| Author: | Pang, Chi-kong Peter |
| Title: | The developmental eye movement test and its application to Cantonese-speaking children |
| Degree: | M.Phil. |
| Year: | 2004 |
| Subject: | Hong Kong Polytechnic University -- Dissertations Eye -- Movements -- Testing Eye -- Diseases -- Age factors Eye -- Movement disorders -- China -- Hong Kong |
| Department: | Department of Optometry and Radiography |
| Pages: | xxvii, 208 leaves : ill. ; 30 cm |
| Language: | English |
| Abstract: | Purpose The developmental eye movement (DEM) test is a visuo-verbal test to determine problems of saccadic eye movements and automaticity in children. Studies have reported that an early diagnosis of problems in saccadic eye movements in children may be remedied by vision training exercises to improve reading skills. However, the DEM test relies heavily on the administrator's subjective judgement in the measurement and quantitative analysis of the raw score. Is there any way to improve the repeatability of scoring the DEM test? The DEM test is a standardized test and the test results should be compared with the given norms, which were derived from English-speaking children. To our best knowledge, there are no norms for languages other than English and Spanish. We do not know whether these norms are suitable for Cantonese-speaking children in Hong Kong. Furthermore, there has been argument as to whether reading disability, which is associated with poor eye movement quality, is related to various visual functions. We would like to know if there are any differences in visual functions among different types of children (normal, saccadic eye movement dysfunction and automaticity dysfunction) as diagnosed by the DEM test. In this study, our first objective is to investigate possible objective ways to improve the repeatability of the measurements of this test, regardless of whether the administrator is experienced or not. Our second objective is to investigate whether the given DEM norms are suitable to Cantonese-speaking children. We will compare the mean of the DEM scores of a group of Cantonese-speaking children aged 6 to 11 years with the existing norms in English and Spanish. Our third objective is to ascertain whether there are any differences in visual skills among the children aged 6 to 8 years with different problems as diagnosed from the DEM scores. Method In the evaluation of the accuracy of the DEM scores, five voice clips were prepared by recording the voices of five children aged 6 to 8 years during a DEM test. Each contained different combinations of reading times and errors. These voice clips were presented to ten DEM administrators. Five of the administrators were experienced in using the DEM test and the other five were naive to the test. Prior training was provided to the naive administrators. The administrators were requested to record the reading times and errors from each voice clip. Then the adjusted vertical and horizontal times for each measure were calculated. The differences from pre-set or expected values of the adjusted vertical and horizontal times from these two groups of administrators were compared. Next, an investigator repeated the measurement of the reading time from ten pre-recorded voice clips of a DEM test. The single, mean of two, mean of three, mean of four and mean of five measurements were compared. In the investigation for the suitability of the DEM norms for Cantonese children, 347 Cantonese-speaking children aged from 6 to 11 years were recruited. A letter describing the study was sent to the principals of 5 primary schools. Information about the study and consent forms were then sent to the parents of the students via the teachers. The children in this study were matched in age-to-grade factor with the original norms (English population study) of the DEM test. The DEM test was administrated individually to each child in a quiet room in the school. The procedures and inclusion criteria followed those in the test manual. A digital recording was made of the voice of the child during the test. The reading times and reading errors in each subtest were recorded and averaged by the investigator, who listened to the voice clips twice after the test. The reading times in both the vertical and horizontal tests were adjusted according to a formula, in which the factors of omission and addition errors were included. A ratio was determined where the adjusted horizontal time was divided by the adjusted vertical time. The mean of the adjusted vertical time and the adjusted horizontal time from boys and girls were compared. The means of each DEM score were compared with the published norms (English and Spanish). The prevalence of automaticity and saccadic eye movement dysfunction in our samples were derived. In the study of the relationship between the DEM test and visual functions, a subgroup of children aged 6 to 8 years (from the above population) were recruited for further visual function assessments. The same investigator measured the following visual functions for each child. Habitual distance and near vision, retinoscopic refraction, near phoria test by Maddox Wing, gradient AC/A (using +1.00 with Maddox Wing), positive fusional amplitude, stereoacuity (using the Randots stereo test), amplitude of accommodation (using the push-up method), accommodative facility (using +1/2.00 flipper at 40 cm) and lag of accommodation (using the MEM at 40 cm) were determined. These children were grouped according to their DEM scores into the four types of diagnosis. The visual functions among different types of diagnosis were compared. This study followed the tenets of the Declaration of Helsinki and informed assent was obtained from the parents of the participants. Results In the repeatability of scoring of the DEM test, all administrators recorded a difference of one second or more from the expected values in each voice clip. There was a significant difference in the mean of the differences in the adjusted vertical time (t-test; p < 0.05) from the pre-set values between the experienced and inexperienced DEM administrators. These results suggest that using the conventional method of assessing DEM test, the test administrators are very likely to make errors regardless of whether they are experienced or not. In addition, the mean of two repeated measurements of the reading time in the DEM test falls within 0.5 seconds of the mean-of-five measurement. It is highly advised that an audio recording be made of the voice of the child and that this be assessed at least twice for an accurate determination of the DEM scores. Three hundred and five children were included in this study. There was no difference in the adjusted vertical and horizontal times between boys and girls in our study. In both vertical and horizontal subtests, the Cantonese-speaking children completed the tests much faster than their English-speaking or Spanish-speaking counterparts in all group groups from 6 to 11 years. The differences of the means of the reading time were statistically significant (unpaired t-test; p< 0.01) in all these age groups. The mean horizontal errors made by the Cantonese-speaking children were similar to the English norms except that the Cantonese-speaking children in age groups of 6 made fewer horizontal errors than their English counterparts. The mean ratios were similar amongst different populations. The results suggested that the published DEM norms in English and Spanish were not suitable to use in Cantonese-speaking population. Hence, Cantonese norms of the DEM test were proposed for verification and adoption. The prevalence of saccadic eye movements and automaticity dysfunction in our samples (ages between 6 and 11) were 4.3% and 6.9% respectively. There was a trend towards increasing prevalence of "automaticity dysfunction" across age. In a group of 108 children aged 6 to 8 years, the children were classified into the four diagnostic types according to the DEM scores. As there were too few cases in the Type IV, only Types I, II and III were included for data analysis. As a result, there were significant differences (one-way ANOVA, p < 0.01) in the means of lag of accommodation among these Type I (normal), H (saccadic eye movement dysfunction) and III (automaticity dysfunction) children. Children with automaticity dysfunction (Type III) had a relatively higher lag of accommodation (+1.20 +-0.19 D). Conclusion The conventional method as suggested in the manual for recording the DEM test scores is not sufficiently accurate. With our findings we established a more objective procedures for the DEM test. We suggest recording the response from the child during the DEM test and this allows re-listening to and reassessment of the data. The recorded time should be measured twice to obtain the mean to ensure good repeatability. We believe that using this method for the DEM test will permit the clinicians to obtain more accurate results and thus reduce the chance of false positive or false negative findings or an incorrect diagnosis. We found significant differences in the DEM scores amongst Cantonese, English and Spanish-speaking populations with matched ages. It is very important to obtain normal values for a particular population to minimize the bias caused by other factors such as languages or education. We established the norms for the Cantonese-speaking children in Hong Kong. Our norms will be communicated to the Department of Health, Department of Education and other clinicians who frequently use the DEM test for adoption and verification. We also established the prevalence of automaticity and saccadic eye movement problems in this population. The prevalence of automaticity dysfunction in our sample is quite high and this figure is alarming. Further investigation into confirming the diagnosis and treatment for this group of children may enhance the referral criteria. There is an association between lag of accommodation and automaticity dysfunction. Further investigation is yet to confirm the validity of our findings. The DEM test is a fast and simple test of saccadic eye movements and automaticity. The norms of the DEM test are language dependent. Therefore, appropriate norms of individual languages should be used if an administrator wants to provide an accurate result and diagnosis for the children. The Cantonese norms of the DEM test are proposed for further verification. |
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| Access: | open access |
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