The human eye grows rapidly over the first 3 years of life; the increase from an average 17.3 mm axial length at birth is approximately 5 mm. Under normal conditions, the axial length increases only an additional 1 mm to full growth by age 14. Greater elongation causes myopia, a visual deficiency common to a large segment of the population, which is usually correctable with spectacles or contact lenses. In some people, however, the globe continues to lengthen to such an extent that it is difficult to restore functional vision by refractive correction. Because the growth of the retinal does not keep pace with the expansion of the sclera, these eyes are at great risk of retinal breaks, detachment, and blindness. Pathologic myopia is associated with structural weakening of the slcera. The goals of this biomaterials research proposal are to determine whether surgically implanted reinforcement bands safely support the sclera to prevent the lengthening of the eye and to develop an optimal sclera reinforcement band. Initial efforts will be directed toward determining the biological effects of candidate scleral reinforcement materials (donor sclera, synthetic polymers) on the rabbit eye. Then, the effects of selected scleral implants on the growth of the feline eye during a period of rapid development will be evaluated. Changes in axial length will be monitored by ultrasonic A-scan. The condition of the macula, the retinal blood flow, and the optic nerve head will be evaluated by ophthalmoscopy and documented by fundus photography and the optic nerve head will be evaluated by ophthalmoscopy and documented by fundus photography. Anatomic examinations will verify the placement of the bands and their gross effects on extraocular structures. The compatibility of the implant materials with ocular tissues at the cellular level and the nature of the interface between the implants and the eye will be examined histologically. Successful feline studies will be followed by trials in infant monkeys. When appropriate, promising results will be followed by a proposal to conduct clinical trials in patients who have advanced pathologic myopia, and then in myopia patients who are at greatest risk of progressing to severe axial elongation. The results of the proposed studies will also be applicable to other uses of synthetic polymers in the eye such as for scleral buckles, muscle patches to prevent scarring, and tissue augmentation.
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