Ronald A. Laing

Changes in the corneal endothelium as a function of age

Abstract In vivo photomicrography has been used to examine the corneal endothelium of humans as a function of age. Sixty-one normal volunteers of both sexes ranging in age from 20 to 89 years of age were photographed. The endothelial photographs were analyzed to determine mean endothelial cell area for the central cornea and the frequency distribution of cell areas for each subject. The mean endothelial cell area was found approximately to double from age 20 to age 80. The increase in mean endothelial cell area with age was found to be statistically significant to better than the 0·1% level. The frequency distribution of cell area and cellular pleomorphism were also found to change with age. There was a statistically significant variability in the values of the difference in mean endothelial cell area between the two eyes of the population studied with age.

Optisol Corneal Storage Medium

Optisol is an investigational, intermediate-term corneal storage medium containing chondroitin sulfate and dextran to enhance corneal dehydration during storage. We used scanning electron microscopy to grade endothelial cell morphologic characteristics in terms of cell shape, cell borders, cell swelling, and apical holes in pairs of corneas stored in Optisol and Dexsol. Optisolstored corneas showed significantly fewer morphologic changes after 14 days at 4 degrees C than did Dexsol-stored corneas. No significant differences were seen after 1 to 4 days at 26 degrees C. Temperature-reversal analysis showed no significant change in corneal thickness with warming after 2-week storage at 4 degrees C in either medium, although Optisol-stored corneas were significantly thinner than those stored in Dexsol at all times. The results of scanning electron microscopy suggest that preservation at refrigerator temperature for 2 weeks in Optisol is superior to preservation in Dexsol. Both media may be useful in preserving endothelial structure for limited periods at room temperature, which could provide a measure of safety in shipping or storage where refrigeration is unreliable.

Morphological Changes in Corneal Endothelial Cells After Penetrating Keratoplasty

Fifteen patients who had had a successful penetrating keratoplasty were photographed with the clinical specular microscope and the resulting endothelial photomicrographs were analyzed. The average endothelial cell area was one to six times larger and the average endothelial cell perimeter was one to 2 1/2 times larger than that of a normal cornea of a subject the same age as the donor. In each corneal graft, endothelial cell areas and perimeters clustered tightly around a mean value, although the mean value for different corneas varied significantly. The thickness and transparency of each graft was normal, indicating that within the observed limits the success of the transplantation procedure did not depend on final endothelial cell size or perimeter.

Evidence for Mitosis in the Adult Corneal Endothelium

Intracellular structures probably representative of mitotic figures were seen by specular microscopy in the endothelium of a corneal graft following a rejection reaction. Serial measurements over an eight month period initially showed grossly enlarged cells and apparent mitotic figures. Subsequently, clusters of cells smaller than any cells previously seen were observed. Measurements of endothelial cell area over this period demonstrated a highly significant (P less than 0.0001) decrease in cell area, or increase in cell density, with time. These observations indicate that at least under some circumstances mitosis occurs in the endothelium of the adult human cornea.

Multiple Scattering Analysis of Retinal Blood Oximetry

A recently developed instrument, the photographic eye oximeter (PEO), has been used to make extensive measurements of retinal blood oxygen saturation in rabbits. A model for the reflection of light from the ocular fundus is developed to account for the experimental results. This model is based on the multiple scattering of photons by red blood cells (rbcs) and enables three components of detected light to be distinguished, the coherently transmitted, the diffusely scattered into the detector cone, and the diffusely scattered out of the detector cone. The small diameter of these vessels, the wavelength bands selected for measurement, the large total scattering cross section, and the sharply forward peaked scattering pattern of the red blood cells causes the detected signal from the fundus to be composed primarily of light that has diffusely traversed the vessel twice, reflecting from a background layer after a first traverse. The light is attenuated by a saturation dependent molecular absorption. Equations are derived to enable the blood oxygen saturation to be calculated from photometrically measured quantities. A theoretical calibration line for the PEO is calculated and is shown to be in very good agreement with the experimental line, especially at high saturations.

Epidermal growth factor and insulin use in corneal preservation : results of a multi-center trial

Purpose: The ability of DexSol medium, supplemented with two growth factors, human epidermal growth factor (hEGF) and human insulin, to improve long-term endothelial survival after penetrating keratoplasty was evaluated in a multi-center, randomized, prospective, double-masked clinical trial. Methods: Donor cornea pairs, one stored in DexSol and the other in DexSol with hEGF (10 μg/ml) and human insulin (10 pug/ml) (ProCell), were transplanted into 105 pairs of recipients matched by diagnosis and procedure and followed postoperatively for graft and endothelial survival. Results: No primary donor failures occurred in either group. Graft clarity did not differ between the ProCell and DexSol groups at all postoperative periods: 3 months (98% versus 99%), 6 months (94% versus 98%), and 1 year (95% versus 97%), respectively. Postoperative complications (e.g., glaucoma, rejection) occurred with comparable frequencies in both groups. Mean endothelial cell loss did not significantly differ between the ProCell and DexSol groups at 3 months (5.7% versus 5.1%), 6 months (8.1 % versus 10.1 %), and 1 year (12.3% versus 15.6%), respectively. Similarly, there were no clinically and statistically significant differences in other endothelial morphometric parameters. Conclusions: The use of corneas stored in DexSol medium with added hEGF and insulin in corneal transplantation resulted in a safety and efficacy profile comparable with that observed in patients receiving DexSol-stored corneas; however, there were no clinically and statistically significant differences in postoperative endothelial morphometric parameters.

Tricyclic antidepressants and peripheral anticholinergic activity

Peripheral anticholinergic activity of single acute doses of three tricyclic antidepressants (amitriptyline 50 mg, desipramine 50 mg, doxepin 100 mg) and placebo was assessed by several physiologic measures in normal male volunteers. Amitriptyline and doxepin produced similar significant depressions in salivary flow and finger sweating compared to placebo, while desipramine produced no change. Supine and standing blood pressures and standing pulse yielded significant differences among the drugs. Measures in at least three areas (salivation, perspiration, and pulse-blood pressure) offer a simple and reliable battery of tests for the peripheral autonomic effects of tricyclic antidepressants.

Morphometric analysis of corneal endothelium following radial keratotomy

ABSTRACT We performed morphoinetric analysis of the central corneal enclothelium on 24 eyes of 19 patients who had had anterior radial keratotomy. The endothelium was analyzed for a variety of parameters, including cell area, perimeter, side lengths, cell shape, and number of sides. Mean, standard deviation, and coefficient of variation were calculated for each parameter. The mean cell density decreased from 2,8:35 to 2,677 cells/mm2, mean cell perimeter increased from 71.4 &mgr;m to 74.3 &mgr;m, and mean side length increased from 11.8 &mgr;m to 12.3 &mgr;m following surgery. The changes in these three parameters were statistically significant (P < 0.05). The coefficient of variation of cell area (polymegathism) changed from 0.319 to 0.307, the hexagonality changed from 62.5% to 59.6%, and the cell shape changed from 0.872 to 0.867. The changes in these parameters were not statistically different before and after surgery. The group of patients that had no reported microperforations shoNved only a small decrease of cell density (1.6%), while the group of patients that had microperforations showed a large decrease of cell density (14.3%). The cell perimeter and side lengths showed a similar pattern. The group of corneas with the optical zone diameter less than 3.5 nun showed a decrease in mean cell density from 2,994 to 2,725 cells/mm2, and the cell shape changed from 0.874 to 0.866 following surgery. The changes in these parameters were statistically significant (P < 0.05) before and after surgery. Among all factors associated with radial keratotomy, microperforation and a small diameter of central optical zone appear to be the two greatest risk factors.

Changes of corneal redox state in diabetic animal models

Metabolic and biochemical changes of the corneal epithelium and endothelium were studied in experimental diabetic animal models. Ocular redox fluorometry was used to noninvasively determine tissue reduction-oxidation (redox) changes in organ cultured rabbit corneas incubated in high glucose concentration media, alloxan-induced diabetic rabbits, and nonobese diabetic mice. The ratio of autofluorescence from reduced pyridine nucleotide to oxidized flavoproteins (PN/Fp) was used as the indicator of the redox state. Chemical assays for NADH and NAD+ were performed on in vitro materials. Analysis of corneal endothelial morphology using specular microscopy was performed to study possible correlations with metabolic changes. Both the PN/Fp and NADH/NAD+ ratios increaseed in the corneal endothelium under all experimental conditions. Changes in redox state were not observed in the corneal epithelium in any of the models. Morphologic analysis of the corneal endothelium revealed no significant changes. These results indicate that redox changes occur in the diabetic corneal endothelium, but not the corneal epithelium. Ocular redox fluorometry is capable of detecting changes in the corneal endothelial redox state noninvasively.

Clinical Examination of the Crystalline Lens by Retrocorneal Specular Microscopy

Normal crystalline lenses and a variety of primary and secondary cataracts were photographed with a contact clinical specular microscope having a new W10X long working distance objective. In the normal lens, the anterior and posterior cell pattern and the lens fiber pattern could be seen. In patients with developing cataracts, a variety of abnormal structures was observed; in some cases the detailed morphologic structure of the light scattering objects could be appreciated. In pseudophakic patients, precipitates, leukocytes, and debris were observed on the surface of IOL implants. The methods described enable cellular and morphologic changes occurring with time in the lens and capsule to be studied. The results obtained show the potential usefulness of specular microscopy for evaluation and documentation of retrocorneal pathologic structures at high magnification.