New divers learn that water has magical magnification properties making objects appear 33% bigger and 25% nearer.
Nonetheless, if you use corrective lenses for everyday activities, it doesn't necessarily mean that you will see clearly underwater without some assistance to aid your poor vision.
You do not need perfect 20/20 vision for scuba diving, but if you wear contact lenses; prescription spectacles for reading, driving, or work related tasks, and want to do scuba diving with glasses, your underwater diving experiences will benefit enormously from extra sharpness to your sight.
We have some tips for divers with poor eyesight to see the best from the underwater world.
You could expect and presume that the magnifying properties of using a dive mask underwater corrects mild vision problems
After all, you learned about underwater refraction during your open water diver course.
When light is refracted in water, objects seem one-third larger and one-quarter closer. This natural magnification may correct a relatively mild eyesight weakness.
The diver may not suffer any abnormal vision problems and corrective lenses may not be required. Scuba Diving with glasses may not be necessary - or possible for you.
Perhaps the most important issue for this topic is to determine how well the diver needs to see underwater and when you should consider taking steps to correct your vision for scuba?
Taking steps to improve your eyesight for scuba diving begins with safety. You need to see clearly to avoid colliding with underwater structures and you need to recognize and locate your dive buddy throughout the dive.
We agree that less than optimum underwater visibility may impair your natural vision limiting the distance that you can see clearly with some comfort and accuracy. But safe diving practices require you to accurately read you submersible gauges and communicate with your fellow divers.
Impairment of these principle safety issues should prompt you to seek corrective eye-wear for your diving activities.
Scuba diving with glasses is not an option for those with certain types of lenses. This could mean purchasing a prescription dive mask or acquiring some soft contact lenses.
If you need bi-focal glasses for reading small print we recommend using stick-on magnifying lenses on the lower section of your dive mask. The result of adding these tiny sticker lenses are a handy bi-focal scuba mask for reading small numbers such as on your submersible gauges.
We are regularly asked whether you can dive or snorkel while wearing your personal eyeglasses or everyday spectacles. The answer is short and simple. No you cannot do scuba diving with glasses.
The design of eyeglasses means that the arms of the glasses that clip over your ears do not allow the plastic or silicon skirt of the dive mask to seal correctly over your face. The mask skirt needs to create a waterproof seal around your face and everyday spectacles interfere with this application.
Water pressure on the mask face would also cause discomfort and a risk of injury if you were to try diving with eyeglasses. One solution is to buy an optical lens diving mask which has the prescription lenses inserted to compensate correctly for your eyesight loss.
Scuba diving with prescription mask inserts can be achieved by a several methods. Some scuba equipment manufacturers offer dive masks with prescription lenses already inserted during production.
A good example is the Cressi Focus scuba diving and snorkeling mask (optical lenses available). If you choose this option you need to match the scale of correction that you need to the mask lens.
Prescription diving mask inserts are modified by changing the original lenses to optical lenses. The gear manufacturer's stock glass is replaced with prescription lenses.
Whichever option you choose, we have some additional helpful suggestions for divers with poor eyesight.
Another favorite question from our divers and snorkelers is - can I dive wearing contact lenses? We have another short and simple answer to this one too. Yes you certainly can dive or snorkel with soft contact lenses. The exception may be if you wear hard or gas permeable contact lenses.
A renowned diving safety organisation (DAN) suggest that diving with hard contacts may cause suction pressure related issues or eye irritation of air bubbles form inside the lens.
If you dive using soft contact lenses, special care is needed if you remove your mask or if it floods while diving. Close your eyes during the mask removal to avoid losing your lens.
The flooded water may wash the delicate lens away from your eye. It is extremely rare to have problems with soft contact lenses underwater but you might consider storing a re-wetting eye drop solution in your dive kit if the lens sticks to your eye due to excessive pressure from the dive.
In most circumstances diving after routine corrective eye surgery such as laser procedures or treatment for an eye condition is possible. Nonetheless, following the operation you should allow appropriate recovery time and consult an ophthalmologist before diving again.
Eye surgical procedures which may be a contraindication for scuba diving include surgical incisions that compromise the structural integrity of the eye or serious conditions e.g., Glaucoma.
Even though light rays travel in straight lines in air, they bounce when they strike a nontransparent surface (opaque). Simply put, we see an image because the light reflects (bounces) back to our eyes.
But, the process differs when light strikes a transparent object (e.g. water). In this instance, some of the light rays will pass through the water.
Rays of light striking an object straight on will continue traveling in a straight line. However, light entering a transparent object at an angle will change its direction (e.g. light rays will bend).
Refraction is a process best described as the 'bending of light'. So, why does it happen? It occurs because light slows down as it enters an object. So, one side of the light ray will enter before the other (and slows down first) if it enters the object at an angle.
If we look at an object in water from above, it actually appears to be bigger than it does when viewed in air. It's important to understand that the light did not produce a bigger image for our eyes.
Instead, the illusion happens because the image is closer to our eyes. The light rays do not pass straight down so they bend in relation to the surface of the water. The magnification occurs because the image is closer.
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Note: This information is for guidance only and you should always consult a diving Doctor.