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Biomedical subjects

J R Larke

Publications and source records attributed to J R Larke.

At least 19 recordsLinked to original sources
PubMed1991

Evidence for keratin proteins in normal and abnormal human meibomian fluids.

Hyperkeratinization of meibomian glands has been postulated to cause gland dysfunction. Recent investigations on rabbits show that keratin proteins are indeed present in the meibomian fluids of these animals. In this report we present our findings on the presence of these water-insoluble proteins in human meibomian secretions. 6 anti-cytokeratin antibodies, CK8, 18, 19, CK7, CK8, CK14, CK19 and AE1/AE3 were used against the keratin proteins expressed from the human meibomian fluids. Using the immunoblotting (dot blot) technique, abnormal waxy meibomian fluids obtained from subjects diagnosed to have meibomian gland dysfunction (MGD) were compared to normal clear meibomian fluids. The results show that keratins are present in a higher concentration (10%) in the abnormal human meibomian excreta as compared to the normals. Even though the presence of protein markers for keratinization in the abnormal meibomian excreta were not shown, the increased presence of keratin proteins in the abnormal meibomian fluids suggests that, in MGD patients, hyperkeratinization of ductal epithelium may have taken place. More keratin proteins (possibly those of higher molecular weights) were produced in addition to the keratin proteins normally produced by the duct epithelium. The increased amount of keratin proteins in the abnormal meibomian fluids may be explained by the susceptibility of duct epithelium to undergo the process of hyperkeratinization as postulated by other researchers.

Antibodies, Monoclonal↗
PubMed1990

Meibomian gland dysfunction: some clinical, biochemical and physical observations.

Dysfunction of the meibomian glands resulting from contact lens wear has recently been recognized. This study shows that 30% of lens wearers develop some degree of meibomian gland dysfunction after 6 months of wear whereas only 20% of non-lens wearers have similar problem. Thirty-three per cent of the male wearers have dysfunctioning glands compared with 28% of female wearers. The incidence does not depend on the type of lenses worn. There was no detectable differences between the composition of the abnormal fluid secreted by the dysfunctioning glands and the clear fluid coming out of the normal unblocked glands, as shown by thin layer chromatography. On studying the melting point of the lipids, we found that material from abnormal glands melted at approximately 3 degrees C higher than the normal fluid.

Chromatography, Thin Layer↗
PubMed1986

Wave front aberration in the hydrogel lens-wearing eye.

The topography of the vertical and horizontal meridians of the surface of the cornea and a soft lens in situ on the cornea, was measured with photokeratoscopy. From the collected results the wave front aberration was calculated. The data show that at high luminance with small pupil diameters aberrational effects will be minimal, while at low luminances with large pupil diameters visual function is likely to be impaired.

Contact Lenses, Hydrophilic↗
PubMed1985

Visual performance with soft hydrophilic contact lenses.

An instability of the visual correction is sometimes associated with soft hydrophilic contact lenses. However, this problem does not seem to have detracted from the commercial success of this form of refractive aid. To facilitate the quantification of visual performance during soft lens wear, a televised test system was developed and has been fully described elsewhere. Results are now presented of a clinical study using this television (TV) system. Visual performance scores, in conjunction with response latency and blink activity data, were obtained from the eyes of 27 experimentally naïve subjects during the first month of adaptation to soft contact lens wear. The results suggest that the soft contact lens wearer has recourse to a strategy whereby he can optimize his level of visual performance when necessary.

Adult↗
PubMed1984

Measurement of the refractive indices of hydrogel materials by interferometry.

The purpose of this study was to measure the refractive indices of hydrophilic hydrogel materials of different equilibrium water content. The need to measure the refractive indices precisely has been an important factor in the design of soft hydrophilic lenses. The inaccuracy of measuring the refractive index of hydrogel materials using an Abbé refractometer led to the use of a Linnik micro-interferometer. The experimental results showed a close agreement to the theoretical data.

Hydrogel, Polyethylene Glycol Dimethacrylate↗
PubMed1983

Apparent respiration rate of the human corneal epithelium with tetracaine HCl and benoxinate HCl.

Local anesthetics may have a cytotoxic effect which causes a depression in the apparent epithelial oxygen uptake rate (AEOR) of the cornea. We measured the AEOR of human corneas in vivo before and after applying 1% tetracaine (amethocaine) HCl and 0.4% benoxinate HCl. These drugs had no effect on AEOR. In human corneas that had been subjected to a period of hypoxia, AEOR was slightly higher after administration of benoxinate, a result in the opposite direction to that expected on the grounds of toxicity. The increase was not statistically significant. We conclude that clinical doses of tetracaine HCl and benoxinate HCl normally have a minimal cytotoxic effect, and that this is similarly true when benoxinate is applied to the cornea after contact lens wear.

Cornea↗
PubMed1982

Human tear protein fractions during waking hours.

Reliable collection and analysis of human tear proteins presents considerable problems. The volume of unstimulated tear samples is necessarily very small, although stimulated tears may be easily provoked with a consequent change in composition. In the present study, 5-microliters samples of human tear fluid were carefully removed, over a 10 min period, from 10 male Caucasian subjects with the aid of a 5-microliter "microcap". The procedure was repeated at 2-h intervals between 08.00 and 22.00 hours. The collected samples were individually separated into their major protein fractions using gel column electrophoresis. The separated material was stained and scanned, and the concentration of proteins present estimated by comparison with known protein standards. Consistent values for protein concentrations were recorded for all participating subjects, and no variation during waking hours was demonstrated.

Adolescent↗
PubMed1980

Microepithelial cysts observed in extended contact-lens wearing subjects.

After 18 weeks of a controlled comparative study of extended contact lens wear a male subject presented with ocular symptoms. Microepithelial cysts were observed in both eyes and, after examination, in the eyes of 44 other participating patients. The cysts have been photographed and the rate of recovery monitored.

Contact Lenses, Hydrophilic↗
PubMed1980

The evolution of the broken ring visual acuity test figure.

The evolution of the broken ring visual acuity figure is described, with particular reference to the contributions of Snellen and Landolt. Reference is also made to its recent application in a study of visual performance, where an angular version of the figure is generated on a television screen.

Humans↗
PubMed1979

The measurement of the Bausch & Lomb Soflens contact lens by interferometry.

A method is described for the measurement of the anterior and posterior radii of curvature and thickness or a soft (hydrogel) contact lens. The method is based on the observation of an interference pattern that is generated by two beams of light, one reflected from the surface of the lens and the other reflected from the surface of a comparison mirror. It was found that the maximum coefficient of variation for the measured values of the anterior and posterior radii of curvature was 2% and the minimum value was 0.6%. An accuracy of 1:10(3) for the radii of curvature and the center thickness of the lens is claimed.

Contact Lenses, Hydrophilic↗
PubMed1979

Corneal thickness in extended wear of soft contact lenses.

The continual wearing of a soft contact lens for a period of 20 weeks is shown to produce no significant evidence of corneal swelling, although the use of soft lenses in conjunction with a topically applied solution is shown to produce evidence of transient swelling. The extent of corneal thinning during waking hours is also shown to be reduced among wearers of contact lenses for long periods.

Contact Lenses, Hydrophilic↗
PubMed1979

Some clinically observed phenomena in extended contact lens wear.

Two groups of volunteer subjects wearing extended-wear soft lenses were monitored over a period of 20 weeks. Of 6 factors measured only 1, corneal touch threshold, was found to show evidence of progressive change. However, a high incidence of lens surface deposits was encountered.

Clinical Trials as Topic↗
PubMed1978

Thickness of human cornea measured by topographic pachometry.

In the hands of trained user, the topographic pachometer proves to be an instrument of acceptable clinical precision (standard deviation = 0.006mm). An examination of corneal thinning during waking hours revealed a rate of thinning which was greatest upon lid opening and which declined uniformly throughout the day (p = 0.01). An investigation into menstrually related change in corneal thickness revealed that at least 122 subjects would be required to investigate this change on an acceptable statistical basis (p = 0.05).

Cornea↗