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DISCUSSION
In recent ten years, many researches showed the weaken muscle deterioration and fibrotic changes mainly with the muscular atrophy and the decrease in number of fibers, which caused the decreased muscular elasticity and tensity as well as the main reason of exotropia. Zhang et al[1] found that there were obvious pathological changes in the weaken muscle of exotropic patients, which manifested as decreased muscle cells counts, disruption of myofilament, increased stromal components and decreased nerve fibers while there were no evident changes in the lateral muscle. Further more, the changes between the different age group would be more obviously with the development of the disease course and age. Thus, the weaken muscle will be the target for this study.
A method of strabismus scores was used to quantify strabismus and surgical effect. According to the triple visual function, the operation results were presented by the difference of scores before and after the surgery. The score could not represent the strabismus level precisely, but it didnt effect the evaluation because of the same standard. In this study, the difference of scores before and after the surgery in intermittent exotropic group was significantly higher than that in the constant exotropic group and significantly related to disease course, so the difference of the scores could represent the surgical results effectively.
The muscle atrophy was the cause or the result of strabismus? The author supported the former as follows: at first, the atrophy made the unbalance between the bilateral muscles. Then, the cell counts were related to the 6m strabismus angle but 33cm strabismus angle before surgery[2]. Another word was that the close ocular position was not related to atrophy degree but regulation while the distant ocular position was not related to regulation but atrophy degree, which meant that the progression of muscle atrophy enlarged the degrees of ocular deviation movement. If muscle atrophy was the cause, could the good longterm surgery results of most patients with intermittent exotropia be explained by that the recovery of the weaken muscle atrophy induced the equilibrium of the bilateral muscles? If this hypothesis was right, it is the surgery that reversed the atrophy. So the observation of the medial rectus under light microscope long term after surgery was crucial to the cause of the concomitant exotropia[3].
Under light microscope, the medial rectus muscle showed the loosen cells and increased collagen tissues in a different degree. Muscle cells were counted in the same times visual field, which didnt change with the variable ages from 5.4±0.6 to 23.9±9.7 in control group. The cells counts were obviously lower in strabismua group than in control group (P<0.01) and the age between this two group had not statistical significance (P>0.05). So the cells counts were not affected by age. The statistical results showed that the cells counts were highly corrected to the difference of scores before and after the surgery and negatively related to disease course in strabismus group while the strong muscle did not atrophy obviously,which caused the unbalance of the bilateral muscles.The decreased medial rectus cells counts reduced concomitant exotropia directly.It was the crucial causes of the bad surgical results.
【参考文献】
1 Zhang FY, Ji HM, Yang F,Gao CZ. Pathological changes of extraocular muscles in strabismus patient. Chin J Pract Ophthalmol 1997;15(10):626
2 Gralek M, Krawczyk T. Pathomorphological evaluation of the extraocular muscles during strabismus. Klin Oczna 1998;100(6):373375
3 Liu QJ, LI FM. Practice of ophthalmology. 2nd edition, Beijing: Peoples Medical Publishing House 2005:664
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