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Biomedical subjects

W J Stark

Publications and source records attributed to W J Stark.

At least 235 records · Page 13Linked to original sources
PubMed1976

Corneal endothelial degeneration and fibrous proliferation after plana vitrectomy.

A 45-year-old woman with juvenile-onset diabetes had persistent corneal edema after a pars plana vitrectomy and lensectomy procedure. Phase contrast and electron microscopic observation of the patient's cornea revealed extreme attenuation of the endothelial cell layer and abnormal collagenous and basement membrane material interposed between Descemet's membrane and the endothelium. Endothelial fibrous proliferations in this case were consistent with the development of ultrastructurally identical fibrous proliferations in many other situations involving dysfunction of the corneal endothelium.

Basement Membrane↗
PubMed1976

Ultrastructure of keratoconus with healed hydrops.

The corneas of three patients with keratoconus were examined by light and electron microscopy within approximately four months after onset of severe hydrops. The rupture and detachment of Descemet's membrane resulted in formation of extensive ledges. New endothelium completely resurfaced the exposed posterior stroma and the corresponding anterior aspect of the ledges. The endothelium also regenerated considerable basement membrane. In one case, clustered endothelium near the free end of the ledge appeared to have undergone fibrous metaplasia with secretion of extensive fibrillar and basement membrane material.

Adolescent↗
PubMed1975

The histopathology of Peters' anomaly.

Corneal, iris, and trabecular meshwork tissue in a 23-month-old boy with Peters' anomaly were studied with light and electron microscopy. In the cornea, both Descemet's membrane and endothelium were present beneath the area of the corneal opacity except at the point of iris adhesion. However, Descemet's membrane was thin and embryonal in nature, and the endothelium markedly attenuated. The trabecular meshwork demonstrated changes characteristic of old age such as wide-banded collagen and the presence of phagocytosed pigment granules in the endothelium. The iris appeared normal except for anterior synechiae to the corneal opacity. Developmentally, the primary fault appeared to be a failure in the normal differentiation of endothelial cells of the cornea and trabecular meshwork.

Cornea↗
PubMed1975

Defective epithelial adhesion in anterior corneal dystrophies.

Experimental and pathologic studies implicated the role of the epithelial basement membrane and its associated hemidesmosomes and anchoring fibrils in mediating tight adhesion between corneal epithelium and stroma. We evaluated the ultrastructural quality of basement membrane complexes in patients with Reis-Bücklers dystrophy, Cogan's microcystic dystrophy, and nontraumatic recurrent erosion who presented with clinically significant erosive symptoms. Despite the variable clinical and histopathologic appearances among these dystrophies, incompleteness of basement membrane complexes apparently was a common fault shared by these erosive disorders. Such basic incompetence at the basement membrane level can both provoke and sustain erosions, while the more individual pathologic manifestations of a given anterior dystrophy may be of less primary significance.

Adolescent↗
PubMed1975

Intermediate-term corneal storage for penetrating keratoplasty.

Fifty-seven penetrating keratoplasties were performed using human donor corneal material stored in modified Tissue Culture Medium 199 (TC-199). Fifty-six grafts were clear on the first postoperative day and remained clear for at least three weeks. During the follow-up period (average, 3.7 months), only four additional graft failures occurred. The reduced incidence of early graft edema is attributed to prolonged viability of corneal endothelium maintained in modified TC-199 medium prior to keratoplasty.

Adult↗
PubMed1975

Acute glaucoma in systemic mucopolysaccharidosis I-S.

Two siblings, a 56-year-old white man and a 44-year-old white woman, with systemic mucopolysaccharidosis I-S (Scheie's syndrome) developed acute glaucoma successively in each eye. Their management was complicated by an inability to visualize the anterior chamber angle due to corneal clouding by acid mucopolysaccharide (AMP) deposition. The mechanism of their glaucoma resembled angle closure, which may have been related to thickening of anterior ocular structures due to abnormal AMP storage.

Acute Disease↗
PubMedDate not supplied

The use of confocal microscopy in evaluating corneal wound healing after excimer laser keratectomy.

Corneal wound healing following excimer laser keratectomy is the major cause of regression of treatment results. The amount of anterior stromal haze that develops may be influenced by topical medications. Over a period of 6 months, we followed 15 New Zealand white rabbit eyes that underwent excimer laser keratectomy with the VISX 193-nm ArF laser at a fluence of 150 mJ/cm2 for a depth of 130 microns. Eyes were randomized to treatment with prednisolone acetate, diclofenac sodium (Voltaren), a combination of both, and a control group. Drops were administered four times a day for 1 week, two times a day for 3 weeks, and the drops were then tapered. All eyes were reepithelialized by 5 to 7 days. The tandem scanning confocal microscope (TSCM) was used to evaluate the corneal wound in vivo weekly for a month and monthly for 6 months. During the early postoperative period, the TSCM revealed significant anterior stromal keratocyte activation with cell elongation and the spindle-shaped appearance of fibroblasts in all groups. Collagenous stromal scarring was evident initially, then slowly decreased in all treatment groups. This study shows that TSCM is clinically useful for successive in vivo examinations of corneal wounds after excimer laser keratectomy and for comparing the effects of various topical medications.

Animals↗
PubMedDate not supplied

Clinicopathologic features of Chandler's syndrome.

The clinicopathologic features of Chandler's syndrome are elucidated based on a study of nine patients. Keratoplasty, trabeculectomy and/or iris specimens were studied by light, electron and, in six cases, specular microscopy. The prominent pathologic features were abnormalities of the endothelially-derived cells lining the posterior corneal surface, the inner surface of the trabecular meshwork, and the anterior iris surface. In all four corneal buttons, the endothelium was diffusely attenuated and focally absent, and posterior collagen layers were present. Extension of the endothelial cell layer and Descemet's membrane deposition over the trabecular meshwork were observed in two trabeculectomy specimens, and similar proliferation onto the anterior surface of the iris was evident in four iris specimens. Other abnormalities of the endothelial cells included increased intracytoplasmic filaments. These pathologic alterations are consistent with the concept of Chandler's syndrome as representing one variant of the iridocorneal endothelial (ICE) syndrome. Interestingly, although both endothelial proliferative and degenerative responses can be observed in Chandler's syndrome, their occurrence within the same eye is apparently not simultaneous.

Adult↗
PubMedDate not supplied

Excimer laser calibration system.

BACKGROUND: Excimer laser photoablation for refractive and therapeutic keratectomies has been demonstrated to be feasible and practicable. However, corneal laser ablations are not without problems, including the delivery and maintenance of a homogeneous beam. We have developed an excimer laser calibration system capable of characterizing a laser ablation profile. METHODS: Beam homogeneity is determined by the analysis of a polymethylmethacrylate (PMMA)-based thin-film using video capture and image processing. The ablation profile is presented as a color-coded map. Interpolation of excimer calibration system analysis provides a three-dimensional representation of elevation profiles that correlates with two-dimensional scanning profilometry. Excimer calibration analysis was performed before treating a monkey undergoing phototherapeutic keratectomy and two human subjects undergoing myopic spherocylindrical photorefractive keratectomy. Excimer calibration analysis was performed before and after laser refurbishing. RESULTS: Laser ablation profiles in PMMA are resolved by the excimer calibration system to .006 microns/pulse. Correlations with ablative patterns in a monkey cornea were demonstrated with preoperative and postoperative keratometry using corneal topography, and two human subjects using video-keratography. Excimer calibration analysis predicted a central-steep-island ablative pattern with the VISX Twenty/Twenty laser, which was confirmed by corneal topography immediately postoperatively and at 1 week after reepithelialization in the monkey. Predicted central steep islands in the two human subjects were confirmed by video-keratography at 1 week and at 1 month. Subsequent technical refurbishing of the laser resulted in a beam with an overall increased ablation rate measured as microns/pulse with a donut ablation profile. A patient treated after repair of the laser electrodes demonstrated no central island. CONCLUSIONS: This excimer laser calibration system can precisely detect laser-beam ablation profiles. The calibration system correctly predicted central islands after excimer photoablation in a treated monkey cornea and in two treated human subjects. Detection of excimer-laser-beam ablation profiles may be useful for precise calibration of excimer lasers before human photorefractive and therapeutic surgery.

Animals↗
PubMedDate not supplied

Subregions of differing refractive power within the clear zone after experimental radial keratotomy.

After radial keratotomy (RK), some patients experience a mild decrease in best corrected visual acuity, visual distortion, or monocular diplopia. These optical effects of radial keratotomy are best explained by subregions of different refractive powers within the surgery-free clear zone. To investigate the topography of the clear zone, we performed four- and eight-incision radial keratotomy in eight cadaver eyes. After radial keratotomy, we found subregions within the clear zone of two types: 1) small, very flat regions at the ends of the radial incisions (seven of eight eyes), and 2) a series of concentric rings centered on the visual axis with a continuously progressive decline in refractive power toward the periphery of the clear zone (all eyes). The clear zone after radial keratotomy is often nipple-shaped, with a more myopic segment centrally and a more hyperopic region near the periphery of the clear zone.

Cornea↗