By Nigel Little 

Glasses for children  have been shown to perform significantly less well than overnight corrective contact lenses in halting the progression of short-sightedness (known as ‘myopia') according to a new study from Japan recently published in the leading clinical journal ‘Investigative Opthalmology & Visual Science'. This two year study measured changes in eyeball elongation across a group of 92 children all aged around 12 years with a similar initial level of myopia of -2.5 diopters and eyeball length. The distance between the front and back of the eyeball is an important metric given that an increase in this distance is recognized as a primary cause of myopia progression.

Of the 92 children, 42 were fitted with special overnight corrective contact lenses which are small rigid gas permeable lenses worn only while sleeping. The lenses gently reshape the eye while the child sleeps - a process known as orthokeratology or ortho-k - to correct eyeball elongation temporarily and provide the child with clear 20-20 vision after the lenses are removed in the morning. This temporary correction lasts for a full day so the child has perfect vision until the lenses are re-inserted at night before going to bed. Conventional prescription glasses for children  were worn by the other 50 participants so the two groups were also differentiated by the fact that those wearing glasses required their corrective visual aid throughout the day whilst the ortho-k group did not require anything after removal of their lenses in the morning.

After two years, the study results showed that the mean eyeball length in those children who had worn prescription glasses had increased by 0.61mm which was significantly greater than that recorded for the children wearing the special overnight corrective contact lenses. This led researchers to conclude that ortho-k can slow or halt the progression of myopia in children whilst prescription glasses for children  do not provide the same benefit. Other clinical investigations in Hong Kong, Spain and the US have reached similar conclusions about ortho-k. The largest of these investigations is The SMART Study which is tracking myopia progression over a group of 300 children in Chicago split between those wearing conventional soft lenses and those wearing overnight ortho-k lenses and the results from the third year of this five year study will be released later this month.

Check if your child is suitable for overnight corrective contact lenses .