Why babies born in June may develop eye problem

Poor vision sometimes starts early in life. Myopia is a vision problem that allows people to see close-up objects while distant objects appear blurred and scientists say aside from genetic factors, (a person’s) date of birth is another determinant of those who may end up becoming nearsighted, reports Sade Oguntola.

There are a lot of mysteries surrounding why some people develop nearsightedness (myopia).

While scientists think genetic factors could play the strongest role in determining those that may end up becoming nearsighted, some experts, based on a new study are now suggesting that one’s date of birth may actually help predict some people that may develop this poor sight problem.

They said that light exposure before and just after birth generates biological signals that influence the development of the eye’s ability to focus and refract light properly.

The researchers suggested that the influence of light on vision development in the period before a baby is born could have occurred through mother-baby biological signals before birth, or through the baby’s direct exposure after birth, or both.

Myopia is a vision problem that allows people to see close-up objects clearly while distant objects appear blurred. The condition is on the rise worldwide, but its causes remain uncertain. People with the condition are at a higher risk for their retina detaching from where it is attached and other complications.

The retina is the light-sensitive inner layer of the eye, which receives images formed by the lens and transmits them through the optic nerve to the brain.

Dr. Yossi Mandel and his research team found a suitable study group in candidates for Israeli military service who were medically evaluated between year 2000 and 2004. All 276,911 participants (157,663 male, 119,248 female) were born in Israel, ensuring their exposure to the same seasonal light variations. Myopia prevalence rates, determined by visual examination and defined at three levels of severity, were: mild, 18.8 per cent; moderate, 8.7 per cent; and severe, 2.4 per cent.

The risk of moderate and severe myopia varied with seasonal levels of light, or photoperiods, with highest rates in babies born in June/July and lowest in December/January. These correlations were considered highly statistically significant. The findings were adjusted for other known myopia risk factors, such as gender, education level, and father’s country of origin.

Mild myopia was not associated with season of birth or exposure to light before birth.

Meanwhile, since the link to seasonal birth date was most pronounced for severe myopia, Dr. Mandel concluded that: “It seems reasonable to assume that only a fraction of the population might be genetically prone to develop myopia if exposed to environmental risk factors such as a long perinatal photoperiod. Further exploration of the mechanisms underlying the effect of light on the development and progression of myopia in humans is needed to devise effective preventive measures.”

Since the effect of light levels on myopia (nearsightedness), if any, was likely to be slight, a large population study was needed to further explore the question in the April 2008 issue of Ophthalmology, the journal of the American Academy of Ophthalmology.

However, the factors previously suggested to be the reason some develop myopia (nearsightedness) were heredity and the amount of time a child spends studying or reading. They found that, per week, myopic children spent more time studying and reading for pleasure and less time playing sports than non-myopic children. In fact, myopic children also scored higher on a test of basic reading and language skills than did children with normal vision.

Donald Mutti, an associate professor of optometry at Ohio State University and his colleagues in the 2003 edition of the journal Investigative Ophthalmology & Visual Science believed that there was a definite link between paper-based pursuits – like studying and reading – and myopia but none linked watching TV or using a computer.

In addition to this, there was controversy on the contribution of leaving a light on in a sleeping infant’s room increasing the child’s chance of becoming nearsighted.

While a study published in the year 2000 edition of the journal Nature suggested that leaving the light on in a sleeping infant’s room would not increase the child’s chance of becoming nearsighted, another one contradicted it in another issue of the same journal. They found that babies younger than two years old who slept with the light on were at increased risk of developing myopia - nearsightedness - later in childhood.

Interestingly, the possibility of one’s birth day determining whether one will develop nearsightedness, Dr. Gboyega Ajayi, an ophthalmologist at Ojulowo Eye Clinic, Mokola, Ibadan, said to some extent is dependent on the environment where one is born.

According to him, the light levels in different parts of the world vary with their seasons. Equally, the level of light one is exposed to is dependent on whether there is longer day and shorter night. In Britain, during summer there is daylight till up to 8 p.m. or 9 p.m. and by 3 a.m. or 4 a.m. the daylight is back.

“It will however be totally incorrect to attribute a myopia to one factor because there are other environmental conditions that prevail from one continent to the other that could affect, say the woman’s diet and so indirectly impact on the development of an unborn child, “ Dr. Ajayi said.

“So myopia is really something that should have a multiple influence and which the summary of the time of birth is a mere coincidence with the time of birth of the baby. The events that happen during conception are more or less those that can then manifest after birth after nine months.”

Meanwhile, Dr. Ajayi said many things have been attributed to nearsightedness. For instance in China, some said the fact that children are made to start to read early and that they read too much hurt their eyesight, thus resulting in myopia.

“I believe people are searching for factors that possibly contribute to people developing myopia and then from all of them further narrow down the factors to the most possible causes of myopia,” he said.

“As of now, its commonest cause is heredity and it has nothing to do with diet,” he concluded.