Investigation Of The Videooculograph And The Ultrastructure Of The Extraocular Muscles In Congenital Nystagmus

ObjectiveTo provide more objective basis for estimating the therapeutic benefits of modified Kestenbaum procedure through analysing the clinic manifestation and ocular movement parameters of videooculograph of CN. To observe the ultrastructural changes of the extraocular muscles (EOMs) in CN subjects and discuss the pathogenesis of CN.Methods1. The modified Kestenbaum procedure treated the16subjects of CN with compensatory head posture. Modified Kestenbaum procedure was conducted on patients with CN. When the angle of compensatory head posture was from25°to30°, Parks5-6-7-8method was choosen. The amoune of surgery was adjusted if the angle of compensatory head posture exceeded30°. The york muscles were recessed for the bidirectional null zones. The horizontal rectus muscles and vertical muscles were simultaneously weakened if the subject had a face turn with chin elevation.2. Routine ophthalmologic examinations including best corrected visual acuity, refractive error, ocular anterior segments, fundus, eye position, eye movement, direction and degree of compensatory head posture, prism adaption test.3. The16subjects were examined with videooculograph before and after the surgery. The ocular movement parameters were analyzed, including amplitude, frequency, foveation time,NAFX value and the field of null zone. The parameters were analysed with paired test and Pearson correlation method.4. Ultrastructure of the removed EOMs with the subjects was observed under light and transmission electron microscopy. Controls were obtained from subjects underwent enucleation for ocular injury and normal autopsy specimen, which had no any ocular motility disorders and the patients with concomitant strabismus.Results1. The compensatory head posture of all subjects had prominently improved or disappeared after the surgery, the residual face turn was mean4.8°. The30°face turn of one subject with bidirectional horizontal null zones disappeared after weakening the horizontal york muscles. One subject with face turn and chin elevation had a residual head turn5°after weakening the horizontal rectus muscles combining vertical muscles. The subjects had no A-V pattern and other strabismus before and after surgery. The best visual acuity improved of8subjects,(Snellen visual acuity was changed log visual acuity, t=-2.373, p=0.031,). The Titmus improved of11subjects, but the statistic analysis had no different,(t=1.147, p=0.270).2. The waveform of the16subjects with horizontal jerk nystagmus is a slow phase with an increasing velocity. Of them,11mixing vertical components. The nyatagmus damped by convergence in13subjects.9subjects had menifest nystagmus with latant component. Comparing the amplitude,NAFX value and the field of null zone before and after surgery, the statistic results were significant different,(all p<0.05), The amplitude was correlated with NAFX value,(r=-0.528,p=0.002) but frequency was not correlation with NAFX,(r=-0.263, p=0.145). The foveation time was nolinear correlated with NAFX value.3. Ultrastructure of the EOMs with CN:The myofibrillae of the EOMs arranged irregularly and the cell nucleus appeared long.The sarcoplasmic reticulum was vacuolated. Mitochondria were swollen in which the arrangement of inner crest was disordered even disappeared. The lamellar structure of palisade endings dissolved, replaced by black substances which like osmic acid. The palisade endings mainly located at the distal myotendinous junction of horizontal rectus muscle, while them had almost not been observed at the insertion of the horizontal rectus muscles.Conclusion1.Modified Kestenbaum procedure is a successful method to improve compensatory head posture and may decrease nystagmus intensity and broaden the field of null zone of CN in short term.2. The NAFX value can objectively and accurately estimate the effectiveness of modified Kestenbaum procedure. The videooculography can be helpful to the diagnosis and treatment of CN.3. The ultrastructure of the EOMs of CN subjects are obviously changed compared with the controls. These alterations are probably related to the etiology and pathogenesis of CN.