Significance. This work will advance understanding of ocular mechanics and strabismus with data not obtainable from human subjects. The proposed studies in monkeys will lead directly to a more realistic model of ocular statics, which will facilitate the development of better diagnostic and surgical procedures for strabismus. We will better understand the response of extra-ocular muscles to surgical stretching and relaxation, and will gain some evidence concerning the involvement of proprioception in strabismus; these studies will lead to improvements in the long-term success rate of surgery.
Aims and Methods. (1) An implantable extra-ocular muscle force transducer, developed previously, will be tested for long-term stability in vivo. (2) We will then use this transducer to chronically measure horizontal rectus muscle force as a function of voluntary gaze. Results will be compared with predictions of the SQUINT mathematical model of strabismus, and will be used to verify the """"""""law of reciprocal innervation"""""""" in the general case of 3-dimensional eye rotations. We will also collect correlated records of eye position and muscle force during saccades and pursuit eye movements. (3) We will measure the innervation-length-tension relationships of rectus muscles, using the muscle force transducer in conjunction with a suction contact cap, to control the length of the measured muscle. These results, with earlier data on orbital geometry and muscle paths in monkeys, will complete a monkey model of strabismus mechanics. (4) We will study the slow changes in force that occur following muscle resection surgery, using force measurement and length control, as above. Our method will determine if such changes occur and, if so, discriminate changes in tissue elasticity from changes in innervation, possibly due to proprioceptive feedback. All studies will involve chronic implantation of our EOM force transducer in monkeys trained to fixate.
