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Biomedical subjects

S J Tuft

Publications and source records attributed to S J Tuft.

48 records · Page 3Linked to original sources
PubMed1989

Corneal topography: a new photokeratoscope.

The assessment of the topography of the cornea is an important modality in the management of surgical procedures complicated by astigmatism. Additionally, the outcome of corneal refractive surgery is often best illustrated by photokeratoscopy. Currently available photokeratoscopes suffer from a number of deficiencies that include (i) the lack of topographic detail from the central cornea, (ii) the difficulty in transporting these units, (iii) the cost of such units. A photokeratoscope which addresses these shortcomings is described.

Cornea↗
PubMed1989

Limbal vernal keratoconjunctivitis: clinical characteristics and immunoglobulin E expression compared with palpebral vernal.

Limbal and palpebral vernal keratoconjunctivitis (VKC) are usually considered to be different expressions of the same disease. This single centre population of 120 patients with VKC had 32 patients with limbal VKC, 54 with palpebral VKC and 34 with mixed palpebral and limbal VKC. There were higher proportions of females (p = 0.015) blacks, Indians and Asians (p = 0.0001) in the limbal group and fewer limbal patients had other atopic diseases (p = 0.03). The age of presentation was similar for all groups; 87/112 (78 per cent) presenting before the age of 16. The follow-up period was shorter in the limbal VKC patients (p = 0.004) suggesting a shorter disease course. Only one limbal VKC patient developed corneal opacities compared to fifty (47 per cent) with palpebral or mixed VKC, 24 (27 per cent) of whom lost vision. Tear and serum levels of total IgE and specific IgE to the major inhalent allergens cat, house dust mite and grass pollen were compared in 17 patients with palpebral or mixed VKC and ten with limbal VKC; no statistically significant differences were shown. However the significant variations in sex, racial distribution and associated atopic disease suggest that limbal VKC may be a different disease from palpebral VKC although this is not expressed in terms of IgE production.

Adolescent↗
PubMed1989

The measurement of IgE in tear fluid: a comparison of collection by sponge or capillary.

We have used commercially available reference concentrations of immunoglobulin E (IgE) and tear samples from atopic patients to compare the recovery of IgE from fluid collected in cellulose sponges or glass capillary tubes. There was no statistically significant difference in the values for IgE in the reference samples recovered from capillaries or sponges (P = 0.16), but at some concentrations both methods produced a higher reading than the control samples (P less than 0.001). There was no significant difference when the values for IgE in the first or second of paired tear samples were compared using either sponges or capillaries for collection, but the mean value of samples collected by capillary tubes was lower (P = 0.02). The collection of tears in sponges for IgE estimation is less time consuming than capillary collection and for clinical practice it is as sensitive as collection in capillaries.

Conjunctivitis↗
PubMed1989

Corneal toxic changes after cataract extraction.

Over an 18-month period 10 patients (12 eyes) presented with severe corneal toxic changes after cataract extraction. Defined stages in the keratopathy included punctate epithelial keratopathy, pseudodendrite, central epithelial ulcer and central stromal ulcer. Periods of up to 13 months were required for resolution of the defects. Axial scarring and nonhealing epithelial defects resulted in a final visual acuity of counting fingers and hand movement in two patients. We believe that exposure during the postoperative period to benzalkonium chloride contained in ophthalmic medications represents the most likely cause of the toxic changes and that no single ophthalmic medication can be held responsible. The past ocular histories of the patients included chronic open-angle glaucoma, dry eye syndrome and anterior membrane dystrophy. Prior exposure to benzalkonium-containing antiglaucoma medications, tear film deficiencies or abnormalities of epithelial adhesion may have predisposed the corneas in these patients to the development of benzalkonium-related toxic changes.

Benzalkonium Compounds↗
PubMed1989

Corneal repair following keratectomy. A comparison between conventional surgery and laser photoablation.

We have used the fluorescent dye dichlorotriazinyl aminofluorescein (DTAF) to demonstrate corneal remodeling following keratectomy in the rabbit. The dye was applied to the surface of 3.5 mm diameter anterior keratectomy wounds produced by either lamellar dissection or photoablation with an excimer laser (193 nm) to a depth of 15, 50 or 75 microns. Stromal wounds that had been ablated in 12 concentric steps to produce a graded profile with a central depth of 15 or 30 microns were also studied. The repair process was followed for periods of up to 6 months. These results were compared to wounds of similar dimensions in which an intrastromal keratectomy was performed and the anterior stromal surface replaced. Sections examined by fluorescence microscopy showed that connective tissue was deposited beneath the epithelium of all anterior keratectomy wounds irrespective of their mode of induction or depth. The deposition of this new tissue, and an associated thickening of the epithelium over the wound surface, appeared to be complete by 1 month and tended to restore the original surface contour. The synthesis of connective tissue, but not the hyperplasia of the epithelium, was reduced by local steroid treatment. In contrast, an intrastromal keratectomy only stimulated the deposition of small amounts of new connective tissue at the wound junction without as marked a thickening of the overlying epithelium. These observations emphasize the importance of the epithelium in moderating repair after stromal loss, and suggest that remodeling may result in corneal haze and a change in the desired refraction if refractive surgery is attempted by anterior keratectomy.

Animals↗
PubMed1986

Endothelial repair in the rat cornea.

Destruction of the central endothelium of the rat cornea was produced by mechanical injury, total debridement, or transcorneal freezing. Endothelial repair was then studied using specular microscopy, histological staining, pachymetry, and autoradiographic analysis of the incorporation of tritiated thymidine into nuclear DNA. Following an initial process of cell slide to cover the endothelial defect, extensive cellular division occurred at the margins of the wound, with approximately 45% of cells in the wound area showing incorporation of tritiated thymidine. An intact monolayer of irregularly shaped cells was reestablished by 2-14 days, depending on the wound. These results suggest that the corneal endothelial repair processes in the rat are more analogous to those of the rabbit than to those of the cat or primate.

Animals↗
PubMed1983

Toxocariasis: a neglected entity.

Toxocara canis infects many dogs yet has been seldom implicated as a cause of human disease in New Zealand. Nine patients with diagnostic titres for Toxocara canis who were seen in Christchurch Hospital over a five-year period are described. Ophthalmoscopic signs of toxocaral infection were visible at the optic disc or posterior pole of all ten affected eyes. A localised disciform detachment of the macula or a focal granuloma on the disc or retina were the commonest lesions. Vision was reduced to 6/60 or less in five affected eyes while the remaining five eyes lost 2-4 lines of vision on the test chart.

Adolescent↗
PubMedDate not supplied

Corneal stem cells in review.

The cornea provides the eye with protection and the refractive properties essential for visual acuity. The transparent epithelium is highly specialized with basal and stratified squamous cells that are renewed throughout life from a stem cell population. The stem cells are thought to reside at the corneal limbus and may be maintained by a variety of intrinsic and extrinsic factors such as the local environment, survival factors, and cytokines. A number of markers have been localized to the limbus in an attempt to identify stem cells; however, definite stem cell identification remains elusive. During homeostasis and following injury to the corneal epithelium, the limbal stem cells divide to produce daughter transient amplifying cells that proliferate, migrate, and differentiate to replace lost cells. However, this cannot occur if the stem cell population is depleted. Limbal stem cell deficiency then results in corneal re-epithelialization by the neighboring conjunctiva, causing pain, poor vision, and even blindness. This review will focus on corneal epithelial stem cells in ocular surface repair and regeneration. The current knowledge of stem cell biology in the corneal epithelium, clinical consequences of stem cell deficiency, and therapeutic strategies aimed at reversing stem cell deficiency will be discussed.

Animals↗