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Biomedical subjects

M G Harris

Publications and source records attributed to M G Harris.

At least 127 records · Page 7Linked to original sources
PubMed1976

Effect of tinted contact lenses on color vision.

This study was designed to investigate the effects of various contact lens tints on color vision. Color vision performance of eight subjects was evaluated with the Farnsworth-Munsell 100 Hue Test while each subject wore each of 13 differently tinted contact lenses. No significant differences in color vision were found with the various lenses. However, performance on the test was affected by repetition. Regardless of the lens tints tested, color discrimination for the blue quadrant of the 100 Hue Test was the poorest. Further research is needed to determine the effect of tinted contact lenses on scotopic and mesopic vision.

Adult↗
PubMed1976

Blood viscosity in man following decompression: correlations wiht hematocrit and venous gas emboli.

Whole blood viscosities were measured in U.S. Navy personnel before and after chamber compressions to 5 ATA (132FSW) and 7.4 ATA (210 FSW) by a new method described here. Bubble scores as a quantitative measure of venous gas emboli were determined during decompression and for 30 min thereafter. Hematocrit was measured both before and after each dive. There were five cases of decompression sickness in the two groups. No significant changes in whole blood viscosity, or hematocrit, were noted either in the group that was affected by decompression sickness or in all of the subjects taken as a group. No correlations between total bubble score and changes in viscosity or hematocrit could be made. These results imply that no major changes in viscosity occur in the usual forms of decompression sickness encountered in human beings.

Blood Viscosity↗
PubMed1975

Rotation of spin-cast hydrogel lenses.

This study was designed to determine if spin-cast hydrogel contact lenses rotate on the eye, and if so, to investigate the parameters which influence rotation. If these lenses do rotate, correction of residual astigmatism may be difficult, if not impossible. We monitored the lens rotation associated with 12 specially marked B and L Soflens TM contact lenses on six corneas after insertion and 30 minutes later by use of high speed motion pictures. To analyze lens rotation, the film was projected with a stop action projector and the amount of rotation measured with a protractor. Thirty-one percent of the 144 observations made showed some lens rotation, the majority of which was encyclorotation. Most of the lenses showed little or no change in rotation between the two time periods. Corneal curvature was the only lens or eye parameter associated with rotation. Why lenses were more likely to rotate on steeper corneas is not fully understood. Our findings indicate that Softlenses TM may rotate, but there is no definite way of determining in advance if a given lens will rotate on a given eye. This emphasizes the need for individualized lens fitting and proper patient monitoring.

Adult↗
PubMed1975

Corneal edema and vertical striae accompanying the wearing of hydrogel lenses.

Changes in corneal thickness and the ocurrence of vertical striae were monitored on 27 patients who wore both the "F" and "N" series Bausch and Lomb Soflens-TM (polymacon) contact lenses. Changes in corneal thickness were observed with both lenses; however, the "N" series lens caused slightly more corneal swelling. Vertical striae occurred in about 50% of the patients and was correlated with the development of corneal edema. In most cases where significant corneal edema was measured, it was possible to observe the edema using the biomicroscope.

Adult↗
PubMed1975

Corneal curvature and refractive error changes associated with wearing hydrogel contact lenses.

To determine if there are corneal curvature and refractive error changes associated with hydrogel lens wear, 27 patients wearing F series Bausch & Lomb SOFLENS-TM contact lenses were examined regularly for nine months. During the first month of lens wear, a mean corneal steepening of 0.23 DK plus or minus 0.18 and an increase in with-the-rule toricity were found, which persisted during the following eight months of wear. A mean increase in myopia of 0.35 DS plus or minus .211 DS was found after nine months of lens wear for five randomly selected patients. This amount of change was statistically significant and was highly correlated with the observed corneal steepening. Their lenses were removed after nine months of lens wear. Both corneal changes and the increase in myopia persisted during the 14 days after lens removal. If long term studies with larger samples show similar results, the effect of hydrogel lenses on corneal curvature and refractive error will have to be considered in the decision to fit this type of lens.

Adult↗
PubMed1975

Corneal curvature and supplemental power effect of the Bausch and Lomb SOFLENS contact lens.

The supplemental power effect (SPE) of F series Bausch and Lomb SOFLENS (polymacon) Contact Lenses was determined for a sample of 54 eyes. The mean value was +0.34 D=S.D.+/-0.37 D, range zero to +1.00 D. A significant correlation was present between the SPE and the apical lens-cornea bearing relationship. (p less than 0.01). The results of this study provide refractive evidence that a central lens-cornea alignment is achieved when the posterior apical radius of the lens is about 0.5 mm flatter than the flat radius of the cornea, S.D.+/-0.35 D. This information is clinically useful in assessing the patient's visual response as well as the fit of the lens.

Adult↗
PubMed1975

Patient response to PMMA contact lenses.

This study was designed to determine patient response to hard (PMMA) contact lenses and evaluate how lens modifications and refitting affect success. The subjects of this study were 178 randomly selected contact lens patients fitted at the University of California School of Optometry. Six to nine months after the patients were examined and fitted, their response to contact lenses was evaluated using the standard of Sarver and Harris. 44.4% of the patients were successful with the initial lenses while an additional 35.4% of the patients became successful after appropriate lens changes were made. The majority of the changes made were to eliminate ocular tissue changes. Our results indicate that lens modifications or refittings are often necessary to achieve a successful response to contact lenses.

Consumer Behavior↗