| ObjectiveTo evaluate the ocular accommodation and convergence functions in patients who have intermittent exotropia, and compare them with the normal people. To evaluate the accommodative functions in IXT patients with a dominant eye. To find out whether there is any relationship between the ocular accommodation and intermittent exotropia. To compare the different examinations for binocular vision in IXT, and analyze the relationship among them.MethodsCase-control study. One hundred and fifteen patients aged from7to30years old were selected from the IXT patients in basic type who visited Tianjin Eye Hospital from November2010to August2011. All patients with anisometropia, high myopia, hyperopia, high astigmatism, CI or ocular disease were excluded. The patients’ horizontal deviation is larger than15Δ and can be controlled sometimes. Meanwhile we set up the normal control group, including those who have good vision, also no anisometropia, no high myopia, no hyperopia or astigmatism, no surgical history, horizontal phoria is between-6Δ～+2Δ at near and between-4Δ～+2Δ at distance, normal eye movement.Each patient had to complete a questionnaire related with the exotropia first, and then underwent a detailed sensory and motor examination, including measurements of visual acuity, the angle of strabismus, accommodation amplitude (with the minus lens&moving near measurement), accommodative response (MEM&FCC), accommodation facility, relative accommodation, accommodative convergence/accommodation (AC/A) ratio, NPC, relative convergence, physiological diplopia, stereo acuity and so on. To compare these parameters with the regular people, and try to find out if there is any difference. To find out whether there is difference between the IXT’s two eyes in such tests. To compare the different examinations for binocular vision in IXT, and analyze the difference between them.Results1. The dominant eye’s mean refraction error was (-1.95±1.99) D while the non-dominant eye’s was (-2.07±2.00) D, and there were no differences in the refraction error between the IXT’s two eyes (P=0.132).The dominant eye’s mean AA was (6.40±2.24) D while non-dominant eye’s was (5.76±1.78) D, and it showed a statistical difference between the two eyes(P=0.000).The dominant eye’s mean AMP was (8.78±3.73) mm while non-dominant eye’s was (9.14±4.43) mm, and it showed a statistical difference between the two eyes (P=0.001).The dominant eye’s mean AR was (-0.24±0.40) D while non-dominant eye’s was (-0.24±0.40) D, and it showed a statistical difference between the two eyes (P=0.000).The dominant eye’s mean AF was (13.37±4.29) cpm while non-dominant eye’s was (12.30±4.30) cpm, and it showed a statistical difference between the two eyes (P=0.000). So, there do exist the asymmetric on ocular accommodation functions between both eyes during binocular viewing, where the nondominant eye showed an abnormal accommodation amplitude, decreased accommodative response and accommodation facility.2. Setting age, refractive error and strabismus angle as the covariates, and doing the statistical calculation with SPSS. It showed that the two control score systems were effected by the exotropia as well as the refractive error, and the R12was0.495, the R22was0.545. Furthermore, the AA tested in two ways were both associated with the angle of strabismus and the refractive error, however, the AMP was also effected by the age. We also found that the two relative accommodation were effected by the exotropia as well as the age and refractive error, and the RNRA2was0.401, the RPRA2was0.361. The AF was associated with the angle of strabismus and the age, the R2was0.417. The NPC was associated with the angle of strabismus and the age, the R2was0.126. It has been found that the AC/A ration was related with the strabismus angle, the age and the refractive error, the R2was0.287. The PRC and NRC at far were related with the strabismus angle, while the PRC and NRC at near were related with the strabismus angle and the refractive error.3. The IXT’s mean AR was (-0.24±0.39) D while the normal people’was (0.30±0.32) D, and it showed a statistical difference in the AR between the two groups(P=0.000). The IXT’s mean AF was(9.56±3.54)cpm while the normal people’ was (14.69±2.59) cpm, and there was a statistical difference in it between the two groups(P=0.000). The IXT’s mean NRA was(1.92±0.60)D while the normal people’ was (2.19±0.42) D, and it showed a statistical difference in NRA between the two groups (P=0.000). The IXT’s mean AMP was (8.87±2.83) mm while the normal people’was (8.17±2.11) mm, and there was a statistical difference in it between the two groups (P=0.037). The IXT’s mean NPC was (5.47±3.93) mm while the normal people’was (4.36±3.09) mm, and it showed a statistical difference in it between the two groups (P=0.020). In summery, there was statistically significant difference between the IXT and the normal group under such ocular parameters, including the AA, AR, NRA, AF, AC/A, NPC and convergence (P<0.05)4. The abnormal rate of various binocular examinations were different, but the detection rate of the test with Brock line to check homonymous diplopia and the distant stereopsis test were similar, the former one was57.39%and the latter one was56.52%, meanwhile there was no statistieally difference between these two measurements (P=0.280)Conclusions1. Patients with intermittent exotropia with a dominant eye tend to have asymmetric ocular accommodation functions between both eyes during binocular viewing, where the dominant eye is better than the other eye. This phenomenon may be one of the causes that lead to intermittent exotropia, or we can say it is the result of exotropia.2. The ocular accommodation and vergence function in IXT had changed from health persons due to the strabismus. Such as the IXT’s NRA, AF and convergence are lower than the normal people. These showed that the IXT’ PRC was poorer as well as the related accommodation functions.3. It is better to test the patient’s physiologic diplopia, especially the homonymous diplopia.4. The role of accommodative convergence in binocular fusion in exotropia do exist to certain extent as well as the fusional convergence. |
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