Influence Of Myopic Anisometropia On Binocular Motion Parameters

Objective:To investigate visual function and the effect of anisometropia on binocular vision,by measuring binocular motion parameters in myopic anisometropia patients with daily glasses.Subjects:1,Myopic anisometropia group:A total of 49 persons were selected randomly,including patients who visited Tianjin Eye Hospital from August 2008 to June 2009 and some students of Tianjin Medical University. Criteria:(1)Between two eyes, the difference of sphere≥1.50D and/or cylinder≥1.00D, as well as cylindrical power is less than half of spherical power.(2)All of people are myopic anisometropia. (3)With daily glasses,monocular corrected visual acuity≥0.8, and the duration of wearing glasses is more than half a year. (4) No organic lesion of eye.(5) No significant strabismus with cover test. (6) No presbyopia and other physiological accommodative dysfunction.2,Control group:44 persons with no anisometropia were recruited in study during the corresponding period. Criteria:(1)Emmetropia, myopia and myopic astigmatism patients (difference of sphere<1.50D and/or difference of cylinder<1.00D).(2) No strabismus, amblyopia and other eye organic disease. (3) No presbyopia and other physiological accommodative dysfunction.Methods:Using retinoscopy (objective refraction) and phoropter (subjective refraction) to measure corrected visual acuity for all subjects of two groups. Tested back vertex power of glasses by focimeter, checked horizontal distance of optical centers,and made sure the corrected visual acuity with glasses.On the basis of glasses power and horizontal distance of optical centers,measuring the separated lateral phoria at distance (5m) and near (40cm) to calculate AC/A ratio. Measuring fusional vergence ranges,near-point of convergence, accommodative function, as well as accommodative function including AA, accommodation lag, RA and AF to draw the binocular vision chart and analyze binocular vision status using the Sheard criteria.Results:1,Comparison of the separated lateral phoria. Subjects of two groups had exophroia mostly, and the separated lateral phoria in anisometropia had significant increase than that of normal group (P<0.05).2, Comparison of the AC/A ratio.AC/A ratio of two groups were close to the normal level. There was no significant difference (P>0.05).3,Comparison of the level of vergence(1)The level of vergence at distance (5m). All the values, including the break point and recovery point of BI and blur point, break point and recovery point of BO, were less in anisometropia group. No significant difference was found (P>0.05).(2) The level of vergence at near (40cm).All the values,including the blur point, break point and recovery point of BI and BO, were less in anisometropia group, only the recovery point of BO had significant difference between two groups (P<0.05).4, Comparison of accommodative function(1)In anisometropia group,differences in AA is greater and AF is weaker than that of the control group, which showed significant differences between two groups (P<0.05).(2) Relative accommodation and accommodation lag in two groups were nearly the same,no significant difference was found(P>0.05)5,Comparison of the NPC.The NPC of anisometropia group was farther,but no significant difference was found between two groups (P>0.05).Conclusion:1,Anisometropia can affect the horizontal eye position, especially in near separated horizontal eye position,which presents a larger degree of exophoria.2,As for anisometropia, the level of vergence at distance and near are reduced, and decreased fusion reserve has effect on normal binocular vision. Patients can own normal binocular single vision at distance,some may be have monovision at near.3,For patients with anisometropia,there are evident differences in amplitude of accommodation between two eyes.It may be due to under correct of high myopia and differences of corrected visual acuity.4, AF of anisometropia is weak,indicating that fusion function is affected.5,AC/A ratio, NPC and accommodation lag can return to normal if the patients with anisometropia wear glasses over a long period of time.It demonstrates the necessity of accurate and prompt correction in maintaining normal binocular single vision.6,Sheard criteria plays an important role in evaluating binocular vision,but the compliance of anisometropia is low.