A total of 1638 boys and 1998 girls (3636 in all) aged 6−18 (mean age 12.1, SD 3.4) were examined. The examined children, students of elementary and secondary schools, were examined in the school’s consulting rooms. All the children in the selected schools were asked to participate
in the study. the examined students were caucasian and were residents of szczecin, Poland and neighboring areas.
Most of the children participated in the previous investi-gations [4] however, in this paper a group of persons with anisometropia was selected.
Participation was voluntary and informed consent was obtained from the school principals and parents of all the students. The studies were approved by the Bioethics committee of the Pomeranian medical University.
The examination included skiascopy after cycloplegia.
Cycloplegia was administered with two drops of 1% tropi-camide instilled 5 minutes apart. Thirty minutes after the last drop, skiascopy was performed.
Myopia was defined as a refractive error < -0.5 D, hyperopia as a refractive error > +1.5 d, astigmatism as a refractive error > 0.5 DC. Anisometropia was diagnosed when the difference in the refraction of both eyes was
> 1.0 d.
The parents of all the students examined completed a questionnaire on the child’s light exposure before the age of two. The questionnaire was written in the Polish language. The questions asked whether the child before the age of two slept at night in darkness or with light turned on. Other questions asked what type of artificial light was used in the living room, dining room, child’s room, parents’
bedroom, kitchen, and bathroom.
The study group involved persons with emmetropia, myopia, hyperopia, astigmatism, and anisometropia. Stu-dents with other eye diseases were excluded from statisti-cal analysis. The data were analyzed statististatisti-cally using χ2 test. P values of less than 0.05 were considered statistically significant.
results
It was observed that sleeping until the age of two in a room with a light turned on is associated with an increase in the occurrence of anisometropia (p < 0.02) as well as with a reduction in the prevalence of emmetropia (p < 0.05) (Tab. 1).
It was also found that the use of fluorescent lamps in the parents’ bedroom is associated with an increase in the oc-currence of astigmatism (p < 0.01), while fluorescent lamp
t a b l e 1. Prevalence of refractive errors in relation to the type of night lighting used during the first two years of life. Shown are percentages and numbers (in parentheses) of students
t a b e l a 1. Częstość występowania wad refrakcji w zależności od typu używanego w pierwszych dwóch latach życia oświetlenia w nocy.
W nawiasach obok procentów podano ilość uczniów Type of night lights /
Typ oświetlenia w nocy
Patients / Pacjenci emmetropic /
emetropijni myopic /
krótkowzroczni hyperopic /
nadwzroczni astigmatic /
z niezbornością anisometropic / różnowzroczni
No light / Bez światła 66 (1910) 15 (426) 11 (319) 4 (131) 5 (119)
Light / Światło 62 (452) p < 0.05 16 (113) p < 0.58 12 (91) p < 0.26 4 (31) p < 0.75 6 (44) p < 0.02
incandescent / żarowe 63 (380) 15 (92) 13 (79) 4 (22) 5 (32)
fluorescent / fluorescencyjne 57 (72) p < 0.23 17 (21) p < 0.68 10 (12) p < 0.27 7 (9) p < 0.07 9 (12) p < 0.06
Total number of patients / Ogółem 65 (2362) 15 (539) 11 (410) 4 (162) 5 (163)
35
OCCURRENCE OF REFRACTIVE ERRORS AMONG STUDENTS
lighting in kitchens leads to a reduction in the prevalence of emmetropia (p < 0.01) – table 2.
discussion
In our study it was observed that sleeping until the age of two in a room with a light turned on is associated with an increase in the occurrence of anisometropia. In addition the findings of Czepita et al. [4] that light emitted by fluorescent lamps is associated with an increase in the prevalence of astigmatism was confirmed. A higher occurrence of my-opia among persons who until the age of two have slept in lighted rooms was not proved. This was probably caused by the use of other criteria in defining refractive errors and selecting group of people with anisometropia.
In experimental research it is known that rearing chicks in light provokes a flattening of the cornea, an enlargement of the eyeball, a decrease of the thickness of the cornea, sclera, retina and choroidea as well as anatomical changes in the retina [5, 6, 9, 11]. Boelen and Cottriall [1] have in-dicated that rearing chicks in continuous light reduces the level of 3,4-dihrodroxiphenylacetic acid in the vitreous.
Possibly among humans the process of sleeping with a light turned on can inflict a decrease of dopaminergic activity and what goes along with it, a lower release of dopamine as well as augmentation of eye growth. that is why it seems likely that disturbances of the daily light/dark cycle during the period of time when refraction is developing may disrupt emmetropization and lead to refractive errors.
recently, Loman et al. [12] described a greater progres-sion of myopia among 23−44 year old law school students subjected to a longer exposition of light at night. Vannas et
al. [18] in the cross-sectional survey of Finnish conscripts found that myopia was not associated with the month of birth. There was a trend towards a higher prevalence of myopia among conscripts living above the Arctic Circle, consistent with the hypothesis that ambient lighting might influence refractive development. Those studies suggest that light association may not be restricted to the first two years of life. The critical period for an influence of the light/dark cycle on refractive development, if it exists at all, is not of a duration measured in months.
In the performed investigations a frequent occurrence of astigmatism was observed among persons who before the age of two lived with light emitted by fluorescent lamps, in comparison to those who lived with light emitted by incandescent lamps. This association has been already described by Czepita et al. [4]. The creation of astigmatism must likely be linked with the influence of light emitted by fluorescent lamps on the corneal and anterior chamber development. Perhaps in that process a particular function is also being played by the ciliary ganglion and ciliary muscle [10, 11].
Acknowledgments
We would like to thank Professor R. A. Stone from the Department of Ophthalmology, University of Pennsylvania School of Medicine, Philadelphia, PA, U.S.A. for his criti-cal review of the manuscript, Professor C. T. Keaveney from the Department of Modern Languages, Linfield College, McMinnville, OR, U.S.A. for his improvement of the English version of the manuscript, and A. Pechmann for assistance during data collection.
t a b l e 2. Prevalence of refractive errors in relation to the type of room lighting used during the first two years of life. Shown are percentages and numbers (in parentheses) of students
t a b e l a 2. Częstość występowania wad refrakcji w zależności od typu używanego w pierwszych dwóch latach życia oświetlenia w pomieszczeniu. W nawiasach obok procentów podano ilość uczniów
Type of room / Living room / Pokój dzienny
incandescent / żarowe
fluorescent / fluorescencyjne 65 (2332)
75 (30) p < 0.18 15 (536)
fluorescent / fluorescencyjne 65 (2315)
60 (47) p < 0.37 15 (527)
15 (12) p < 0.88 11 (400)
13 (10) p < 0.66 4 (157)
7 (5) p < 0.39 5 (159) 5 (4) p < 0.78 Child’s room / Pokój dziecięcy
incandescent / żarowe
fluorescent / fluorescencyjne 65 (2330)
66 (32) p < 0.80 15 (531)
17 (8) p < 0.91 11 (405)
10 (5) p < 0.85 4 (160)
4 (2) p < 0.92 5 (162) 3 (1) p < 0.54 Parents bedroom / Sypialnia rodziców
incandescent / żarowe
fluorescent / fluorescencyjne 65 (2340)
55 (22) p < 0.18 15 (532)
fluorescent / fluorescencyjne 65 (2213)
58 (149) p < 0.01 15 (493)
fluorescent / fluorescencyjne 65 (2281)
67 (81) p < 0.64 15 (520)
16 (19) p < 0.78 11 (398)
10 (12) p < 0.63 4 (157)
4 (5) p < 0.86 5 (159) 3 (4) p < 0.52
Total number of patients / Ogółem 65 (2362) 15 (539) 11 (410) 4 (162) 5 (163)
36 DAMIAN CZEPITA, WOJCIECH GOSŁAWSKI, ARTUR MOJSA
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r o c z n i k i p o m o r s k i e j a k a d e m i i m e d y c z n e j w s z c z e c i n i e AnnAls of tHe PomerAniAn medicAl University, 2005, 51, 37–40
tom li/1 2005 volUme li/1
ewa Tomasik1, damian czepiTa2, MARIA ŻEJMO3, FLORIAN CZERWIŃSKI1