By Jacqui Mayhew 

Ortho-k lenses  worn only while sleeping not only correct short-sightedness - otherwise known as Myopia - but also can prevent short-sightedness from getting worse. This new innovation in vision correction comes at a timely moment given that a recently issued report by the US National Eye Institute has highlighted that more adults now have eye disease than ever before. The report, titled "Vision Problems in the US," show that the number of people age 50 years and older with late age-related macular degeneration has increased 25% compared with the previous report conducted in 2000; similarly, the number of people age 40 and older with cataracts has increased 19% and the number of people age 40 and older with open-angle glaucoma has increased 22%.

Whilst an aging population is one of the factors behind this rapid growth in eye health problems amongst older adults, another key driver is the equally rapid growth in myopia which now affects some 35-40% of adults in the western world. The World Health Organisation now rates this growth in myopia as an epidemic and one of the major disease threats globally since more children are becoming short-sighted at an earlier age and reaching adulthood with much higher prescription levels than their parents' generation. High myopia is directly associated with eye health problems in later life so the ability of ortho-k lenses  to stop myopia worsening may represent a critically important vision correction breakthrough.

Based on the long-established optical science of orthokeratology, ortho-k lenses  work by gently flattening the surface of the eye using the mild pressure of closed eyelids during sleep. This reduces the distance between the surface of the eye and the retina at the back of the eye so that after the lenses are removed each morning light entering the eyes focuses directly on the retina rather than in front of it which is when distant objects appear blurred. The effect lasts 24 hours so the wearer enjoys perfect natural lens-free vision all day long until the lenses are reinserted at night. Most importantly, the lenses stop the eyeball from continuing to lengthen which is how myopia worsens over time - and which conventional glasses or daytime contact lenses cannot prevent.