Biomedical subjects

J R Paugh

Publications and source records attributed to J R Paugh.

8 recordsLinked to original sources

PubMed1992

Equivalent oxygen percentage as a function of hydration in hydrogel lenses: an in vivo study.

Although many investigations have examined the parameters of hydrogel lens hydration loss, the in vivo effect (in humans) on lens oxygen behavior has not been characterized previously. Human subjects wore 2 different lenses (a thin, 38% water polymacon lens and a thin, 55% water bufilcon lens) for 5-min periods under either fully hydrated (i.e., with saline regularly applied to the lens) or partially hydrated (i.e., with "normal" wear of 1 blink every 5 s) conditions. An equivalent oxygen percentage (EOP) technique and a gravimetric method were used to determine lens oxygen behavior and hydration, respectively. The hydration results demonstrate that significant lens dehydration occurs during the partially hydrated (normal blink rate) condition compared to the in situ, fully hydrated situation. A corresponding, statistically significant diminution in oxygen equivalency was also observed.

Adult↗

PubMed1990

Prevalence of Meibomian gland dysfunction.

This study was performed to determine the prevalence of Meibomian gland dysfunction (MGD) and to determine which patient profile factors might be associated with the syndrome. Patients were randomly selected, apparently normal patients presenting for routine vision examinations. Of the 398 patients for whom Meibomian gland expression was performed and a detailed history obtained, 155 patients or 38.9% exhibited MGD based on the principal clinical criterion of an absent or cloudy Meibomian gland secretion upon expression. Patient profile factors of gender, age, allergy occurrence, and contact lens wear were analyzed for correlation with MGD. Age was found to be the only significant correlating factor (positive correlation, p less than 0.0001).

Adolescent↗

PubMed1990

Meibomian therapy in problematic contact lens wear.

Utilizing the principal diagnostic criterion of an absent or cloudy Meibomian gland secretion upon repeated expression, patients with Meibomian gland dysfunction (MGD) were selected to participate in a study of the efficacy of lid scrubs and massage in the treatment of MGD. Twenty-one patients with contact lens intolerance unrelated to lens, care system, or health factors were randomly assigned to treatment of one eye with common clinical therapy for MGD. After 2 weeks of treatment, gland expression, biomicroscopy, staining, comfort, and fluorescein breakup time were assessed in a masked manner. Analyzed using a paired-data t-test, the results indicated a significant increase in mean tear film breakup time (BUT) in the treated eye at follow-up compared to baseline (mean increase = 4.0 s, p = 0.0001). The control eye demonstrated no significant change (mean increase = 0.2 s, p = 0.5955). These objective results were corroborated by reports of improved subjective comfort with contact lens wear after therapy.

Adult↗

PubMed1989

Reliability of corneal oxygen flux measurements.

Serial oxygen flux measurements were obtained from the same cornea of 5 human subjects after exposure to ambient air, a test gas mixture (2% oxygen, balance nitrogen) and 100% nitrogen at 2 individual measurement sessions. Analysis of variance (ANOVA) of the individual flux measurements for the test gas indicates that there were significant differences in corneal oxygen flux rates among subjects and sessions. Referencing the flux data for the test gas to the data for ambient air reduced the variability of data between sessions, although significant intersubject differences were still present. By referencing the flux data for the test gas to the concurrent air and nitrogen data, differences among subjects, as well as sessions, were reduced to the extent that they were not statistically significant. Standardization of data is important in the interpretation of corneal oxygen flux data so that intersubject and intersession differences can be minimized.

Air↗

PubMed1988

Ocular response to hydrogen peroxide.

A controlled, randomized, double-masked study was conducted on eight human subjects to determine the threshold level of hydrogen peroxide, which is toxic when introduced into the eye via a high water content (75%; Durasoft 4) hydrogel contact lens. Subjective comfort, conjunctival hyperemia, corneal and conjunctival epithelial staining, and corneal oxygen uptake were assessed in response to 5-min wear of lenses that were presoaked in isotonic saline solutions of physiologic pH containing 0, 25, 50, 100, 200, 400, and 800 parts per million (ppm) hydrogen peroxide. Higher levels of hydrogen peroxide were associated with greater discomfort (p less than 0.05) and increased conjunctival hyperemia (p less than 0.001). The highest level of hydrogen peroxide tested (800 ppm) did not induce significant corneal or conjunctival epithelial staining or alter the corneal aerobic response. We conclude that residual concentrations of hydrogen peroxide in contact lens care systems should not exceed 100 ppm. Practitioners can use these data to estimate the level of residual hydrogen peroxide to which a patient may have been exposed upon lens application after neutralization.

Adult↗

PubMed1987

Plus acceptance in hard contact lens wearers.

Hyperopes fitted with contact lenses often exhibit more plus acceptance compared to full spectacle correction beyond that accounted for by vertex distance considerations. The objective of this investigation was to attempt to identify the possible factors involved with this phenomenon. Eight hyperopes, one myope, and one control hyperope between 20 and 30 years of age were fitted with polymethyl methacrylate lenses, and over-refractions performed on different days with and without corneal anesthesia. The result was that every test hyperope accepted more plus without anesthetic than with anesthetic, by an average of 0.725 D, which was significant (p = 0.0000). One possible mechanism appears to be neurosensory feedback between corneal sensation and the level of accommodative tonus of the ciliary body.

Adult↗

PubMed1984

Polymorphic corneal abnormalities.

Alterations of the deep corneal layers, which are manifest primarily as Hassall-Henle bodies in older patients, are a relatively frequent finding in the normal population. Changes which occur in Descemet's membrane and the endothelium earlier in life can be ascribed to various causes, including dystrophy, herpetic infections, and birth trauma. Six cases in which clear vesicles and scalloped lesions were found exclusively at the level of Descemet's membrane and the endothelium are reported. Although the polymorphic changes were in some cases extensive, visual acuity and, apparently, corneal physiology remained normal. The etiology for all cases was uncertain, but the evidence suggested a dystrophic origin or the occurrence of posterior corneal vesicles of a nonfamilial variety.

Adult↗

PubMed1982

Is flatter and thinner always better?

In the current controversy regarding the relative importance of basecurve selection in hydrophilic lens design, one key to basecurve (bearing-relationship) predictability may lie in its subtle inter-action with another design parameter, lens thickness.

Contact Lenses, Hydrophilic↗