Stopping Myopia

Orthokeratology seems to slow the progression of myopia

Myopia, or nearsightedness, is a condition of the eye that refers to a person’s inability to see clearly at a distance.

People who are myopic have blurred distance vision, and clear near vision.

Myopia progression usually occurs because the eye grows too long and light is not focused correctly onto the retina. New research indicates that one of the causes for the progression of Myopia is peripheral retinal blur. Glasses and single vision contact lenses focus the central vision, but do not focus peripheral vision very well due to the shape of the retina. While the visual system is still developing, through the 20s and 30s, the eye grows to try to improve focusing. The growth is driven by blur on the peripheral retina. With glasses, the peripheral retina is blurred as only the central retina is clearly focused. This results in further growth of the eye and further shortsightedness.

Practitioners who fit orthokeratology lenses sometimes comment that the normal increase or progression of Myopia in children is slowed when these lenses are worn. Although these anecdotal reports are encouraging, at present there is no scientific proof of Myopia control with orthokeratology lens wear.

A recent study from Hong Kong suggested that myopia progression may be slowed by up to 50% during overnight orthokeratology. Similar results have also been reported from a study conducted at Ohio State University. However, the authors of these studies found that there was no way to predict the effect for individual children. There were also a number of scientific weaknesses in the design of these studies, and because of these limitations the results are not definitive.

Further research is currently underway to determine whether orthokeratology lenses can reduce the rate of progression of childhood Myopia, using more rigorous study designs. The MCOS study, being conducted in Spain, is comparing two groups of children wearing overnight orthokeratology versus spectacles, while the SMART study in the US is comparing orthokeratology with silicone hydrogel contact lens daily wear. A different approach is being taken in a study in Sydney, in which children wear an overnight orthokeratology lens in one eye, and a conventional daily wear rigid lens in the other. Results from these studies are expected in the next year or so, and are awaited with interest.

A new Japanese study has concluded that overnight ortho-k slows the progression of myopia by reducing the increase in axial length.

92 children were split into two groups, with one wearing overnight Ortho-K lenses and the other age-matched group wearing only glasses. The children were all eligible for Ortho-Keratology and were an average age of 12 at the start of the study. Over a two-year period, measurements of axial length were compared. At the beginning of the study, both groups were about -2.57 and their axial length was around 24.7mm. At the end of the study, the increase in mean axial length of the eyes in the glasses group was 0.61, which was significantly greater than the 0.39 found in the Ortho-K group.

A full report of the study appears in the journal Investigative Ophthalmology & Visual Science