Associated convergence and accommodative insufficiency

Nine patients were described with a syndrome consisting of accommodative and convergence insufficiency. All but two had received extensive orthoptic therapy without benefit in the past. Near points of convergence and accommodation, fusional amplitudes and the AC/A ratio were determined and the data compared with those from a group with ordinary convergence insufficiency. The results show that this syndrome is a distinct and separate entity from ordinary convergence insufficiency. Special therapeutic measures include base in prisms and bifocal correction.From the Wilmer Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland.This study was supported by Research Grant EY-00274 from the National Eye Institute, Bethesda, Maryland.     

The synkinetic interaction of convergence accommodation and accommodative convergence

An experimental paradigm is presented to test the long-standing theory that binocular vergence is supported by an addition of tonic, proximal and accommodative convergence (as measured monocularly) along with a supplemental fusional component. Results show accommodative convergence is less than, and the fusional component greater than, predicted by this traditional theory. An alternative theory is presented which includes the influence of convergence accommodation and which correctly predicts the experimental results.     

The first and second order dynamics of accommodative convergence and disparity convergence

Main sequences, the function describing the relationship between eye movement amplitude and velocity, have been used extensively in oculomotor research as an indicator of first-order dynamics yet it is difficult to find main sequence analyses for accommodative vergence or for disparity vergence in isolation when all mitigating factors have been well controlled and there are no studies in which accommodative vergence and disparity vergence main sequences have been generated for the same group of subjects. The present study measured main sequences in: (1) accommodative vergence with disparity vergence open loop, (2) disparity vergence with accommodation open loop, and (3) combinations of accommodative and disparity vergence. A dynamic AC/A ratio was defined and was found to be similar to the traditional static AC/A ratio. Vergence acceleration was measured for all conditions. A pulse-step model of accommodation and convergence was constructed to interpret the dynamics of the crosslinked interactions between the two systems. The model supports cross-coupling of both the pulse and step components and simulates the primary empirical findings that: (1) disparity vergence has a higher main sequence slope than accommodative vergence, (2) both accommodative and disparity vergence acceleration increase with response amplitude whereas accommodation acceleration does not.     

Gain changes in the accommodative convergence cross-link

The output of the accommodative vergence cross-link, the AC/A ratio, was measured before and after subjects viewed through a telestereoscope which increased their interocular separation (pd) approximately fourfold. The initial paradigm was designed to force an increase in the AC/A ratio in that subjects alternately fixated targets set at differing distances. In this paradigm, the varying vergence demands could not be met by a constant increase in phasic or tonic vergence responses. In a second paradigm, only one target was viewed at a fixed position from the eye. Now the constant vergence demand could be met by a set increase in phasic and/or tonic vergence. A significant increase in the AC/A ratio was found in the two-target study but not in the single-target study. Increases in the accommodative vergence gain did show considerable individual differences. Tonic vergence changes were interpolated from the data. This parameter increased significantly in both cases but more so when two targets were alternately fixated. This finding is consistent with current near triad models which predict that accommodative convergence input acts along with disparity vergence input to increase tonic levels of convergence. When AC/A ratios were calculated using clinical measures of the phoria at 6 and 0.4 m, increases were found in the two-target study and to a lesser degree in the single-target study. This clinical method of AC/A measure appears to have been confounded by changes in tonic vergence.     

LASIK术后调节辐辏融合功能的研究

目的研究准分子激光原位角膜磨镶术（LASIK）手术后，近视屈光不正患者双眼视功能的改变状况。方法选取施行LASIK屈光手术的患者90例。按术前屈光度分为三组，每组30例（-6．00D以下；-6．25～-10．00D；-10．25D以上）。设正常对照组30例，屈光度在＋0．50～-0．50D。使用综合验光仪、近点计，检查手术患者术前、术后1周、1个月和3个月四个不同时期的相对调节、辐辏等视功能，分析改变情况。结果术后随着屈光度的改变，术后实性相对调节能力逐渐提高；虚性相对调节术后与术前相比并无改变。术后随着调节超前的消失，实性辐辏量减低，虚性辐辏量增加。结论LASIK手术进一步增强了调节、辐辏、融合功能。     

客观调节性集合/调节比率的研究

目的利用眼动追踪仪和红外自动验光仪获得刺激性调节性集合/调节（accommodative convergence/accommodation,AC/A）和反应性AC/A值,分析两者相关性及差异。方法选取34名健康在校学生和年轻工作人员[年龄为20～35岁,平均（25.8±3.4）岁],在集合反馈回路打开（遮盖左眼）的条件下,用310型眼动追踪仪分别记录调节性集合;用wv500红外自动验光仪测量注视眼在各调节刺激下的调节反应,从而分别得出刺激性AC/A和反应性AC/A,对两者数据采用配对t检验进行分析。结果用眼动追踪仪法测量所有受试者所得的刺激性AC/A和反应性AC/A有显著相关性（r=0.871,P=0.000）和明显差异,反应性AC/A为（7.50±3.60）△/D,刺激性AC/A为（4.77±1.84）△/D,反应性AC/A平均值与刺激性AC/A平均值相比为1.57,两者差异有显著统计学意义（P=0.000）。结论反应性AC/A高于刺激性AC/A,大多数个体均有一定程度的调节滞后量。     

调节与辐辏因素导致视疲劳的诊断和治疗

视疲劳的临床表现复杂,因其症状的非特异性给临床诊断和病因治疗带来一定的困难.随着对该病的认识深入,发现其病因甚为复杂,并且往往是多因素混合导致发病.如果只是单纯的对症治疗效果并不理想,探寻病因进行对因治疗才是根本的治疗策略.目前已经明确多种因素可导致视疲劳,通过必要的眼科及视光学检查可确保明确且全面的病因诊断.目前针对视疲劳的病因治疗难易不同.一些病因只要去除和矫正就能避免视疲劳,而另一些就显得相对困难,调节和辐辏因素导致的视疲劳即属于后者.另一方面由于调节和辐辏检查的专科性,使得它们在视疲劳中的诊断和治疗具有一定的难度和特殊性.我们对目前调节和辐辏在视疲劳中的诊断和治疗现状进行总结,以期为临床诊治带来帮助.