implications of self-prescribed OTC ocular formulations, the difference between UV risk vs. "blue light hazard" and ongoing clinical trials.

Case report: prismatic redirection of vision for progressive supranuclear palsy.

Limitation of extraocular movements in progressive supranuclear palsy is a significant and uncomfortable problem. Specially designed mirror-prism spectacles make it possible for these patients to read and feed themselves.

Presumed Toxocara canis with peripheral retinal granuloma and secondary macular hole.

Ocular manifestations of a presumed parasitic infection Toxocaris canis were discovered in the eye of a 53-year-old male presenting for a routine examination. Current serologic and skin tests were of little value in establishing the diagnosis, although the ELISA immunosorbent agglutination serologic test was helpful but not definitive. The clinician therefore was forced to diagnose this disease based on the characteristic clinical findings.

Mobility spectacles for a patient with ankylosing spondylitis.

A patient with severe postural deformity and mobility difficulties due to ankylosing spondylitis benefits from specially designed rim-less spectacles incorporating yoked fresnel base-down prisms.

Toward the design of an optimal filter for enhancement of dichromat monocular chromatic discrimination.

Based on Farnsworth's theories of color confusion and discrimination, "rose-colored" or "pink" filters such as the X-Chrom material of 0.16 mm in thickness or the Kodak Wratten no. 30 filter act as monocular chromatic enhancers for red/green color deficients by virtue of colorimetrically lengthening color space in a direction perpendicular to the dichromatic axis of color confusion. Using derived formulas for dichromat colorimetry, a set of representative isoluminant-isochroma spectral hues, and interactive computer graphic colorimetric tools, it is possible to determine an optimum spectrophotometric filter curve. Such a filter has minimal middle wavelength transmission and is optimal in terms of providing maximal monocular chromatic clues for discriminative tasks involving confused colors.

Effect of ophthalmic filter thickness on predicted monocular dichromatic luminance and chromaticity discrimination.

The majority of ophthalmic filters, whether they be in the form of spectacles or contact lenses, are absorbance type filters. Although color vision researchers routinely provide spectrophotometric transmission profiles of filters, filter thickness is rarely specified. In this paper, colorimetric tools and volume color theory are used to show that the color of a filter as well as its physical properties are altered dramatically by changes in thickness. The effect of changes in X-Chrom filter thickness on predicted monocular dichromatic luminance and chromaticity discrimination is presented.

Caruncle lesions: the use of histological evaluation in determining a definitive diagnosis.

Caruncle tumors are rare and difficult to definitively diagnose using standard clinical examination techniques. Because some of these lesions may be cancerous, eventually leading to local invasion of tissue, metastasis, and even death, biopsy with histologic evaluation may be indicated. A brief discussion of caruncle tumors and a case report is presented.