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Biomedical subjects

R I Myers

Publications and source records attributed to R I Myers.

8 recordsLinked to original sources
PubMed1995

Ulcerative keratitis from overnight contact lens wear compared with other life risks.

Wearers of extended wear contact lenses are at increased risk for ulcerative keratitis compared with daily wear contact lens users. Using incidence rates, we compared ulcerative keratitis in contact lens wear with other diseases and serious life risks. "Comparative risk," a theoretical construct for this paper, is a framework through which the incidence rates are compared. Although the risks of ulcerative keratitis in extended wear are greater than with daily wear contact lenses, the risks of extended soft contact lens wear are 2-10 times less than the risks for non-fatal, serious and disruptive occurrences in a general population. Contact lens associated ulcerative keratitis is in the range of 10-20 times greater than the incidence of common causes of death in a low risk, middle-age population.

Adult↗
PubMed1991

Quantity of protein deposited on hydrogel contact lenses and its relation to visible protein deposits.

The purposes of this study were to determine if the quantity of protein deposited (QPD) upon hydrogel lenses was affected by enzymatic cleaning and to test the potential relation between QPD and visible protein deposition (VPD) and change. Seventy-four contact lens patients classified as "heavy depositors" wore new lenses for an average of 80 (SD = 32) days. Cleaning and disinfection solutions varied. One lens was cleaned weekly by a papain enzymatic treatment. The distribution of QPD measurements was bimodal and was related to the FDA material for nonionic, low water content lenses (FDA Materials Group no. 1). The mean deposition was 45 micrograms/cm2 (N = 112) compared with that of ionic, high water content lenses (FDA Materials Group no. 4), which was 1010 micrograms/cm2 (N = 30). VPD distributions were the same for the FDA Group no. 1 and no. 4 lenses. Enzymatic treatment did not significantly reduce QPD; however, enzymatic treatment did reduce VPD. Thus QPD and VPD are independent phenomena and possible reasons for this are given.

Adult↗
PubMed1990

Rotational characteristics and stability of soft toric lenses.

Toric soft contact lenses of a double slab-off design were fitted to 72 patients (128 days) with varying refractive requirements. Rotational characteristics and lens stability were studied as related to sphere power, cylinder power, and axis orientation. The patients were followed over a 1-month period. Although rotation of all lenses was skewed nasally, the total number of all lenses showing no rotation or temporal was somewhat greater than those with nasal rotation. In addition lenses of oblique axis displayed the least amount of rotational instability. Finally this study suggests some differences when comparing the rotational characteristics between with-the-rule and against-the-rule astigmatism correction, low vs. high myopia, and myopia vs. hyperopia.

Adult↗
PubMed1989

Lens rotation and spherocylindrical over-refraction as predictors for soft toric lens evaluation.

Prospective data from 72 patients (128 eyes) fitted with one type of soft toric lens of the double slab-off design were analyzed for lens rotation and spherocylindrical over-refraction (SCO) for the purpose of assessing their accuracy as predictors in soft toric evaluation. Initial trial lens data were compared with final lenses and best spectacle refraction. The mean difference in lens rotation between the initial and final lens visits was 9.9 degrees (SD = 11.5 degrees), and the mean difference between the actual refractive astigmatism and the expected astigmatism, calculated from ophthalmic cross-cylinder equations, was 0.22 D (SD = 0.12 D). Considerable variability existed in lens rotation in the various ametropias during the course of several assessments; SCO provides the best evidence of the fit of toric soft lenses. The implications for other lens types are discussed.

Astigmatism↗