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Biomedical subjects

M A Lemp

Publications and source records attributed to M A Lemp.

At least 19 recordsLinked to original sources
PubMed1992

Digital image acquisition in in vivo confocal microscopy.

A flexible system for the real-time acquisition of in vivo images has been developed. Images are generated using a tandem scanning confocal microscope interfaced to a low-light-level camera. The video signal from the camera is digitized and stored using a Gould image processing system with a real-time digital disk (RTDD). The RTDD can store up to 3200 512 x 512 pixel images at video rates (30 images s-1). Images can be input directly from the camera during the study, or off-line from a Super VHS video recorder. Once a segment of experimental interest is digitized onto the RTDD, the user can interactively step through the images, average stable sequences, and identify candidates for further processing and analysis. Examples of how this system can be used to study the physiology of various organ systems in vivo are presented.

Animals↗
PubMed1992

Comparison of in vivo and ex vivo cellular structure in rabbit eyes detected by tandem scanning microscopy.

Using the tandem scanning microscope, in vivo confocal microscopic images of living eyes were compared to images obtained from ex vivo, freshly enucleated or fixed tissue in the rabbit. In the normal cornea, microscopic details of the superficial epithelium, basal lamina, stromal fibrocyte nuclei, nerves and endothelial cell borders were easily discernible. Removal of the eye from the intact animal resulted in loss of detail with distortion of the normal structural interrelationships within the corneal stroma whilst enhancing details of the corneal epithelium. Formalin fixation further enhanced details of the basal and suprabasal corneal epithelial cell nuclei and the stromal fibrocyte cell borders whilst inducing prominent brightly reflecting folds in the thickened stroma with concomitant enhancement of the edge contrast of the collagen lamellae. These changes appeared to be related, in part, to hydration of the cornea and artefactual pooling of water between structures that may enhance reflectivity by increasing the difference between the refractive index of the cellular and extracellular elements. We conclude that microscopic examination of ex vivo preparations of corneal tissue, although providing increased resolution similar to conventional light microscopic techniques, significantly altered the normal structural relationships and could lead to erroneous measurements of the physiological properties of the tissue as compared to in vivo microscopy of undisturbed, intact tissue.

Animals↗
PubMed1992

Morphology and movement of corneal surface cells in humans.

We examined the morphology of the corneal surface epithelial cells in 13 eyes of 13 subjects using specular microscopy. We determined cell area, perimeter, and shape comparing the central cornea with the inferior and superior periphery. We found surface epithelial cells are significantly smaller in the central cornea. The cells measured 560 +/- 93 square microns in the central cornea, 850 +/- 135 square microns in the superior cornea and 777 +/- 176 square microns in the inferior cornea (p less than .005). Newly emerged surface cells are smaller and are thought to enlarge with time. We postulate that lid shearing forces are greater in the central cornea and contribute to epithelial cell exfoliation. We further postulate that preferential shearing of central corneal surface cells is an important factor driving the centripetal movement of corneal epithelial cells.

Adult↗
PubMed1992

Morphologic effects of contact lens wear on the corneal surface.

We used specular microscopy of the corneal epithelium to examine 29 eyes of 29 patients each wearing one of five different types of contact lenses. We compared these with 24 eyes of 24 age-matched control patients. We found patients with aphakic extended wear soft contact lenses had significantly larger cells (818 +/- 186 microns2) than all other groups; and they were significantly larger than their age-matched control group (573 +/- 174 microns2) (P less than .002). The epithelial cells of extended wear soft contact lens patients (609 +/- 97 microns2) and daily wear rigid gas permeable contact lens patients (613 +/- 103 microns2) were larger than their control group of normal young patients (513 +/- 53 microns2). The cells of daily wear soft contact lens patients (484 +/- 111 microns2) and hard contact lens patients (517 +/- 46 microns2), however, were not different from controls. This study demonstrates a statistically significant shift in mean cell area of corneal epithelial cells in patients wearing some types of contact lenses.

Adult↗
PubMed1991

In vivo, real-time confocal imaging.

We have adapted a tandem scanning confocal microscope for real-time, non-invasive imaging of cells under in vivo conditions. This form of in vivo confocal imaging relies on the optical sectioning abilities of the confocal microscope to obtain en face, sequential, reflected light images of cells at various depths, up to 1 mm, within opaque organs in living animals. Of major consideration in the design of an in vivo confocal microscope is maximizing the real-time detection of signals reflected from low contrast structures which can be affected by the microscope design, objective, and image detector systems. Using an in vivo confocal microscope design with a 20 x BioOptics surface contact objective we have obtained live cellular images from selected tissues including cornea, kidney, liver, adrenal, thyroid, epididymis, and muscle and connective tissue of rabbits and rats. Images were captured, digitized, and processed using a DAGE Mti low light level SIT camera coupled to a Gould IP9527 image processor. In vivo images were also compared with conventional bright field light and scanning electron microscopic images of "dead," fixed tissues. Overall, in vivo confocal imaging can provide remarkable detail of living cells comparable to that of conventional microscopic images of "dead," fixed, and stained tissue. A more unique feature of in vivo confocal imaging is the ability to study cellular structure and function sequentially over time in the same organ or tissue and represents a fundamentally new paradigm in microscopy. With continued refinements in the microscope, objective and detection system designs and their consequent improvements in lateral and axial resolution, in vivo confocal microscopy will enable us as observers to see what no one has been able to see before.

Animals↗
PubMed1991

Vortex keratopathy of the corneal graft.

We examined the surface epithelium of 30 eyes with color specular microscopy at 3-month intervals 1-18 months following penetrating keratoplasty. At least three examinations were performed on most eyes. We found a vortex keratopathy to be present in 70% of these eyes. In nine eyes, this vortex pattern was present at every examination, and in 12 eyes, it was present at some examinations and not at others. There was no vortex pattern seen at any examination in nine eyes. We also found alterations in the normal epithelial morphology around sutures and at the wound margin, with palisading parallel to the sutures and perpendicular to the wound edge. This altered morphology was also demonstrated by digitization of cells for shape and size, which showed significant differences compared with normals. We conclude that the morphology of the epithelial cells on the surface of the cornea remains abnormal for up to 18 months following penetrating keratoplasty.

Cell Movement↗
PubMed1991

Corneal steepening with final suture removal after penetrating keratoplasty.

We reviewed 53 patients after they underwent penetrating keratoplasty, comparing the change in average corneal curvature before and after final suture removal 15-18 months postsurgery. In 29 eyes with keratoconus, there was a significant increase in average curvature of 3.48 diopters +/- 3.76 (p less than 0.0005). In 24 eyes with other diagnoses, there was also a significant increase in the average curvature of 3.26 diopters +/- 3.98, (p less than 0.0005). The difference between these groups was not significant. The amount of steepening correlated negatively (-.6494) with the average corneal curvature before suture removal (p less than 0.005). We found no change in the average astigmatism after suture removal; however, large changes in astigmatism occurred unpredictably with some patients. This study shows that corneal curvature after penetrating keratoplasty steepens after suture removal, particularly in flat corneas, and astigmatism may shift unpredictably.

Adult↗
PubMed1991

Tight lens syndrome associated with a 24-hour disposable collagen lens: a case report.

Tight lens syndrome occurred 8 hours after a 24-hour Bio-Cor bandage collagen lens (Bausch & Lomb, Inc.) was placed on the eye of a 19 year old female patient with a history of Stevens-Johnson syndrome and recurrent corneal abrasions. Because collagen bandage contact lenses share some physical and fitting properties with hydrophilic lenses, they should be used with caution in patients at high risk for a tight lens.

Adult↗
PubMed1990

Estrogen and progesterone receptors and human conjunctiva.

Freshly frozen conjunctival tissue from premenopausal and postmenopausal women and male subjects were processed for estrogen and progesterone receptors by using monoclonal antibodies and a peroxidase-antiperoxidase technique. No immunocytochemical staining was localized in the nuclei of the cells treated with the monoclonal antibodies to human estrogen receptor or human progesterone receptor in any of the conjunctival specimens, in contrast to the strongly positive staining in breast adenocarcinoma controls. Immunocytochemical staining disclosed no evidence for estrogen or progesterone receptors on cells of the ocular surface.

Adenocarcinoma↗
PubMed1990

[Tear film diagnosis in contact lens wearers].

Contact lenses have an intimate relationship with the precorneal tear film and it is important to attempt to prognosticate the likelihood of successful contact lens wear by evaluating, both quantitative and qualitative aspects of the precorneal tear film. Aspects of history diagnostic methods and general aspects which are necessary to notice prior to contact lens fitting are described in this review.

Contact Lenses↗
PubMed1990

Is the dry eye contact lens wearer at risk? Yes.

Numerous studies have demonstrated that patients with dry eyes have a compromised ocular surface. Furthermore, these patients suffer deficiencies of various surface defense mechanisms, such as tear volume, tear components (lysozyme, lactoferrin, and beta-lysin), the mucin network, cellular exfoliation, and subsurface immune secretions. When such individuals wear contact lenses (CLs), a special set of circumstances arises that increases the risk of ocular infection. The risk is greatest if the lenses are soft and, therefore, provide for little tear exchange beneath their surface. Under such circumstances, limited tear flow allows for a greater buildup of lens deposits and metabolic wastes, while permitting increased tear evaporation from the lens surface. The pathogenesis of infection is attributed to various mechanisms, including decreased tear flow beneath the lens, decreased tear components, stagnation of the mucin network, changes in surface cell exfoliation, and putative changes in the subsurface immune secretory system. Dry eye patients who wear soft CLs also run a greater risk of bacterial conjunctivitis, blepharitis, and sterile corneal infiltrates.

Contact Lenses↗
PubMed1990

The effect of relaxing incisions with multiple compression sutures on post-keratoplasty astigmatism.

We describe a surgical technique for correction of astigmatism following penetrating keratoplasty performed after all keratoplasty sutures have been removed. Two relaxing incisions of 3 clock hours, at 3/4 depth, 0.5 mm inside the keratoplasty wound are used in combination with two sets of three compression sutures placed 90 degrees from the incisions. Selective removal of the compression sutures allows for a graded reduction in overcorrection. With this technique, a mean preoperative astigmatism in 10 patients of 14.25 diopters was reduced to 6.33 D 3 months postoperatively (P less than .002). There were no intraoperative or postoperative complications such as inadvertent perforation, wound dehiscence, or graft rejection.

Adult↗