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3663 children from elementary and secondary schools were examined (1738 boys and 1925 girls, aged 6–17 years, mean age 11.1, SD = 3.2). The weight at birth was 1500–2500 grams (mean 2184, SD = 271) in 254 and more than 2500 grams (mean 3398, SD = 441) in the remaining 3409 chil-dren. The children were Caucasian whites and resided in and around Szczecin, Poland. Participation was voluntary and informed consent was obtained from the school principals and parents of all children. Parents completed a questionnaire on the child’s weight and term of birth. The study protocol complied with the Helsinki Declaration on research involving human subjects and was approved by the Bioethics Com-mittee of the Pomeranian Medical University.

Ophthalmologic examination was performed in the school’s consulting room. Cycloplegia was induced with two drops of 1% tropicamide instilled 5 minutes apart to each eye. Skiascopy was performed thirty minutes after the last drop. All refractive error readings were reported as spherical equivalent (SE) (sphere power plus half nega-tive cylinder power). Myopia was defined as SE < -0.5 D, hyperopia as SE > +1.5 D. Anisometropia was diagnosed when the difference in the refraction of both eyes was

> 1.0 D. Data from the right eye were analyzed in myopia and hyperopia and from both eyes in anisometropia. Data analysis was performed using χ2 test. P values of less than 0.05 were considered statistically significant.

Results

Hyperopia was more frequent among 6–7 year-old chil-dren whose birth weight was > 2500 grams (p < 0.05) –

ta-ble 1. Additionally, it was found that anisometropia was less frequent in 10–11 year-old children whose birth weight was

> 2500 g (p < 0.05) – table 2. A relationship between birth weight and prevalence of myopia was not observed.

T a b l e 1. Prevalence of hyperopia in relation to birth weight T a b e l a 1. Częstość występowania nadwzroczności w zależności

od wagi urodzeniowej

Age (years)

Wiek (lata) Hyperopia Nadwzroczność

Number of students with birth weight Liczba uczniów z wagą

urodzeniową p

1500−2500 g > 2500 g

6−7 present / obecna 20 288

< 0.05

absent / nieobecna 31 208

8−9 present / obecna 7 183

> 0.05

absent / nieobecna 28 485

10−11 present / obecna 8 126

> 0.05

absent / nieobecna 58 627

12−13 present / obecna 5 80

> 0.05

absent / nieobecna 36 493

14−15 present / obecna 2 61

> 0.05

absent / nieobecna 36 446

16−17 present / obecna 1 17

> 0.05

absent / nieobecna 22 395

Total Ogółem

present / obecna 43 755

> 0.05

absent / nieobecna 211 2654

T a b l e 2. Prevalence of anisometropia in relation to birth weight T a b e l a 2. Częstość występowania różnowzroczności w zależności

od wagi urodzeniowej Age (years)

Wiek (lata) Anisometropia Różnowzroczność

Number of students with birth weight / Liczba uczniów

z wagą urodzeniową p 1500−2500 g > 2500 g

6−7 present / obecna 1 7

> 0.05

absent / nieobecna 50 489

8−9 present / obecna 2 20

> 0.05

absent / nieobecna 33 648

10−11 present / obecna 4 11

< 0.05

absent / nieobecna 62 742

12−13 present / obecna 1 20

> 0.05

absent / nieobecna 40 553

14−15 present / obecna 1 25

> 0.05

absent / nieobecna 37 482

16−17 present / obecna 0 13

> 0.05

absent / nieobecna 23 399

Total Ogółem

present / obecna 9 96

> 0.05

absent / nieobecna 245 3313

THE INFLUENCE OF LOW BIRTH WEIGHT ON REFRACTIVE ERRORS AMONG SCHOOLCHILDREN 65

Discussion

The human eyeball undergoes significant changes throughout life. Changes are most intense from the mo-ment of birth till puberty and are connected with growth and maturation. The development of the eyeball passes through a phase of dynamic growth during the first year of life, a phase of rather fast growth between the first and third year of life, and a phase of steady but slow devel-opment from the third year of life till around (according to different sources) the tenth [26, 27], thirteenth [28], or even the fourteenth year of life [29, 30] when the eyeball reaches adult size.

It has conclusively been shown that the eyeball develops incorrectly in low-birth-weight infants leading to the forma-tion of refractive errors. The pathomechanism of refractive error formation in preterm infants has not been definitely established. Some researchers assume that changes take place in axial length while others presuppose that changes concern the anterior chamber. However, it is certain that infants with low birth weight demonstrate disturbances of emmetropisation – the harmonious optic development of the eye [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21].

In a recent study, Tomasik et al. [31] found that axial length, equatorial and corneal diameter of the eye increase during fetal development. The eyeball expands symmetri-cally in all directions indicating that there is no predisposi-tion to myopia during prenatal life.

Choi et al. [2] and Scharf et al. [19] stated that preterm infant myopia begins to appear at six months of age and its severity increases between the age of six months to three years. At six years of age, prematurely born infants exhibit shallower anterior chambers, thicker lenses, and greater axial lengths with growing degree of myopia.

Other researchers reported increased prevalence of myo-pia and anisometromyo-pia among low-birth-weight infants. These refractive errors occur frequently in children at infancy and early childhood [2, 3, 4, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19]. While anisometropia and myopia occur rarely among older children, a more frequent occurrence of hyperopia has been observed [1, 3, 5, 7, 8, 13, 21].

Our present study in older children confirmed that hyperopia is more frequent in 6–7 year-old schoolchildren whose birth weight was greater than 2500 grams and that anisometropia is less frequent in such children at the age of 10–11 years. However, a correlation between low birth weight and prevalence of myopia among schoolchildren was not found, confirming the results of Fledelius [7] in children aged 10–18 years.

Conclusion

Low birth weight may have an effect on the prevalence of refractive errors among schoolchildren.

Acknowledgments

We would like to thank A. Pechmann for assistance dur-ing data collection.

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A propos

Retinopatia wcześniaków rozwija się u dzieci urodzonych przedwcześnie poniżej 36 Hbd z niską wagą urodzeniową poniżej 2500 g, które były poddane tlenoterapii. Występuje średnio u 20% wcześniaków. Objawy kliniczne schorzenia zależą od stopnia niedojrzałości wcześniaka. Przy wadze uro-dzeniowej poniżej 1000 g występuje ona u 67% dzieci. Wraz ze zwiększeniem się wagi urodzeniowej procent jej występowania zmniejsza się i przy wadze 2000–2500 g stwierdzana jest tylko u 1% wcześniaków. U 5–8% dzieci dotkniętych retinopatią dochodzi do zmian, które mogą powodować całkowitą utratę widzenia. U pozostałych dzieci występuje samoistne cofanie się zmian, przy czym u wielu z nich występuje osłabienie widzenia, które jest powodowane wadami refrakcji.

Według licznych autorów (Gallo, Quinn, Repka) retino-patia wcześniaków wiąże się z częstszym występowaniem wad refrakcji. Keith, Mondon sugerują możliwość korelacji wad refrakcji z masą urodzeniową dzieci. Z roku na rok wzrasta liczba dzieci i młodzieży z wadami wzroku, szcze-gólnie z krótkowzrocznością. Na całym świecie prowadzone są badania nad ustaleniem przyczyn. Badania Kubatko--Zielińskiej i współ. wykazały, że większość przedwcześnie urodzonych dzieci ma wadę refrakcji.

Autorzy niniejszej pracy: Damian Czepita, Maria Żejmo i Artur Mojsa prowadzili badania na bardzo dużej populacji – 3663 dzieci i stwierdzili, że u dzieci z wagą urodzenio-wą poniżej 2500 g częściej występuje różnowzroczność, a rzadziej nadwzroczność. Różnowzroczność może być przyczyną niedowidzenia, jeżeli nie zostanie wcześnie skorygowana szkłami okularowymi.

prof. dr hab. n. med. Danuta Karczewicz

ANNALES ACADEMIAE MEDICAE STETINENSIS

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

2006, 52, 1, 67–72

MONIKA MODRZEJEWSKA

RETINOPATIA WCZEŚNIAKÓW – PATOGENEZA I WYSTĘPOWANIE