By Michael Hutton
Contact lenses for sport which are only worn while sleeping and are specially designed to enable water sports participants to see clearly without requiring prescription goggles also provide the perfect solution for those who enjoy the extreme sport of freediving. Freediving is an aquatic technique which has a number of competitive variants all involving extended breath-holding and the current no-limits female world record holder is Briton Tanya Streeter who reached a depth of 525 feet in March 2002. At that point this was a world best for men and women and justified her earlier induction in 2000 into the Women Divers Hall of Fame. But freediving is not just a sport.
For people like the Bajau of South-East Asia who live in stilt houses at the edge of the sea, freediving is a way of life and they can fish underwater for up to five minutes on one breath. Due to spending so much time in the water as children when their eyes are developing, the Bajau have unusually strong underwater vision. Their eye muscles have adapted to constrict the pupils more and to change the lens shape to increase light refraction which makes their underwater eyesight twice as strong. However, studies have shown that this naturally achieved attribute can be matched by people who take up freediving later in life which is where the special contact lenses for sports become a key factor.
Successful freedivers make use of the mammalian dive reflex which is a series of automatic adjustments made when submerged in cold water, reducing the heart rate and metabolism to slow the rate of oxygen consumption. Whilst holding breath for an extended period, oxygen stores reduce and the body starts diverting blood from hands and feet to the vital organs. This is compensated by the effect of the underwater pressure constricting the spleen thus squeezing out extra haemoglobin, the protein in red corpuscles that carry oxygen around the body. However, like scuba divers, freedivers have to manage the issue of decompression carefully as they return to the surface to avoid ‘the bends' and hence great eyesight provided by the special contact lenses for sport are a key aid to monitor depth changes as they ascend.
See if you are suitable for orthok corrective contact lenses .