Complement-induced retinal arteriolar occlusions in the cat.

PURPOSE: To develop an animal model of complement-induced retinal vasculopathy and determine whether it resembles Purtscher's retinopathy. METHODS: Intravenous cobra venom factor was used to achieve intravascular activation of the complement system in cats. After a single bolus of cobra venom factor (75 units/kg), retinal blood flow was monitored at regular intervals by fluorescein angioscopy and angiography. RESULTS: Multiple small retinal arteriolar occlusions were present during the initial fluorescein transit of the immediate postinjection fluorescein study in 12 of 12 animals. Small, rapidly moving gaps in the fluorescein column were seen in two thirds of the animals observed continuously by fluorescein angioscopy. Angiographically, the obstructions were transient, and filling of the associated patches of capillary nonperfusion occurred within 3 minutes. Purtscher's-like ischemic retinal infarcts did not develop in any eye. Histopathologic analysis failed to demonstrate the nature of the transient vascular obstructive lesions, but indirect evidence suggested the possibility of granulocyte aggregates. CONCLUSION: Intravascular activation of the complement system produces transient microembolic retinal arteriolar occlusions in the cat. Although this model may represent a mild form of Purtscher's retinopathy, factors in addition to complement activation appear necessary to induce ischemic retinal infarcts.

Regression of Kayser-Fleischer rings during oral zinc therapy: correlation with systemic manifestations of Wilson's disease.

Fourteen patients presenting with neuropsychiatric manifestations of Wilson's disease were treated with oral tetrathiomolybdate (TM) for 8 weeks followed by oral zinc (Zn) maintenance therapy. The patients were evaluated prospectively at baseline and at yearly intervals for up to 5 years by slit-lamp biomicroscopy and photography, quantitative neurologic and speech pathology examinations, 24-h urine copper collection, and a quantitative scoring of magnetic resonance imaging (MRI) of the brain. Kayser-Fleischer (KF) ring size decreased significantly during the 5-year study period (p < 0.0001). Although results of neurologic examination, speech pathology examination, and 24-h urine copper level analysis in symptomatic Wilson's disease patients improved during the study period, KF ring regression did not correlate with the improvement in these clinical parameters (p > 0.05). However, there was a correlation between MRI scores and KF ring regression (p = 0.02). Anticopper therapy with TM followed by zinc maintenance therapy is a safe and effective treatment for patients with neurologically symptomatic Wilson's disease. This treatment leads to reduction in KF ring size; however, KF ring reduction is not a good predictor of clinical improvement for patients with neuropsychiatric manifestations of Wilson's disease.

Interleukin-8. A corneal factor that induces neovascularization.

A rabbit corneal pocket model was used to demonstrate that physiologic concentrations of human recombinant (r) IL-8 may induce corneal neovascularization. Computer-assisted analysis of sequential fluorescein angiograms showed that rIL-8 doses ranging from 2 to 40 ng/cornea (P = 0.01), but not high dose rIL-8 (400 ng/cornea), results in neovascularization within 14 days. Repeat fluorescein angiograms 6 weeks after placing angiogenic doses of rIL-8 demonstrated significant regression (P = 0.01) of the vascularity present at 2 weeks, suggesting that IL-8 angiogenesis undergoes dynamic modulation similar to that normally seen in wound healing. To our knowledge, this is the first study showing an angiogenic role for IL-8, a finding that emphasizes the interplay between inflammation and wound healing. Our results imply that corneal-derived IL-8 may be important in corneal neovascularization, in particular, and that IL-8 may modulate wound healing in general. Finally, these results raise the possibility that corneal-derived cytokines, such as IL-8, may obfuscate the effects of agents tested in experimental corneal pocket models.

Size variation of the lacrimal punctum in adults.

This is the first reported study on accurate computerized measurements of lacrimal punctal size in normal adults. There was a wide variation found between patients. The lower lid puncta were consistently noted to be larger than those of the upper lids. This is clinically significant in dry-eye patients who may need to be treated with punctal plugs of various sizes.

Is there a racial difference in physiologic cup size?

Although many clinicians believe that there is a racial difference in the size of the physiologic cup, this premise has not been studied. To evaluate this, we prospectively examined 100 black and 100 white volunteers. Stereoscopic optic disc photographs taken of each subject were masked to block out the fundus pigmentation, randomized, and then evaluated by an experienced clinician. The average cup/disc ratio in blacks (0.35) was significantly greater (P less than 0.0001) than that in whites (0.24) for both right and left eyes. Forty percent of the optic discs of blacks and 14% of the optic discs of whites had a cup/disc ratio greater than or equal to 0.4.

Unexplained heterochromia. Intraocular foreign body demonstrated by computed tomography.

Standard radiographic techniques are often inadequate in demonstrating the presence and location of intraocular foreign bodies. Computerized axial tomography was used to confirm the presence of a metallic foreign body in a patient with heterochromia iridis and suspected ocular siderosis in whom no foreign material was found by conventional examination methods.

Evidence for corneal endothelial cell hypertrophy during postnatal growth of the cat cornea.

Endothelial cell counts made from specular micrographs of 1-month-old kitten and adult cat corneas demonstrate that a progressive increase in endothelial cell size and a reduced endothelial cell density occurs during the postnatal development of the cat cornea. In addition to confirming the difference in cell size, scanning electron micrographs show that kitten endothelial cells are much more pleomorphic than those of the adult. When the number of corneal endothelial cells/mm2 and the size of the whole cornea are calculated for the kitten and adult, hypertrophy rather than mitosis appears to be the principal mechanism responsible for maintaining a confluent endothelial cell monolayer during the postnatal development of the feline cornea. Hypertrophy also appears to play a role in establishing the adult corneal endothelial cell population of the rabbit when the previously published data of others are treated in a similar manner to those of the kitten and adult cat. Thus, endothelial cell hypertrophy plays a role in establishing an "adult" endothelial cell monolayer in species that have a widely divergent corneal endothelial cell mitotic capacity.

Penetrating keratoplasty in the cat. A clinically applicable model.

A series of 28 consecutive penetrating keratoplasties were performed on adult cats. Donor corneas (n = 14) were maintained in culture medium for 14--24 hours prior to transplantation. Rotational autografts (n = 7) were used to control for cell loss caused by culture maintenance as well as for the effects of surgery. Additional homografts (n = 7) were transplanted following removal of the corneal endothelium to study the extent of host corneal endothelial cell regeneration. Pre- and post-operative endothelial cell counts of the homografts made from specular micrographs demonstrated an average cell loss of 30% one month following surgery. A similar 30% average cell loss was present in the rotational autografts. Clinically, both homografts and autografts remained clear and were near normal in thickness. Homografts lacking endothelium exhibited persistent, severe edema that correlated with the inability of the host corneal endothelium to resurface the graft. Clinical and morphologic evidence of mild homograft rejection as observed in 15% of the animals that received normal homografts. Corneal endothelial cell loss following penetrating keratoplasty in the cat approximates that observed following the same procedure in the human. Additionally, regenerative capacity of the corneal endothelium in the cat, like that of the human, is limited. These features suggest that this cooperative, hardy animal is an excellent model in which to study many aspects of corneal transplantation that have direct application to the treatment of human corneal disease.

Complications associated with bovine corneal endothelial cell-lined homografts in the cat.

Cultured bovine corneal endothelial cells were subcultured onto feline corneas from which the native endothelium had been mechanically removed, and transplanted into cats via penetrating keratoplasty. Although the transplants remained thin and clear in the immediate postoperative period, correlative clinical and morphologic analysis disclosed evidence of a host response directed against the heterologous endothelium by the ninth postoperative day. Eyes with rotational autografts or transplanted homografts did not disclose evidence of a similar host response.

Familial foveal retinoschisis.

Three young women, offspring of a nonconsanguineous marriage of normal parents, manifested mild visual loss associated with a bilateral foveal dystrophy that resembled the macular involvement in juvenile sex-linked retinoschisis. Electrophysiologic and psychophysiologic tests showed less severe involvement than the gonosomal equivalent. An autosomal recessive inheritance is proposed.

Pigmented iris angiography.

A small volume of concentrated fluorescein was used in a technique of fluorescein angiography in rabbits. The procedure is not accompanied by the usual risks of general anesthesia in rabbits. Angiographic findings demonstrated that the pigmented rabbit iris vessel pattern is similar to that found in albino rabbits.