If you wear glasses or use contact lenses then using a mask fitted with corrective lenses is essential for enjoying your dive or snorkelling trip. Off the shelf replacement lenses are the most cost effective way of adding corrections to your mask but manufacturers offer varying ranges of corrections and typically only in 0.5 dioptre increments. Whilst the available range is sufficient for most the biggest problem with off the shelf lenses is that they can't correct for astigmatism which means that even if the spherical correction can be made your vision is still likely to be distorted or blurry if you have a astigmatism higher than around 2.00.
We are here to help with a solution though. We have teamed up with an optical specialist that can custom make your exact prescription and fit it to virtually any twin lens mask, even to your existing one if you like.You'll no longer be limited to just the models manufacturers decide to make replacement lenses for.
What types of lenses are available?
The bespoke lenses are available in three types, Single-Vision, Bifocal and Reading Segments.
Single-Vision will fill as much of the lens aperture as possible depending on the style of mask and your prescription. This option is typically used to correct distance vision.
Bifocals generally provide correction for distance vision across the majority of the lens but with an area towards the bottom of the lens for correcting close vision, reading gauges, checking camera settings, etc.
Reading Segment lenses, also known as Franklin Split lenses offer one correction in the top for distance vision and another correction in the bottom for reading.
Will the standard lenses be replaced?
No, the corrective element of the lenses (which are made from high-quality optical glass) are permanently UV bonded to the inside surface of the original lenses. Unlike some self-adhesive lenses that are available, these corrections are not designed to come off.
Not all masks are designed to readily come apart once manufactured and tested so by bonding the correction to the original lenses it opens up your mask options considerably.
Are all masks suitable for all prescriptions?
Generally speaking all twin lens masks (have a frame bridging piece down the nose) are suitable with the only exception being very ‘Low Volume’ masks, which are not recommended for higher prescriptions – especially with plus correction. This is due to the thickness of the lenses (at the centre with plus correction and at the edges with minus prescriptions), will often place the glass too close to the eye and lashes
Do I still need to clean the lenses with toothpaste before using the mask?
No, any protective film left on the glass following manufacture will have been removed by the bonding process. The lenses are also thoroughly cleaned before dispatch.
Do I need to adjust my prescription for water?
No. Whilst water does have a higher refractive index than air it is largely countered by the fact that the lenses are further from the eye than they would be with glasses. We always recommend that our customers match their prescription as closely as possible when purchasing off the shelf lenses and this is certainly no different.
Why can't I just wear my contact lenses?
It is a common question and you've gone to the trouble to order contact lenses already so why not use them? Here are a few reasons:
- Acanthamoeba is a protozoa that lives freely in both salt and fresh water. This tiny single celled organism can cause Acanthamoeba Keratitis, an infection of the cornea which is painful, sometimes permanently damaging or could even cause the loss of an eye. A contaminated contact lens significantly increases the risk of infection. If you want to be put off wearing them whilst diving or snorkelling then look it up on your preferred search engine.
- If your mask floods, the extra fluid may displace your contact lenses which in itself is not particularly pleasant but add the fact that the higher osmolarity of seawater or lower osmolarity of freshwater compared to tears, can actually cause soft contact lenses to adhere to the eyes. The only way to ‘unstick’ them is irrigation with isotonic saline. Not something found on too many dive or snorkelling sites.
- Soft contact lenses can also absorb mask de-fogging solutions which in turn can irritate the eye.
- If you wear hard or gas-permeable contact lenses you may experience blurred vision after diving. During the dive nitrogen is absorbed into the fluid around our eyes as it does with the rest of our body. During ascent the fluid and cornea are unable to eliminate the inert gas as quickly as they would without the contact lenses in place, causing bubbles to form between the lenses and cornea, affecting its surface and causing the blurring.