The modulation of ocular growth in rabbits with peripheral retinal ablation.

PURPOSE: To study the effects of transcleral cryotherapy and laser photocoagulation of anterior retina on ocular growth. METHODS: Twenty-one rabbits underwent transcleral cryotherapy or indirect ophthalmoscopic laser photocoagulation of the anterior retina on one of their eyes between 2 and 8 weeks of age. RESULTS: After the rabbits were killed between 3 and 6 months of age, treated rabbit eyes were found to be significantly smaller in axial length (P < 0.001), average equatorial diameter (P < 0.01), average corneal diameter (P < 0.05), and in total ocular volume (P < 0.01). The difference in eye size was not due to lowered intraocular pressure. CONCLUSIONS: The results demonstrate that these treatments slow growth of both the anterior and posterior segment of rabbit eyes.

Congenital and developmental myopia.

Both hereditary and environmental factors are important in the interactive growth of the ocular tissues responsible for determining the refractive state of the eye. Myopia has a low prevalence in otherwise healthy children and is seen with an increased prevalence early in life in many systemic and ocular diseases. Predicting how refractive error will change in any individual child after birth or at any stage of ocular development is not possible at present, although, trends can be seen in longitudinal studies. In the disease states associated with an increased prevalence of myopia, information regarding the time of onset of myopia and the specific values for the refractive components, is lacking, so that underlying mechanisms of myopia development and whether the myopia is congenital or developmental, are not known. In adults, three different types of myopia can be characterised on the basis of clinical characteristics which have prognostic significance for ocular disease. The mechanisms of ocular growth that lead to these forms of myopia are not clear. At present, treatments to prevent or slow myopic progression have been marginally beneficial and of questionable value.

Scleral reinforcement in rabbits using synthetic graft materials.

Because of disappointing results using homologous collagen for scleral reinforcement in the treatment of pathologic myopia in humans, we undertook a series of experiments in rabbits to test the mechanical properties and long-term biocompatibility of three different synthetic graft materials. Grafts made from two of these materials, Gore-Tex Soft Tissue Patch (expanded polytetrafluoroethylene) and Miragel (poly[methyl acrylate-co-hydroxy-ethyl acrylate]), were easy to position about the globe. Both materials, however, were resistant to invasion by fibrovascular tissue. The third material, woven Dacron (polyethylene terephthalate), though more difficult to position, permitted extensive invasion of fibrovascular tissue, which made all parts of the graft firmly adherent to the globe. Our results indicate the long-term compatibility of all three of these materials when used as periscleral grafts in rabbits. However, our results also suggest that a woven material such as commercially available Dacron is a more suitable graft material for scleral reinforcement in humans than collagen, Miragel, or Gore-Tex.

Eye disease in a geriatric nursing home population.

All 225 tenants (181 female and 44 male patients) of a nursing home in New York City underwent eye examinations at least once within a 1-year period to determine the prevalence of senile cataract, age-related macular degeneration (AMD), open-angle glaucoma, and diabetic retinopathy. The average age was 85.4 years (range, 60-108 years). With aphakia and pseudophakia included in the diagnosis of "cataract," the respective prevalences were found to be 81, 37, 11, and 2.1%. There was a statistically significant increase in the prevalence of cataracts and AMD in those patients 85 years of age or older when compared with the younger patients in the nursing home (P less than 0.05). Of those patients without organic brain syndrome, 44% (66/151) had a visual acuity of 20/40 or better in at least one eye. Thirty percent (45/151) had a visual acuity of 20/200 or worse in both eyes. Although this study has no control population of patients outside nursing homes, a review of the literature suggests that geriatric nursing home patients may have a higher prevalence of eye disease than their chronologic peers outside nursing homes. Further study is necessary to determine whether residents of geriatric nursing homes are receiving adequate ophthalmic care.

Circulating melanoma-associated antigens in ocular melanoma.

A pilot study was performed to test for melanoma-associated antigens (MAAgs) in the sera of patients with localized uveal melanoma, using monoclonal antibodies (MoAbs). Both whole sera and polyethylene glycol (PEG) 2.5% serum precipitates from 18 patients with clinically localized uveal melanoma and two patients with localized invasive conjuctival melanoma were analyzed for two human cutaneous MAAgs by an enzyme-linked immunosorbent assay (ELISA). These antigens could not be identified when whole sera were used. However, after PEG precipitation, a MoAb specific for the p210 MAAg reacted with four of 20 patient samples and none of 17 controls. A second MoAb specific for the p97a MAAg reacted with one of 20 patients and none of 17 controls. These findings indicate the existence of antigens common to both uveal and cutaneous melanoma and suggest that the refinement of assays to screen sera with a battey of MoAbs may be of value in diagnosing and/or monitoring patients with uveal melanoma. Circulating immune complexes were detected in the sera of six patients but did not correlate with any clinical features or with the presence or absence of detectable MAAgs.

Scleral reinforcement: two case reports.

We report two cases of unilateral scleral reinforcement undergone for progressive pathologic myopia. Examination ten years after the operations showed the supportive effect of the scleral grafts. The effect, however, was localized and did not appear to block the overall progression of posterior staphyloma formation significantly.

Long-term results of scleral reinforcement surgery.

Of 40 scleral reinforcement operations for progressive severe myopia, 23 patients were followed up for a minimum of five years. Ten of 23 patients showed an essentially stable postoperative course (43%) while 13 (57%) had increases in myopia of -1.0 diopter or more. Among the operated on eyes, 17 of 23 eventually had some increase in myopia. Of the 20 eyes that had preoperative axial measurements, 18 (90%) had increases in axial diameter of 0.3 mm or more. There were complications in six of the 40 eyes, including anterior uveitis, motility disorders, and retinal detachment. Progression of posterior staphyloma formation or the onset of myopic fundus degeneration was observed in ten eyes. Two problems with this surgery are the limited scleral area reinforced by narrow grafts and the possible late involvement of graft collagen in the disease process of host sclera.

Scleral hyperplasia induced by heat.

We evaluated low-level heating as a stimulus to induce hyperplasia of normal rabbit sclera. Heat treatments were administered by placing an etched-element heater on bare sclera. Contact thermotherapy with a conductive device provided a favorable dose distribution for local scleral heating. A purely conductive heat source was selected to minimize intraocular heat penetration and to determine whether the scleral reaction was a primary thermal effect. Histologic examination of treated specimens showed thickening of normal rabbit sclera with preservation of the underlying normal ocular structures. Electron microscopic examination of treated sclera showed newly formed collagen fibrils adjacent to sclerocytes. These fibroblasts were activated, as manifested by well-developed rough-surfaced endoplasmic reticulum and hypertrophic Golgi complexes.