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Biomedical subjects

D R Meyer

Publications and source records attributed to D R Meyer.

At least 73 records · Page 4Linked to original sources
PubMed1993

Evaluating the visual field effects of blepharoptosis using automated static perimetry.

BACKGROUND: Quantitation of the effects of blepharoptosis on the visual field has largely been limited to manual kinetic perimetry using a single peripheral isopter. The authors evaluated the visual dysfunction caused by blepharoptosis using automated static full-threshold perimetry. METHODS: A custom static full-threshold 60 degrees test strategy on the Humphrey field analyzer was used to assess the visual fields of 20 volunteers at their normal baseline and after inducing mild and moderately severe blepharoptosis by applying gold weights to the eyelids. Threshold sensitivities were measured at points along the eight principal meridians, separated by 45 degrees, traditionally used to assess visual field impairment. RESULTS: For mild blepharoptosis, essentially all test points along the superior meridian were significantly depressed (P < 0.01), with an increase in slope secondary to greater decreases in sensitivity at more eccentric points. For moderately severe blepharoptosis, depression of the superior meridian was expectedly greater than that seen with mild blepharoptosis. Additionally, depression of the horizontal meridians and to a lesser extent the lower meridians also was noted. CONCLUSIONS: These results suggest that even mild blepharoptosis may be associated with depression of the superior visual field extending close to fixation. Ophthalmologists should be aware of the effect of blepharoptosis when testing for other ophthalmic or neurologic disorders using automated static perimetry. Full-threshold static perimetry can be used to quantitate the visual field loss associated with blepharoptosis as a means of evaluating visual impairment.

Adult↗
PubMed1993

Lacrimal disease and surgery.

The lacrimal drainage system includes the nasolacrimal duct, lacrimal sac, and canaliculi. Stenosis or obstruction at any portion of the lacrimal drainage system or an impaired lacrimal pump may cause bothersome epiphora. Tear stasis may also be associated with ocular or adnexal infections. This article reviews the recent literature pertaining to anatomy and physiology, pathology, and clinical evaluation and treatment, as well as complications of lacrimal drainage-system disorders.

Dacryocystorhinostomy↗
PubMed1993

Child support and welfare dynamics: evidence from Wisconsin.

This paper provides estimates of the effect of child support on exiting and reentering welfare for a sample of divorced women in Wisconsin. Modest amounts of child support do not have large effects on exiting welfare in this sample. The percentage of women who return to welfare is higher than has been reported previously. Receiving child support significantly decreases the likelihood of returning to welfare.

Aid to Families with Dependent Children↗
PubMed1992

Bilateral localized orbital neurofibromas.

BACKGROUND: The authors report on a 30-year-old man who presented with progressive bilateral exophthalmos over a 2-year period. FINDINGS: Computed tomography showed large heterogeneous masses in the superior aspect of both orbits. Excisional biopsy via bilateral lateral orbitotomies showed the tumors to be well-circumscribed, relatively avascular, localized neurofibromas. The patient had several features suggestive of multiple endocrine neoplasia type IIB, including Marfanoid habitus, enlarged corneal nerves, thickened lips, and mucosal neuromas. CONCLUSION: Localized neurofibromas are rare in the orbit and, unlike plexiform neurofibromas, are not typically associated with von Recklinghausen's neurofibromatosis. Bilaterality of such localized neurofibromas has not been previously reported. Recognition of ophthalmic lesions suggestive of multiple endocrine neoplasia IIB should prompt evaluation for systemic manifestations of this disorder.

Adult↗
PubMed1992

Detection of contralateral eyelid retraction associated with blepharoptosis.

The association between induced contralateral upper eyelid retraction and blepharoptosis, although well known, has not been well analyzed. The authors prospectively studied 50 consecutive patients with blepharoptosis. Interpalpebral fissure measurements of the contralateral "normal" or relatively less blepharoptotic eyelids were made in the resting position, with the blepharoptotic eye occluded, manually elevated, and after instillation of phenylephrine 2.5%. Ocular dominance also was tested. Contralateral interpalpebral fissure height decreased greater than or equal to 1 mm in 10 of 50 patients (20%) after manual elevation. Blepharoptosis was present or greater in the dominant eye in 7 of 10 (70%) patients in this group, but in only 7 of 40 (18%) patients in the group not showing such a response (P less than 0.001). Of 12 patients with congenital blepharoptosis, none demonstrated this response. In patients with acquired blepharoptosis, contralateral decrease in eyelid position also was directly associated with severity of blepharoptosis in the opposite eye. These findings suggest that contralateral induced eyelid elevation or retraction is frequently associated with blepharoptosis and is more apparent as visual impairment secondary to blepharoptosis increases. Detection of contralateral eyelid retraction is important in the preoperative evaluation of blepharoptosis.

Adolescent↗
PubMed1992

Susceptibility of corneas from various animal species to in vitro binding and invasion by Acanthamoeba castellanii [corrected].

A crucial requirement for establishing corneal infection by the extracellular protozoal parasite, Acanthamoeba, is the ability of the parasite to bind to the corneal surface. In a series of in vitro studies, we examined the ability of Acanthamoeba castellanii [corrected] to adhere, invade, and damage normal, intact corneas of 11 mammalian and one avian species. A. castellanii [corrected] (80-90% trophozoites and 10-20% cysts) were incubated with corneas for 24 hours in vitro and examined by scanning electron microscopy (SEM). Results of several independent SEM experiments revealed that parasites not only failed to produce cytopathic effects but did not even bind to the corneal epithelium of mice, rats, cotton rats, horses, guinea pigs, cows, chickens, dogs, and rabbits. However, parasites adhered, invaded, and produced severe damage to human, pig, and Chinese hamster corneas during the 24-hour in vitro incubation period. Additional in vitro experiments quantified the binding of A. castellanii [corrected] to the corneas of selected susceptible and nonsusceptible species. In vitro binding assays revealed scant binding of parasites to mouse, rat, and rabbit (range = 5-20 parasites/7.07 mm2 corneal button). In contrast, extensive binding was observed on Chinese hamster, pig, and human corneas (range = 100-200 parasites/7.07 mm2 button). The results indicate that A. castellanii [corrected] exercises rigid host specificity at the host cell surface.

Acanthamoeba↗
PubMed1991

Anatomy of the orbital septum and associated eyelid connective tissues. Implications for ptosis surgery.

The anatomy of the orbital septum and associated eyelid connective tissues was examined using cadaver dissection, histologic sections, surgical observations, and special radiologic imaging. The embryologic development of the eyelid connective tissues was also reviewed. Examination revealed a distinct layer of fibroadipose tissue in the eyelid and eyebrow posterior to the orbicularis and frontalis muscles, and anterior to the orbital septum. Fibrous septa within the submuscular fibroadipose tissue become contiguous with more compact lamellae of the orbital septum posteriorly imparting a multilayered quality to the orbital septum. Fat within the fibroadipose layer anterior to the orbital septum may be mistaken for the preaponeurotic fat pad by the unwary surgeon and may lead to surgical error. The orbital septum and the levator aponeurosis were found to join 2 to 5 mm above the superior tarsal border (average, 3.4 mm). Recommendations for ptosis surgery based on these anatomic principles are given.

Adipose Tissue↗
PubMed1991

In vitro penetration of human corneal epithelium by Acanthamoeba castellanii: a scanning and transmission electron microscopy study.

Human corneal buttons were exposed to Acanthamoeba castellanii trophozoites and cysts for 12 hours at 35 degrees C. The buttons examined by light microscopy and scanning and transmission electron microscopy had severe epithelial ulceration and penetration by trophozoites. Observations on trophozoites below the surface suggest that penetration is accomplished by both secreted cytolytic enzymes and phagocytosis. It is likely that the secretion of one or more enzymes constitutes the initial step in preparing the host tissue for endocytosis or that the secretory mechanism is used by the amebas to move through the outer squamous layer to the basement epithelium where phagocytosis occurs. Based on this study and a previous study, it appears that entry into the cornea is a two-step process involving adherence and penetration by trophozoites.

Acanthamoeba↗
PubMed1991

In vitro intercellular adherence of Acanthamoeba castellanii: a scanning and transmission electron microscopy study.

Human corneal buttons were exposed to trophozoites and cysts of Acanthamoeba castellanii for 12 hours. Examination of the buttons by scanning electron microscopy showed numerous trophozoites on the surface of the epithelium. Trophozoites examined by transmission electron microscopy had limited regions of attachment to the epithelium but extensive regions of attachment to each other. Attachment regions were characterized as plaque-like maculae of an incomplete desmosome junction. Firm attachment mechanisms may explain how penetration of the human cornea occurs.

Acanthamoeba↗
PubMed1991

In vitro transfer of rabbit corneal epithelium from carriers to denuded corneas or cryolathed lenticules.

Rabbit corneal basal epithelial cells seeded onto fixed gelatin membranes or commercial collagen shields formed 3 to 5 cell layers after 1 to 3 weeks of culture at 35 degrees C in nutrient medium. The cells grew better, by comparison, in the collagen shields and eventually formed a multilayered tissue that resembled the stratified morphology of native epithelium. Transfer of multilayered cultures (prior to stratification) from these carriers in vitro to denuded corneal buttons or cryolathed lenticules resulted in complete adhesion of the grafted tissue to the underlying recipient buttons after 24- to 48-h incubations. After mechanically removing the carriers, most of the epithelial cells remained attached to the stromal surface. Our experimental findings indicated that both kinds of carriers may be suitable for epithelial transplantation, although the collagen shield is probably superior because of its better biocompatibility and physical characteristics.

Animals↗
PubMed1991

Differential effect of chelation on the pH tolerance of corneal epithelium in tissue culture.

The impact of chelation on the biocompatibility of various vehicles was determined after 1- to 32-min exposures using stratified rabbit corneal epithelial cultures. Each formulation was tested at either pH 5.0 or 7.5 to mimic the specifications of most commercial ophthalmic preparations. Adding ethylenediamine tetraacetic acid (EDTA) to balanced salt solutions was unremarkable, and all of the formulations were essentially nontoxic. In contrast, EDTA moderately reduced the toxicity of the acidic acetate/citrate-buffered vehicles, but enhanced the toxicity of the alkaline solutions. The preservative, on the other hand, had little impact on the biotolerance of acidic unbuffered and phosphate-buffered vehicles, although it also increased the toxicity of the alkaline formulations. These findings are interpreted in terms of the different pKa values of the chelating agents, and an unsuspected interaction between citrate and the preservative. We believe that this type of testing can be used to develop guidelines for the use of buffers, excipients and preservatives in commercial formulations.

Animals↗
PubMed1991

Outpatient dacryocystorhinostomy.

We report 105 dacryocystorhinostomy procedures in 87 patients performed on an outpatient basis. Seventy-six patients received local, and 29 received general, anesthesia. The patients left the hospital an average of 2.6 hours after surgery, but 14 were admitted after surgery--9 immediately, and 5 after some delay, primarily for epistaxis. There were no serious complications related to the outpatient nature of the surgery. The success rate was 94%. We conclude that outpatient dacryocystorhinostomy is successful, well accepted by patients, and safe, provided that inpatient care facilities are readily available should they be needed.

Adolescent↗
PubMed1991

The role of tetracycline in chronic blepharitis. Inhibition of lipase production in staphylococci.

Tetracycline administered in low doses can be effective in the long-term management of patients with meibomian keratoconjunctivitis (MKC). However, the mechanism of action does not appear to be a reduction of bacteria. Seventy-five percent of the ocular staphylococci in such patients are resistant to tetracycline. An alternative mechanism of action could be the inhibition of production of extracellular enzymes by the ocular flora. Inhibition of lipase production could result in lowered levels of toxic hydrolysis products (free fatty acids), which may exacerbate the disease process. The authors tested this hypothesis by examining the differential effect of tetracycline on growth and lipase production in a tetracycline-resistant and tetracycline-sensitive strain of Staphylococcus epidermidis and S. aureus isolated from patients with MKC and Staphylococcal blepharitis. Tetracycline caused significant decreases in the production of lipase in the sensitive and resistant strains of S. epidermidis without concominant decreases in growth. In contrast, S. aureus strains showed parallel decreases in both lipase production and inhibition of growth. The authors propose that the sensitivity of lipase production to tetracycline, in tetracycline-resistant S. epidermidis, may partially explain the clinical improvement observed in MKC patients.

Blepharitis↗