| Abstract |
PURPOSE
It is obvious that during recent years more and more teenagers and adults present refractive errors. The purpose of this study is to examine the hypothesis which indicates that accommodative defects (especially lag of accommodation) can become factors of myopiogenesis. In order to proceed a) we examined accommodative ability in school age children groups of different refractive status b) we examined the accommodative response in adults under physiological stimulus conditions and under pilocarpine’s effect.
METHODOLOGY
In the first part of the study 381 students were examined (elementary and high school), of 11 – 16 years old, who were emmetropes and low myopes (corrected or uncorrected). Visual acuity performance was tested with an EDTRS chart with habitual correction in place, and objective refractive measurements have been taken with an autorefractor and a COAS aberrometer. In 260 subjects we also measured the accommodative response of a -4,11D stimulus with a badal optometer along with high order aberrations recordings (the analysis referred to 3,5 mm pupil’s diameter).
In the second part, the accommodative response of six adults (23 – 36 years old, having dark pupils) were measured in two ways: (i) “physiologically” for an accommodative demand ranging from +0,84 to -8,05 and (ii) pharmacologically with installation of one drop of pilocarpine 4%. The dynamic recordings were conducted with 5 minutes intervals. Process of the data was done with MICROSOFT EXCEL, MATLAB and SPSS tools.
RESULTS
In the student group a small myopic shift (-0,48D for elementary school students and -1,00D for high school students) was confirmed. Although a high percentage of students reported visual acuity > 1,0, there is 1 out of 3 in elementary school and 1 out of 2 in high school children presenting visual acuity < 0,8. The mean lag of accommodation was found slightly higher especially in older females and among myopes (-1,48 D) as compared to emmetropes (-1,19 D) and astigmatic ones (-1,33 D). Spherical aberration was higher (0,04) for the myopic group compared with other refractive groups.
The study on the physiological accommodative response in adults confirmed an lag of accommodation response for high accommodative stimulus. The maximum response to a -8,05 D stimulus was found to be -5,44 D (average) while the spherical aberration was decreasing during the response (towards lower positive or even negative values). The accommodative response after pilocarpine’s installation, showed an increasing rate till reaching maximum state and a grading decrease later towards the starting point. Significant differences were noted among subjects concerning the maximum accommodative response (-2,65 D to -10,086 D) and time reaction too (37 to 85 minutes). Spherical aberration presented decreasing values at the beginning in all subjects until reaching half of the total accommodative amount (in 20 minutes more or less), while for higher accommodative response the aberration was presenting more positive values.
CONCLUSIONS
In total, 1 out of 3 children and 1 out of 2 teenagers has limited visual acuity (<0,8) in the classroom, with younger females tending to present statistically higher difference compared to older females and also between two sexes in older years. It has been statistically confirmed that emmetropes show higher accommodative responses than myopes. The lag of accommodation show differences between females in elementary and high school (males show no differences). This fact seems to be close related to bodily developmental changes from 13 to 16 years old. The increasing frequency of the myopic errors in teenagers is believed to depend on environmental factors such as close work, reading, computer use. It is also possible that lag of accommodation in school age children, may lead in increasing axial length which is an important factor in myopia development. A bigger sample group is needed to be tested in order to extract more stable results.
During “physiological” accommodation (target present), a linear correlation of accommodative demand and accommodative response was found, with simultaneous changes in spherical aberration towards more negative values when increasing demand. Under pilocarpine’s effect there are differences in maximum responses and time in which this takes place. Spherical aberration seemed to decrease towards negative values for small accommodative demands but reverse response for higher accommodative demands. No correlation was found between “physiologically” and “pharmaceutically” induced accommodation, which means that the use of pilocarpine is not reliable when trying to simulate physical accommodative response.
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Αξιολόγηση προσαρμοστικής ικανότητας σε παιδιά σχολικής ηλικίας και ενήλικες
