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Biomedical subjects

H A Backman

Publications and source records attributed to H A Backman.

7 recordsLinked to original sources
PubMed1991

Ocular hypersensitivity to thimerosal in rabbits.

Rabbits were immunized to thimerosal conjugates and challenged with specific antigen-sensitized contact lenses. The symptoms of acute ocular hypersensitivity observed included corneal edema, corneal infiltration and erosion, infiltration of the anterior chamber, iritis, conjunctival edema and hyperemia, and a significant increase in mucous production. Occasional evidence of corneal neovascularization and giant conjunctival papillae were seen. All these parameters were assessed on a five-point scale (0 to +4) and tabulated as an ocular index. The index of ocular hypersensitivity correlated with the titers of the serum antibodies to thimerosal. The major class of serum antibodies consisted of immunoglobulin (Ig) G, with IgA compromising approximately 5% of serum antibodies. During the ocular challenge, the total and IgG tear antibody titers increased as a result of increased vascular permeability. The tear IgA titers increased to a lesser extent than IgG. The influx of serum proteins directly into the tear film was confirmed by a protein-dye tracer technique. Histologic analysis showed that the ocular inflammatory response was accompanied by both polymorphonuclear and mononuclear cell infiltrates into the cornea and conjunctiva. In conclusion, thimerosal-immunized rabbits show an exquisite sensitivity to the minute quantities of thimerosal conjugates adsorbed to contact lenses. Both serum and tear antibodies correlate with the severity of the ocular inflammatory response. This model would appear to simulate an antibody-mediated immune complex or Arthus type of ocular hypersensitivity commonly seen to foreign antigens including preservatives.

Animals↗
PubMed1990

Adsorption and removal of protein bound to hydrogel contact lenses.

Tear film proteins are known to adsorb to new hydrogel contact lenses. Using a radioiodine tracing technique, proteins were shown to adsorb to contact lens surfaces. The quantity of protein adsorbed to the contact lenses within 2 to 4 h was 1 to 3 micrograms/lens. The degree of protein adsorption varied from lens-to-lens depending in part on the water content of the lens. High water content ionic lenses bound the most protein, whereas lower water content and nonionic lenses bound less protein. Enzyme cleaning of the protein-coated contact lenses removed about 75% of the adsorbed protein. When the enzyme-cleaned lenses were reincubated with protein, similar quantities were quickly readsorbed within a similar period of time. The rate of readsorption appeared to vary with the type of enzyme used to clean the lenses. Hydrogel lenses adsorb protein from the tear film rapidly and irreversibly. Cleaning the lenses has only a partial and temporary effect on the bound protein. The lens-bound proteins could become partly denatured during their binding to the lenses. These observations suggest a possible role for such proteins in ocular sensitivity to contact lenses.

Adsorption↗
PubMed1978

How environment affects visual development: a selected review.

This selected review covers 60 papers on animal and human studies in which the development of vision, particularly the neural pathways, has been investigated in terms of environmental stimuli or their absence. Most of these studies are summarized in a single table. Emphasis is given to the early treatment of vision deficits.

Age Factors↗
PubMed1976

Visual accommodation variations during trans-atlantic cockpit duties.

Twenty airline pilots measured their near point of accommodation employing a modified Princes' Rule. Measurements were performed periodically travelling east- and west-bound. Five clerical control subjects performed the same measurements over 2 consecutive days. The ranges of variability of the nearpoint of accommodation were compared between the two groups, directions and days. No statistically significant differences in the variability of accommodation were found in the comparisons.

Accommodation, Ocular↗
PubMed1976

Medicare in Quebec.

A provincial health insurance system was introduced through Canada more than five years ago. The program and fee schedules for optometric and some ophthalmologic services are presented. Statistics are provided by the government concerning the utilization of optometric and some medical eye services according to the distribution of age and sex in the Quebec population. Relative costs of these services as well as the incomes of health care professionals are compared. It is hoped that this information will aid in the planning and development of the U.S. Medicare program.

Adolescent↗
PubMed1975

The design and prescription of multifocal lenses for civil pilots.

The aging (presbyopic) pilot has difficulty with near vision which can be a serious problem in the cockpit because of the complexity and uniqueness of his visual tasks. Numerous individual studies have been reported, but the aviation industry and vision care professionals do not have available to them a set of guidelines to permit the optimum fitting of spectacles for civil aviation pilots. In this study the cockpit vision environment was studied in ten contemporary aircraft. Twenty-five pilots of seven of these aircraft types participated in a spectacle design study. Experimental spectacles were designed for each pilot and evaluated for performance. Problems of pilot acceptance of reading aids, custom designing to the geometry of a given aircraft, balancing of the visual gains from complex designs versus difficulties in use and manufacture have been analyzed. Results of this study should be of value for human factors engineering, vision testing and accurate prescription for the presbyopic pilot.

Adult↗