Contact lenses and keratitis.
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Contact Lenses↗
Biomedical subjects
M Guillon
Publications and source records attributed to M Guillon.
Corneal desiccation staining with hydrogel lenses: tear film and contact lens factors.
This investigation monitored the response of established contact lens wearers using contact lenses made from Filcon 4a 77% water-content material in three different thicknesses (0.08, 0.10 and 0.12 mm) over a 6-hour period of wear under adverse environmental conditions. The results obtained showed the following. (1) In accordance with previous studies carried out with lenses of similar water content, the present lenses produced corneal desiccation staining under the challenging conditions of use. However, the staining produced was similar for all three lens thicknesses tested. (2) Corneal desiccation staining was present despite the good and stable fitting characteristics observed during the study, confirming that mechanical trauma is not a necessary cause for soft-lens-induced desiccation staining. (3) Corneal desiccation staining was associated with a rapidly destabilizing pre-lens tear film (PLTF) and a thinning lipid layer. The initial break-up of the PLTF and corneal staining were recorded with a higher incidence in the vertical quadrants than in the horizontal quadrants. The PLTF is thinnest and most unstable at the tear prism margin border, hence least efficacious at preventing evaporation. Corneal desiccation staining may be due, at least partly, to excessive evaporation at the contact lens front surface.
Adult↗
Hypoxic effects on corneal morphology and function.
Normal corneal metabolism depends on a critical level of oxygen, below which a series of acute corneal responses occur, including an increase in stromal lactate, a reduction in intercellular pH, and an increase in corneal hydration. These acute responses are reversible when normal oxygen is restored; however, it has been shown that chronic exposure to low oxygen levels can result in permanent morphologic changes in the corneal endothelium. Clinicians have expressed concern that these observed structural changes may also be accompanied by alterations in corneal physiology. Whether such effects occur is not known, since it has been difficult to assess human corneal function accurately. Recently, we have developed an in vivo test, able to measure overall corneal hydration control, that can be used to study the effects of hypoxia on corneal function. This test provides information on several characteristics of hydration control, one of which is the percent corneal thickness recovery per hour (PRPH) after inducing corneal swelling. In this study, we assumed that corneal hypoxia accompanies both extended and polymethylmethacrylate (PMMA) contact lens wear and that the dose received is related to the years of past lens wear. Using this paradigm, we explored the relationship of hypoxic dose to an endothelial polymegethism index (EPI), endothelial cell density (ECD), and PRPH in 36 subjects with varying contact lens wearing histories. Based on multiple regression analysis, the relative change (expressed as percent per year) associated with hypoxic dose (adjusted for age and gender) was found to be dose-dependent and corresponded to estimated changes of 1.70%/yr, -0.25%/yr, and -1.26%/yr, with 95% confidence limits of (-0.3, 3.7), (-1.4, 0.9), and (-2.6, 0.06) for EPI, ECD, and PRPH, respectively. These preliminary data suggest that hypoxic exposure alters endothelial morphology and reduces corneal function; however, it is important to indicate that this was a exploratory investigation with several limitations, and that therefore these results should be viewed as preliminary until more definitive studies are completed.
Adolescent↗
Hydrogel lens wettability during overnight wear.
The in vivo wettability of soft contact lenses worn by a group of 10 subjects was monitored over a 24-hour period including 8 hours closed eye. Two types of lenses were tested: Igel 67 (Prima) and Bausch & Lomb 70. They were each worn once in both eyes by all the subjects. The in vivo wettability of the lenses tested was evaluated by measuring the pre-lens non-invasive break-up-time (NIBUT) and assessing the nature of the pre-lens tear film structure. The results obtained showed good wettability throughout the study and no difference between the two materials tested, but a significant difference between open and closed eye wear. The tear film was far more stable (p less than 0.01) immediately upon waking (mean NIBUT 21.2 s) than during open eye wear (mean NIBUT 11.2 s). Also at waking the pre-lens lipid layer was thicker than during open eye wear and the lens surface had a greater mucous coating. The presence of a more stable pre-lens tear film at waking was associated with a different tear film structure. We believe these differences in pre-lens tear film structure are responsible for the greater stability recorded.
Adult↗
Effect of target contrast and luminance on soft contact lens and spectacle visual performance.
The visual performance of four soft contact lenses was investigated using visual acuity charts at six contrast levels (from 90 to 8%) under normal (250cd/m2) and reduced 92.5cd/m2) luminances. This investigation reveals significant differences not detected by conventional visual acuity measurements; in general, reducing luminance or contrast increases the magnitude of any recorded difference. Furthermore, the study pointed to a significantly poorer visual performance with spectacles compared to standard thickness soft contact lenses under low luminance and contrast conditions. Finally, a recommended examination routine is described.
Adult↗
Epithelial and endothelial effects from the extended wear of contact lenses.
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Adult↗
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↗
'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↗
[Incidence of mother-child contamination by Candida albicans during labor].
Two different studies assessed that materno-fetal contamination at time of delivery is not the usual way of colonization of newborns with Candida albicans. In a first study, occurence of Candida albicans in neonate units disappeared owing to prophylactic measures, such as strict care in hospital hygiene. In a second study, detailed herein and performed in an obstetric ward, it was found that despite a rate of vaginal Candida carrier of 19 %, candidiasis in newborns was exceptional.
Candidiasis↗