Expanding the scope of lamellar keratoplasty.
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PURPOSE: To investigate whether applications of current technology, such as cryolathe and excimer laser, might improve outcomes and increase use of lamellar keratoplasty. METHODS: Six studies were performed, beginning with animals and progressing to human subjects. The first study compared cryolathed with hand-dissected rabbit corneas to ascertain which created a smoother donor interface. The second animal pilot study was done to determine whether thickness of donor cornea resection could be accurately predicted with the cryolathe. A prospective animal trial was then undertaken to compare lamellar keratoplasty outcomes using cryolathed versus hand-dissected tissue. The fourth work extrapolated previous animal findings to lamellar keratoplasty in human disease. Finally, two ongoing studies are described. The first explores the possibility of sutureless lamellar keratoplasty. The second utilizes the excimer laser to dissect the recipient stromal bed. RESULTS: The initial animal pilot study demonstrated a clearer stromal surface in cryolathed versus hand-dissected corneal tissue. The second pilot showed that plano-powered donor tissue could be generated to predetermined thickness. The prospective animal trial revealed that clear grafts of intended thickness could be obtained with cryolathing. Human studies suggested that lamellar keratoplasty using cryolathe-prepared donor tissue may offer superior results to free-hand dissection. Finally, one ongoing study indicates that sutureless lamellar keratoplasty is untenable, and the other shows that clear grafts can be obtained by combining cryolathed donor tissue with recipient photoablation. CONCLUSION: This body of work demonstrates that use of new lamellar keratoplasty technology may offer expanded scope and better outcomes than traditional lamellar keratoplasty techniques. (+info)
Cultured corneal epithelia for ocular surface disease.
(26/900)
PURPOSE: To evaluate the potential efficacy for autologous and allogeneic expanded corneal epithelial cell transplants derived from harvested limbal corneal epithelial stem cells cultured in vitro for the management of ocular surface disease. METHODS: Human Subjects. Of the 19 human subjects included, 18 (20 procedures) underwent in vitro cultured corneal epithelial cell transplants using various carriers for the epithelial cells to determine the most efficacious approach. Sixteen patients (18 procedures on 17 eyes) received autologous transplants, and 2 patients (1 procedure each) received allogeneic sibling grafts. The presumed corneal epithelial stem cells from 1 patient did not grow in vitro. The carriers for the expanded corneal epithelial cells included corneal stroma, type 1 collagen (Vitrogen), soft contact lenses, collagen shields, and amniotic membrane for the autologous grafts and only amniotic membrane for the allogeneic sibling grafts. Histologic confirmation was reviewed on selected donor grafts. Amniotic membrane as carrier. Further studies were made to determine whether amniotic membrane might be the best carrier for the expanding corneal epithelial cells. Seventeen different combinations of tryspinization, sonication, scraping, and washing were studied to find the simplest, most effective method for removing the amniotic epithelium while still preserving the histologic appearance of the basement membrane of the amnion. Presumed corneal epithelial stem cells were harvested and expanded in vitro and applied to the amniotic membrane to create a composite graft. Thus, the composite graft consisted of the amniotic membrane from which the original epithelium had been removed without significant histologic damage to the basement membrane, and the expanded corneal epithelial stem cells, which had been applied to and had successfully adhered to the denuded amniotic membrane. Animal model. Twelve rabbits had the ocular surface of 1 eye damaged in a standard manner with direct removal of the presumed limbal stem cells, corneal epithelium, and related epithelium, followed by the application of n-heptanol for 60 seconds. After 6 weeks, all damaged eyes were epithelialized and vascularized. Two such treated eyes were harvested without further treatment, to be used for histologic study as damaged controls. The remaining 10 rabbits received composite grafts (consisting of amniotic membrane with expanded allogeneic rabbit corneal epithelial cell transplants) applied to the ocular surface in a standard manner followed by the application of a contact lens. At 16 days following transplantation, 5 of the rabbits were sacrificed and the corneal rims were removed for histologic study. At 28 days, the remaining rabbits were sacrificed and the previously damaged eyes were harvested for histologic and immunohistochemical study. RESULTS: Human subjects. Of the 19 total patients admitted to the study, the presumed corneal epithelial stem cells of 1 patient did not grow in vitro. Of the remaining 18 patients (20 procedures, 19 eyes), 3 patients had unsuccessful results (3 autologous procedures), 1 patient had a partially successful procedure (allogeneic procedure), and 1 patient had a procedure with an undetermined result at present (allogeneic procedure). One unsuccessful patient had entropion/trichiasis and mechanically removed the graft and eventually went into phthisis. The other 2 unsuccessful patients suffered presumed loss of autologous donor epithelium and recurrence of the ocular surface disease (pterygium). The partially successful patient receiving an allogeneic transplant had infectious keratitis delay of his re-epithelialization; he has only minimal visual improvement but has re-epithelialized. The patient receiving the second allogeneic graft lost his donor epithelium at day 4. Additional donor epithelium was reapplied, but the result is undetermined at present. Amniotic membrane as carrier. The in vitro preparation of the amniotic membrane with corneal epithelial stem cell graft overlay was successful. Histology documented removal of the amniotic epithelium and reapplication of corneal epithelial cells. Animal model. The 2 rabbits that had no reparative surgery following standard ocular surface injury had histology and immunopathology consistent with incomplete corneal epithelial stem cell failure with vascularization and scarring of the ocular surface. Light microscopy and immunohistologic staining with AE5 confirmed the conjunctival phenotype of the ocular surface repair but also documented the incomplete model. The allogeneic stern cell transplants had varying results. One rabbit had a suppurative infection and lost the graft. Reparative surgery failed in 2 of the rabbits, failed partially in 3 of the rabbits, was partially successful in 3 others, and was successful in 1 rabbit at 28 days. Histologic and immunopathologic study documented successful growth of corneal epithelium onto the recipient surface. CONCLUSIONS: 1. Presumed corneal epithelial stem cells can be harvested safely from the limbus and expanded successfully in vitro. 2. Expanded corneal epithelial cell cultures can be grown onto various carriers, but currently denuded amniotic membrane seems to be the best carrier for ocular surface repair. 3. Expanded corneal epithelial cell transplants appear to resurface damaged ocular surfaces successfully, but cellular tracking and further confirmation are required. 4. Expanded allogeneic corneal epithelial cell transplants are technically possible and may represent alternative treatment modalities for selected ocular surface problems. 5. These techniques potentially offer a new method of restoring a normal ocular surface while minimizing the threat of damage or depletion to the contralateral or sibling limbal corneal epithelial stem cells. 6. The rabbit model was probably incomplete and should be interpreted with caution. The complete eradication of all corneal epithelial stem cells from any eye is difficult, making confirmation of such work challenging. 7. The results of the rabbit model suggest that allogeneic grafts may restore a nearly normal ocular epithelial surface to certain ocular surface injuries. (+info)
Recurrent erosion of the cornea.
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Altogether, 80 patients aged between 24 and 73 years with recurrent erosion of the cornea have been studied and compared with a control group of 200. The patients' erosions were divisible into macroform and microform types. The macroform occurred in 10%, the microform in 56%, and both types in the same patients in 31%. The macroform was more commonly related to trauma than the microform. However, many (40%) were spontaneous in origin. The most common cause of the initial trauma was a finger nail. The recurrences occurred at around the time of waking, either just before or just after. Difficulty in opening the eye occurred in 10%. There was little evidence of precipitating factors, but eye rubbing was admitted by 10% and barbiturates were implicated in 3%. The corneae were examined in the healed state, when a high incidence (59%) were found to have superficial corneal dystrophies of the fingerprint lines, bleb, and Bietti's lacunar (map-like) types. These are considered individually, particular attention being paid to the distinction between the various types of line resembling the fingerprint line. Epithelial microcysts were also a common finding (59%) and were sometimes of the Cogan type. In only 11% of patients were there no corneal signs in the healed state. The need for careful examination of the cornea by retroillumination, using both the iris and the fundus, is stressed. The control group, in contrast, showed a very low incidence of dystrophies and cysts. Treatment was given initially with either drops or ointment and no differences in healing were found. Debridement was performed in 12 eyes as an initial treatment and also in four eyes which were not healing on medical treatment. Debridement assisted healing, but did not prevent recurrence. One eye was treated with debridement and scarification and seven with carbolization. These procedures appeared to reduce the recurrence rate. Sodium chloride ointment 5% was found useful as a prophylactic taken at bedtime, and the recurrence rate increased when it was withdrawn. (+info)
Immunohistochemical localization of NQO1 in epithelial dysplasia and neoplasia and in donor eyes.
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PURPOSE: To examine the expression of NAD(P)H:quinone oxidoreductase 1 (NQO1, DT-diaphorase), a potential bioactivating enzyme for mitomycin C in corneal and conjunctival epithelial dysplasia and neoplasia and in normal tissues from human donor eyes, by immunohistochemistry. METHODS: Formalin-fixed, paraffin-embedded sections of human donor eyes and tissue sections with histologic diagnoses of corneal and conjunctival epithelial dysplasia and neoplasia from the Eye Pathology Laboratory, University of Colorado Health Sciences Center were analyzed. Detection of NQO1 in tissues was performed using standard immunohistochemical techniques with monoclonal antibodies against NQO1 and immunoperoxidase staining. RESULTS: All 20 tumors stained positive for NQO1. In seven eyes from four donors, positive staining for NQO1 was detected in all epithelial and endothelial layers, in fibroblasts, in all retinal layers except the photoreceptor outer segments, and in the fascicles and arachnoid of the optic nerve. Only minimal staining was detected in the photoreceptor outer segments and the optic nerve pia and dura. Immunostaining was markedly reduced in all tissues in both eyes from donor 5. Genetic analysis confirmed that this individual was homozygous for a polymorphism in NQO1 (NQO1*2). CONCLUSIONS: NQO1 was detected by immunohistochemistry in every examined section of corneal and conjunctival epithelial dysplasia and neoplasia, suggesting that NQO1 may play a role in the bioactivation of mitomycin C in these tumors. However, the presence of NQO1 in the corneal, conjunctival, and ciliary epithelium; the retinas; and the optic nerves of donor eyes may indicate the potential for mitomycin C toxicity, particularly at higher doses. (+info)
Excimer laser phototherapeutic keratectomy: indications, results and its role in the Indian scenario.
(29/900)
PURPOSE: To report indications, technique, and results of excimer phototherapeutic keratectomy (PTK), and describe possible reasons for the small numbers of such procedures performed in a referral institute in India. METHODS: Retrospective review of case records of 10 patients (11 eyes) who underwent excimer PTK at our institute between February 1994 and September 1997. RESULTS: Corneal scars were the most common indication for treatment. Best-corrected visual acuity (BCVA) improved in 6 eyes (mean: 2 lines of Snellen acuity). All eyes had BCVA > or = 6/12 after treatment. None of the patients experienced loss of BCVA after treatment. Unaided visual acuity improved in 3 eyes and decreased in 2 eyes. Change in spherical equivalent refraction > or = 1 diopter occurred in 77.8% of eyes after treatment. Treating central corneal scars resulted in a significant hyperopic shift in refraction. CONCLUSIONS: Excimer PTK is a safe and effective procedure for the treatment of superficial corneal opacities. Post-treatment ametropia may require further correction with optical aids. Inappropriate referrals, deep corneal scars, and cost of the procedure could have contributed to the small numbers of PTK performed at our institute. Improved understanding of procedural strengths and limitations could lead to increased use of this procedure, with satisfying results in selected patients. (+info)
Reconstruction of damaged corneas by transplantation of autologous limbal epithelial cells.
(30/900)
BACKGROUND: Stevens-Johnson syndrome, ocular pemphigoid, and thermal or chemical burns can cause scarring and opacification of the cornea and loss of vision. Transplantation of epithelial cells from the limbus of the contralateral cornea can restore useful vision. However, this procedure requires a large limbal graft from the healthy eye and is not possible in patients who have bilateral lesions. METHODS: We took specimens of limbal epithelial cells from the healthy contralateral eyes of six patients with severe unilateral corneal disease. The epithelial cells were cultured and expanded on amniotic membrane. The amniotic membrane, together with the sheet of limbal epithelial cells, was transplanted to the denuded corneal surface of the damaged eye after superficial keratectomy to remove fibrovascular ingrowth. The mean (+/-SD) follow-up period was 15+/-2 months. RESULTS: Complete reepithelialization of the corneal surface occurred within two to four days of transplantation in all six eyes receiving transplants. By one month, the ocular surface was covered with corneal epithelium, and the clarity of the cornea was improved. In five of the six eyes receiving transplants (83 percent), the mean visual acuity improved from 20/112 to 20/45. In one patient with a chemical burn who had total opacification of the cornea, the acuity improved from the ability to count fingers at 40 cm to 20/200. No patient had recurrent neovascularization or inflammation in the transplanted area during the follow-up period. CONCLUSIONS: Transplantation of autologous limbal epithelial cells cultured on amniotic membrane is a simple and effective method of reconstructing the corneal surface and restoring useful vision in patients with unilateral deficiency of limbal epithelial cells. (+info)
Corneal structure and sensitivity in type 1 diabetes mellitus.
(31/900)
PURPOSE: Corneal wound healing is impaired in diabetic cornea. The purpose of this study was to examine patients with type 1 diabetes mellitus for changes in corneal morphology and to correlate corneal sensitivity, subbasal nerve morphology, and degree of polyneuropathy with each other. METHODS: Forty-four eyes of 23 patients with diabetes and nine control eyes were included. Corneal sensitivity was tested with a Cochet-Bonnet esthesiometer (Luneau, Paris, France), and corneal morphology and epithelial and corneal thickness were determined by in vivo confocal microscopy. The density of subbasal nerves was evaluated by calculating the number of long subbasal nerve fiber bundles per confocal microscopic field. The degree of polyneuropathy was evaluated using the clinical part of the Michigan Neuropathy Screening Instrument (MNSI) classification, and retinopathy was evaluated using fundus photographs. RESULTS: A reduction of long nerve fiber bundles per image was noted to have occurred already in patients with mild to moderate neuropathy, but corneal mechanical sensitivity was reduced only in patients with severe neuropathy. Compared with control subjects the corneal thickness was increased in patients with diabetes without neuropathy. The epithelium of patients with diabetes with severe neuropathy was significantly thinner than that of patients with diabetes without neuropathy. CONCLUSIONS: Confocal microscopy appears to allow early detection of beginning neuropathy, because decreases in nerve fiber bundle counts precede impairment of corneal sensitivity. Apparently, the cornea becomes thicker in a relatively early stage of diabetes but does not further change with the degree of neuropathy. A reduction in neurotrophic stimuli in severe neuropathy may induce a thin epithelium that may lead to recurrent erosions. (+info)
Identification and characterization of TUP1-regulated genes in Candida albicans.
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TUP1 encodes a transcriptional repressor that negatively controls filamentous growth in Candida albicans. Using subtractive hybridization, we identified six genes, termed repressed by TUP1 (RBT), whose expression is regulated by TUP1. One of the genes (HWP1) has previously been characterized, and a seventh TUP1-repressed gene (WAP1) was recovered due to its high similarity to RBT5. These genes all encode secreted or cell surface proteins, and four out of the seven (HWP1, RBT1, RBT5, and WAP1) encode putatively GPI-modified cell wall proteins. The remaining three, RBT2, RBT4, and RBT7, encode, respectively, an apparent ferric reductase, a plant pathogenesis-related protein (PR-1), and a putative secreted RNase T2. The expression of RBT1, RBT4, RBT5, HWP1, and WAP1 was induced in wild-type cells during the switch from the yeast form to filamentous growth, indicating the importance of TUP1 in regulating this process and implicating the RBTs in hyphal-specific functions. We produced knockout strains in C. albicans for RBT1, RBT2, RBT4, RBT5, and WAP1 and detected no phenotypes on several laboratory media. However, two animal models for C. albicans infection, a rabbit cornea model and a mouse systemic infection model, revealed that rbt1Delta and rbt4Delta strains had significantly reduced virulence. TUP1 appears, therefore, to regulate many genes in C. albicans, a significant fraction of which are induced during filamentous growth, and some of which participate in pathogenesis. (+info)