Relationship between pathology of concomitant exotropia medial rectus and surgical results
【摘要】 To evaluate the relationship between the medial rectus cells counts in concomitant exotropia and surgical results. METHODS: A total of 32 pieces of medial rectus muscle were collected for HE staining in this study, of which 18 pieces were from patients with concomitant exotropia and 14 pieces were from healthy individuals. A method of strabismus score was used to assess the operative effect.RESULTS: The difference of strabismus score before and after the operation in the intermittent exotropia group was significantly higher than that in constant exotropic group (P<0.01). Under light microscope, the loosen muscle fibers and the increased stromal components in the cross sectional area of medial rectus were observed in strabismic group. The muscle cells counts was obviously lower in strabismic group than in control group (P<0.01), which was related to the difference of strabismus score before and after the operation (P<0.05).CONCLUSION: The decreased medial rectus cells counts induce concomitant exotropia directly. It is the crucial causes of the bad surgical results.
【关键词】 concomitant exotropia medial rectus pathology surgical results
INTRODUCTION
In recent years, many researches showed that the weaken muscle pathological changes including muscle atrophy, the increased stromal components and decreased never fibers while the tissue structure of the strong muscle was normal, which caused the unbalance of the bilateral muscle. All of these induced the happen and development of strabismus. The clinical practice showed that the therapeutic results of concomitant exotropia were corrected to the strabismus types and the treatment time. The patients with intermission should be treated early, but the therapeutic results of patients of congenital exotropia and constant exotropia with no intermission were much better than the former. This study discussed the relationship between the medial rectus muscle atrophy of the concomitant exotropic patients and the surgical results pathologically.
MATERIALS AND METHODS
Materials From early August to the middle ten days of November in 2008, 18 subjects free from disease history (trauma history including childbirth injury history, surgical history e.g.) were recruited from the Department of Ophthalmology at the Affiliated Hospital of Medical College of Qingdao University, which were further divided into three subgroups: the congenital exotropia subgroup, the intermittent exotropia subgroup and the constant exotropia subgroup. Before surgery, the children under age 12 were examined by cycloplegic retinoscopy. The dioptre of children under age 12 and above was from 0.50D to +2.25D and 2.50D to +2.00D, respectively. All the patients visual acuity was normal except an amblyopic adult (No.12). Before and six months after operation, triple visual function examination and strabismus angle examination were performed on all the cases (Table 1). Fourteen pieces of medial rectus muscle (14 eyes) from healthy corneal graft donors were considered as control group, which were further divided into two subgroups according to age (Table 2). The whole of 32 specimens were coded randomly and observed in a doubleblind controlled trial.
Sample Collection and Preservation To gain the medial rectus muscle, the end of the muscle was pulled with a squint hook, snipped, and then marked. At last, the samples were reserved in 100g/L neutral formaldehyde at 4℃for 24 hours.
Score of Strabismus Examination The score was calculated as follows:1) Simultaneous perception: the patients’ score with no subjective squint angle (sub), subjective squint angle not equal with objective squint angle (obj), sub equal with obj and both equal to +3° was 3, 2, 1, and 0 points, respectively. 2) Fusion: the patients with no fusion and with fusion were calculated as 1 point and 0 point respectively. 3) Near stereoacuity: in titmus table, the score of the class 0, class A, class B and class C was 3 points, 2 points, 1 point and 0 point respectively. 4) Distance stereoacuity: the patients with distance stereoacuity and with no distance stereoacuity were calculated as 1 point and 0 point respectively.
Procedure of Wax Block and Light Microscopy Clean glass slides were handled with APES glue and then dried in order to prevent organization to slide off. In the case of 60℃,the rectus muscle was handled by acetone dehydration for 40 minutes 3 times, xylene transparent processing for 30 minutes and wax dip overnight. The next morning along the horizontal axis of the muscle fibers, the muscle were paraffinembedded into wax blocks and preserved at room temperature. Before sliced, the wax was frozen in the refrigerator at 20℃ for 10 minutes, and then cut to 5μm thickness slice along the horizontal axis of each muscle tissue. The slices were baking overnight (60℃). Each specimen was handled by HE staining, and then observed under light microscope and taken pictures. The average of the muscle cells which were randomly counted under five optical visual field was checked.Table 1The clinical data and HE stain results of concomitant exotropia group（略） Table 2The clinical data and HE stain results of medial internal rectus muscle group（略）
Image Process According to the doubleblind principle, the muscle cells were counted at visual inspection to make no bias between the strabismus group and the control group. All the tissue section with HE were taken photos by digital camera.
Statistical Analysis The data was analyzed with SPSS software (version 13.0). ANOVA was used to analyze the cells counts in the cross sectional area and linear correlation was used to analyze the muscle cells relation to the surgery age and disease course as well as the difference of score before and after the surgery. There would be significant differences if P<0.05 or P<0.01.
RESULTS
Clinical Results The difference of score before and after the surgery in intermittent exotropic group was significantly higher than that in the constant exotropic group (P<0.01). The congenital exotropic group wasnt included in the comparison because of the fewer cases. The difference of score before and after the surgery was negatively related to disease course (r=0.6069, P<0.05) and the score before the operation (r= 0.4889, P<0.05)HE Staining Under the microscopy, the arrangement of the muscle fibers in control group was compact, regular and in the same direction while the arrangement of the muscle in strabismus group was loose, irregular and in the different direction, with the stromal components in the control group more than those in the strabismus group. In some individual cases, no fiber but massive collagen tissues were observed.
There was no difference in the cells counts between the two subgroups in the control group(t=0.021,P>0.05), so the com parison must be performed after the two subgroups were combined. While there was significantly difference between the control group and the strabismus group (t=4.78, P<0.01, Table 3).
Relation of the Cells Counts to the Scores In strabismus group, the cells counts were significantly related to the difference of score before and after the surgery(r=0.8789, P<0.01), negatively related to disease course (r=0.803, P<0.01) and more negatively related to operation age(r=0.8165, P<0.01); On the other hand, it was not significantly related to the 33cm strabismus angle before the operation(r33cm=0.4399, P>0.05), was significantly related to the 6m strabismus angle before the operation (r6m=0.4985, P<0.05) and not significantly related to attack age (r=0.3477, P>0.05). Table 3Comparisons of muscle cells, Mcadherin and NGF between strabismus
subgroup and the control group(略)
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