Interesting that almost all the opinions here are in favour. I remember reading a similar thread on another board just a few years ago and it was full of warnings about the risks.
Just for info a couple of quotes:
Extract from BSAC TECHNICAL PUBLICATIONS Information Sheet T.3
- - - - - - - - - - - -
CORRECTED VISION
Advice for divers who normally wear glasses or contact lenses.
To ensure the best and clearest view of the underwater world, those who regularly wear glasses or contact lenses are likely to require a mask which is optically corrected to suit their individual requirements.
Contact lenses can be worn when using a diving mask, but there is a risk of losing them. There are times when a mask may flood or be displaced - and the diver needs to open his / her eyes to recover and refit it. Also, the technique of clearing water from a flooded mask is a basic and essential skill which has to be learned, and it is usual to require trainees to keep the eyes open while practising it. Risk of losing the lenses is high.
Furthermore, it has been suggested that gas micro-bubbles could accumulate between the inside face of a contact lens and the eyeball when diving, possibly clouding vision and maybe causing damage the surface of the eyeball, though there is little factual evidence to bear this out. There are also reports of negative reactions from an accumulation of salts between lenses and the eye, which may cause irritation. All these reasons create a sound case for not using contact lenses while diving.
On the other hand, there are also numerous reports of trouble-free use from those who do regularly wear contact lenses - especially soft lenses - while diving. It also needs to be borne in mind that you can buy several sets of (disposable) soft contact lenses for the price of a mask with prescription lenses. It might be more economic to carry at least one spare set of contact lenses in your dive bag and bear the risk of occasional losses.
- - - - - - - - - - - -
Extract from other medical site:
It is important to keep in mind that not all contact lenses are suitable to wear during diving. RGPs and the old hard (PMMA) lenses have been known to "dig in" to the eyes below certain depths, because of pressure. Also, soft lenses can collect waterborne organisms, becoming contaminated and causing disease. This can happen in pools as well as fresh- and saltwater bodies. Your prescribing doctor must give specific permission for you to wear the lenses underwater, or damage to the eye can occur.
- - - - - - - - - - - - - - - - -
And another contact lens supplier:
Contact Lens Wearers: If you wear contact lenses under your mask for diving, you need to make sure you blink a lot.