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Biomedical subjects

C J Koester

Publications and source records attributed to C J Koester.

At least 19 recordsLinked to original sources
PubMed1997

Scanning slit confocal microscopy of fungal keratitis.

In vivo scanning slit confocal microscopy was performed in a patient with Fusarium solani keratitis. Morphologically distinctive abundant filamentous structures were observed intrastromally. Confocal microscopy of the culture plate growing F solani from the patient's corneal scraping revealed filaments morphologically similar to the filaments observed in vivo. After 1 week of medical therapy, subsequent confocal microscopy showed an increased load of filaments, supporting the decision to perform a penetrating keratoplasty. Confocal microscopy confirmed that all of the fungus was eradicated. This aided in the decision to administer corticosteroids and quickly discontinue antifungal agents.

Adolescent↗
PubMed1995

Scanning slit confocal microscopic observation of cell morphology and movement within the normal human anterior cornea.

PURPOSE: Noninvasive in vivo observations of the anterior human cornea were performed to study cell structure and dynamics. Cellular elements were identified by their location, morphology, and pattern of movement. The hypothesis that cells in the epithelial layer of the normal cornea migrate centripetally was tested. METHODS: Using a scanning slit confocal microscope with a new 0.75-numeric aperture contact objective, individual cells of normal human corneas were observed over time, quantifying the velocity and direction of cellular movement within the basal epithelial layer. RESULTS: Basal epithelial cells, wing cells, the basal epithelial nerve plexus, and the subepithelial nerve plexus were identified readily. Centripetal motion was observed for three corneal cell types: basal epithelial cells, basal epithelial nerves, and unidentified cellular elements (possibly Langerhans cells). The unidentified cellular elements moved along the length of the basal epithelial nerves. The basal epithelial nerve plexus maintained a roughly stable topology as it slid centripetally. New nerve material appeared at the site of entry of the nerve into the epithelium. No growth cones were present at the distal termini of the growing epithelial nerves. CONCLUSION: In the midperiphery of the normal human cornea, basal epithelial cells and nerves slide centripetally, probably in concert. Unidentified cellular elements used the basal epithelial nerve plexus as a pathway for intraepithelial movement. Observations in this study suggest that neurite growth occurred by the addition of new membrane material along the length of the axon rather than at a distal growth cone.

Adult↗
PubMed1994

In vivo scanning slit confocal microscopy of Acanthamoeba keratitis. A case report.

A 29-year-old woman presented with clinical signs and symptoms of Acanthamoeba keratitis. Scanning slit confocal microscopy revealed a 26-mu-diameter object, resembling an Acanthamoeba cyst, in the anterior stroma. Numerous ovoid objects (possibly inflammatory cells, trophozoites, or altered keratocytes) were present. Normal keratocyte nuclei and the anterior corneal mosaic, readily imaged by scanning slit confocal microscopy of the normal cornea, were noticeably absent. Subsequent corneal biopsy confirmed the diagnosis of Acanthamoeba keratitis.

Acanthamoeba↗
PubMed1993

Intraocular lens performance in air, in water, and in situ: a computer study.

Computer analysis is used to predict performance of four intraocular lenses with assigned values of aberration. Cylinder error and asphericity error are used as examples of possible manufacturing errors. Three measures of performance are calculated: maximum optical path difference, root mean square optical path difference, and modulation transfer function. For evaluation in air these standard test conditions are assumed: collimated green light incident on the convex surface of a plano-convex lens, with a 3 mm aperture. All four lenses show substantially improved performance in water compared to air, and a further improvement in the simulated eye (i.e., in situ). However, an aberrated 30 diopter (D) lens with performance in air comparable to an aberrated 20 D lens, performs worse in situ than does the 20 D lens. This suggests that a performance test in air that is suitable for a 20 D lens (e.g., 100 line pairs per millimeter resolution) may not be adequate for a 30 D lens. A test in air at 30% resolution efficiency may be more suitable.

Air↗
PubMed1993

Clinical microscopy of the cornea utilizing optical sectioning and a high-numerical-aperture objective.

A doublet contact element was added to a long-working-distance objective to increase the numerical aperture to 0.75 and to maintain the focus during in vivo examination of the eye. Optical sectioning by use of confocal slits permits visualization of weakly scattering structures within the cornea. With photographic film and a 1/60-s exposure time to limit the effect of eye movement, an effective optical section half-thickness of approximately 20 microns was realized. Structures observed in the cornea include epithelial cells (surface, wing, and basal cells), nerve-fiber bundles in the subepithelial region, keratocytes and inflammatory cells in the stroma, and endothelial cells.

Cornea↗
PubMed1993

Optical zone diameters for photorefractive corneal surgery.

PURPOSE: To examine the physiological optics of photorefractive corneal surgery and to study the effect on glare production of the optical zone diameter. METHODS: An optical analysis computer program was used to generate rays that define the edge of the optical zone for any given pupil size and glare-free field. RESULTS: The optical zone diameter must be based on the postoperative corneal curvature because the determines magnification of the pupil. The minimal optical zone diameter of uniform optical power was determined both for myopic and hyperopic surgery and for two values of anterior chamber depth. CONCLUSIONS: Optical zone diameters must be at least as large as the entrance pupil diameter to preclude glare at the fovea, and larger than the entrance pupil to preclude parafoveal glare.

Computer Simulation↗
PubMed1990

In vivo measurement of posterior chamber intraocular lens decentration and tilt.

We report what to our knowledge is the first extensive in vivo clinical study of intraocular lens decentration and tilt. Measurements of posterior chamber intraocular lenses, all implanted by the same surgeon in 89 eyes, showed that decentration and tilt consistently differed between right and left eyes. Lenses tended to decenter superotemporally and tilt with their superonasal edges tipped forward. Decentration magnitude relative to the cornea light reflex axis and line of sight averaged 0.64 mm, with decentration increasing slightly with increased axial length. Average tilt was 6.75 degrees, and the average tilt-induced astigmatism was 0.27 diopter. Tilt magnitude decreased with increased axial length, as did tilt-induced astigmatism and plus sphere.

Adult↗
PubMed1990

The barrier function in extracapsular cataract surgery.

The distribution of fluorescein between the anterior chamber and the anterior vitreous was measured in two groups of patients after oral administration: group I, extracapsular cataract extraction (ECCE) patients with intact capsule and posterior chamber intraocular lens (PC IOL) (n = 12); group II, intracapsular cataract extraction (ICCE) patients with anterior chamber IOL (AC IOL) (n = 13). The fluorescein concentrations were measured by fluorophotometry and the penetration ratios were calculated. The penetration of fluorescein into the anterior vitreous was significantly less in the ECCE group (group I, penetration ratio = 2.03 +/- 1.00 X 10(-3) min-1; group II, penetration ratio = 5.99 +/- 4.89, X 10(-3) min-1, P less than 0.01). The authors concluded that in ECCE versus ICCE a significantly smaller proportion of fluorescein is found in the anterior vitreous relative to the aqueous after passage through the blood-aqueous barrier. This suggests a barrier to posterior movement of other molecules that may initially gain access to the eye in the anterior segment (e.g., prostaglandins).

Aged↗
PubMed1989

Endothelial cell counts following pars plana vitrectomy in pseudophakic and aphakic eyes.

In 13 pseudophakic eyes, endothelial cell counts remained stable following pars plana vitrectomy. The posterior chamber pseudophakos apparently had a protective effect on the corneal endothelium, even though the posterior lens capsule was removed during surgery. By contrast, in nine aphakic eyes, a statistically significant (p greater than .05) cell loss of 7.6% occurred after pars plana vitrectomy. We conclude that vitrectomy therefore poses an increased risk to the cornea in aphakic, but not in pseudophakic eyes.

Aged↗
PubMed1988

Silicone intraocular lens resolution in air and in water.

The resolution efficiencies of 31 biconvex silicone intraocular lenses, ranging in power from 16.0 to 23.5 diopters, were tested in air and in water to see if a predictable relationship existed as previously reported with polymethylmethacrylate lenses. Resolution efficiency is defined as the percentage ratio of the actual resolving power of a lens to that of a perfect lens of the same focal length which is only limited in resolution by diffraction. The lenses ranged from 29% to 58% resolution efficiency in air. No lenses exhibiting multiple images were included. All 31 lenses achieved at least 73% resolution efficiency in water, and one lens achieved 82%. Based on these findings, a biconvex silicone lens that exceeds 30% resolution efficiency in air and does not produce multiple images can perform near its diffraction limit when implanted in the eye.

Air↗
PubMed1988

Measurement of intraocular lens decentration and tilt in vivo.

A method for measuring the tilt and decentration of intraocular lenses (IOLs) in the static eye using the Purkinje image locations is presented. The patient fixates on a target that is coaxial with the camera or is at a predetermined angle with the camera axis. A telecentric stop is introduced in the camera so the positions of the Purkinje images on the film are independent of their distance from the camera. Measurements of the image locations on the film are used with anterior chamber depth and corneal curvature measurement to calculate the tilt and decentration of the IOL. In a group of 14 randomly selected patients with posterior chamber IOLs, 13 gave Purkinje images that could be measured. The average tilt was 7.8 degrees and the average decentration was 0.7 mm.

Humans↗