Comparison of calculated and gradient AC/A ratios among normal, exophoria and esophoria / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To analyze the clinical application of calculated and gradient accommodative convergence/accommodation ratio(AC/A)in different eye positions.<p>METHODS: A total of 127 myopes in ophthalmology were included. The calculated AC/A was obtained by near/distance phoria and the gradient AC/A was obtained by near addition +1.00D. The differences of eye positions of the calculated and gradient AC/A were compared. <p>RESULTS:The calculated AC/A value was higher than the near +1.00D gradient AC/C(<i>P</i><0.01); Comparing the same method in different eye positions revealed that the calculated AC/A and gradient AC/A were significantly different, which has the highest AC/A in the esophoria group and the lowest AC/A in the exophoria group; Comparing the two methods in the same group revealed that the calculated AC/A in the esophoria group and the normal group was higher than the gradient AC/A(<i>P</i><0.01), and there was no significant difference in the AC/A measured by the two methods in the exophoria group(<i>P</i>>0.05).<p>CONCLUSION: The calculated AC/A is higher than the gradient AC/A, especially in patients with esophoria and emmetropia, it is easy to obtain high AC/A values by using the calculation method, resulting in erroneous diagnosis. The gradient method is more recommended.

Study on the function of regulating aggregation in children with different types of intermittent exotropia / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To investigate the binocular accommodative amplitude(AMP)and accommodative facility(AF), near point of convergence(NPC), accommodative convergence/accomodation ratio(AC/A), positive relative convergence(PRC)of intermittent exotropia(IXT)children, according to the convergence insufficiency type, basic type, divergence excess type, and to compare with the normal children, investigating the differences of regulation and collection function.<p>METHODS: Totally 40 IXT children were divided into three groups according to the different types of the IXT patients, the convergence insufficiency group(12 children), the basic group(18 children)and the divergence excess group(10 children). And the 20 non-exotropia children were set up as the control group. AMP was measured with improved push-up test, and AF was measured with turning over convex and concave lens test. NPC was measured with push-up test. AC/A ratio were measured with the lens gradient method. PRC was measured with BO prism. The binocular accommodative and convergence function of four groups were compared.<p>RESULTS: The difference of AMP, AF, NPC, AC/A ratio and PRC among four groups was significant difference(<i>P</i><0.05), and we did the further pair wise comparisons. AMP of the IXT group was less than the control group, and AMP of the convergence insufficiency group was the least; AF of the convergence insufficiency group was less than the basic group and the control group; NPC of the convergence insufficiency group was the largest; AC/A ratio of the convergence insufficiency group and the basic group was lower than the other two groups; PRC of the IXT group was less than the control group when fixating at near target of 33cm, and the mean of the convergence insufficiency group was the least; PRC of the IXT group was less than the control group when fixating at far target of 6mo(<i>P</i><0.05).<p>CONCLUSION: There are differences in the ocular function of accommodation and convergence in different types of IXT children, and the function of the convergence insufficiency IXT is the worst. The binocular accommodative and convergence function of IXT children is worse than non-exotropia children.

Efficacy of vision therapy in impaired stereoscopic depth with intermittent exotropia (true divergence excess) with unilateral amblyopia: a case report

Divergence excess (DE) can be described clinically as exotropia at far greater than the near deviation by at least 10 prism dioptres (PD). We are reporting a rare case of 25-year-old female visited in the eye department for a routine eye check-up with a history of decreased vision in one eye. On examination, it was detected as a case of unilateral amblyopia with intermittent exotropia of true divergence excess with high accommodative-convergence over accommodation (AC/A) ratio. The patient was asymptomatic from exo-deviation due to the presence of binocular vision and good fusional reserve. The patient was started on active conventional vision therapy along with occlusion therapy. Post 16 weeks of constant therapy, a vision assessment with complete squint assessment along with binocular vision tests were performed. The result interprets to support the use of active conventional vision therapy as an integral part of the clinical treatment of amblyopia and intermittent exotropia. The rate of recovery of several monocular functions monitored during the vision therapy period provides the evidence of neural plasticity at multiple sites in the visual pathway in this adult amblyope. Therefore, if an ordered plan is being followed for the management of the patient of unilateral amblyopia and divergence excess, it can yield long-lasting improvement in visual acuity and binocular functions of any age.

Comparison of the AC/A Ratio by the Grdient Method and the Heterophoric Method in Normal Subjects

To determine and compare the AC/A ratio in normal subjects, the AC/A ratio was measured by three different methods;near gradient method, distant gradient method and heterophoric method. The 33 normal subjects were enrolled in this study. All of them met the following criteria:(1)no known ocular disorders such as anisometropia, strabismus, and amblyopia.;(2)refractive error under -4D and corrected visual acuity more than 0.9.;(3)stereoacuity of 40 arc sec on Titmus test. The AC/A ratio was measured under full correction of the refractive error. Ages ranged from 6 to 25 years with a mean age of 16 years. The mean refractive error of the subjects was -1.33 D in right eye and -1.38 D in left eye. The near gradient method showed a mean AC/A ratio of 3.36:1 ranging from 1.33 to 4.67 ;the distance gradient method showed a mean ratio of 1.79:1 ranging from 0.67 to 3 ;and the heterophoric method showed a mean ratio of 5.71:1 ranging from 4.13 to 9. There was no significant difference in the AC/A ratio between the sexes and in the AC/A ratio between ages less than 11 years and more than 11 years. Different AC/A ratio values were obtained using three different methods. Among the three methods, the heterophoric method tended to give a higher value than the gradient method, and the near gradint method tended to give a higher value than the distance gradient method.

Treatment for Convergence Excess Esotropia by Slanted Medial Rectus Muscle Recession

To investigate whether the slanted medial rectus recession can correct excess esotropia at near without overcorrection at distance and reduce the distance-near deviation difference, we examined 11 convergence excess esotropia patients who had deviation at near exceeding distance esotropia by 15PD or more, and underwent this operation. They composed of 7 partially accommodative esotropia with high AC/A ratio and 4 nonaccommdodative convergence excess esotropia. The surgical procedure consisted of bilateral, symmetrical slanted recession of the medial rectus muscle. The amount of recession of the upper and lower margins were calculated so as to correct the esotropia with correction at distance, and near respectively. The preoperative mean near and distance deviation were 33.8PD and 15PD, and each decreased to 9.2PD and 4.3PD postoperatively. The preoperative mean distance-near deviation difference were 18.8PD, and decreased to 5.4PD postoperatively. The 3 patients decreased over 10PD in the distancenear deviation difference. In conclusion, the surgical procedure, as bilateral slanted medial rectus recession, can correct excess esotropia at near without overcorrection at distance and reduce the distance-near deviation difference. Therefore, the bilateral slanted medial rectus recession may be used as the method of surgical treatment in convergence excess esotropia.

Treatment of Near Esotropia with High AC/A Ratio

The patients with accommodative esotropia due to high AC/A(accommodative convergence/accommodation) ratio show prominent esodeviation and can not fuse without bifocals at near. The purpose of this study is to eliminate prominent near esotropia in those patients and let them fuse at near without bifocals. We performed unilateral or bilateral medial recti recti recessions according to the angle of near esotropia in 14 patients. Twelve patients showed orthophcria or small esophoria less than 12 delta. Eleven of these patients obtained solid fusion after surgery except 3-year-old patient who could not understand the stereopsis test. One patient had esophoria of 20 delta after surgery and showed gross stereopsis. The other patient recurred 27 delta of intermittent esotropia. Twelve of 13 patients(92.3%) could fuse without bifocals at near. The recession of medial rectus or recti was effective on the removal of prominent near esotropia and obtaining fusion without bifocals. Furthermore it did not disturb angle of deviation and fusion at distant. We recommend this procedure as a secure and effective treatment for near esotropia caused by high AC/A ratio.