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Biomedical subjects

S J Tuft

Publications and source records attributed to S J Tuft.

At least 37 records · Page 2Linked to original sources
PubMed1995

Long-term refraction and keratometry after penetrating keratoplasty for keratoconus.

We looked for continued corneal ectasia after penetrating keratoplasty (PK) for keratoconus by measuring long-term changes in keratometry and refraction after final suture removal. The records of 587 patients who had had PK for keratoconus and who had attended a single center over a 7-year period were examined. For 184 eyes keratometry or refraction data were available from the first operated eye from the 6-month interval after final suture removal, and, in these patients, these readings were repeated as they continued to be seen for review. The changes in mean keratometry, spherical equivalent, and cylinder over the period of follow-up were then calculated, and these data were assessed by regression analysis. We found no significant change with time in the amount of cylinder when measured by either refraction or keratometry. There was a trend (p = 0.075) toward an increase in the mean keratometry with time, suggesting a gradual flattening of the cornea, and there was a clinically small, but statistically significant (p < 0.001), time-dependent increase in the residual myopia in the years after final suture removal. In conclusion, we found a wide range in the individual values for changes in keratometry or refraction in the years after suture removal following PK for keratoconus but no evidence overall to suggest continued corneal ectasia or a recurrence of keratoconus in these grafts.

Cornea↗
PubMed1995

Iris ischaemia following penetrating keratoplasty for keratoconus (Urrets-Zavalia syndrome)

A fixed and dilated pupil is an uncommon postoperative complication after penetrating keratoplasty (PK) for keratoconus. Although the clinical features have been well described, the precise aetiology is uncertain. We performed anterior segment fluorescein angiography in the early postoperative period on three patients who developed fixed, dilated pupils after apparently uncomplicated surgery. All of the eyes had severe iris ischaemia. A possible role for a postoperative rise in intraocular pressure in the aetiology of this syndrome is discussed.

Adult↗
PubMed1994

Acute corneal hydrops in keratoconus.

PURPOSE: To determine the clinical factors associated with the development of acute corneal hydrops and its subsequent outcome. METHODS: The authors identified 147 eyes (124 patients) with acute hydrops from a database of 5242 eyes (2723 patients) with keratoconus. They compared the clinical features of patients in whom hydrops developed with unaffected patients and assessed the progression to penetrating keratoplasty by actuarial methods. RESULTS: Patients in whom acute hydrops developed tended to be younger males who had advanced corneal ectasia and a poor corrected Snellen visual acuity at the diagnosis of their keratoconus (P < 0.001). Acute hydrops also was more common in the presence of severe allergic eye disease (P < 0.001). The development of hydrops was a very significant risk factor for subsequently receiving a penetrating keratoplasty (P < 0.00001) and at the end of the study period 87 (59%) of the 147 eyes had surgery for visual rehabilitation. These eyes had a greater rate of graft rejection than eyes grafted without hydrops (P = 0.02). After resolution of the hydrops, 46 of the 60 unoperated eyes had been refitted with contact lenses, of which 28 (61%) achieved a Snellen visual acuity of 20/40 or better, although a better visual acuity often was present in the contralateral eye. Microbial keratitis developed in two of these eyes after refitting. CONCLUSIONS: Although a penetrating keratoplasty often is indicated for visual rehabilitation after acute corneal hydrops, there is an increased rate of rejection. Only a minority of eyes were re-established in contact lenses after resolution of hydrops, but some patients achieved a functional level of visual acuity such that the procedure could be delayed or avoided.

Acute Disease↗
PubMed1994

Prognostic factors for the progression of keratoconus.

PURPOSE: The progression of keratoconus to a stage where penetrating keratoplasty (PK) is required for visual rehabilitation has considerable implications for affected patients. To assist with counselling, the authors have attempted to identify which factors measurable early in the course of the disease may indicate the likelihood of subsequent surgery. METHODS: The authors reviewed the records of all patients who attended a single center over a 7-year period for contact lens management of their keratoconus. The influence of clinical variables on the time taken for the worst eye to progress to PK was evaluated by actuarial methods and multivariate analysis. RESULTS: Included in the study were 2723 patients with a mean follow-up for unoperated eyes from the first visit of 4.5 years (range, 3 months to 28 years). Data were available for multivariate analysis in 2363 patients. At the end of the study period, 757 eyes (21.6% of all patients) had been grafted. The number of eyes progressing to PK was independently related to both the maximum and minimum keratometry, a corneal cylinder of more than 1.9 mm, the Snellen acuity, the racial group (P < 0.0001), and the age at presentation (P = 0.0006). Sex, laterality, systemic atopic disease, maternal or paternal age at birth, joint hypermobility, and a family history of keratoconus were not statistically related to outcome. Progression to PK in one eye increased the risk of progression in the contralateral eye (P < 0.0001) and a linear model of disease progression is proposed. CONCLUSIONS: Several clinical variables can be measured in patients at the presentation of keratoconus that influence the probability of a subsequent PK.

Adolescent↗
PubMed1993

The origin of keratopathy in chronic allergic eye disease: a histopathological study.

Although the clinical features of atopic keratoconjunctivitis have been well described, it is recognised that some adults with severe chronic allergic conjunctivitis do not develop a keratopathy despite having marked disease of their lid margins and conjunctiva. The aetiology of the keratopathy of chronic allergic eye disease is not known but may result from the release of toxic mediators from mast cells, eosinophils and neutrophils in the inflamed conjunctiva. To examine this theory we have counted these cells in tarsal and bulbar conjunctival biopsies from patients with severe allergic conjunctivitis and compared the numbers in samples from patients with or without keratopathy. Our results indicate that patients with chronic allergic conjunctivitis with keratopathy have higher cell numbers in their conjunctiva than patients with no keratopathy, especially those staining for eosinophil cationic protein in the tarsal epithelium. A statistically significant difference between disease groups could only be demonstrated, however, when the combined totals of mast cells, eosinophils and neutrophils were compared.

Adult↗
PubMed1992

Proteoglycan and collagen morphology in superficially scarred rabbit cornea.

We have examined the changes in collagen and proteoglycan morphology in superficial lamellar keratectomy wounds produced in rabbit corneas. The ultrastructural location within the tissue of keratan sulphate and chondroitin sulphate proteoglycans was demonstrated using the cationic dye Cuprolinic Blue under critical electrolyte conditions. Large proteoglycan filaments (up to 500 nm long) appeared in the early stages of wound healing; these were most common after two weeks' wound healing, after which they decreased both in number and size. At these early stages of scar formation, spaces containing proteoglycans were present amongst bundles of collagen fibrils. As proteoglycans play an important role in controlling corneal hydration, the presence of the large proteoglycan-filled spaces would result in an abnormally high water content which is found in early scar tissue.

Animals↗
PubMed1992

Role of Staphylococcus aureus in chronic allergic conjunctivitis.

A study was undertaken to test the hypothesis that Staphylococcus aureus colonization of the lid margins could determine the expression of allergic eye disease in atopic patients. The authors compared lid isolates of S. aureus from 23 adults who had both atopic dermatitis and chronic conjunctivitis and isolates from 14 patients who had atopic dermatitis but who lacked ocular disease. No significant difference was found in either the staphylococcal protein A or hemolytic toxin production by isolates from the two disease groups, and there was no difference between groups in the quantity of serum IgG nor IgE antibodies to staphylococcal ribitol-teichoic acid. In seven patients with chronic allergic conjunctivitis who were challenged with staphylococcal protein A or heat-killed S. aureus, delayed-type hypersensitivity was not enhanced. These results suggest that although S. aureus colonization of the lids is common in atopic patients, neither the pattern of toxin production nor humoral or cell-mediated immunity to S. aureus play a role in the expression of chronic allergic conjunctivitis.

Adolescent↗
PubMed1992

Peripheral corneal oedema following cataract extraction (Brown-McLean syndrome).

We describe the clinical features of 21 eyes of 15 patients who developed peripheral bullous corneal oedema following cataract extraction. The peripheral oedema was asymptomatic in all cases and was only noted at a review examination. Although the onset of the peripheral oedema was probably delayed for several years after surgery, it was not documented to progress in any patient or to involve the central cornea. Endothelial specular microscopy did not reveal any endothelial features that are specific for this condition, but confirmed that the central endothelial cell density can be as high as 2150 cells/mm2 in the presence of peripheral corneal decompensation. Despite the surface irregularity resulting from the peripheral corneal oedema 12 patients (18 eyes) continued to wear contact lenses to correct their aphakia.

Adult↗
PubMed1992

A morphological study of rabbit corneas after laser keratectomy.

We have examined the morphology of the collagen and proteoglycans in rabbit corneas that have undergone excimer laser photorefractive keratectomy using a clinical, 193 nm excimer laser. The photoablation was carried out to a stromal depth of 100 microns and a diameter of 6 mm. All ablated corneas developed a haze that was most intense between week 4 and week 8 and which showed no improvement after week 16. The corneas were stained with the cationic dye cuprolinic blue to visualise proteoglycans and were then processed for transmission electron microscopy. The ultrastructural location of proteoglycans (keratan sulphate and dermatan sulphate) was observed in the corneal wounds at different time intervals. Corneas that had undergone steroid treatment post-operatively were also examined. In the healing tissue proteoglycan filaments of abnormal size were observed, which became most prominent after 2 weeks. As healing progressed these abnormal filaments decreased but after 45 weeks some were still present, indicating that the proteoglycan content had not returned to normal.

Animals↗
PubMed1992

Myopia following penetrating keratoplasty for keratoconus.

The frequent occurrence of spherical myopia after penetrating keratoplasty for keratoconus is partly the result of the excessive dioptric power of the grafted cornea which occurs when the diameter selected for the donor button is greater than the diameter of the host incision. This excessive power could be reduced by eliminating disparity between the diameters of the graft and host. To determine what proportion of the myopia in these eyes would persist as a result of axial myopia the axial lengths of 60 patients grafted for keratoconus and 25 emmetropic controls were compared. A keratometry, objective refraction, and contact probe ultrasonic biometry were performed on all eyes. A comparison of the results with a representational schematic eye indicated that the mean spherical refractive error of the grafted keratoconic eyes (-4.83 dioptres) was the combined effect of steepness of the corneal graft (mean radius of curvature 7.46 mm) and an abnormally great axial length (mean 24.84 mm). The increased axial length was mainly the result of elongation of the posterior segment of the globe with a small contribution from an increased anterior chamber depth. Though axial myopia is common in keratoconus, a further study of 70 keratoconic eyes that had not been grafted showed no statistically significant correlation between the posterior segment length and the severity of corneal ectasia. These data suggest that even if excessive corneal power is eliminated after penetrating keratoplasty for keratoconus the associated axial myopia would still produce a mean spherical refractive error of at least -2.8 dioptres.

Adult↗
PubMed1992

Synchrotron x-ray diffraction studies of keratoconus corneal stroma.

The aim of this study was to determine any differences in the collagen molecular and fibrillar packing, or the arrangement of the proteoglycans along the fibril axis, in the stroma of keratoconus and control corneas. High and low-angle x-ray diffraction patterns from the fibrillar and molecular packing of collagen in keratoconus and control corneas were obtained using a synchrotron radiation source. The results indicate no difference in interfibrillar spacing between keratoconus and control corneas at normal physiological hydration, or over a range of hydrations (H = 1-11). This unambiguously demonstrates that the thinning of the stroma that occurs in keratoconus is not a result of closer packing of the collagen fibrils in the stroma. Intermolecular spacings were shown to be significantly (P less than 0.001) lower in keratoconus corneas at normal physiological hydration and over a range of hydrations (H = 1-11). Meridional patterns from the axial distribution of electron density along the collagen fibrils were obtained from untreated control and keratoconus corneas and from the corneas after their proteoglycans were stained with cupromeronic blue. Analysis of the integrated intensities of the first nine orders of these reflections show there is a difference in the staining behavior of collagen-associated proteoglycans in control and keratoconus corneas. Determination of the electron density vectors along the collagen fibrils of cupromeronic blue-stained corneas by the use of Patterson functions indicates that the keratoconus corneal stroma has a specific, ordered proteoglycan that is present in lower numbers along the collagen fibrils, and that it stains less with cupromeronic blue or is in a more disordered arrangement than in the controls.

Adult↗
PubMed1991

Conjunctival necrosis after administration of topical fortified aminoglycosides.

We treated 11 episodes of bulbar conjunctival necrosis that occurred in ten patients after therapy for suppurative keratitis with topical fortified aminoglycosides. Chemosis and mucous discharge preceded the development of an area of conjunctival pallor, which stained with fluorescein and was 5 to 10 mm from the corneoscleral limbus. Typical lesions developed in the inferior bulbar conjunctiva after a mean of 4.8 days and 112 mg of gentamicin sulfate (109 drops). The fortified aminoglycoside was the only agent common to all cases. The conjunctival defects healed completely between five and 13 days after treatment was modified to reduce or eliminate aminoglycoside exposure.

Administration, Topical↗
PubMed1991

Progression of scleral disease.

The clinical features of 290 patients with scleral inflammation were reviewed to determine whether a classification based on the anatomical site and clinical appearance of the disease at presentation reflected its natural history. The authors' results confirm that the majority of patients remain in the same clinical category throughout the course of their disease. Of the 104 (35.9%) patients who experienced a recurrence of their disease, only 12 had progressed from diffuse to nodular disease, and 10 patients who originally had nodular disease developed scleral necrosis. Patients with necrotizing scleritis were older than patients in the other groups and more frequently had an associated systemic disease than patients with either diffuse or nodular disease; necrotizing scleritis was the most difficult disease to treat. Diffuse anterior scleritis had a lower incidence of visual loss (9%) than either nodular scleritis (26%) or necrotizing disease (74%), and, therefore, the authors consider nodular scleritis a disease of intermediate severity between diffuse scleritis and necrotizing disease. In this series, 12% of patients presented with posterior scleritis, and visual loss was most frequent in this group (84%).

Adult↗
PubMed1991

Clinical features of atopic keratoconjunctivitis.

The clinical spectrum of ocular disease in 37 patients with atopic keratoconjunctivitis (AKC) is described. Patients typically had a severe blepharoconjunctivitis. Associated corneal scarring, suppurative keratitis, or keratoconus were the major causes of visual loss. Serum and tear samples from these patients were analyzed to quantify total and specific IgE antibodies. The results were compared as a case control study with results from samples from 55 patients with other forms of atopic disease and 16 nonatopic volunteers. Although the mean values for total and specific IgEs in the serum of patients with atopic disease were markedly higher than the values from nonatopic controls (P less than 0.00002), a difference between the disease groups could not be demonstrated (P greater than 0.05). There were also differences between both the total IgE (P = 0.0002) and pollen-specific IgE (P = 0.015) in tears from patients with atopic disease and nonatopic controls, but not for house dust mite or cat dander-specific IgEs. These results suggest that clinical differences between groups of patients with chronic allergic external eye disease are not associated with specific patterns of IgE production.

Adolescent↗
PubMed1990

The corneal endothelium.

The endothelium is a monolayer of cells on the posterior corneal surface that transports water from the stroma into the anterior chamber. This movement of water counters a natural tendency for the stroma to swell and is necessary to maintain a transparent cornea. Embryologic studies, in particular the demonstration of the derivation of the endothelium from the neural crest, have provided insight into the factors that govern the response of this tissue to disease. In some species the endothelium can regenerate after injury, but in man cellular enlargement is the main mechanism of repair after cell loss. A clinical estimate of endothelial cell density and function is provided by specular microscopy, fluorophotometry and pachymetry. In this paper we review the development, structure and function of the corneal endothelium, and then consider the pathological processes that can affect this tissue.

Animals↗
PubMed1990

Quantification of lens opacification with a commercially available lensometer.

A clinical trial was undertaken to determine whether a commercially available lens opacity meter (LM701), which measures backward scattered light from the lens, provides reliable clinical information about the effect of lens opacities on visual acuity. At the 0.001 level of probability we found a significant relationship between the lens opacity meter reading and both the Snellen acuity and patient's age. For a given individual there was also a relationship between the difference in the lens opacity readings between eyes and the difference in the Snellen acuities. We could not demonstrate a relation between the lens opacity reading and either the refractive error, pupil size, or near visual acuity at this level of significance.

Adult↗