Comparison of near heterophoria tests under varying conditions on an adult sample

PURPOSE: This study compared the near phoria measurement using the Bernell muscle balance card with and without prism neutralization, using both trial frame and phoropter correction, and compared with the conventional Maddox rod method. METHODS: Forty young normal Chinese adults had their near phoria measured with trial frame correction using the conventional muscle balance card method (method 1). Any deviation was compensated with a prism bar as an alternative approach (method 2). The conventional Maddox rod method (method 3) was also carried out for comparison. These three methods were repeated with phoropter correction and considered as methods 4, 5 and 6. RESULTS: The phorias obtained from these six methods were not significantly different from each other (repeated measures anova, p > 0.05). More than half of the subjects were exophoric. Although the difference in phoria was not significant, phoria measurement using phoropter correction yielded a greater coefficient of variation. CONCLUSIONS: Near phoria measurement using the muscle balance card conducted with trial frame correction was less variable, and was also more natural and similar to a real reading situation. The use of prism for compensation did not affect the phoria results. Exophoria seems to be more common than esophoria in young Chinese adults.     

Forced vergence fixation disparity parameters with and without a central fusion lock

The effect of a central fusion lock on forced vergence fixation disparity curve parameters, that is, magnitudes of fixation disparity and associated phoria, curve type and the central slope of the curve, was studied in 84 subjects because of ambiguity in the previous studies. It was found that the magnitudes of exo fixation disparity and exo associated phoria decreased significantly when they were measured with the central fusion lock. The central lock had no noticeable effect on the type of the curve, although, the central slope of the curve was flatter in the presence of the central lock.     

近视性屈光参差对水平隐斜视及聚散力的影响

目的：通过测量屈光不正患者戴镜后的水平隐斜视及聚散力,探讨近视性屈光参差对双眼视觉的影响。方法：随机选择近视性屈光参差患者48例,测量日常戴镜状态下的矫正视力,使用VonGraefe法检查远方（5m）、近方（40em）的分离性水平隐斜视,利用梯度法计算AC／A比率;使用综合验光仪上的Risley棱镜检查远方、近方的水平聚散力。40例近视患者作为对照组。结果：屈光参差组远方、近方的分离性水平隐斜程度均大于对照组．差异有统计学意义（心0．05）;AC／A比率与对照组相比差异无统计学意义（P〉0．05）。屈光参差组水平聚散力的模糊点、破裂点、恢复点值均小于对照组,除近方BO恢复点两组差异有统计学意义（P〈0．05）外,其他检查结果差异均无统计学意义（P〉0．05）。结论：屈光参差影响水平眼位,减弱聚散力,患者可拥有双眼单视功能,但注视近方距离时,患者可能存在单眼视状态。     

近视眼戴镜对外隐斜与调节的影响

目的:探讨不同戴镜情况对儿童、青少年近视患者的外隐斜度及AC/A率的影响。方法:将研究对象分持续戴镜组、未戴镜组和间断戴镜组三组,隐斜测定仪测定外隐斜度,同视机测量AC/A率并进行比较。结果:近视眼持续戴镜组近外隐斜度均值低于未戴镜组及间断戴镜组,而三组间远隐斜度比较无明显差异。持续戴镜组AC/A率均值低于未戴镜组及间断戴镜组。结论:儿童、青少年近视患者易发生外隐斜,近视伴外隐斜者经常戴镜可使外隐斜度降低,AC/A率下降,视疲劳得到一定程度的缓解,减轻眼的近视化。     

Age-related changes of phoria myopia in patients with intermittent exotropia

Purpose  To investigate the age-related changes in a myopic shift under binocular conditions (phoria myopia) in patients with intermittent exotropia (IXT). Methods  Forty-five patients with IXT were studied: 21 were ≤9 years old (children), 11 were between 10 and 19 years (adolescents), and 13 were between 20 and 43 years (adults). The angle of strabismus was determined by the alternating prism cover test. The spherical refractive error was measured at 1 m using infrared video retinoscopy under monocular and binocular viewing conditions. Results  The change in the spherical refractive error (ΔR) between binocular and monocular conditions was significantly larger in adults (ΔR = −1.11 ± 1.01 diopters (D), average ± standard deviation) than in children (ΔR = −0.34 ± 0.34 D; P < 0.05, analysis of variance). ΔR was significantly correlated with the angle of exotropia only in adults (r = 0.55, P = 0.04). After strabismus surgery, ΔR decreased in adults (n = 3). Conclusions  Because a significant myopic shift under binocular conditions was detected in IXT patients older than 20 years, phoria myopia can occur after age 20 even if functional disturbances are not observed in children or adolescent IXT patients, a fact that specialists need to bear in mind when treating younger patients.     

内隐斜视青少年近视眼矫正时个体化下加的确立方法

目的 探讨在青少年近视眼矫正时不同视近下加条件下,调节滞后及隐斜的变化,并构建下加与调节滞后、隐斜间关系的数学公式,以期得到使调节滞后与隐斜量同时最小的最适视近下加范围.方法 招募110例单纯性近视眼的内隐斜视青少年患者,据MPMVA原则验光配镜后依次予以佩戴5种不同下加试镜片(OD、+0.75D、+1.50D、+2.00D、+2.50D)后测量双眼视近33 cm的调节反应(Shin-Nippon,日本)以及遮盖试验+排棱镜测量视近隐斜度;采用线性回归统计学分析视近下加与调节滞后、隐斜度间关系.结果 随着下加度数增加,视近调节滞后量逐渐减少,而内隐斜量逐渐变小并向外隐斜方向变化;不同下加条件下调节滞后量[F(262.76,4),P＜0.01]以及隐斜度[F(223.45,4),P＜0.01]都存在统计学差异;内隐斜患者的最适下加与初始调节滞后存在线性相关性(r=0.526,P＜0.01),且最适下加与初始隐斜状态也存在线性相关性(r=0.523,P＜0.01).结论 根据青少年近视眼患者个体的初始近调节滞后量和近隐斜度,可获得适合该患者的视近下加范围,从而为青少年内隐斜近视眼确立个体化视近下加提供参考策略.     

The effect of positive-lens addition and base-in prism on accommodation accuracy and near horizontal phoria in Chinese myopic children.

The effect of positive-lens addition (0, +0.75, +1.50, +2.25, +3.00 D each eye) and base-in prism power (0, 1.5, 3 Delta each eye) on both near focusing errors and latent horizontal deviations was evaluated in 29 Chinese myopic children (age: 10.3 +/- 1.9 years, refractive error: -2.73 +/- 1.31 D). Accommodation response and phoria were measured by the Shin-Nippon auto-refractor (right eye) and Howell-Dwyer near phoria card at 33 cm with each of the 15 lens/prism combinations in random order. The initial accommodative error was -0.96 +/- 0.67 D (lag) and near phoria was -0.8 +/- 5.0 Delta (exophoria). The positive-lens addition decreased the accommodative lag but increased the exophoria as the power increased (e.g. up to -9.1 +/- 4.1 Delta with +3 D). A 6-Delta base-in prism totally controlled the exophoria induced by a +1.50 D addition (-0.3 +/- 4.3 Delta), but the accommodative lag was still considerable (-0.69 +/- 0.54 D). In the graphical analysis of the data, a lens addition of +2.25 D combined with a 6-Delta base-in prism minimized both the lag and lens-induced exophoria to -0.33 D and -2.4 Delta respectively (regression analysis). This lens and prism combination decreased the lens-induced exophoria by 4.5 Delta compared with that measured with +2.25 D alone (-2.4 Delta vs -6.9 Delta). The results suggest that incorporating near base-in prism when prescribing bifocal lenses for young progressing myopes with exophoria could reduce the positive lens-induced oculomotor imbalance.     

Gaze-related near heterophoria incomitance

Background: Gaze-related changes in the magnitude and type of phoria have important clinical implications with respect to the attainment and maintenance of comfortable single binocular vision. Previous investigations were either limited to the mid-vertical and lateral directions of gaze or involved head positions with input from neck proprioceptors. The results of such studies have been ambiguous. Method: The Hess-Lancaster screen was used to study the variations of near horizontal phoria in nine positions of gaze among subjects with normal binocular vision. Head movement was restrained by a head support system. Subjects were divided into orthophoric, esophoric and exophoric groups based on their phoria in the primary position. Results: The orthophoric and esophoric subjects demonstrated small but insignificant increases in esophoria at secondary and tertiary positions of gaze. However, the changes for the exophoric subjects were significant and ranged from 0.34 prism dioptres less exophoria at right gaze to 2.61 prism dioptres less exophoria at down and left gaze. Conclusions: Significant gaze-related changes in phoria were obtained among exophoric subjects at non-primary positions of gaze. Possible explanations for this finding include horizontal and vertical muscle involvement and differences in perceived size of objects at non-primary positions. The results indicate the need to measure phoria at all major positions of gaze.