Diane L. Van Horn

Comparative Toxicity of Intraocular Irrigating Solutions on the Corneal Endothelium

Isolated rabbit and human corneas were perfused in vitro with Plasma-lyte 148 solution and with a glutathione bicarbonate Ringers solution. The corneal swelling rate and ultrastructure were compared to corneas perfused with three commonly used intraocular irrigating solutions. Corneas perfused with Plasma-lyte 148 swelled at a rate of 47 mu/gr and the endothelial cells separated from each other and showed extensive damage after three hours of perfusion. By comparison, corneas perfused with 0.9% NaCl increased in thickness by 98 mu/hr, lactated Ringers by 39 mu/hr, balanced salt solution by 24 mu/hr, and glutathione bicarbonate Ringers solution by 4 mu/hr. These results indicate that endothelial cell damage and increased corneal thickness observed during perfusion was related to the incomplete composition of 0.9% NaCl, Plasma-lyte 148, and lactated Ringers and that endothelial cell damage can be prevented if the intraocular irrigating solution contains concentrations of inorganic and organic constituents that are similar to those in aqueous humor.

Effect of Epinephrine on the Corneal Endothelium

Intracameral epinephrine has been advocated for treatment of iris bleeding and inadequate pupillary dilatation during intraocular surgery. Commercial epinephrine 1:1000 with its preservative sodium bisulfite damaged corneal endothelial function and ultrastructure in rabbit and monkey eyes with sodium bisulfite the source of the damage. Endothelial damage can be prevented with a 1:5000 dilution of commercially available epinephrine in 0.1% sodium bisulfite or freshly prepared epinephrine bitartrate 1:1000 with a bicarbonate Ringers.

Late Complications of Pars Plana Vitreous Surgery

Late complications (following hospital discharge) occurring in 206 consecutive pars plana vitrectomy cases, comprising a subgroup of 100 consecutive cases for diabetic retinopathy, are reviewed. Ocular hypertension, occurring as neovascular glaucoma, was present in 18% of diabetic eyes, but other causes of ocular hypertension gave an overall incidence of 26%. Electron microscopy, scanning, and transmission photographs document the devastating ocular neovascularization occurring postvitrectomy.

Astrocytic Hamartoma of the Retina Not Associated with Tuberous Sclerosis

A 6-year-old boy had a peripapillary lesion diagnosed as retinal astrocytic hamartoma, which was not associated with tuberous sclerosis, neurofibromatosis, or intraocular extension of a glioma. The patient was observed for nine years, during which time the lesion grew significantly. Because of this growth and the evidence of proximal optic nerve involvement on computed tomography, radiation therapy was administered with a resultant marked reduction in visual acuity. The eye was subsequently enucleated. The enucleated eye was studied by both light and transmission electron microscopy. The specimen had a retinal astrocytic hamartoma with sparse vascularization and only superficial optic nerve involvement. Additionally, it revealed optic nerve drusen in varying stages of development, significant accumulations of subretinal macrophages, and an almost total loss of retinal outer segments with the preservation of the retinal pigment epithelium.

Corneal Preservation Using M-K Medium

Human eye bank corneas were preserved in M-K medium for varying periods of time after which viability of the endothelial cells was evaluated by vital staining and scanning and transmission electron microscopy. Endothelial viability and ultrastructural integrity was maintained in some corneas up to four days. Twenty-five consecutive keratoplasties were performed utilizing human donor material stored in M-K medium. There were clear grafts in 92% of the cases and there were no primary graft failures. After the ninth postoperative week, the average central corneal thickness was 0.47 mm and 23 of the 25 grafts remained clear to moderately clear. All of the donor material used for keratoplasty was stored in M-K medium for less than 80 hours.

A Metabolic and Electron Microscopic Study of Human Organ-Cultured Cornea

We examined the glucose metabolism and ultrastructure of human corneas stored for 11 to 37 days in organ culture using a modified Eagles minimum essential medium. Changing the media twice weekly provided a stable pH of 7.22 to 7.28 but the glucose concentration of the media decreased from 110 mg/100 ml to 30 mg/100 ml, and lactate concentration increased from 7 mg/100 ml to 84 mg/100 ml before media replacement. The initial rate of glucose uptake and lactate release averaged 149 mug/hr and 95 mug/hr, respectively, and the rates decreased approximately 50% by day 12. The glucose uptake rate stabilized between 40 and 60% of the original rate to day 37, but the lactate release rate decreased again at day 25 from 64 to 25%. The lactate/glucose ratio averaged 65 to 82% during the first 25 days of organ culture and 33 to 53% from days 28 to 37. Electron microscopy revealed that the endothelium formed a complete monolayer of normal appearing cells covering Descemets membrane. Intracytoplasmic deposition of glycogen granules was present in endothelial, stromal, and epithelial cells.

Experimental Cataract Surgeryelectron Microscopy

Scanning and transmission electron microscopic examinations were performed on cat corneas after the steps usually taken to perform cataract extraction were completed. The endothelium did not replicate, but showed nuclear division or segmentation occasionally. In each case, the anterior segment was free from any evidence of inflammation one year after surgical treatment—unless a pseudophakos had been inserted: in some of these cases, significant numbers of white cells were present, a condition that may contribute to anterior segment complications from implants.

Ultrastructural alterations associated with loss of transparency in the cornea of buphthalmic rabbits

Pathological alterations in the corneas of buphthalmic rabbits were described by biomicroscopy, seanning and transmission electron microscopy. The degree of corneal clouding correlated with the increase in corneal thickness. Intraocular pressure was highest in those buphthalmic eyes with clear corneas. Intercellular epithelial edema and bullae were present in cloudy corneas and were usually associated with subepithelial fibrosis. The epithelial basement membrane was discontinuous in these eyes. Loss of stromal transparency was due to edema and scarring. The endothelial cells formed an intact monolayer in all eyes, but the cells were reduced in number per area. In addition. Descemets membrane was either increased in thickness or a posterior collagen layer was present.

Effects of vitamin A deficiency on [3H]retinoid binding to cellular retinoid-binding proteins in rabbit cornea and conjunctiva

[ 3 H]Retinol binding to cellular retinol-binding protein was markedly decreased in corneal and conjunctival epithelia of vitamin A-deficient as compared with normal or control rabbits, indicating that as these epithelia become keratinized there is a significant biochemical change involving a protein which may play a role in mediating the function of vitamin A. Although [ 3 H]retinoic acid binding to cellular retinoic acid-binding protein was very low in corneal epithelium and undetectable in conjunctival epithelium from normal rabbits, such binding was increased in corneal epithelium and present in detectable amount in conjunctival epithelium from vitamin A-deficient rabbits.

Effects of Phenylephrine on Bovine Corneal Endothelium in Culture

The cytotoxicity of phenylephrine HCl in various concentrations (0.001 %–10%) was determined using bovine corneal endothelial cell cultures. Exposure to concentrations as low as 0.01% for 1 h resulted