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Biomedical subjects

John K G Dart

Publications and source records attributed to John K G Dart.

9 recordsLinked to original sources
PubMed2006

Patterns of rejection after deep lamellar keratoplasty.

PURPOSE: To describe 7 patients with keratoconus who underwent graft rejection after deep lamellar keratoplasty (DLK). DESIGN: Retrospective case series and literature review. PARTICIPANTS: Seven patients who underwent DLK for keratoconus between 1997 and 2001. These cases were compared with a previously reported case series of DLK for keratoconus between 1994 and 2001. METHODS: The clinical records of patients with rejection after DLK for keratoconus were examined to obtain details of the surgery, the interval to the rejection episode and its treatment, best-corrected visual acuity (BCVA), and presence of potential risk factors for rejection. The clinical features and course of rejection were compared with reports of corneal graft rejection in the literature. Patient characteristics were compared with the reported series of patients who had DLK for keratoconus. MAIN OUTCOME MEASURES: Final BCVA and number, type, and features of rejection episodes. RESULTS: The mean age was 28 years, with a median follow-up of 40 months after DLK. Rejection occurred between 3 and 41 months postoperatively. Four patients were atopic, 4 had a penetrating keratoplasty in the fellow eye, and 1 had deep stromal vessels in the host cornea. Isolated epithelial rejection occurred in 1 patient and stromal rejection in 3 cases, and there were 3 cases of mixed stromal and epithelial rejection. Topical steroid therapy led to reversal of rejection in 5 cases. Two patients had progressive vascularization with graft failure and poor vision. The median final BCVA was 6/9 (range, 6/6-6/36). CONCLUSIONS: Deep lamellar keratoplasty avoids the risk of endothelial rejection, but epithelial or stromal rejection may still occur. Recognition and appropriate treatment are needed to prevent graft failure with subsequent visual loss.

Administration, Topical↗
PubMed2006

AlphaCor: Clinical outcomes.

PURPOSE: To study the outcomes of AlphaCor implantation. METHODS: : The AlphaCor artificial cornea is indicated for corneal blindness not treatable by donor grafting. Prospective preoperative and follow-up data were collected. Data were evaluated using SPSS for statistical analysis of outcomes, trends, and associations. RESULTS: This report includes data returned through February 28, 2006, for all 322 devices implanted, with mean follow-up in situ of 15.5 months and a maximum of 7.4 years. The probability of AlphaCor retention at 6 months and 1 and 2 years for protocol cases was 92%, 80%, and 62%, respectively, and off-label cases were at higher risk (P = 0.010), as were cases not prescribed medroxyprogesterone (MPG; P = 0.001). Currently, the most common complications were stromal melting, fibrous reclosure of the posterior lamellar opening, and white intraoptic deposits, with incidences in 2005 of 11.4%, 5.1%, and 2.6%, respectively. MPG seems to protect against melts, and eyes with a history of herpetic keratitis were not at increased risk. A history of glaucoma or the presence of tubes did not affect device retention. Complications culminated in loss of an eye in 1.3%. Mean preoperative visual acuity (VA) was hand movements. The VA achieved postoperatively (light perception to 20/20) was affected by previous pathology and postoperative course, with a mean improvement of 2 lines. CONCLUSION: AlphaCor provides a treatment option where a donor tissue graft would not succeed in severe corneal conditions, while being reversible to a donor graft in the event of complications for anatomic integrity. Surgical technique and adjunctive therapies are evolving with experience. Continued data collection is important for a fuller understanding of AlphaCor's role.

Adult↗
PubMed2005

Evaluation of mucous membrane pemphigoid with ocular involvement in young patients.

OBJECTIVES: Mucous membrane pemphigoid with ocular involvement (MMPO) is a sight-threatening autoimmune disease that may lead to severe conjunctival cicatrization and keratopathy. The peak age of onset is in the seventh decade, although the disease may also occur in younger patients (< 60 years). This study was designed to evaluate the clinical features of young patients with MMPO and to assess the clinical outcome when compared with patients in the > 70 age group. DESIGN: Retrospective, comparative, interventional case series. PARTICIPANTS: Eighteen patients under the age of 60 years and 18 patients above the age of 70. METHODS: Patients with documented MMPO were identified from the External Diseases Immunosuppression Database. MAIN OUTCOME MEASURES: Stage of disease (Foster, Mondino), visual acuity, and ocular complications (lid, conjunctival, corneal) were evaluated at presentation, the time when immunosuppression was commenced, and final follow-up. Disease progression, control of ocular inflammation with systemic immunosuppression, the incidence of mucocutaneous lesions, and surgical intervention were also assessed. RESULTS: Patients in the 2 groups (young and classic age groups) were observed for 61 (range, 29-218) and 69 (range, 12-193) months, respectively (P = 0.94). Median ages at the start of immunosuppression were 48.7 (range, 29-60) and 77.6 (range, 71-85) years. Mucocutaneous involvement was more common in the young than in the classic age group (13 [72%], 7 [39%]; P < 0.05). Ocular staging (Mondino, Foster) at presentation, the start of immunosuppression, and final follow-up was more advanced in the younger patients. There was no statistical difference in visual acuity, individual ocular complications, or incidence of surgical intervention between the 2 groups throughout the course of the study. CONCLUSION: Younger patients with MMPO present with more severe ocular and systemic disease and, despite immunosuppression, progress more rapidly.

Adult↗
PubMed2004

Effect of cataract surgery on the corneal endothelium: modern phacoemulsification compared with extracapsular cataract surgery.

PURPOSE: To investigate whether modern phacoemulsification surgery results in more damage to the corneal endothelium than extracapsular cataract extraction (ECCE), and to examine which preoperative, operative, and postoperative factors influence the effect of cataract surgery on the endothelium. DESIGN: Randomized controlled trial. PARTICIPANTS: Five hundred patients 40 years or older were randomized into 2 groups (ECCE, 249; phacoemulsification, 251). METHODS: Central corneal endothelial cell counts, coefficient of variation of cell size, and hexagonality were assessed before surgery and up to 1 year postoperatively. MAIN OUTCOME MEASURE: Endothelial cell count. RESULTS: Four hundred thirty-three patients completed the trial. The initial preoperative mean cell count for the entire sample was 2481 (standard error [SE]: 18.6), reduced at 1 year postoperatively to 2239 (SE: 23.5). An average 10% reduction in cell count was recorded by 1 year postoperatively. There was no such change in hexagonality or in the coefficient of variation. There was no significant difference in overall percentage cell loss between the 2 treatment groups. Factors associated with excessive cell loss (> or =15% by 1 year) were a hard cataract (odds ratio [OR]: 2.1, 95% confidence limits: 1.1-4.1; P = 0.036), age (OR: 1.04, P = 0.005), and capsule or vitreous loss at surgery (OR: 2.38, P = 0.106). Phacoemulsification carried a significantly higher risk (OR: 3.7, P = 0.045) of severe cell loss in the 45 patients with hard cataracts relative to ECCE (52.6% vs. 23.1%; chi-square test, P = 0.041), with both procedures achieving similar postoperative visual acuity outcomes. CONCLUSIONS: No significant difference in overall corneal endothelial cell loss was found between these 2 operative techniques. The increased risk of severe cell loss with phacoemulsification in patients with hard cataracts suggests that phacoemulsification may not be the optimal procedure in these cases, and that ECCE should be preferred.

Adult↗
PubMed2004

Comparison of deep lamellar keratoplasty and penetrating keratoplasty in patients with keratoconus.

OBJECTIVE: To compare the therapeutic outcomes after deep lamellar keratoplasty (DLK) and penetrating keratoplasty (PK) in patients with keratoconus. DESIGN: Retrospective case-control study. PARTICIPANTS: We reviewed the clinical notes of 47 patients diagnosed clinically with keratoconus who had received DLK (26 eyes of 25 patients) or PK (25 eyes of 22 patients) at Moorfields Eye Hospital or the Royal Shrewsbury Hospital between 1994 and 2001. The patients in the 2 groups were matched for severity of their keratoconus by preoperative visual acuity. METHODS: Deep lamellar keratoplasty was performed with the Melles technique in 7 eyes and the technique described by Sugita and Kondo in 19 eyes. Penetrating keratoplasty was performed with a standard technique using a Hessburg-Barron trephine. A single continuous 16-bite 10-0 nylon suture was placed and adjusted in both groups. MAIN OUTCOME MEASURES: Best-corrected visual acuity (BCVA), refractive results, surgical techniques for DLK, and complication rates were analyzed. RESULTS: The 25 patients with keratoconus who underwent DLK had a mean age of 32.6 years and a median follow-up of 28 months. The mean age of the 22 patients who underwent PK for keratoconus was 34 years. This group was followed up for a median time of 55 months. The median final BCVA of patients in the DLK group was 6/9 and in the PK group 6/6 (no statistical significance). The median result for the final spherical equivalent power in both groups was mild myopia, although the DLK group had more myopia, and the median astigmatism was less than 5.00 diopters cylinder for both groups. Complication rates were similar for DLK and PK, although the nature of the complications varied. CONCLUSIONS: Penetrating keratoplasty is no longer an automatic choice for the surgical treatment for keratoconus; DLK seems to be a safe alternative. Best-corrected visual acuity, refractive results, and complication rates are similar after DLK and PK. Deep lamellar keratoplasty is more technically challenging but allows the risk of endothelial rejection to be avoided and may reduce the risk of late endothelial failure.

Adolescent↗
PubMed2004

Ultrastructural examination of two cases of stromal microsporidial keratitis.

Two cases with chronic stromal keratitis are described in immunocompetent hosts where the diagnosis was originally thought to be herpetic or adenoviral disease. Light microscopy and ultrastructural examination of corneal tissue by electron microscopy were performed following penetrating keratoplasty (case 1) and corneal biopsy (case 2). Specimens from both cases were analysed for viral identification by PCR. Two different species of Microsporidia were identified. Case 1 represents the fourth reported case of corneal stromal Vittaforma corneae where the spores measured 3.3 x 1.4 microm, arranged in characteristic linear groups of about four to eight. Each spore contained a diplokaryotic nucleus and a single row of ten polar tube coils. By contrast, case 2 is the first reported case of stromal keratitis caused by Trachipleistophora hominis. In this case, spores measured 4 x 2.4 microm, located typically within packets. In this species, the polar tube was arranged as a single row of about 10-13 profiles. Viral DNA could not be amplified by PCR. In conclusion, microsporidial stromal keratitis should be considered in culture-negative cases refractory to medical therapy. As microbiological culture techniques are unsuccessful, diagnosis may only be established following histopathological and ultrastructural examination of corneal tissue.

Adult↗
PubMed2003

Persistently culture positive acanthamoeba keratitis: in vivo resistance and in vitro sensitivity.

PURPOSE: To characterize the risk factors, clinical course, treatment outcome and the association between in vivo resistance and in vitro sensitivity for subjects with persistently culture-positive Acanthamoeba keratitis. DESIGN: Retrospective noncomparative case series. PARTICIPANTS: Eleven subjects with repeatedly positive cultures for Acanthamoeba treated between January 1990 and December 2000, were reviewed. Only subjects with 2 or more positive cultures, availability of the clinical data, and availability of the last Acanthamoeba isolate were included in this study. METHODS: The medical records were analyzed, and the last isolate from each case was tested in vitro for the antiamoebic drugs used clinically: polyhexamethylene biguanide (PHMB), chlorhexidine, propamidine and hexamidine. MAIN OUTCOME MEASURES: Risk factors, the clinical outcome and in vitro cysticidal drug sensitivity assay. RESULTS: Eleven subjects (11/180, 6.1%) had 2 or more positive cultures of whom 8 eyes of 8 subjects (8/180, 4.45%) were included in this study. Seven of eight (87%) subjects were diagnosed over 1 month from onset (late diagnosis). The most common presenting findings were diffuse stromal infiltrate (5/8, 62.5%), ring infiltrate (5/8, 62.5%), and corneal ulceration (3/8, 37.5%). The clinical course of the disease in all subjects consisted of recurrent episodes of corneal and scleral inflammation, with a mean duration of 13.4 +/- 9 months. All subjects received PHMB, and 5/8 (62.5%) chlorhexidine too; hexamidine was used in combination in 6/8 (75%), and propamidine in 1/8 (12.5%). All subjects had topical steroids, and 5/8 (62.5%) systemic immunosuppression. The disease resolved with corneal scarring in 3/8 (37.5%) subjects, corneal (or impending) perforation treated with therapeutic keratoplasty in 4/8 (50%), and enucleation in 1/8 (12.5%). Final visual acuity was 0.43 +/- 0.37. In vitro most isolates were resistant to propamidine, hexamidine was cysticidal in high concentrations, and PHMB and chlorhexidine had excellent sensitivity profiles. CONCLUSIONS: In our large series of Acanthamoeba keratitis with a positive microbiologic diagnosis at presentation, nearly 5% developed recurrent episodes of corneal and scleral inflammation with viable Acanthamoeba in the cornea despite prolonged treatment with biguanides and/or diamidines. There was no correlation between in vitro drug sensitivities and the in vivo response for biguanides.

Acanthamoeba↗
PubMed2002

Acanthamoeba sclerokeratitis: treatment with systemic immunosuppression.

OBJECTIVE: This study describes the clinical features, management, and outcome of 19 patients who had severe Acanthamoeba sclerokeratitis (ASK) unresponsive to conventional management, requiring systemic immunosuppression to control disease. DESIGN: Retrospective, non-comparative, interventional case series. PARTICIPANTS: Records of all patients with Acanthamoeba keratitis treated at Moorfields Eye Hospital between 1989 and 2000 were reviewed. From more than 200 patients, 19 who developed ASK treated with systemic immunosuppression were identified. MAIN OUTCOME MEASURES: Visual acuity, level of pain, and degree of inflammation were recorded after immunosuppressive treatment. RESULTS: ASK requiring immunosuppression occurred in 20 eyes of 19 patients (11 males and 8 females). The mean age (mean +/- standard deviation) at onset was 38.6 +/- 13.2 years. On presentation, best-corrected visual acuity was counting fingers or worse in 11 eyes (55%), 6/18 to 6/60 in 5 eyes (25%), and 6/12 or better in 4 eyes (20%). The mean time between onset of initial symptoms of Acanthamoeba keratitis and commencement of systemic immunosuppression was 4.8 +/- 3.5 months. The mean duration of immunosuppression required to control inflammation was 7.2 +/- 3.9 months. Severe scleritic pain remained uncontrolled in two patients and resulted in enucleation. Best-corrected visual acuity at final follow-up was counting fingers or worse in eight eyes (40%), 6/18 to 6/60 in six eyes (30%), and 20/40 or better in six eyes (30%). The mean follow-up period after resolution of inflammation was 24.3 +/- 20.9 months (range, 0.2-59.7 months). CONCLUSIONS: ASK is an uncommon complication of Acanthamoeba keratitis. The scleritis associated with this infection seems to be an immune-mediated response. After topical amebicidal treatment, systemic immunosuppression may be required to control the pain and tissue destruction associated with ASK.

Acanthamoeba Keratitis↗