Inter-examiner repeatability of heterophoria tests.

Relatively few studies have reported on the repeatability of heterophoria (phoria) measurement procedures. The purpose of this study was to assess the inter-examiner repeatability of seven clinical tests of phoria measurement, using correlational and mean difference analyses. Two experienced optometrists performed each of the 7 phoria tests on 72 healthy adult subjects. Subjects ranged in age from 22 to 40 years, had visual acuity correctable to 20/20 in each eye, had no strabismus or amblyopia, and had normal eye health. The seven phoria tests used were: (1) the estimated cover test, (2) the prism-neutralized objective cover test, (3) the prism-neutralized cover test with subjective reporting of target movement, (4) the von Graefe phorometry with continuous target presentation, (5) the von Graefe phorometry with flashed target presentation, (6) the Thorington method, and (7) the modified Thorington method. All tests were performed in the same way by both examiners in random sequence, using standard clinical procedures. Inter-examiner correlations were determined for each test, as well as the mean and standard deviation of the differences between each examiner measurement (in prism diopters) on each subject. The modified Thorington method had the smallest mean difference and standard deviation of all tests and, thus, may be considered the most repeatable. This test also had the highest inter-examiner correlation. The prism-neutralized cover test with subjective reporting of target movement had the second highest correlation and the second lowest 95% limits of agreement, but had the largest mean difference of all tests. von Graefe phorometry methods were the least repeatable of the phoria tests.

Reliability of and comparisons among three variations of the alternating cover test.

One of the most commonly used methods for measuring heterophoria is the alternating cover test. Differences in specific procedures and observational criteria used by examiners may result in different measurements of heterophoria on the same patient. This study evaluated the inter-examiner reliability of three different cover test techniques: the estimated cover test, the prism neutralized objective cover test, and the prism neutralized subjective cover test. Two examiners performed each technique on each of 72 subjects. Reliability was assessed using correlational methods and mean difference calculations. Although there were some inter-examiner differences for the different techniques, all of these differences were within previously determined minimum detectable eye movement ranges. Therefore, when used by experienced clinicians, each of these techniques appears to be a reliable method of heterophoria determination, and their results are comparable.

Reliability of and comparisons among methods of measuring dissociated phoria.

Many methods of heterophoria measurement are available clinically. This paper reviews several studies which have examined the reliability of phoria measurements, and have compared various tests of phoria measurement. Different methods of data analysis make comparison of studies difficult. Two studies indicated 95% limits of agreement of 2 to 4 delta for reliability of modified Thorington, von Graefe, and Maddox rod phoria tests. Studies using correlational analysis to compare different measurement methods have found a high degree of association of the results of these methods. Studies using statistical methods assessing the agreement of test results found a high level of agreement among some tests and a low level of agreement among some tests. Some of the various phoria measurement methods differ in the technique used for dissociation, in the ability to control accommodation adequately, in the level of proximal convergence induced, or in the method by which the phoria is quantified. These differences can result in different phoria measurements on the same patient.

Ocular dimensions and refractive power in Malay and Melanesian children.

A cross-sectional study of 753 Melanesian children in Vanuatu and 904 Malay children in Malaysia included measurement of refractive error and ocular dimensions. All children were between the ages of 6 and 17 years. The prevalence of myopia in Malay children was 4.3% at 7-8 years and 25.6% at 15-16 years with corresponding figures of 0.8% and 4.3% for Melanesian children. The range of refractive error was greater for Malay children at all ages. Mean refractive error for Malay children showed greater hypermetropia, together with a shorter axial length at 6 years, than Melanesian children, but at 17 years the situation reversed and Malay children had more myopia and longer axial lengths than their Melanesian counterparts.