Metabolic studies of galactosemic cataract

Experimental diabetic and galactosemic animal models are widely used to study diabetes-induced complications. Galactose feeding can rapidly produce cataract, retinopathy and nephropathy; it is therefore favored over the diabetic model. Although the common feature for both models is the activation of aldose reductase, there are substantial differences between the two--not only does the rate of cataract progression differ but the metabolic patterns are far more complex than for polyol production alone. We here present the result of a comparison between diabetic and galactosemic lenses and show the differences in phosphorus and aldose metabolism, cell integrity and osmotic environment.

Specular microscopic observation of eye-bank corneal endothelium using the clinical specular microscope

A special holder for endothelial evaluation of eye-bank corneas using the clinical specular microscope was developed. Using this holder, pictures of the corneal endothelium can be taken without the eye-bank specular microscope.

Conjunctival brush cytology

In order to collect conjunctival cells efficiently, we developed a special brush that is a modification of the Cytobrush used in cervical cytology. The conjunctival brush is small and made of nylon bristles. Cells collected by these brushes were rinsed into a buffered solution, from which filter preparations were made. This technique produced adequately cellular samples from temporal bulbar conjunctiva; these preparations stained well with the Papanicolaou stain. Under normal conditions, three cell types were observed in the brushing samples; one was the polygonal epithelial cell, the second type was a small rounded cell, and the third type was a mucus-secreting goblet cell. Samples from dry-eyed patients contained keratinized cells with or without a decrease in goblet cells. Elongated cells were seen in samples from postirradiation and postoperative patients. Irritation caused by the brushing was of the same intensity as irritation caused by collecting cytologic specimens by impression or by the use of cotton swabs. These findings suggest that brushing cytology of the conjunctiva is a relatively noninvasive technique and can provide valuable information for evaluation of conjunctival conditions.

[Brush cytology for the evaluation of dry-eye]

A special brush was developed for collection of conjunctival cells with better integrity of the harvested specimens. Using this brush, cells were collected from temporal bulbar conjunctiva of 20 normal eyes and 40 eyes with dry-eye, and were stained by the modified Papanicolau method, Keratinized cells (K) and goblet cells (G) were classified into 5 categories, from (-) to ( ) according to the numbers of the cells observed. Normal eyes were categorized as K (-):16, K(+/-):4, G (+):2, G(++):18, Eyes with dry-eye were K (-):3, K (+/-):8, K (+) 13, K (++):11, K ( ):5, and G (-):7, G (+/-):7, G (+):22, G (++):4. Clinical severity and the rose Bengal score corresponded to these categories. This technique can detect cytological changes in conjunctival cells in terms of shape and quality of staining. Eyes with dry-eye could be evaluated in relation to the numbers of keratinized cells and goblet cells.

Image analysis of the corneal epithelium

The method for quantifying corneal epithelial images has been examined. When pictures were developed, the images were stored in the memory of the image processing system by video camera. The distribution of the density of the images was analyzed. The density of each pixel of an image was assigned one of 256 grades, from completely black to completely bright. The average (AV), the standard deviation (SD), the coefficient of variation (CV), the skewness (SK) and the sharpness (S) of the density were calculated. Normal epithelium could be differentiated from abnormal by subjectively observing the shapes of the cells, the sizes of the cells and the irregularity of the cell pattern. But there were no statistical differences between the two groups with regard to the AV, SD, CV, SK and S of normal (n = 4) and abnormal (n = 8) corneal epithelial images. Simple analysis of density distribution could not be used as a parameter for the evaluation of the cells.

Application of erbium: YAG laser in ocular ablation

Recent developments in lasers have provided us the possibility of laser ocular surgery. The xenon, argon, neodymium:YAG and dye lasers have been successfully used in out-patient clinics. The excimer laser has been attracting researchers' interest in the new application of laser to cornea and lens. The erbium:YAG laser emits a 2.94-microns beam that can ablate the transparent ocular tissues such as lenses and corneas. The author has applied this laser to the cornea, lens, vitreous and other ocular tissues. The erbium:YAG laser beam was directed through a 1.5-meter-long, 200-microns-diameter fiberoptic guide. The radiant energy measured about 50 mJ at the end of the probe. The laser was emitted as a 400-microsecond pulse. Freshly enucleated rabbit eyes were used in this study. Laser burns were applied to the tissue surface at various energy settings. At minimal power, the tissues were coagulated by the erbium:YAG laser application. At a power of more than 636-954 mJ/mm2, tissue began to evaporate; the tissue loss was observed under a surgical light microscope. Corneal photoablation, lens ablation, iridotomy, trabeculotomy, cutting of the vitreous and retinal ablation were easily performed. Like the excimer laser, the erbium:YAG laser is a potential tool for ocular surgery.

Hard contact lens-induced metabolic changes in rabbit corneas

The biochemistry of contact lens-cornea interaction is not well understood, although previous studies have suggested that corneal metabolic changes may be the underlying factor in morphological alterations. Using a rabbit model, this interaction has been examined with 31P nuclear magnetic resonance (NMR) spectroscopy, which detects signals principally from the epithelium. The examination was supplemented with electron microscopy and histochemistry. Polymethylmethacrylate lenses caused reversible changes, including activation of anaerobic glycolysis and disturbance of membrane metabolite levels. These changes were far more severe than those occurring during prolonged eye closure. There appears to be an association between cellular deterioration and loss of membrane metabolites. On the other hand, oxygen-permeable silicone lenses allowed maintenance of nearly normal metabolic patterns. These results show multifaceted corneal response to hard contact lens wear.

Lens redox fluorometry: pyridine nucleotide fluorescence and analysis of diabetic lens

We performed both ex vivo and in vivo fluorometric analyses of pyridine nucleotides (PN) in rabbit and rat lenses. Rabbit lens PN fluorescence (99% NADH) was found to have an excitation maximum at 366 nm and an emission maximum at 462 nm (366:462). The only other fluorescent chromophore in that region of the spectrum has excitation and emission peaks at 328 and 460 nm, respectively. Anaerobic glycolysis in the lens was stimulated by KCN, a known inhibitor of mitochondrial respiration, after which a time-study of fluorescence intensities was performed. Over the course of a 3.5 hr period following treatment with KCN, the PN signal showed a statistically significant increase relative to that in the control lenses (those treated with KCl). while the 328:460 signal (which may be due to some protein involved in energy transfer with the PN) had a significantly greater decrease. We also found that fluorescence intensity of NADH in solution is linearly proportional to physiologic-range concentration. Moreover, there was a close correlation between fluorescence intensity of rat lens PN as measured on a specular microscope-coupled redox fluorometer capable of in vivo use, and the lens PN levels as determined by the analytical cycling assay technique. This fluorometer was then employed to assess the redox state in rats with streptozotocin-induced diabetes. The normalized ratio of PN to flavoproteins (Fp) in the lens epithelium increased from 0.96 +/- 0.12 in the normal state to 1.48 +/- 0.30 2 weeks after diabetes induction. In contrast, the ratio in the diabetic lens treated with an aldose reductase inhibitor, sorbinil, did not increase. The increase in the PN:Fp ratio therefore reflects activation of the polyol pathway and its associated metabolic activities, which results in an increase in the NADH:NAD ratio in the diabetic rat lenses. Our results indicate that the non-invasive, real-time method of redox fluorometry may be useful in the early detection and evaluation of cataracts and other disorders in lens metabolism, long before opacities occur. It can be used to monitor the disease process and evaluate the efficacy of such drugs as aldose reductase inhibitors on a biochemical level.

Thermal cycling effects on the stored rabbit cornea

Specular microscopy has proven itself a useful tool for evaluation of donor corneas. In many eye banks, corneas are stored at 4 degree C and warmed to room temperature for specular microscopic evaluation. On occasion it would be desirable to put the cornea back into storage provided there were no detrimental effects of the recooling and subsequent rewarming. The effects of repeated cooling and rewarming (thermal cycling) on the corneal endothelium were determined using rabbit corneas stored in M-K medium at 4 degree C. Some corneas were left in the refrigerator for a 7-day storage interval while others were removed daily, warmed to room temperature, evaluated morphologically and biochemically with the specular microscope and the redox fluorometer, respectively, and then placed back in the refrigerator. At the end of the 7-day storage period there were no statistically significant differences in either the biochemical signals or the specular appearance between thermally cycled corneas and corneas that were continuously stored at 4 degrees C for the same period of time. Repeated warming, specular microscopic observation, and cooling of the cornea appear not to be detrimental to the corneal endothelium.

Noninvasive metabolic analysis of preserved rabbit cornea

With the method of corneal redox fluorometry, the autofluorescence of reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) in rabbit corneal endothelium was measured as a function of storage time in McCarey-Kaufman (MK) medium and K-Sol medium. Measurements were started immediately after preparation of the corneal button, and the corneas were followed up for up to three weeks of storage. In both media, the PN/Fp ratio of the endothelium initially increased slightly in the first or second day and then began to decrease toward a level lower than baseline. This initial increase is possibly a result of an adaptive mechanism. The PN/Fp ratio maintained itself in the range of baseline values up to one week in MK medium but not in K-Sol medium. With scanning electron microscopy, the surface of the membrane and cell border were maintained for a three-week preservation period, and no apparent differences were found between the corneas stored in the two media. With transmission electron microscopy, the intracellular organelles appeared almost normal through one week of preservation in corneas stored in either media. During weeks 2 and 3, however, intracellular edema with increased endothelial thickness became prominent in the corneas stored in both media. Although no visual difference in the morphological features of the endothelium was apparent between corneas stored in either medium, computer-assisted morphometric analysis showed a statistically significant increase in the coefficient of variation of mean cell area for the corneas preserved in K-Sol medium but not for those preserved in MK medium.

Corneal endothelial changes following minor trauma

The healing processes that occur when corneal endothelial cells are subjected to only mild trauma are not known. To study these processes we have developed a system that enables only a few endothelial cells to be traumatized or destroyed under continuous specular microscopic observation in vitro. Experiments in which a small group of cells were traumatized by gentle wounding with a microglass tip produced an immediate and distinct dark area having the same size as the tip. Using this method we have produced and observed two types of wound by controlling the force of wounding. The first type of wound, produced by a gentle touch, recovered within 1 hr. The second type of wound, produced by moderate touch, took about 24 hr to recover completely from the trauma. In the second type of wound, we observed migration, elongation, coalescence and mitosis during the healing process. Histological examination revealed that in the first type of wound, the cells remained intact with no apparent damage seen by vital staining and light microscopy. For the second type of wound, the cells were completely missing although there was no apparent damage to Descemet's membrane.

Clinical features of a newly recognized type of lattice corneal dystrophy

We examined five patients with an undescribed type of lattice corneal dystrophy. All patients were in the seventh to ninth decades of life and had developed decreasing vision late in life. None of the patients had suffered from recurrent epithelial erosions, there was no overt evidence of systemic amyloidosis, and the lattice lines were much thicker than those usually observed in lattice corneal dystrophy types I and II. Available pedigree data from two families of three patients indicated that the corneal disorder affected several siblings but not the parents or offspring. Two patients had no affected family members. There was no known consanguinity in any of the four families.

Noninvasive measurements of pyridine nucleotide and flavoprotein in the lens

Abnormalities in glucose metabolism are thought to be among the main causes of cataract formation. The authors have made noninvasive biochemical measurements of the lens that provide information concerning glucose metabolism in the lens epithelium. The autofluorescence of reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) within the rabbit lens were noninvasively measured as a function of depth using redox fluorometry. The peak of the autofluorescence at 440 nm (excited at 360 nm) and 540 nm (excited at 460 nm) were determined at the lens epithelium. When 8 mM sodium pentobarbital, a known inhibitor of mitochondrial respiration, was applied to the lens, the autofluorescence peak at 440 nm increased and that at 540 nm decreased. The 440 nm autofluorescence is thought to be from reduced pyridine nucleotides, whereas the 540 nm autofluorescence is from the oxidized flavoprotein. Blocking lens respiration with pentobarbital caused an increase in the PN/Fp ratio by a factor of 3 within 3.5 hr after pentobarbital application.

Morphometric analysis of corneal endothelium following radial keratotomy

We performed morphometric analysis of the central corneal endothelium 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 2,835 to 2,677 cells/mm2, mean cell perimeter increased from 71.4 micron to 74.3 micron, and mean side length increased from 11.8 micron to 12.3 micron following surgery. The changes in these three parameters were statistically significant (P less than 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 showed 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 mm 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 less than 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.

Lattice dystrophy type 1: a report of 8 families

Eight families with lattice corneal dystrophy are reported. The symptoms and signs are almost identical with the typical lattice corneal dystrophy type 1 in western countries. Lattice corneal dystrophy has been considered to be a rare disease until recently, but it might be a more common disorder. This is the first report of a large series of lattice corneal dystrophy in Japan.

Adenocarcinoma of the ciliary body pigment epithelium in a child

Tumors arising from the pigment epithelium of the ciliary body are rare and most commonly occur in white adults. We describe a tumor that was clinically indistinguishable from a melanoma or medulloepithelioma occurring in a 7-year-old Japanese boy. Three months after initial evaluation, the eye was enucleated because of intractable intraocular pressure elevation and pain. On pathologic examination the tumor was found to fill approximately one third of the anterior chamber. Light microscopic and ultrastructural findings were consistent with an adenocarcinoma of the ciliary body pigment epithelium. To our knowledge, this is the youngest patient described with this tumor.