Distance stereotesting using vision test charts for intermittent exotropia

Abstract

PurposeTo assess the role of distance stereoacuity using the System Chart SC-1600 Pola (SC) to evaluate intermittent exotropia (IXT).MethodsStereoacuity testing was performed in 28 children with IXT and 25 age-matched control subjects using the SC test, the distance Randot stereotest for distance, and the Titmus stereotest for near stereoacuity. Ocular alignment control was defined using the revised Newcastle Control Score (NCS). The correlations between the stereotests and NCS were evaluated using Spearman’s correlation test.ResultsDistance stereoacuity was better in both groups when using the SC test than when using the distance Randot stereotest (median: patients with IXT, 90 arcsec and 400 arcsec; control, 60 arcsec and 100 arcsec; P<0.001 for both comparisons). The two test scores were not correlated in either group (IXT: rs=−0.003, P=0.99; control: rs=0.37, P=0.07). A positive correlation was found between the distance NCS and SC test scores (rs=0.49, P=0.004) and the total NCS and SC test scores (rs=0.49, P=0.004). However, no correlation was observed between any NCS and the distance Randot stereotest or Titmus stereotest scores.ConclusionStereoacuity, as measured by the SC test, may be an objective measure of IXT control.

Subnormal Binocular Contrast Sensitivity Summation in Patients with Intermittent Exotropia

“… 8 31 Previous studies revealed the relationship between control scale and stereoacuity in the patients with IXT. 5 10 32 In addition, Yulek et al 9 reported that significantly lower binocular summation in patients with IXT with higher control scoring (poor control state) using low-contrast acuity charts test, and they concluded decreased binocular summation was associated with less control in IXT patients. We also have similar results that binocular contrast sensitivity summation ratio have negative correlation with office-based control scale in the patients with IXT when low frequencies CST condition.…”

“… 2 3 Although stereoacuity testing is considered the standard method for clinically evaluating binocular vision of patients with IXT, there have been concerns about the usefulness of near stereoacuity because near stereoacuity is generally expected to be normal and it usually remains stable in patients with IXT, 4 5 whereas distance stereoacuity in patients with IXT varies depending on the characteristics of the test used. 6 7 There is increasing recognition of the importance of assessing control status in IXT, 8 which correlate to severity of XT and stereoacuity in the patients with IXT, 9 10 however there is no consensus regarding the best method by which to measure control in IXT patients. 11 As an alternative approach, binocular summation (the improved visual performance of binocular vision relative to monocular vision), as a measure of binocular vision may play an additional role in evaluating and monitoring of certain ocular diseases or conditions.…”

Effects of Target Size and Test Distance on Stereoacuity

“…Recently, not only the near stereoacuity test, but also the far stereoacuity test has been used widely in clinical ophthalmology [ 16 – 18 ]. There are many reports demonstrating that the far stereoacuity test is superior for detection of an abnormality (especially intermittent exotropia) versus the near stereoacuity test [ 17 , 19 – 24 ]. In addition, there is a report that stereoacuity, which the near stereoacuity test cannot detect, is detected by the far stereoacuity test [ 15 ].…”