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Biomedical subjects

M Ruben

Publications and source records attributed to M Ruben.

At least 37 records · Page 2Linked to original sources
PubMed1981

Clinical aspects of the measurement of oxygen flux into the cornea.

A comparison was firstly done of the oxygen flux through the Bausch and Lomb Plano T lens, the Bausch & Lomb U3 lens, and the Duragel 75 lens with a sensor on the normal eye. The results showed that the Bausch and Lomb Plano T lens was the best for use with the sensor probe. The sensor was then used to obtain a comparison with the normal oxygen flux through a therapeutic lens on keratoplastic eyes and eyes with bullous keratopathy. The results showed that both conditions had a lower oxygen consumption than normal and that eyes with bullous keratopathy predictably had the lowest value.

Contact Lenses, Hydrophilic↗
PubMed1980

Penetration of mercury from ophthalmic preservatives into the human eye.

Single corneas of nine patients about to undergo full-thickness corneal keratoplasty were exposed to thiomersal by application of a hydrophilic gel contact lens preserved with this mercurial agent. These lenses were removed at operation 4 h later, and the lenses, corneal buttons, and samples of aqueous were taken for determination of total mercury by wet digestion and flameless atomic absorption. The contact lenses contained little residual mercury, but mercury was readily detected in the corneal buttons and in the samples of aqueous over the range of 1--60 ng/ml. Five control samples of aqueous obtained without exposure to mercurial preservatives contained less than 1 ng/ml mercury. Although specific effects on ocular function are not described, the use of these preservatives is associated with penetration of mercury into the aqueous in concentration similar to those reported with systemic poisoning by organic mercurials.

Aqueous Humor↗
PubMed1980

The pathology of soft contact lens spoilage.

Our study of a random series of more than 300 spoiled soft contact lenses reveals that virtually all lenses currently in use for daily or extended wear are subject to deterioration due to extraneous deposits, physical and chemical changes in the lens material, and microbial invasion. Common causes include ocular secretions, finger dirt and cosmetics, disinfecting and cleansing techniques, environmental factors, manufacturing defects and polymer impurities, mechanical stress and breakage, as well as aging and decay of the lens material. Mucoprotein-lipid deposits, with or without calcium, and calcareous deposits constitute the major forms of lens spoilage. Removal of encrusted deposits leaves surface irregularities and matrix defects which facilitate secondary spoilage including microbial invasion, and such lenses should be discarded. As virtually no soft lens material currently in use is "safe" for extended wear, the practitioner must carefully evaluated and follow his patients to identify those at risk of lens failure and spoilage complications. To eliminate spoilage, new lens materials and improved manufacturing techniques are needed. In the interim, for many patients, an inexpensive disposable soft lens which can be easily replaced, perhaps weekly or bi-weekly, may be the answer.

Acrylates↗
PubMed1979

Keratoconus, keratoplasty thickness, and endothelial morphology.

A group of successful keratonic grafts (51 eyes) up to 10 years from operation were examined to establish a relationship between graft thickness and acuity. Best acuity occurred in the grafts of normal corneal thickness. No grafts were thinner than normal; thus no tendency to keratonic thinning occurred. No relationship between age of graft and thickness was determined. Endothelial cell studies in vivo of a small number of grafts showed that cell counts a third of normal coexisted with normal acuity and corneal thickness.

Cornea↗
PubMed1979

Keratoplasty sensitivity.

Analysis of graft sensitivity showed a return to normal after 3 years in only one-third of the eyes. It is not known whether this is due to regeneration of abnormal or superficial nerve fibres. Contact lens wearers showed less sensitivity than spectacle wearers.

Contact Lenses↗
PubMed1979

Keratoconus keratoplasty curvatures and contact lens wear.

Fifty-three grafted keratoconus corneas chosen at random from several hundred operated upon over a 10-year period showed an increase in myopia after removal of sutures but a decrease in astigmatism. With the photoelectrokeratograph machine the spherical zone was shown to be limited to 3 mm with gross eccentricities. Half the patients chose to wear contact lenses after surgery and 10% had no correction. Contact lens wearers showed a much greater decrease in astigmatism than spectacle wearers.

Astigmatism↗
PubMed1979

'Silicone rubber' lenses in aphakia.

Tesicon, one of the commercially available 'silicone rubber' lenses, was used in the correction of aphakic patients. In 74% of cases the lenses were considered successful for a daily wear regimen by the patient. Furthermore, a small number of patients could wear this lens without interruption for 3 to 6 days at a time. Despite this good acceptance by patients, corneal problems (mainly staining) and lens problems (dry surfaces) were frequently encountered.

Adolescent↗
PubMed1978

Constant perfusion for dry eyes and sockets.

Several techniques have been used to treat dry eye, to irrigate the eye surface, or to apply drugs in solution. The commonest method is to apply drops. But a technique is needed for giving solutions over long periods either as drops or continuously. The apparatus described here consists of a replaceable plastic tank under mechanical pressure attached to capillary tubing which is kept in contact with the inner canthus of the eye. It was found to alleviate symptoms in severe dry eye conditions not alleviated by other methods.

Humans↗
PubMed1977

Keratoconus and coexisting atopic disease.

The association of keratoconus and atopic disease has been reported on several occasions but the only controlled clinical study that has so far been published found no evidence to support this view. Since it is now known that atopy is often associated with changes in various immunoglobulins, particularly IgE, it was considered desirable to determine the immunological profiles of a large series of keratoconus cases in order to seek evidence for coexistence of the two conditions in one individual. In this study of 182 cases of keratoconus a definite history of atopy was found in 35% compared with 12% in the matched control group. The serum IgE was significantly raised (P less than 0.001) in keratoconus and markedly so in those cases with associated atopic disease. Serum levels of IgG and IgM were also raised, but contrary to the findings of other observers IgA levels were normal. These findings suggest that atopic traits are more common in patients with keratoconus than in general ophthalmic patients.

Female↗
PubMed1977

Tear calcium levels and contact lens wear.

Hydrophilic contact lens spoliation can be associated with the deposition of calcium salts. The relationship between the concentration of calcium in tear fluid and contact lens use has been studied in healthy volunteers and in patients using various forms of hard and soft contact lenses, tear samples being collected with Schirmer strips and with lenses in situ. Methods are suggested for correcting data on calcium per strip to concentration when this cannot be directly determined. Further data were obtained by direct extraction of freshly removed soft contact lenses. The collected results indicate some variation in tear calcium concentrations, but values are unrelated to use of contact lens and type of lens fitted, and to the rates of tear flow with our procedures for collection. Local calcium concentrations are unlikely therefore to be a significant primary factor in soft contact lens spoliation, but the enlargement of the tear pool associated with the use of a soft contact lens does greatly increase the amount of calcium present, and this may be a factor in secondary deposition.

Adult↗
PubMed1977

Laboratory studies in the management of soft contact lens use.

Laboratory procedures may be of great value in dealing with lens spoilation and in monitoring the state of the cornea during lens wear. Deposition of calcium-rich material remains the only defined non-mechanical process involved in spoilation although other forms of deposit and discolouration occur. Excess calcium levels in tear fluid are not a feature of contact lens wear, but changes in the sodium-potassium concentration ratio of tears are found. The basis for this effect is obscure but ratio changes may be useful empirical indices of corneal function.

Adolescent↗
PubMed1976

Acute eye disease secondary to contact-lens wear.

In a three-month survey of some hospital consultant ophthalmic services, 82 instances of complications of contact-lens wearing were reported. Some of the complications gave rise to discomfort, but in only 5 cases was vision impaired.

Acute Disease↗