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Correlation Between Worth Four Dot Test Results and Fusional Control in Intermittent Exotropia

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Correlation Between Worth Four Dot Test Results and Fusional Control in Intermittent Exotropia Original Article Correlation between Worth Four Dot Test Results and Fusional Control in Intermittent Exotropia Mohammad Etezad Razavi1, MD; Marzieh Najaran1, MS; Raheleh Moravvej1, MS Mohammad-Reza Ansari Astaneh1, MD; Abbas Azimi2, PhD 1Eye Research Center, Khatam-al-Anbia Hospital, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran 2Faculty of Optometry, Paramedical School, Mashhad University of Medical Sciences, Mashhad, Iran Purpose: To compare the results of Worth 4-dot test (WFDT) performed in dark and light, and at different distances, with fusional control in patients with intermittent exotropia (IXT). Methods: Dark and light WFDT was performed for new IXT subjects at different distances and the results were compared with level of office-based fusional control. Results: Fifty IXT patients including 17 male and 33 female subjects participated in the study. A significant difference (P<0.05) was observed between levels of home and office-based fusional control (P<0.05). A weak correlation was present between the results of WFDT and level of office-based fusional control; the highest agreement (Kappa=0.088) was observed with dark WFDT performed at a distance of 4m. Conclusion: Evaluation of fusional state by far WFDT, especially in a dark room, shows modest correlation with office-based fusional control in IXT patients and can be used as an adjunct to more complex tests such as far stereoacuity. Keywords: Intermittent Exotropia; Fusion; Worth Four Dot Test J Ophthalmic Vis Res 2012; 7 (2): 134-138. Correspondence to: Mohammad Etezad Razavi, MD. Associate Professor of Ophthalmology, Eye Research Center, Khatam-al-Anbia Hospital, Gharenai Blvd., Mashhad 919 59, Iran; Tel: +98 511 7281401, Fax: +98 511 7245363; e-mail: [email protected] Received: February 10, 2011 Accepted: December 27, 2011 improves following surgery. Hence deterioration INTRODUCTION in distance stereoacuity has been considered as Exotropia is a manifest outward ocular deviation an objective measure of IXT severity and used which occurs in 1 to 2% of the pediatric as a means to evaluate the need for surgery.5-10 population; intermittent exotropia (IXT) is the Different instruments have been employed for most common form of childhood exotropia.1 measuring distance stereoacuity in IXT patients Non-surgical treatments for this condition but most of them are out of production and no include orthoptic eye exercises, part time longer widely available; the Baylor visual acuity occlusion, minus lens therapy, and prisms.2-4 tester (BVAT) and the binocular vision testing There is no consensus on a definite method system (Mentor O&O, Norwell, MA, USA) for to specify optimal timing for therapy in IXT instance, are currently unavailable. patients. Conventionally, intervention has been Some studies on the other hand, do not recommended when the deviation becomes recommend employing distance stereoacuity clearly noticeable at home or in the office. thresholds; Holmes et al7 demonstrated that Previous studies on distance stereoacuity measurable distance stereoacuity thresholds in IXT cases have suggested that this parameter in IXT are highly dependent on the type 134 JOURNAL OF OPHTHALMIC AND VISION RESEARCH 2012; Vol. 7, No. 2 Worth Four Dot Test in XT; Etezad Razavi et al of employed tests. Furthermore, isolated child is observed for distance viewing), and measurements of stereoacuity cannot be relied poor (squint/monocular eye closure seen at upon as an indicator for IXT severity or its distance and near fixation). Office-based fusional alterations over time when one needs to decide control was based on the outline suggested by for an appropriate time for intervention.11 Rosenbaum and Santiago12 and categorized as Central suppression occurs prior to loss of good (deviation becomes manifest only after distance stereoacuity in IXT patients.13 The worth cover test and fusion resumes without need 4-dot test (WFDT) evaluates binocular fusion for blinking or refixation), fair (blinking or and can be performed in different sizes and refixation is required to control the deviation at variable distances. Darkness can overcome after cover test), and bad (deviation is manifest peripheral fusion and far distance testing can spontaneously or any form of disruption of better evaluate central suppression. fusion without recovery). In the current study, we compared the Before disruption of fusion by cover testing, results of dark and light WFDT performed at WFDT was performed using 1 red, 2 green and variable distances with the level of office-based 1 white flashlight dots at different distances of fusional control in patients with IXT. We aimed 15cm, 33cm, 50cm and 1, 4 and 6m with the to introduce an easy-to-use and objective method WFDT box under light and dark conditions. To for evaluating patients with IXT. evaluate the correlation between WFDT results and office-based assessment of fusional control, WFDT results were classified into three groups: METHODS fusion, suppression and alternate suppression/ Fifty new consecutive IXT patients with no diplopia. history of surgical or non-surgical therapy who Kappa coefficient, Kendall Tau test and had been referred to the strabismus clinic at paired t-test were used to measure the correlation Khatam-al-Anbia hospital were enrolled for between the aforementioned groups, evaluate the purpose of the study. All cases had basic differences between home and office-based type intermittent exotropia (no more than 10 fusional control levels, and assess differences in prism diopter [PD] difference between far and the amount of deviation measured by different near deviation) with various levels of fusional methods, respectively. All measurements were control. Only cooperative patients were enrolled; performed by the same trained optometrist. other inclusion criteria included uncorrected visual acuity (UCVA) of at least 0.7 (decimal RESULTS notation) in both eyes, and no more than two lines of difference in visual acuity and less Fifty consecutive patients with IXT including 17 than 2 diopters (D) of anisometropia based on male and 33 female subjects with mean age of cycloplegic refraction. Informed consent was 12.5±3.2 years were enrolled; 28 subjects were obtained from the patients or their guardians 4 to 10 years of age and the rest were older after explaining the study and its goals. than 10 years. Table 1 displays the angle of The amount of ocular deviation was deviation in the study participants. The amount measured with an accommodating target at far of far deviation increased significantly after (6m) and near (33cm) with a +3.00 lens, and after occlusion of one eye for 30 minutes (P<0.001). occlusion of one eye for 30 minutes. Fusional Near deviation also increased significantly control was assessed utilizing subjective (home after the occlusion test, and following the use control) and objective (office-based control) of a +3 lens (P<0.001). A significant difference criteria. Home control was categorized as (P<0.05) was observed between the results excellent or good (squint/monocular eye closure of home and office-based assessment of seen <50% of the time when the child is observed fusional control (Table 2). Figure 1 displays for distance viewing), fair (squint/monocular the correlation between dark and light WFDT eye closure seen >50% of the time when the performed at different distances with the JOURNAL OF OPHTHALMIC AND VISION RESEARCH 2012; Vol. 7, No. 2 135 Worth Four Dot Test in XT; Etezad Razavi et al Table 1. Amount of deviation in different clinical situations Far deviation Near deviation Far deviation Near deviation With +3D lens after occlusion after occlusion Number 50 50 46 50 27 Missing 0 0 4 0 23 Mean (∆D) 23.8 26.2 19.15 24.74 27.59 S.D (∆D) 7.632 9.353 8.162 9.262 11.219 Min (∆D) 10 12 0 6 10 Max (∆D) 45 50 40 50 50 ∆D, prism diopter; Missing, missed data; SD, standard deviation; Min, minimum deviation; Max, maximum deviation Table 2. Results of home and office-based fusional control Office Control Total Poor Fair Good Number 9 2 0 11 Poor Percent 18.00% 4.00% 0.00% 22.00% Number 7 7 0 14 Home Control Fair Percent 14.00% 14.00% 0.00% 28.00% Number 14 7 4 25 Good & Excellent Percent 28.00% 14.00% 8.00% 50.00% Number 30 16 4 50 Total Percent 60.00% 32.00% 8.00% 100% Figure 1. Correlation between office-based fusional control and dark and light WFDT results at different distances. results of office-based fusional control; a weak DISCUSSION correlation was noted between the results of WFDT and that of office-based fusional control As demonstrated by Guyton, central suppression (kappa=0.001 to 0.088). Kappa coefficient was occurs before significant loss of distance higher in dark than light at almost all distances; stereoacuity; some patients who elicit distance the highest kappa coefficient belonged to stereoacuity on the vectographic contour circle dark WFDT performed at a distance of 4m test demonstrate a suppression scotoma.13 This (kappa=0.088). theory was the rationale behind choosing WFDT 136 JOURNAL OF OPHTHALMIC AND VISION RESEARCH 2012; Vol. 7, No. 2 Worth Four Dot Test in XT; Etezad Razavi et al for evaluating binocular fusion in IXT patients In summary we may conclude that dark in the current study. WFDT at a distance of 4m can be used along Stimulus angle for the WFDT flashlight with reliable tests such as far stereoacuity and at different distances from the subject were: office-based control levels as a readily available 6 degrees at 33cm, 4 degrees at 50cm, and 2 test for evaluation of fusional control in IXT degrees at 100cm. The distance WFDT subtends patients. Since far stereoacuity tests are not 1.25 degrees at 6 meters and slightly more at 4 widely available and surgeons cannot rely on meters.
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