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Biomedical subjects

M A Pavilack

Publications and source records attributed to M A Pavilack.

15 recordsLinked to original sources
PubMed2001

Site of potential operating microscope light-induced phototoxicity on the human retina during temporal approach eye surgery.

OBJECTIVE: To determine the site of focal illumination on the retina of phakic human cadaver eyes from an operating microscope positioned for temporal approach eye surgery. DESIGN: Experimental study. METHODS: A Zeiss OPMI-6SFR operating microscope (Zeiss Humphrey Systems, Dublin, CA) was positioned over two phakic human cadaver eyes to measure the site of the focal illumination on the retina by directly observing the illumination on the posterior scleral surface of the globe. External localization of the foveola was made by direct observation using scleral indentation and indirect ophthalmoscopy. Various combinations of microscope angulation and field of view were analyzed. MAIN OUTCOME MEASURES: Distance of focal illumination from the operating room microscope relative to the foveola was measured. RESULTS: The diameter of the "hot spot" of focal illumination on the retina was 4.0 mm. With the eye positioned straight ahead and the level operating room microscope positioned for temporal approach eye surgery, the center of retinal illumination was 0.9 and 1.4 mm nasal relative to the foveola when the microscope field of view was centered over the cornea and temporal limbus, respectively. With the microscope angled 5, 10, 15, and 20 degrees temporally (oculars tilted toward surgeon), the center of the illumination was displaced nasal to the foveola by 1.1, 1.5, 3.8, and 5.1 mm, respectively, when the field of view was centered over the cornea and 1.5, 2.6, 4.7, and 6.0 mm, respectively, nasal to the foveola when centered over the temporal limbus. CONCLUSIONS: Retinal illumination from an operating microscope positioned for temporal approach eye surgery has the potential for light-induced injury to the fovea. Angulation of the operating microscope by up to 10 degrees temporally when the microscope field of view was centered over the cornea and up to 5 degrees temporally when centered over the temporal limbus was not adequate to displace the focal illumination off the foveola when the eye was in the straight-ahead position. Tilting the operating microscope 15 degrees or more temporally when centered on the pupil and 10 degrees or more when centered over the temporal limbus should safely displace the retinal light exposure away from the fovea during temporal approach surgery. Suggestions for reducing the risk of iatrogenic phototoxicity are reviewed.

Cataract Extraction↗
PubMed1999

Risk factors for anterior capsule contraction syndrome with polypropylene or poly(methyl methacrylate) haptics.

PURPOSE: To determine the effect of haptic composition on the development of anterior capsule contraction syndrome (CCS) requiring neodymium: YAG anterior capsulotomy. SETTING: Ophthalmology practice in Lancaster, Pennsylvania, USA. METHODS: This retrospective study covered a 30 month period during which 1 surgeon discontinued implanting AMO SI-30NB intraocular lenses (IOLs) with polypropylene haptics (n = 216) in favor of SI-40NB IOLs with poly(methyl methacrylate) (PMMA) haptics (n = 127). The transition was motivated by the suspicion that the PMMA haptics would maintain the capsulorhexis opening better and reduce the need for an anterior capsulotomy. RESULTS: Three eyes with SI-30NB IOLs (1.4%) required anterior capsulotomies; 2 eyes had preoperative pseudoexfoliation syndrome and required the capsulotomy within 3 months of surgery. Three eyes with SI-40NB IOLs (2.4%) required anterior capsulotomies within 4 months; 2 eyes had preoperative pseudoexfoliation syndrome and 1 had traumatic zonular weakness. The incidence of anterior capsulotomy did not differ significantly between the 2 IOL populations (P > .5), although preoperative pseudoexfoliation syndrome was a significant risk factor in both groups (P < .005). CONCLUSIONS: The polypropylene haptics of the SI-30NB IOL and the PMMA haptics of the SI-40NB IOL did not differ significantly in their ability to prevent CCS requiring anterior capsulotomy. Regardless of IOL haptic composition, eyes with preoperative zonular weakness associated with pseudoexfoliation syndrome or ocular trauma can develop CCS within 3 months of surgery and should, therefore, be followed closely in the early postoperative weeks to minimize the sequelae of anterior capsule fibrosis.

Aged↗
PubMed1995

The incidence of atonic pupil following cataract surgery.

OBJECTIVE: To determine and compare the incidence of atonic pupil following modern extracapsular cataract extraction and small-incision phacoemulsification with lens implantation in a large series of consecutive patients. PATIENTS AND DESIGN: A retrospective review was undertaken of 1283 consecutive cases of cataract surgery with posterior chamber intraocular lens implantation (919 extracapsular and 364 small-incision phacoemulsification) performed by two surgeons between October 30, 1991, and June 30, 1993. Postoperative atonic pupil was defined as a pupil that, following cataract surgery, was 6 mm or more in diameter and minimally or nonreactive to light, accommodation, or 1% pilocarpine hydrochloride. RESULTS: Postoperatively, 25 (1.95%) of 1283 eyes developed an atonic pupil following cataract extraction with posterior chamber intraocular lens implantation (21 [2.29%] of 919 extracapsular and four [1.10%] of 364 phacoemulsification procedures). When an atonic pupil was present following surgery, disturbing glare often resulted, despite a well-centered intraocular lens. CONCLUSIONS: To our knowledge, this is the first large, consecutive study of the incidence of atonic pupil following modern cataract surgery and the first study to compare the incidence of atonic pupil following extracapsular surgery vs small-incision phacoemulsification. Although the incidence of atonic pupil may be lower following phacoemulsification, caution is advised in the implantation of ever-smaller optic lenses.

Adult↗
PubMed1993

Peripseudophakic membrane. Pathologic features.

A 70-yr-old woman underwent anterior segment reconstruction with repeated penetrating keratoplasty for visual rehabilitation. On removal of the failed keratoplasty button, the posterior chamber intraocular lens was found to be encased in a dense fibrous membrane that almost totally obliterated the anterior and posterior chambers of the eye. Anterior segment reconstruction included excision of the fibrous membrane, removal of the intraocular lens, iridoplasty, gonioplasty, anterior vitrectomy, and repeated penetrating keratoplasty. Recognition of fibrous tissue that extended through each of the four positioning holes of the optic of the lens implant and its transection was essential in avoiding complications during removal of the intraocular lens. Histopathologic and ultrastructural examination of the excised membrane revealed areas of metaplastic lens epithelium and fibrous scar tissue. This study, using immunofluorescence, is the first, to our knowledge, to characterize the specific collagenous components of a peripseudophakic membrane.

Aged↗
PubMed1992

Through curettage in the treatment of chronic canaliculitis.

While various techniques have been proposed for the treatment of canaliculitis, there have been no published series that evaluate the efficacy of simple curettage in the treatment of persistent or recurrent canaliculitis. We report the effectiveness of thorough, simple curettage (without canaliculotomy) in 11 patients with chronic canaliculitis. All patients had a history of canaliculitis-related symptoms for a minimum of 6 months and clinically detectable canalicular concretions before initial treatment. Thorough, simple curettage (without canaliculotomy) resolved the chronic canaliculitis in all of the patients. Ten of the 11 patients were cured with a maximum of two sessions of curettage. One patient required three treatments of curettage and silicone intubation for common canalicular narrowing to render her free of symptoms. No surgical complications occurred in any of the patients. Our report confirms the effectiveness and low morbidity of thorough curettage in the treatment of persistent or recurrent cases of canaliculitis.

Adult↗
PubMed1992

Intercellular adhesion molecule-1 (ICAM-1) and HLA-DR antigens in herpes keratitis.

PURPOSE: Intercellular adhesion molecule-1 (ICAM-1) is a cell surface glycoprotein that binds leukocyte function antigen-1 receptor on leukocytes, thereby regulating leukocyte trafficking and function at sites of inflammation. Recently, the authors demonstrated ICAM-1 in human corneas exposed to proinflammatory cytokines, but ICAM-1 has not been reported in corneal disease. In this study, the presence of ICAM-1 in human disciform herpes simplex virus (HSV) keratitis is investigated. METHODS: Immunohistochemistry was performed for ICAM-1 on 4 keratoplasty specimens from patients with corneal scarring due to disciform HSV keratitis and 1 corneoscleral biopsy of a patient with active HSV keratoscleritis using specific, characterized monoclonal antibody to ICAM-1. Negative immunohistochemical controls included monoclonal antibodies to other vascular endothelial adhesion molecules or mouse serum. RESULTS: All 5 specimens demonstrated intense ICAM-1 immunoreactivity of keratinocytes, stromal keratocytes, and endothelial cells, predominantly in regions of leukocytic infiltration. Diffuse, intense HLA-DR positivity was detected throughout the corneas. The specimens failed to react with control antibodies. CONCLUSION: These results are the first to demonstrate ICAM-1 in human corneal disease and suggest important roles for ICAM-1 and HLA-DR co-expression in generating immune responses in HSV keratitis. Increased ICAM-1 expression in regions of leukocytic infiltration may regulate leukocyte-corneal cell binding, thereby promoting immune responses and damage by activated leukocytes.

Adult↗
PubMed1992

Pneumotonometry using sterile single-use tonometer covers.

Current methods for cleaning pneumotonometer tips include soaking the removable tip in various chemical agents. Disadvantages of this technique include the potential for incomplete disinfection, corneal contact with cleaning solutions, tip damage or loss, and soaking time. The authors studied the use of an available, disposable latex cover placed over the pneumotonometer tip for measuring intraocular pressure (IOP) in 46 eyes with normal corneas from a glaucoma screening clinic and 141 eyes with normal and abnormal corneas from a cornea and external disease clinic. The mean absolute IOP difference comparing with and without the tonometer cover was 1.6 mmHg for the glaucoma screening patients and 1.8 mmHg for the cornea clinic patients. A tonographic-like effect due to repeated tonometry also was shown. An additional study measuring a series of known IOP values in a cadaver eye showed no significant difference between uncovered and covered readings. These data suggest that placement of a disposable, latex cover over the pneumotonometer tip enables accurate IOP measurements and is a sanitary and convenient alternative method to repeated chemical disinfection.

Adolescent↗
PubMed1992

Modulation and function of intercellular adhesion molecule-1 (CD54) on human retinal pigment epithelial cells.

As part of the blood-retina barrier, the neuroectodermally-derived retinal pigment epithelial (RPE) monolayer is strategically positioned to interact with circulating leukocytes and regulate their access to the retina. We, therefore, studied whether human RPE cells express intercellular adhesion molecule-1 (ICAM-1), a specialized cell surface glycoprotein that binds the leukocyte function antigen-1 receptor present on all leukocytes. Using specific monoclonal antibody to ICAM-1, immunohistochemical staining of freshly-isolated primary and fourth passaged human RPE cells resulted in delicate reaction product that increased dramatically upon exposure to human recombinant (r) interferon-gamma (rIFN-gamma), interleukin-1-beta (rIL-1 beta), or tumor necrosis factor-alpha (rTNF-alpha). Fluorescence-activated cell sorting analysis demonstrated 2-fold increases in constitutive RPE ICAM-1 expression within 6 hours of exposure to physiologic concentrations of rIFN-gamma, rIL-1 beta, or rTNF-alpha. In standardized leukocyte adherence assays, cultured RPE cells showed avid binding of neutrophils that increased significantly after stimulation with rIFN-gamma, rIL-1 beta, or rTNF-alpha (p less than 0.001). In parallel assays, monoclonal antibody to either ICAM-1 on RPE cells, or subunits of leukocyte function antigen-1 receptors on leukocytes significantly blocked leukocyte binding to unstimulated (p less than 0.001) or rIFN-gamma-stimulated RPE cells (p less than 0.001). To demonstrate RPE ICAM-1 expression in intact human tissue, fresh uveoretinal explants were exposed to rIFN-gamma, rIL-1 beta, or rTNF-alpha and stained using mAb to ICAM-1. Tissue sections of cytokine-stimulated explants revealed dramatic increases in RPE ICAM-1 immunoreactivity over the low levels observed in unstimulated uveoretinal tissue. Our results indicate that: (a) ICAM-1 is expressed at low levels on unstimulated RPE cells, (b) RPE ICAM-1 may be augmented by inflammatory cytokines, and (c) RPE ICAM-1 is a functional receptor mediating leukocyte binding. ICAM-1 on RPE cells at the blood-retina barrier may regulate leukocytic infiltration in ocular diseases in which leukocytes are important pathogenetically and may be important to the generation of ocular immune responses.

Cell Adhesion↗
PubMed1992

Differential expression of human corneal and perilimbal ICAM-1 by inflammatory cytokines.

The mechanisms that regulate corneal infiltration by circulating leukocytes in inflammatory diseases are poorly understood. In this study, we investigated the effects of pro-inflammatory cytokines on corneal endothelial (CE) and stromal (CS) expression of intercellular adhesion molecule-1 (ICAM-1), a specialized cell surface glycoprotein that binds the leukocyte function antigen-1 (LFA-1) receptor present on all leukocytes and enhances immune responses. Using specific monoclonal antibody (mAb) to ICAM-1, immunohistochemical staining of intact human corneas resulted in discrete, granular reaction product in CE and CS cells as well as perilimbal vascular endothelium that increased dramatically when exposed to human recombinant interleukin-1-beta (rIL-1 beta), tumor necrosis factor-alpha (rTNF-alpha), and interferon-gamma (rIFN-gamma). Immunoreactive ICAM-1 in CE and CS cells was differentially increased by each of these cytokines. In contrast, immunoreactive endothelial-leukocyte adhesion molecule-1 and vascular cell adhesion molecule-1 were not detected in any CE or CS cells of unstimulated or cytokine-stimulated corneas. In standardized leukocyte adherence assays, neutrophil binding to CE surfaces of whole corneas increased significantly upon exposure to rIL-1 beta, rTNF-alpha, or rIFN-gamma (P less than 0.001). In parallel assays, mAb to ICAM-1 on CE cells or subunits of LFA-1 receptors on leukocytes, but not control mAb, significantly blocked leukocyte binding to unstimulated (P less than 0.01) or rIFN-gamma-stimulated corneas (P less than 0.001). Our results indicate that: (1) ICAM-1 is expressed at low levels on unstimulated CE cells, CS cells, and perilimbal vascular endothelium; (2) ICAM-1 may be augmented differentially in corneal and perilimbal tissue by pro-inflammatory cytokines; and (3) ICAM-1 is a functional ligand mediating corneal-leukocyte binding. Differential expression of ICAM-1 within corneal tissue may regulate keratitic precipitate formation, leukocyte trafficking and accumulation, and localized generation of immune responses.

Cell Adhesion Molecules↗
PubMed1991

Human and monkey corneal endothelium expression of low-density lipoprotein receptors.

Receptors for low-density lipoprotein are necessary for high-affinity uptake of lipid and protein essential to cell structure and function. Distinct receptors for acetoacetylated low-density lipoprotein internalize oxidized or enzymatically modified low-density lipoprotein and extracellular matrix components. We identified low-density lipoprotein receptors on cultured human and monkey corneal endothelial cells by the avid incorporation of fluorescently labeled low-density lipoprotein that was competitively inhibited by excess unlabeled low-density lipoprotein but not by unlabeled acetoacetylated low-density lipoprotein. Specific uptake of labeled low-density lipoprotein was greatest in nonconfluent, growing cells and increased after low-density lipoprotein deprivation. Intact endothelial monolayers of whole human cornea also incorporated low-density lipoprotein but not acetoacetylated low-density lipoprotein. After scratch injury of human corneas, spreading endothelium adjacent to areas of cell loss internalized more fluorescent low-density lipoprotein than cells distant from the injury. Blood-aqueous barrier breakdown occurring in ocular diseases and after surgical and nonsurgical trauma may allow leakage of circulating low-density lipoprotein, which provides a rich supply of lipid and protein for endothelial use. Efficient, receptor-mediated, low-density lipoprotein uptake may facilitate repair of damaged corneal endothelial membranes and regeneration of intact, functional cell monolayers.

Acetoacetates↗
PubMed1991

Intercellular adhesion molecule-1 in human corneal endothelium. Modulation and function.

The endothelium lining the posterior corneal surface performs physiologic pump functions essential to corneal clarity and integrity. A hallmark of keratitis, anterior ocular inflammation, and corneal allograft rejection is leukocyte adherence to the corneal endothelium (CE) forming keratitic precipitates. To elucidate mechanisms governing cornea-leukocyte interactions, cultured human CE cells and intact corneas were examined for expression of intercellular adhesion molecule-1 (ICAM-1), which binds the lymphocyte function-associated antigen-1 (LFA-1) on all leukocytes and enhances delayed-type hypersensitivity mediated by class II major histocompatibility complex antigens. Immunohistochemistry on culture CE cells using monoclonal anti-ICAM-1 antibody yield positive staining that increased after exposure to interleukin-1-beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (gamma-IFN). Standard leukocyte adherence assays demonstrated ICAM-1-mediated CE-neutrophil binding, which was specifically blocked by antibody to ICAM-1 or antibodies to LFA-1 on neutrophils. In whole human corneas, gamma-IFN increased CE and stromal keratocyte ICAM-1 immunoreactivity and enhanced CE-neutrophil adherence. As in CE cell cultures, antibody to ICAM-1 effectively blocked neutrophil binding to the CE cells of whole corneas. These results are the first to demonstrate ICAM-1 in ocular tissue. They indicate that CE cells express functional ICAM-1, which may be modulated by inflammatory cytokines, ICAM-1 provides mechanisms for keratitic precipitate formation, regulation of corneal leukocyte trafficking and the generation of immune responses that may be crucial to allograft rejection.

Cell Adhesion Molecules↗
PubMed1991

Human corneal interleukin-8. IL-1 and TNF-induced gene expression and secretion.

Corneal leukocytic infiltration is an important component of numerous ocular diseases, but specific corneal-derived leukocyte chemotaxins have not been identified. In this study, the authors identified interleukin-8 (IL-8), a known neutrophil and lymphocyte chemotaxin, to be an important chemotaxin produced by human corneal tissue. In situ hybridization and immunohistochemistry of corneas exposed to human recombinant (r) interleukin-1-beta (rIL-1 beta) or tumor necrosis factor-alpha (rTNF-alpha) revealed significant increases in corneal endothelial and stromal cell IL-8 mRNA (P less than 0.001) and marked increases in cell-associated immunoreactive IL-8 compared with unstimulated controls. ELISA assays revealed four- to eight-fold increases in corneal IL-8 secretion after 24-hour exposures to either cytokine over that obtained with unstimulated corneas (P = 0.01). In neutrophil chemotactic bioassays, significant increases in functional IL-8 were detected in media conditioned by corneas exposed to rIL-1 beta or rTNF-alpha for 24 hours (P less than 0.001). Preincubation of these corneal media with anti-IL-8 antibody significantly reduced neutrophil chemotaxis by more than 80%. These results suggest that the cornea is an active participant in ocular inflammation and raise the possibility that agents used in experimental corneal pocket models may produce indirect effects by inducing corneal secretion of other factors, such as IL-8.

Chemotaxis, Leukocyte↗
PubMed1990

Unsuspected paperboard-endophthalmitis in ruptured eye.

The eye of a 3-year-old boy was directly exposed to the explosion of an M-80 firecracker which he had been holding in his hand. The cornea and lens were ruptured. Although not evident on an initial CT scan, pathologic examination revealed a paperboard foreign body lodged in the vitreous. This paperboard, rather than the burnt powder, was likely the central focus of the subacute endophthalmitis that developed.

Child, Preschool↗
PubMedDate not supplied

Corneal topographic changes induced by pterygia.

BACKGROUND: This study characterizes the topographic changes induced by pterygia. METHODS: Using data obtained from a videokeratoscope (TMS-1), we assessed the topographic changes of corneas from 24 consecutive eyes with pterygia. RESULTS: Each pterygium induced a localized area of flattening central to its apex of 38.00 +/- 2.80 diopter (D) which was significantly flatter (p < .0001) than the mean corneal power (43.70 +/- 1.70), minimum corneal power (MinK, 42.70 +/- 2.10), and the power of the flattest corneal meridian (42.90 +/- 1.90). CONCLUSIONS: Our topographic findings characterize an area of localized corneal flattening central to the apex of pterygia. It is not known if this pterygium-associated corneal flattening influences the centripetal growth of pterygia or their tendency not to cross the visual axis.

Cornea↗