Visual field defects after macular hole surgery. A new finding

PURPOSE: The purpose of the study is to report the problem of a temporal visual field defect occurring after macular hole surgery. METHODS: The authors reviewed the records of 13 patients found to have visual field defects after vitrectomy for macular holes. Fluorescein angiograms (13 patients), optic nerve photographs (13 patients), focal electroretinograms (3 patients), and nerve fiber analyses (8 patients) were performed in patients with visual field defects. RESULTS: An absolute, temporal, usually inferior field defect was noted in 13 patients. In eight patients, the defect was detected because of specific reports or retrospective field examination results. Five patients examined in a prospective manner were found to have field defects. No history of abnormal intraocular pressure or direct trauma to the optic nerve or retinal vessels was identified. Four patients showed optic nerve pallor and three had an anomalous-appearing disc. Focal electroretinograms were of similar amplitude in the involved retina compared to corresponding areas in the healthy fellow eye. Nerve fiber analysis showed a reduction in nerve fiber layer thickness correlating to the visual field defect in those eight patients in which this test was used. CONCLUSION: A significant temporal field defect may occur in patients after otherwise uncomplicated surgery for macular holes. The cause is unclear; however, reductions in nerve fiber layer thickness from the superior and nasal peripapillary area suggest that acute surgical release of the posterior hyaloid and the use of long-acting intraocular gas may in certain patients result in visual field defects.     

Building-in reliability into VLSI junctions

A nondestructive test is presented for monitoring junction quality and reliability in a manufacturing environment. Using a properly selected two-temperature measurement of the activation energy associated with reverse-biased junction leakage, it was demonstrated that the activation energy was more sensitive to slight changes in junction quality than was the commonly used method of monitoring the ideality factor. The activation energy method was found to be an effective and efficient metric for controlling normal process variation. As such, this method was found to be an excellent tool for building-in quality and reliability into junctions     

Evaluation of current techniques of corneal epithelial removal in hyperopic photorefractive keratectomy

PURPOSE: To determine the efficacy of 3 current methods used to remove corneal epithelium prior to photorefractive correction of hyperopia and to compare clinical data in patients who had rotary brush or blunt scrape epithelial removal in the treatment of hyperopic photorefractive keratectomy (PRK). SETTING: University of Ottawa Eye Institute, Ottawa General Hospital, Ottawa, Ontario, Canada. METHODS: The epithelium from human eye-bank eyes was removed using a Paton spatula, 15% alcohol, and the Amoils rotating plastic brush. The effects were examined by scanning and transmission electron microscopy. Twelve month postoperative data were obtained on 25 eyes with refractions of +1.00 to +4.00 diopters (D) that had been treated for hyperopia with the VISX Star excimer laser, using blunt scrape or the rotary brush to remove the corneal epithelium. RESULTS: All 3 methods effectively removed corneal epithelium. The Paton spatula, however, left small nicks in Bowman's layer. Both the rotating brush and alcohol debridement left Bowman's layer intact. Alcohol treatment required follow-up epithelial debris removal, while brushing left minimal amounts of debris. There was a strong trend toward rapid epithelial healing in the brushed corneas compared with the scraped ones, but this was not statistically significant. Clinically, at 12 months postoperatively, brushed corneas showed a trend toward more superior outcomes than scraped corneas in actual refractive outcome, uncorrected visual acuity (UCVA), lines of UCVA gained, and predictability of the desired outcomes. However, only the outcome in UCVA of 20/40 or better and the decreased incidence of haze in the brushed corneas over scraped ones were statistically significant. CONCLUSIONS: Both alcohol and the rotating brush provide a quick, effective means of removing the corneal epithelium with minimal risk of damage to Bowman's layer. In our experience, the brush technique was as effective as and possibly superior to the blunt scrape for epithelial removal in hyperopic PRK.     

Experimental reproduction and antibody inhibition of marble spleen disease of pheasants

An extract of spleens from three pheasants affected with marble spleen disease was used as an intravenous inoculum to transmit the disease to pen reared pheasants (Phasianus colchicus x Phasianus torquatus). The disease was prevented by specific convalescent pheasant antiserum and by antiserum from turkeys that had recovered from hemorrhagic enteritis of turkeys. The causative agent of the disease passed through 0.22 mu filters, resisted chloroform and retained its precipitin antigen quality after propagation by bird passage. Filterability, chloroform resistance, antigenic characteristics and in vivo response to antibody strongly indicate that the causative agents of marble spleen disease is a virus very similar to the virus which causes hemorrhagic enteritis of turkeys.     

Lectins as probes of chromatin structure. Binding of concanavalin A to purified rat liver chromatin

Concanavalin A (Con A) binds specifically to rat liver chromatin. The extent of binding is directly proportional to both chromatin and concanavalin A concentration. It is reversible and inhibited by specific sugars for which concanavalin A has a binding site. Scatchard analysis reveals the presence of one type of Con A-binding site, with an apparent dissociation constant of 3 X 10(-7) M. A maximum of 10 pmol of Con A binds to 10 microgram of chromatin, indicating an average of one binding site/1400 base pairs of DNA. To identify the polypeptide chains which contain Con A-binding sites, chromosomal proteins were separated by electrophoresis on polyacrylamide gels containing sodium dodecyl sulfate. Con A receptors were localized by incubating the gel in 125I-Con A and subsequent autoradiography. Three major polypeptide bands which bind Con A were identified among the nonhistone chromosomal proteins. The apparent molecular weights of these glycoproteins are 135,000, 125,000, and 69,000. We suggest that lectins may serve as probes for the study of the organization of specific components in chromatin.