Epithelial and endothelial effects from the extended wear of contact lenses.
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Adult↗
Biomedical subjects
A Vannas
Publications and source records attributed to A Vannas.
Effects of long-term extended contact lens wear on the human cornea.
The effects of long-term extended wear of soft contact lenses on the human cornea were determined by examining 27 patients who had worn a high water content hydrogel contact lens in 1 eye only for an average of 62 +/- 29 months (mean +/- SD). The other eye, which was either emmetropic or amblyopic, acted as a control. The lens-wearing eye showed a 14.8% reduction in epithelial oxygen uptake (P less than 0.001), a 5.6% reduction in epithelial thickness (P less than 0.05), a 2.3% reduction in stromal thickness (P less than 0.05), the induction of epithelial microcysts, and a 22.0% increase in endothelial polymegathism (P less than 0.001). Endothelial cell density was unaffected by extended lens wear. No interocular differences in any of these physiological characteristics were found in a matched control group of anisometropic and amblyopic subjects who did not wear contact lenses. The patients ceased lens wear for up to one month and recovery of corneal function was monitored during this period. Epithelial oxygen uptake and thickness recovered within 33 days of lens removal. The number of microcysts increased over the first 7 days, but decreased thereafter; some microcysts were still present 33 days after lens removal. Recovery from stromal thinning had not occurred after 33 days following lens removal. There was a slight reduction in polymegathism in some patients, but overall this was not statistically significant. These findings establish (1) that the extended wear of hydrogel lenses induces significant changes in all layers of the cornea; (2) that lens wear suppresses aerobic epithelial metabolism, which may compromise the epithelial barrier to infection; and (3) that changes to the stroma and endothelium are long-lasting. Lens-induced effects on corneal physiology can be minimized by fitting lenses that have greater oxygen transmissibility (are thinner), are more mobile, more frequently removed, and more regularly replaced.
Adolescent↗
Surgical incision alters the swelling response of the human cornea.
The ocular characteristics and responses were examined in patients who had undergone extracapsular cataract extraction (ECCE), intracapsular cataract extraction (ICCE) and penetrating keratoplasty (PKP) in one eye only. In each of the three groups, corneal sensitivity (the inverse of corneal touch threshold), oxygen uptake rate, and endothelial cell density were lower in the operated eye than in the normal healthy fellow eye. For the subjects as a whole, the differences in ocular characteristics between the two eyes were proportional to the angular size of the corneal incision, with ECCE patients (33 degrees incision) showing the least differences and PKP patients (360 degrees incision) showing the greatest differences. Five patients from the ICCE group were subjected to an osmotic stress test. There was no statistically significant difference in the corneal swelling response between the operated eye (5.1%) and the unoperated eye (4.7%), indicating that surgically induced scar tissue does not restrict the swelling properties of the cornea. When subjected to a hypoxic stress test, all three groups manifested less corneal edema in the operated eye (ECCE -0.7%, ICCE -4.0%, and PKP -3.3%). The reduction in hypoxic corneal swelling could not be attributed to removal of the crystalline lens since a similar reduction was seen in the PKP group who had phakic eyes. The corneal swelling response correlated inversely with the corneal touch threshold and directly with epithelial oxygen uptake, but did not correlate with endothelial cell density.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Homozygosity of HLA-B27 antigen in the recipient and susceptibility to the corneal allograft reaction.
Our series consists of six penetrating grafts to recipients who were carriers of homozygous HLA-B27 antigen. The donor cornea had only a single or, in one case, no HLA-B27 antigen and thus all presented with at least one incompatible HLA-B antigen to the recipient. Five of six grafts failed, four due to an allograft reaction; in one case corneal oedema of unknown aetiology developed 10 months postoperatively. These results give further support to the hypothesis that the recipients bearing HLA-B27 antigen form an 'at risk' group.
Adult↗
Prostaglandin-inhibitor naproxen does not affect contact lens-induced changes in the human corneal endothelium.
A randomized, double-masked, placebo-controlled study was conducted to determine the effect of the prostaglandin-inhibitor naproxen on the bleb response of the corneal endothelium during hydrogel contact lens wear. Naproxen did not significantly alter the bleb response. This finding suggests that the endothelial bleb response is not prostaglandin-mediated.
Adolescent↗
Effect of prostaglandin-inhibitor naproxen on the corneal swelling response to hydrogel contact lens wear.
Previous studies have demonstrated that the prostaglandin-inhibitor naproxen can reduce post-surgical corneal oedema, which is largely due to an inflammatory process. To determine whether there is an inflammatory component in the oedematous response of the cornea to contact lens wear, we conducted a randomized, double-masked, placebo-controlled study on the effect of naproxen on contact lens-induced corneal swelling. This drug did not have a significant effect, suggesting that prostaglandins are not involved in the hypoxic oedema response. The discrepancy between the effect of naproxen on lens- and surgically-induced corneal oedema can be attributed to the different aetiologies of these oedema responses.
Adolescent↗
The ultrastructure of contact lens induced changes.
The endothelium of 15 human corneas was studied with specular and electron microscopy after exposure to a thick, low water content, soft contact lens (SCL). Five control corneas (no lens wear) were studied using the same methods. SCL wear produced obvious changes in endothelial morphology in 12 of the 15 eyes. With specular microscopy, the changes consisted of an apparent increase in separation of cells and development of areas of loss of membrane reflectivity (blebs). When viewed with electron microscopy, the changes in the same corneas consisted of oedema in the nuclear area of the cells and bulging of the posterior endothelial surface, in some cases over an area of several cells. In 4 cases, the cellular oedema was marked showing both intracellular and intercellular vacuoles. It was concluded that the transient endothelial changes seen with specular microscopy following SCL lens wear were produced by alterations in the contour of the posterior endothelial surface resulting from disturbance to the endothelial environment.
Adult↗
Deswelling of the graft cornea following hypoxic oedema.
Both corneas of 12 unilateral graft patients were subjected to 9% hypoxic oedema. Following removal of the hypoxic stimulus, the grafted corneas deswelled at a significantly slower rate (P less than 0.01) than the fellow unoperated corneas. We suggest that this can be attributed to a change in the barrier properties and/or pump efficiency of the endothelium. Monitoring corneal deswelling following hypoxic oedema could form the basis of a clinical test of corneal endothelial function.
Adult↗
Virus particles and leukocytes in herpes simplex keratitis.
Nine corneal specimens were obtained after penetrating keratoplasty for ultrastructural analysis. All the corneas had earlier suffered from herpetic infections and scarring. Six corneas presented vascularized interstitial keratitis and three corneas showed chronic keratitis. Five specimens with interstitial keratitis presented stromal herpes virus-like particles. All the corneas containing virus particles showed stromal lymphocytic infiltration, and in four, macrophages were present. In two cases, lymphocytes were in close contact with affected keratocytes, suggesting that cell-mediated immunity plays a role in herpetic interstitial keratitis. The corneas with disciform keratitis were free of virus particles and leukocytic infiltration. The observed ultrastructural findings suggest that retrocorneal ridges, a form of posterior corneal scarring, has its origin in a granulomatous reaction between the stroma and Descemet's membrane.
Adult↗
Bacterial contamination of donor corneas.
Bacterial contamination was studied in 146 donor corneas stored in McCarey-Kaufman (M-K) medium at 4 degrees C. Ninety-six corneas from 48 respirator connected donors were compared with other donor corneas. Staphylococcus epidermidis was the major contaminant. Cultures were more often positive and mixed flora more frequently present in donors who had been on a respirator prior to excision of the corneas. The contamination by bacteria other than Staphylococcus epidermidis and by mixed growth was the leading cause for excluding donor corneas. No case of bacterial endophthalmitis was encountered among 66 recipients, 40 of whom obtained a respirator connected donor cornea.
Adolescent↗
Corneal endothelium in herpetic keratouveitis.
The corneal endothelium underwent changes in 15 patients with unilateral herpetic keratouveitis. Study with both noncontact and wide-field specular microscopes showed that six patients had mild and nine patients severe keratouveitis. Transient endothelial changes indicating endotheliitis were observed in all eyes affected by severe keratouveitis. In three cases nonreflecting areas were observed with the specular microscope one to two days earlier than the conventional signs of anterior uveitis. This finding suggests direct herpes simplex virus invasion into endothelial cells that could be followed by an inflammatory cell attack against the endothelium. The eyes that had experienced severe keratouveitis showed marked pleomorphism of the endothelial cells and a 15% lower central endothelial cell density on average than the healthy fellow eyes. In the eyes with mild keratouveitis, the endothelial mosaic showed only a 1.4% lower endothelial cell density.
Adult↗
Pathology of iridectomy specimens in gyrate atrophy of the retina and choroid.
Gyrate atrophy of the retina and choroid is an autosomal recessive disease characterized by progressive retinal degeneration and ornithine aminotransferase deficiency. We report here the new histological findings and ultrastructural changes in 3 iridectomy specimens from 2 Finnish patients with gyrate atrophy. The iridectomy specimens were removed during routine cataract extraction and studied with a transmission electron microscope. The dilator muscle showed atrophy, abnormal mitochondria, and tubular aggregate type structures similar to those found in skeletal muscle. Degenerative changes such as extracted cellular matrix, dropout of cellular organelles, and dilated intercellular spaces were observed in the pigmented posterior epithelium and the anterior iris epithelium.
Adult↗
Substance P immunoreaction and acetylcholinesterase activity in the cornea and Gasserian ganglion.
Nerves showing acetylcholinesterase (AChE) activity or immunoreactivity for substance P (SP) were demonstrated in the human cornea. AChE-positive fibres were found in stromal nerve trunks from where they penetrated Bowman's membrane and formed a basal epithelial plexus. Intraepithelial terminals arose from this network. SP immunoreactive nerve fibres showed similar architecture but were fewer. Both SP immunoreaction and histochemical AChE reaction were demonstrated consecutively in the same tissue section cut from both human and rabbit cornea. Stromal nerve trunks were found to contain SP immunoreactive and AChE-positive nerve fibres. However, the AChE-positive fibres were much more frequent than those immunoreactive for SP. In the rabbit Gasserian ganglion all neurons showed AChE activity but only some 20% were SP positive. It is concluded that all the sensory trigeminal nerve fibres of the cornea show AChE activity but only a proportion of them contain SP-like material.
Acetylcholinesterase↗
Corneal endothelial cells in mono- and di-zygotic twins.
Noncontact specular microscopy was used to examine the corneal endothelia of monozygotic (MZ) and dizygotic (DZ) twins in the age groups 25-34, 35-49, and 50-69 years. Endothelial photographs were analysed in respect of 100 individual cells from both eyes of 48 subjects. The mean cell areas in MZ twins showed a strong positive pairwise correlation (r (RE) = 0.727, r (LE) = 0.933), but there was no statistically significant pairwise correlation in DZ twins (r (RE) = 0.080, r (LE) = 0.167). Statistically significant pairwise correlations were also found when the lowest or highest deciles of cell areas in MZ twins were compared, but not when respectively compared in DZ twins. It would seem that environmental factors have little effect upon pleomorphism and increase in cell area with increasing age. The endothelial cell characteristics in normal individuals seem to be mainly determined by genetic factors.
Adult↗
Substance P-immunoreactive nerves in the human cornea and iris.
Human corneas and irides obtained from corneal surgery or sector iridectomies were processed according to the indirect immunofluorescence technique for the demonstration of substance P (SP) immunofluorescence by means of a monoclonal SP antibody. SP immunofluorescence was observed in varicose fibers of the corneal epithelium and nerve trunks in the corneal stroma. SP-immunoreactive nerve fibers in the iris were detected mainly in the pupillary margin in both dilator and sphincter areas.
Cornea↗
Supplementary creatine as a treatment for gyrate atrophy of the choroid and retina.
Gyrate atrophy of the choroid and retina is a disease characterized by progressive constriction of visual fields, a 10-fold to 20-fold elevation in plasma ornithine, and depressed activity of L-ornithine:2 oxoacid aminotransferase. Morphologically conspicuous but clinically unimportant atrophy of Type II muscle fibers progresses concomitantly with the eye disease. A pathogenic component of the disease may be deficient formation of creatine, caused by hyperornithinemia, which leads to a shortage of cellular phosphocreatine energy stores. To test the therapeutic value of replenishing the postulated deficiency of creatine, we supplemented the diet of seven patients with 1.5 g of creatine daily. During one year of this treatment the diameters of Type II muscle fibers increased from 34.1 +/- 7.1 to 49.9 +/- 7.0 micron (mean +/- S.D.) (P less than 0.001). There was no significant increase in the diameters of Type I fibers. The visual-field tests showed no further constriction during the therapy. Fundus photography revealed slow impairment at an age otherwise associated with rapid progression of the disease. These promising preliminary results need further evaluation with long-term follow-up studies.
Administration, Oral↗
Gyrate atrophy of the retina and choroid. Two methods for prenatal diagnosis.
We report two methods for prenatal diagnosis of gyrate atrophy of the retina and choroid caused by an inborn error of ornithine aminotransferase activity. A high pressure liquid chromatography assay measures ornithine aminotransferase accurately and directly in cultured amniotic fluid cells. The differential incorporation of 14C-ornithine and 3H-leucine into cell protein measures OAT directly but rapidly and simply.
Amniotic Fluid↗
Herpetic endothelial keratitis. A case report.
Corneal endothelial reaction on a 60-year-old male with acute anterior uveitis following typical dendritic keratitis was studied by bio- and specular microscopes. The epithelial dendritic ulcer of the left cornea healed within 10 days with topical trifluorothymidin treatment. Six weeks later the same eye became red and painful and anterior uveitis was diagnosed. Changes in the endothelium suggested that endothelitis was also present. The non-reflecting black endothelial areas were documented as a new sign, by specular microscopy. The black areas disappeared in 3 days with topical trifluorothymidin and corticosteroid treatment. The pathomechanism of these transient black areas is discussed.
Cornea↗