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Biomedical subjects

S D McLeod

Publications and source records attributed to S D McLeod.

At least 19 recordsLinked to original sources
PubMed2003

Microbial keratitis.

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Bacterial Infections↗
PubMed2003

A dual optic accommodating foldable intraocular lens.

AIM: To design an accommodating intraocular lens with extended accommodative range that can be adapted to current standard phacoemulsification and endocapsular implantation technique. METHOD: Ray tracing analysis and lens design; cadaver eye implantation. RESULTS: Ray tracing analysis indicated that axial movement of an exaggerated converging anterior optic linked by spring loaded haptics to a compensatory static diverging posterior optic produced greater change in conjugation power of the eye compared to axial movement of a single optic lens. A dual optic one piece foldable silicone lens was constructed and implanted via a 4 mm corneal incision into the capsular bag of two cadaver eyes. CONCLUSION: A dual optic intraocular lens design can increase the optical effect of a given displacement and suggests improvements for accommodating intraocular lenses.

Accommodation, Ocular↗
PubMed2003

Bilateral diffuse lamellar keratitis following bilateral simultaneous versus sequential laser in situ keratomileusis.

AIM: To determine the difference in the incidence of bilateral diffuse lamellar keratitis (DLK) in patients undergoing simultaneous versus sequential laser in situ keratomileusis (LASIK) as an indication of intrinsic risk for inflammation. METHODS: A retrospective non-comparative case series of 1632 eyes that had undergone bilateral, simultaneous or sequential LASIK between April 1998 and February 2001 at a university based refractive centre by three surgeons. All cases that developed clinically evident DLK were identified and reviewed. In order to identify isolated cases and exclude those caused by environmental factors, when more than one patient in a given session developed DLK, the session was excluded. The main outcome measure was the incidence of unilateral and bilateral isolated, non-epidemic DLK. RESULTS: Of 1632 eyes, 126 eyes (7.7%) of 107 patients developed at least grade 1 DLK. In six operating sessions, DLK was observed in more than one patient per session, and on this basis 13 patients were excluded. 16 of the 94 remaining patients developed DLK in both eyes (17.0%). Six of 41 patients (14.6%) in the simultaneous group, versus 10 of 53 patients (18.9%) in the sequential group developed bilateral DLK (p >0.5). CONCLUSION: In isolated, non-epidemic bilateral DLK, a similar incidence was observed regardless of whether the surgery was simultaneous or sequential, suggesting an underlying intrinsic cause for DLK.

Humans↗
PubMed2001

Evaluating the human optical system: corneal topography and wavefront analysis.

In this article we review three different systems for evaluating the human optical system: placido-disc based corneal topography, scanning slit topography, and wavefront sensors. We briefly describe the principles of each system, and discuss the strengths and weakness. We suspect all three will be used by ophthalmologists in the coming decade.

Cornea↗
PubMed2001

Excimer laser photorefractive keratectomy.

The excimer laser has proved to be a precise and versatile tool for treating refractive errors. Excimer laser photorefractive keratectomy for myopia is now an established safe and effective alternative to contact lenses and glasses, and should be part of the ophthalmologist's standard armamentarium for treating this condition. This article provides a brief overview of the basic principles underlying excimer laser technology, as well as the surgical technique and postoperative management of myopic correction.

Cornea↗
PubMed2001

Phakic intraocular lenses.

Because of the potential risks associated with phakic IOL implantation, the current use of these devices is mainly in the treatment of high and extreme myopia which are expected to respond poorly to keratorefractive procedures. Overall, in this setting, the outcomes of phakic IOL implantation have been rather favorable, with significant improvement in uncorrected visual acuity, and tolerable visual symptoms in terms of glare and halo.

Humans↗
PubMed2000

Amniotic membrane transplantation for acute chemical or thermal burns.

PURPOSE: To determine whether preserved human amniotic membrane (AM) can be used to treat ocular burns in the acute stage. DESIGN: Prospective, noncomparative, interventional case series. PARTICIPANTS: Thirteen eyes from 11 patients with acute burns, 10 eyes with chemical burns and 3 with thermal burns of grades II-III (7 eyes) and grade IV (6 eyes), treated at 7 different facilities. METHODS: Patients received amniotic membrane transplantation (AMT) within 2 weeks after the injury. MAIN OUTCOME MEASURES: Integrity of ocular surface epithelium and visual acuity during 9 months of follow-up. RESULTS: Ten patients were male and one patient was female; most were young (38.2 +/- 10.6 years). For a follow-up of 8.8 + 4.7 months, 11 of 13 eyes (84.63%) showed epithelialization within 2 to 5 weeks (23.7 +/- 9.8 days), and final visual acuity improved > or = 6 lines (6 eyes), 4 to 5 lines (2 eyes), and 1 to 3 lines (2 eyes); only one eye experienced a symblepharon. Eyes with burns of grade II to III showed more visual improvement (7.3 +/- 3 lines) than those with burns of grade IV (2.3 +/- 3.0 lines; P < 0.05, unpaired t test). In the group with grade II or III burns, none had limbal stem cell deficiency. All eyes in the group with grade IV burns did experience limbal stem cell deficiency. CONCLUSIONS: Amniotic membrane transplantation is effective in promoting re-epithelialization and reducing inflammation, thus preventing scarring sequelae in the late stage. In mild to moderate burns, AMT alone rapidly restores both corneal and conjunctival surfaces. In severe burns, however, it restores the conjunctival ocular surface without debilitating symblepharon and reduces limbal stromal inflammation, but does not prevent limbal stem cell deficiency, which requires further limbal stem cell transplantation. These results underscore the importance of immediate intervention in the acute stage of eyes with severely damaged ocular surface. Further prospective randomized studies including a control group are required to determine the effectiveness of AMT in acute chemical and thermal burns of the eye.

Acids↗
PubMed1999

Benign lymphoid hyperplasia of the conjunctiva in children.

Benign lymphoid hyperplasia of the conjunctiva occurs infrequently in children, and its presentation, clinical course, and appropriate management are not well established. We describe 2 children with nasal conjunctival masses that on pathological examination demonstrated benign lymphoid hyperplasia. Local irradiation of residual tissue was deferred, and the lesions remained stable for 1 year in one case and for 3 1/2 years in the other case. No systemic involvement had occurred. Although the natural history of extranodal lymphoid hyperplasia in children is poorly documented, most cases of nodal lymphoid hyperplasia in children are at very low risk of malignant transformation. Careful observation for local and systemic disease is indicated for ocular adnexal lymphoid hyperplasia in children until a more complete understanding of its natural history is available.

Antigens, CD20↗
PubMed1998

Nonulcerating bacterial keratitis associated with soft and rigid contact lens wear.

OBJECTIVE: An unusual presentation of contact lens-related bacterial keratitis is that of epithelial nodular infiltrates and stromal inflammation without epithelial ulceration. The authors study the initial diagnosis, clinical features, causative organisms, and outcomes of corneal infections presenting in this manner. DESIGN: The study design was a 20-month retrospective chart review. PARTICIPANTS: Five patients with culture-proven bacterial keratitis who had predominantly nodular epithelial lesions were studied. RESULTS: Four infections were associated with soft contact lens wear and one with rigid lens wear. All patients had largely intact epithelium; typical gray-colored epithelial nodules, some with underlying anterior stromal haze; and diffuse, fine, cellular stromal inflammation. Two patients were referred with the tentative diagnosis of Acanthamoeba infection and two as contact lens-related sterile keratitis. Epithelial cultures from three cases yielded Serratia sp., one yielded Corynebacterium, and one Streptococcus pneumoniae. All responded to antibacterial medication; final corrected visual acuity in all cases was 20/30 or better. CONCLUSIONS: Bacterial infection associated with contact lens wear can be established within the corneal epithelium without initially producing an ulcer. A wide range of both gram-positive and gram-negative organisms can be involved. Early recognition and treatment appear to result in a favorable outcome.

Adolescent↗
PubMed1998

The effect of minoxidil on keratocyte proliferation in cell culture.

PURPOSE: To determine if minoxidil inhibits keratocyte proliferation in a nontoxic manner. METHODS: Rabbit keratocytes were cultured in Eagle's minimum essential medium supplemented with fetal bovine serum. Minoxidil varying in concentration from 10(0) to 10(3) micrograms/ml was added to the culture medium and incubated for 7 days. The cultures were inspected for morphologic appearance and the cell number was determined at 1, 3 and 7 days after the addition of minoxidil. After 7 days of incubation, minoxidil was withdrawn from the cell culture medium and the cells were examined 3 and 7 days thereafter. In addition, a nonradioactive cytotoxic assay was performed to determine if toxicity is associated with the presence of minoxidil. RESULTS: Minoxidil inhibited keratocyte proliferation in a dose-dependent fashion. 29% of control growth was achieved when keratocytes were cultured for 7 days in 10(3) micrograms/ml, whereas 82% control growth was achieved when keratocytes were cultured in 10(2) micrograms/ml of minoxidil. Intermediate concentrations between 10(2) and 10(3) micrograms/ml produced a linear decline in cell counts in a dose-dependent fashion. The concentration of minoxidil required for 50% control growth at 7 days extrapolated from the dose-response curve was 600 micrograms/ml. Upon withdrawal of minoxidil, cell counts returned to baseline for concentrations of 10(2) micrograms/ml or less. Phase contrast microscopy revealed that the presence of minoxidil was associated with intercellular separation, enlargement of cell bodies and elongated processes. After the withdrawal of minoxidil, the cells in all media reassumed the morphological features of normal keratocytes which included a regular fusiform shape and extensive intercellular contact. The nonradioactive cytotoxic assay revealed the lack of cytotoxicity at all concentrations of minoxidil based on a lack of lactate dehydrogenase release. CONCLUSIONS: Minoxidil inhibits keratocyte proliferation by a nontoxic mechanism. It might be particularly useful for modulating corneal wound healing following excimer laser photorefractive keratectomy.

Animals↗