An enhancement to the Maddox Wing test for the reliable measurement of horizontal heterophoria

PURPOSE: To attempt to improve the reliability of the Maddox Wing (MW) test for the measurement of horizontal heterophoria at near. METHODS: Horizontal heterophoria measurements at 30 cm using the MW instrument were made on a group of 58 normally-sighted binocular young adult subjects. The procedures were repeated at each of five weekly visits. The standard tangent scale card provided by the instrument's manufacturer was used as the control condition vs four alternative cards designed to enhance accommodative stimulation and improve operational reliability. RESULTS: A statistically-similar mean near phoria value was recorded using each of the five cards. However one of the alternative card designs produced a small but statistically significantly less variable result than the others: this design featured a much smaller typeface (4pt) than that used for the digits on the standard card, and the horizontal row of numbers was flanked by two periods of a low spatial frequency (< 2 c deg(-1)) square wave grating. CONCLUSIONS: It is suggested that for improved reliability of near phoria measurement when using the MW instrument a more appropriately detailed design of tangent card would promote enhanced accommodation, an operational consideration likely to be especially relevant when examining children.     

Comparison of subjective heterophoria testing with a phoropter and trial frame.

PURPOSE: Subjective measurement of the oculomotor deviation at both distance and near is a standard test in optometric practice. A number of procedures are available to the practitioner, and previous studies have demonstrated differences in the repeatability of many of the techniques. However, it is unclear whether testing the subject through a phoropter or in free space (trial frame) will alter the oculomotor deviation. METHODS: Distance and near heterophoria was measured in 60 visually normal subjects between 20 and 34 years of age using the Von Graefe (VG), Maddox Rod (MR), and Modified Thorington (MT) procedures. The deviation was assessed for viewing distances of 6 m and 0.40 m using both a phoropter and trial frame. To examine the repeatability of each technique, the deviation was measured on two separate occasions for each procedure, with the two sessions being separated by at least 24 hours. RESULTS: The mean vertical deviations at both distance and near were extremely close to orthophoria, and only minimal variation was observed. However, the MR procedure, when used with a trial frame, gave the best repeatability for measuring vertical deviations both at distance and near. Regarding horizontal deviations, the repeatability was better for all three procedures when using a trial frame compared with the phoropter. The best repeatability at distance and near was observed when the MT and MR techniques, respectively, were used with the trial frame. Consistent with previous reports, the VG procedure had poor repeatability, especially when used with the phoropter, and the mean findings showed a greater exo deviation when compared with the other two techniques. CONCLUSIONS: Testing oculomotor deviations in free space provides a more repeatable response than when using a phoropter. Accordingly, we recommend that subjective measurements of heterophoria in the clinical setting can best be quantified using either the MR or MT techniques in free space.     

Repeatability and agreement in the measurement of horizontal fusional vergences

PURPOSE: This study was designed to determine the repeatability of fusional vergence ranges measured using the rotary prisms in the phoropter and in free space using the prism bar. The level of agreement between the two methods was also investigated. METHODS: In two separate sessions, negative and positive fusional vergence ranges (NFV and PFV, respectively) were measured at distance and near in 61 young adults (mean age 19.74, S.D. 2.5 years) who were unfamiliar with the methods used. Base-in and base-out blur, break and recovery points were sequentially determined. Both sets of measurements were obtained by the same examiner. At each distance, NFV was determined first and then PFV. The repeatability of the tests and agreement between measurements made with the phoropter rotary prisms and the prism bar were estimated by the Bland and Altman method. RESULTS: For both the phoropter rotary prisms and prism bar, NFV measurements showed better repeatability than PFV at both near and distance. Mean differences recorded for the NFV break and recovery points were non-significant (under 0.5Delta), while those observed for PFV were generally greater than 2Delta. When agreement between the two tests was assessed, it was found that break points were higher when determined using the phoropter rotary prisms, while recovery points were generally higher for the prism bar method. In clinical terms, according to the expected values of the NFV and PFV, agreement between the two techniques can be described as fair, because although mean differences were never greater than 5.5Delta, 95% agreement intervals were as wide as +/-8.00Delta for NFV and +/-13.19Delta for PFV. CONCLUSIONS: The two methods used to measure fusional vergences showed fairly good inter-session repeatability for measuring NFV but repeatability was reduced for PFV measurements. The level of agreement observed between the two methods was such that their interchangeable use in clinical practice is not recommended.     

Vertical vergence adaptation does improve with practice.

PURPOSE: To investigate the effect of repeated testing on adaptation to a 2 Delta vertical prism in subjects with normal binocular single vision. METHODS: Subjects were required to have good visual acuity and normal binocular single vision. The residual deviation was measured after a 1-min period of adaptation to a 2 Delta vertical prism using a modified Maddox Rod technique. This measurement was repeated 10 times, with a 5-min rest period between each trial. RESULTS: For eight young adult subjects, the mean residual deviation at 1 min reduced with consecutive trials, and this effect was statistically significant (p < 0.0001). No significant correlation was present between the amplitude of vertical vergence and the increase in adaptation with repeated demand. CONCLUSIONS: A practice effect for vertical vergence adaptation appears to be present in young adult subjects with normal binocular single vision.     

Quantification of heterophoria and phoria adaptation using an automated objective system compared to clinical methods

Purpose:  To develop a system with which to quantify objectively the heterophoria to be measured throughout eye movement experiments. This study compared precision, resolution and accuracy characteristics of a limbus eye movement tracking system to the alternate cover test and the Maddox rod.
Methods:  Precision testing was performed using each technique with binocularly-normal subjects at different test sessions. Resolution was measured and compared between the three systems. The heterophoria or phoria was measured from 40 cm/16 inches objectively with the limbus eye movement system and the Maddox rod during a sustained convergence-induced phoria adaptation experiment using physical and haploscope visual targets to compare accuracy.
Results:  Precision testing quantified that the responses objectively recorded using the limbus tracking system exhibited similar standard deviations to the Maddox rod and the alternate cover test techniques. The limbus tracking method has the ability to quantify the response decay to phoria and has better resolution when compared to the clinical methods. When physical targets were used to induce phoria adaptation, the correlation was significant between the limbus eye movement tracking system and the Maddox rod after near and far adaptation, where the Maddox rod measurements were slightly more esophoric compared to those measured with the limbus tracking system.
Conclusion:  This objective limbus tracking system offers a better means by which to study the phoria and its adaptation throughout an eye movement experiment. The broader aim of this research is to establish a tool that will further the basic science of oculomotor control and binocular dysfunctions.     

Interexaminer repeatability of a new, modified prentice card compared with established phoria tests.

PURPOSE: The Howell phoria card, a new modification of the Prentice design, has no previously published validity or reliability data. The purpose of this study was to compare the interexaminer repeatability of the Howell phoria card with established tests. METHOD: Experienced optometrists measured the near heterophoria of 72 subjects. Heterophoria was measured in a pseudo-random order using five standardized procedures: (1) Howell phoria card continuous presentation, (2) Howell phoria card flashed presentation, (3) free-space von Graefe method, 4) Bernell Muscle Imbalance Measure (MIM) card continuous presentation, and (5) MIM card flashed presentation. RESULTS: The von Graefe method and the Howell phoria card flashed presentation found significantly less exophoric results than the MIM card. There was no consistent tendency for different examiners to find more exo- or more esophoric results with the phoria measurement techniques used in this study (p = 0.28). Both the Howell phoria card continuous presentation and the MIM card had significantly less variability in interexaminer differences than the Howell phoria card flashed presentation and the von Graefe method (p < 0.05). CONCLUSIONS: Results from this study suggest that the Howell phoria card used in a continuous presentation method has an interexaminer repeatability that is not significantly different from the MIM card but greater than the von Graefe method.     

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.     

Near esophoria is associated with high myopia

Background : A retrospective study was undertaken to examine the hypothesis that esophoria is associated with higher amounts of myopia. Methods : One hundred and forty‐four subjects were selected from the files of optometry clinics at the Department of Optometry, National University of Malaysia, from the years 1995 to 1998 inclusive. These subjects were matched in terms of age group, sex, race and near phoria group. Near phorias were determined by Maddox wing technique and were classified into three groups: more than six prism dioptres exophoria, zero to six prism dioptres exophoria and any esophorias. Results : One way analysis of variance revealed that there were significant differences in mean myopias between the three phoria groups (ANOVA, F(2,141) = 5.34, p < 0.01). Further analysis with the Student‐Newman‐Keuls test showed that the amount of myopia is significantly higher in the esophoric group than in the other two groups. Conclusions : The results support the hypothesis that near esophoria is associated with high myopia. This study suggests that near phoria might be an important factor in myopia development.     

Changes in accommodative and vergence responses when viewing through near addition lenses.

It has been proposed that near addition lenses reduce the lag of accommodation and may slow myopia progression. In this study, we investigated the differences in accommodative response and near phoria in subjects with and without near addition lenses. Fourteen subjects (7 emmetropic and 7 myopic) participated in the study. Monocular and binocular accommodative responses to a target at 40 cm were measured with and without +2.00 diopter (D) lenses using a Canon R-1 optometer (Canon Europe N.V., Amsterdam, The Netherlands). Near dissociated phoria was measured using 3 testing methods: Maddox rod, cover test, and Von Graefe technique. The differences in accommodative response and near phoria between the 2 viewing conditions with and without the near addition lens were significant (P < 0.0001). No significant differences were revealed in accommodative response and near phoria between refractive error groups. The average accommodative responses of all subjects were 2.03 +/- 0.06 (SE) D (without +2.00 D lens) and 0.60 +/- 0.07 D (with +2.00 D lens) under monocular viewing conditions and 2.11 +/- 0.06 D (without +2.00 D lenses) and 0.77 +/- 0.07 D (with +2.00 D lenses) under binocular viewing conditions. The average near phorias of all subjects were -2.08 +/- 0.69 prism diopters (PD, without +2.00 D lenses) and -7.90 +/- 0.68 PD (with +2.00 D lenses). We discuss the effect of near addition lenses on the defocus of the retinal image, accommodative response, and near phoria. In addition, we propose that the observed difference between binocular and monocular accommodation, when viewing through near addition lenses, is caused by an increased vergence accommodation.     

The influence of heterophoria measurements on subsequent associated phoria measurement in a refractive routine

The influence of measuring heterophoria on a subsequent associated phoria measurement was investigated in 50 subjects. After refraction, heterophoria was measured by either von Graefe's technique or Maddox rod and wing. The effect of these procedures was assessed by associated phoria measurements taken before and after the dissociated measures. It is shown that subjects with a history of unstable binocular vision are likely to have an associate phoria induced or changed by the previous dissociated phoria measurement, particularly if von Graefe's technique is employed. It is recommended that, especially for near, associated phoria should be assessed before the dissociated phoria in subjects who are regarded as having a history of unstable binocular vision.     

Convergence Insufficiency Neuro-Mechanism Adult Population Study: Phoria Adaptation Results

PurposeThe purpose of this study was to compare changes in phoria adaptation between young adult binocularly normal controls (BNCs) and participants with symptomatic convergence insufficiency (CI), who were randomized to either office-based vergence accommodative therapy (OBVAT) or office-based placebo therapy (OBPT).MethodsIn the double-masked randomized clinical trial, 50 BNC and 50 CI participants were randomized to the following therapeutic interventions: OBVAT or OBPT with home reinforcement for 12 one-hour office sessions. A 6∆ base-out and 6∆ base-in phoria adaptation experiment at near (40 cm) was conducted using the flashed Maddox rod technique at baseline and at outcome. Measurements included the rate and the magnitude of phoria adaptation.ResultsAt baseline, BNC and CI participants had significantly different rates and magnitudes of base-in and base-out phoria adaptation (P < 0.001). When comparing the outcome to baseline measurements, significant main effect differences in longitudinal measurements were observed for the magnitude and the rate of phoria adaptation for both base-out and base-in experiments (P < 0.05). For the magnitude and rate of phoria adaptation, post hoc analyses using paired t-tests revealed that the CI group administered the OBVAT intervention exhibited a significant increase in the magnitude and rate of phoria adaptation compared to baseline for both base-in and base-out phoria adaptation (P < 0.01) but not for those administered OBPT.ConclusionsPhoria adaptation is significantly different at baseline between those with normal binocular vision and symptomatic CI participants. OBVAT significantly improves the rate and magnitude of both base-out and base-in phoria adaptation at near compared to OBPT. Results have clinical implications for new therapeutic interventions.     

Refractive errors and binocular dysfunctions in a population of university students

PURPOSE: This clinical study was performed to determine the presence of refractive errors and binocular dysfunctions in a population of university students. METHODS: Refraction and binocular function were evaluated in a young patient population (230 students and 234 nonstudent subjects, aged 18-27 years). Distance visual acuity (DVA) and near visual acuity (NVA), refraction, cover test (CT), ocular motility, near-point of convergence, horizontal phoria measurement by Maddox wing, negative and positive vergence amplitude in prism diopters, fusion amplitude in synoptophore, as well as stereoacuity (Titmus test) were tested. RESULTS: Emmetropia was the most frequent refractive status in our student and nonstudent groups (78.7%). Myopia was the most frequent refractive disorder in the whole population (13.1%). Myopia and hypermetropia were significantly more frequent in the students than in nonstudents (chi-square emp 47.55). Exophoria is significantly more frequent in myopic subjects. Vergence amplitude (t test 0.000) and fusion amplitude (t test 0.005) show significantly lower values in student population. Results of Titmus test in the student group is significantly worse than in the nonstudent group (t test 0.000). Maddox wing resulted in significantly higher degree of heterophoria in the student population (t test 0.000). Myopic subjects, in the student group (t test 0.002) as well as in the nonstudent group (t test 0.001), show significantly better results in Titmus test. CONCLUSIONS: High near visual demand could be the most important factor for higher incidence of myopia, worse convergence and fusion amplitude, higher degree of exophoria, and worse results in Titmus test in the student population.     

Clinical predictors of the optimal spectacle correction for comfort performing desktop tasks

Background: The best strategy for spectacle correction of presbyopia for near tasks has not been determined. Methods: Thirty volunteers over the age of 40 years were tested for subjective accommodative amplitude, pupillary size, fusional vergence, interpupillary distance, arm length, preferred working distance, near and far visual acuity and preferred reading correction in the phoropter and trial frames. Subjects performed near tasks (reading, writing and counting change) using various spectacle correction strengths. Predictors of the correction maximising near task comfort were determined by multivariable linear regression. Results: The mean age was 54.9 years (range 43 to 71) and 40 per cent had diabetes. Significant predictors of the most comfortable addition in univariate analyses were age (p < 0.001), interpupillary distance (p = 0.02), fusional vergence amplitude (p = 0.02), distance visual acuity in the worse eye (p = 0.01), vision at 40 cm in the worse eye with distance correction (p = 0.01), duration of diabetes (p = 0.01), and the preferred correction to read at 40 cm with the phoropter (p = 0.002) or trial frames (p < 0.001). Target distance selected wearing trial frames (in dioptres), arm length, and accommodative amplitude were not significant predictors (p > 0.15). The preferred addition wearing trial frames holding a reading target at a distance selected by the patient was the only independent predictor. Excluding this variable, distance visual acuity was predictive independent of age or near vision wearing distance correction. The distance selected for task performance was predicted by vision wearing distance correction at near and at distance. Conclusions: Multivariable linear regression can be used to generate tables based on distance visual acuity and age or near vision wearing distance correction to determine tentative near spectacle addition. Final spectacle correction for desktop tasks can be estimated by subjective refraction with trial frames.     

Vertical heterophoria and susceptibility to visually induced motion sickness

Motion sickness is reported to be a common symptom in patients with vertical heterophoria. The goal of this study was to assess the relationship between vertical phoria and susceptibility to motion sickness in a nonclinical sample of 43 subjects. Vertical phoria was measured with a Maddox rod after 30 s of occlusion. To evaluate susceptibility to motion sickness, subjects read text while sitting inside a rotating optokinetic drum for 10 min. Subjects rated their level of motion sickness at 1 min intervals during drum rotation and the magnitude of 13 motion sickness symptoms after drum rotation ended. The magnitude of vertical phoria ranged from 0 to 2.13 prism diopters (pd) with a mean of 0.46 pd and correlated significantly with both the maximum rating of motion sickness during drum rotation and the summed symptom score following rotation. A vertical phoria of 0.75 pd discriminated best between subjects with low vs high summed motion sickness symptom scores (p < 0.0001). Introducing a prism to artificially increase the phoria of 12 subjects with vertical phorias <0.75 pd increased motion sickness symptoms in only 1 subject. Prisms that reduced the phoria of subjects with vertical phorias > 0.75 pd reduced motion sickness symptoms in 2 of the 4 subjects tested. The results confirm an association between vertical phoria and motion sickness, but suggest the relationship may not be causal.     

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.     

Normative data for modified Thorington phorias and prism bar vergences from the Benton-IU study.

BACKGROUND: The use of a phoropter for measuring phorias and vergences in children is common in the optometric profession. For young children, the use of the phoropter can be confusing, making it difficult to obtain accurate measurements. Free space testing allows for direct observation of the eyes in a natural environment and is easier for children to understand the directions. The normal values for phorias and vergences used with children are derived from testing with a phoropter or free space measurements with mostly adult patients. METHODS: The Benton-IU Project was a large multidisciplinary study of factors affecting school performance conducted by the Indiana University School of Optometry and the Indiana University Department of Speech and Hearing with the cooperation of the Benton Community School Corporation (Benton County, Indiana). This project allowed the authors to obtain data on modified Thorington phorias and prism bar vergences from a nonselected group of first and fourth graders as part of an eye/vision examination. RESULTS: In this report, central tendency and variability statistics for modified Thorington and prism bar vergences are reported based on the data from the Benton-IU Study. CONCLUSION: The data presented in this report can be used by optometrists when deciding if the patient's phorias and vergences are within normal limits for children in the first through fourth grades.     

An esophoric shift associated with sustained fixation

Some subjects show a progressive increase in their near phoria, in the direction of more esophoria, when the test is repeated. Eighteen of 100 subjects showed 5 delta or more esophoric shift. This result suggests that similar phoria changes may occur during prolonged intensive nearwork. The results reported are not the same as prism adaptation because the esophoric shift was found with dissociated targets. Autonomic arousal with sympathetic activation associated with heightened attention and concentration is proposed as the mechanism.     

Nearpoint phoria changes associated with the cessation of childhood myopia progression

BACKGROUND: A convergent (eso) shift in near phoria associated with the onset of myopia has been reported. METHODS: Data from two Midwestern United States optometry practices were used to assess whether the near phoria shifted back in the divergent (exo) direction after the cessation of childhood myopia progression. Data were collected for myopic children who had three or more examinations before the age of 15 years and at least one examination after the age of 17 years. RESULTS: Refractive error data were used to calculate an index of the age of cessation of childhood myopia progression. The phoria at the first examination after the cessation age was designated as the baseline and was normalized to zero. For all previous and subsequent examinations, the changes in phoria with respect to the baseline phoria were calculated. The phoria at the examination just after the cessation age was significantly more divergent than those at the first, third, and fourth examinations prior to the cessation age (1.1, 1.4, and 1.7 prism diopters, respectively). The third visit after the cessation age was 1.8 prism diopters more divergent than the first visit after the cessation age. Thus, these data showed an exo shift in near phoria after the cessation of childhood myopia progression.     

急性共同性内斜视III型的临床特点及三棱镜矫正效果观察

目的：分析三棱镜矫正的急性共同性内斜视（AACE）III型患者的临床特点及三棱镜矫正后三级视功能变化、稳定性及满意度。方法：自身对照研究。AACE III型所引起复视并进行棱镜矫正患者27例,初次戴棱镜时分别予以马氏杆、同视机、Von Graefe棱镜分离行斜视度检查;同时行同视机融合范围测量;给患者试戴棱镜,以复视消除、无不适的处方量作为棱镜最终处方量。随访时间2个月～2 （0.7±0.5）年,再次测量患者各指标。分析戴棱镜前后各数值的变化量,并进行满意度调查。采用配对t检验对数据进行分析。结果：Von Graefe棱镜分离法看远、看近斜视度分别为16.9△±7.0△、 15.1△±7.5△;马氏杆测量看远、看近斜视度分别为22.6△±8.5△,16.3△±9.0△;同视机看远斜视度 为18.0△±8.2△;同视机测量融合范围25.4°±8.8°;处方量6.4△±3.0△。看远棱镜分离斜视度、看近棱镜分离斜视度在配戴三棱镜前后差异无统计学意义（t=0.266,P=0.792;t=0.731,P=0.471）;看远马氏杆斜视度、看近马氏杆斜视度配戴三棱镜前后差异无统计学意义（t=-0.040,P=0.969;t=-0.587,P=0.562）;看远同视机斜视度配戴三棱镜前后差异无统计学意义（t=-0.523,P=0.606）;融合范围配戴三棱镜前后差异无统计学意义（t=-1.210,P=0.237）;棱镜处方量配戴三棱镜前后差异无统计学意义（t=0.000,P=1.000）。患者戴三棱镜前后均存在立体视,无明显变化。戴镜后患者复视消失,对配戴棱镜效果主观评价满意占11%,非常满意占89%。结论：AACE III型具有发病年龄范围广、斜视度范围较大、伴有同侧复视、看远斜视度大于看近斜视度、融合功能和潜在的立体视功能的临床特点。三棱镜矫正是能消除复视,使患者有较好的满意度,不会对斜视程度、融合范围、立体视产生影响。