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Biomedical subjects

B E Cohan

Publications and source records attributed to B E Cohan.

13 recordsLinked to original sources
PubMed2001

Goldmann applanation tonometry in the conscious rat.

PURPOSE: To determine whether the Goldmann applanation tonometer can be modified to measure intraocular pressure (IOP) in the conscious rat. METHODS: In anesthetized rats Goldmann tonometers were tested that had reduced biprism angles in the applanating tips and reduced weights in the tonometer body from those used in humans and species with similar size eyes. Tonometers with tips with biprism angles of 48 degrees and an applied weight of 25 mg per Goldmann scale division (2 g full scale) were calibrated for the rat against manometrically measured IOP. Tonometers, thus modified, were then used in conscious, unsedated rats. RESULTS: In conscious rats the measured mean Goldmann value was 15.5 +/- 0.6 mm Hg (confidence interval = 14.1, 16.6 mm Hg). This was the plateau level reached after the repeated applanations (approximately 10) required to eliminate an artifactual decline in initial Goldmann readings, which was larger than that in humans. CONCLUSIONS: The Goldmann applanation tonometer was modified to measure IOP in the conscious, unsedated rat. This instrument, the standard for measuring this key physiological parameter in the human eye, can now be applied to the laboratory rat. This may advance the use of this important animal as a model in IOP and glaucoma research.

Animals↗
PubMed2001

Measurement of intraocular pressure in awake mice.

PURPOSE: To determine whether the Goldmann applanation tonometer can be modified to measure intraocular pressure (IOP) in the awake mouse. METHODS: Tonometers with reduction of the biprism angles in the applanating tips and in the weight applied by the instrument were tested in anesthetized mice in calibration experiments. Then a tonometer with the appropriate configuration of tip and weight was used in conscious, unsedated mice. RESULTS: Tonometry in mice required a biprism angle of 36 degrees and weight applied of 25 mg per scale division (2 g full scale). This tonometer was calibrated in mice against manometrically measured IOP and showed good agreement across the range of IOP tested (0-50 mm Hg). In conscious mice the measured mean Goldmann value was 13.7 +/- 3.2 mm Hg (mean +/- SD; 95% confidence interval, 13.1, 14.2 mm Hg). CONCLUSIONS: The Goldmann tonometer, the standard for measuring the IOP in the human eye, was modified to measure this fundamental physiologic parameter in the awake mouse. This measurement is required to confirm success in genetically engineering a model in the powerful mouse system, which mimics elevated IOP in humans. The model will open new avenues for studying the causes of the optic neuropathy of glaucoma, the regulation of IOP, and new therapeutic approaches to prevent the irreversible loss of vision from this disease.

Animals↗
PubMed1999

Intraocular pressure measurement in the conscious rat.

PURPOSE: To develop a method for measurement of intraocular pressure in conscious, unsedated rats. METHODS. The animal was gently held with a thick fabric mitten, topical anesthetic drops were instilled and the Tono-Pen was applied to the cornea. RESULT: Measurements in a total of 51 animals did not differ significantly among four strains studied: the overall mean intraocular pressure+/-standard deviation was 13.0+/-1.2 mm Hg. Several intraocular pressure tolerance limits were calculated from this conscious rat data to provide a baseline estimate for future studies. CONCLUSIONS: This measurement method in conscious rats may contribute to making this widely used laboratory animal available for intraocular pressure research.

Animals↗
PubMed1985

An evaluation of ultrastrong polyethylene fiber as an ophthalmic suture.

An ultrastrong polyethylene fiber was evaluated as an ophthalmic suture. Properties of this fiber and of nylon, polypropylene, and polyester sutures were measured by standard techniques for fiber testing and for testing knot characteristics of sutures. Their behavior in cataract and keratoplasty surgery was assessed qualitatively. The ultrastrong polyethylene fiber has great tensile strength, high flexibility, and is very inelastic. Its strength and knot security provide safe incision closure and it has good biocompatibility. Ultrastrong polyethylene fiber is potentially superior to nylon, polypropylene, and polyester in the most important characteristics of a non-absorbable monofilament polymer ophthalmic microsuture.

Biocompatible Materials↗
PubMed1982

The broken nylon iris fixation suture.

Nylon sutures used to secure the Worst intraocular lens broke in 58 of 216 eyes (26.9%). Complete dislocation of the lens occurred in two cases, in one from the broken suture itself and in the other from complete dislocation of the lens. Patients with nylon sutures need not be recalled for special observation, but if a broken suture is discovered during a routine follow-up examination, laser shrinkage should be considered.

Female↗
PubMed1979

Comparison of photo slit lamp and fundus camera photography of the optic disc.

The photo slit lamp has characteristics that may be important in optic disc photography for measuring glaucomatous cupping. This finding led to the question of whether disc photographs with the slit lamp showed less detail than fundus camera photographs. Tests were conducted on in-air resolution and of each instrument's ability to record fine vessel detail in normal human optic discs. The results showed that the instruments performed comparably in each test.

Fluorescein Angiography↗
PubMed1979

Broken nylon iris fixation sutures.

Broken nylon iris sutures, used to fixate the Worst suture lens, occurred in 41 of a series of 215 eyes, a remarkably high frequency. The estimated average time to break was 27.8 months. Over three fourths of the borken sutures were discovered incidentally on a return visit. Complications related to the broken suture occurred in 21 eyes. The characteristic complication was corneal epithelial edema caused by intermittent touch of the endothelium by the broken suture; spontaneous lens dislocation was infrequent. Light and scanning electron microscopy revealed that biodegradation caused the suture break. Broken iris sutures can be avoided by fixation of the lens with a nonbiodegradable suture.

Biodegradation, Environmental↗
PubMed1978

Multiple-slit illumination of the optic disc.

A modification to a photo slit-lamp illuminator adds detail to the human optic disc surface by projecting onto it a pattern of fine parallel lines. These stripes curve as they traverse the disc, and its surface contour is revealed. Application of this technique may improve the reliability of methods used to quantitate disc topography.

Evaluation Studies as Topic↗
PubMed1978

Slit-lamp beamsplitter for two stereoscopic views.

A double binocular beamsplitter, compatible with Zeiss optics, splits the light from each optical train of a slip-lamp microscope to provide an observer the exact stereoscopic view of the examiner. It has advantages in teaching slit-lamp examination techniques. Further, in surgery at the slit lamp, it allows the observer to function as an assistant and the surgeon to have both hands free.

Eye Diseases↗