A PROCEDURE which would allow the lengthening of an extra-ocular muscle beyond that which is usually obtained from the conventional surgical techniques would be of definite advantage in large-angle strabismus and strabismus fixus. Since silicone rubber is well tolerated by ocular and non-ocular tissues, the implantation of a small, thin sheet of this material to lengthen an extra-ocular muscle is a logical approach in this situation. The purpose of this paper is to report an experimental study, using rabbit eyes, and clinical observations in two patients with strabismus, in which this surgical procedure was applied. A long-term follow-up of these two patients and a report of several other clinical cases will be published at a later date. Material and MethodsSilicone rubber sheett, 0010 in. thick, was used in the experiments. The material was sterilized either by immersion in 70 per cent. alcohol or by autoclaving. Twelve adult rabbits weighing 3-4 kg. were used. In each rabbit only one eye was operated on. The silicone was always attached to the superior rectus muscle because it is relatively strong and accessible. The rabbits were anaesthetized with intravenous sodium Nembutal (30 mg./kg.) and ether drip. The hairs and lashes of the side to be operated on were shaved, and the skin was painted with 2 per cent. iodine solution. The eye was anaesthetized with drops of Ophthaine (0 5 per cent. Proparacaine hydrochloride, Squibb) and disinfected with a few drops of Neosporin solution (Burroughs Wellcome).The conjunctiva and fascia bulbi overlying the superior rectus muscle were cut. The muscle was carefully isolated by cutting adhesions with scissors. A muscle forceps was applied close to the insertion and the tendon was transected. A piece of silicone sheet 5 or 6 mm. long was cut in a trapezoidal shape in order to fit the width of the tendon stump anteriorly and the narrower width of the muscle, over the forceps, posteriorly. The implant *

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