How can I correct my vision underwater? It is a frequent question in new divers that need their vision corrected and even some experienced divers who find that their eyesight is not as it was. There are two basic answers, get a prescription mask or wear contact lenses. After hearing the mention of contact lenses there is generally a follow-up question: are they safe?
Many divers have a bias against contacts, however, they are accepted as a safe method to correct vision for diving. Like everything else in diving, there are things you need to understand before diving with contacts.
Scuba Diving With Contacts
Diving with contact lenses is considered safe, however, not all styles of contacts are recommended. There are three common types of contacts, they are hard, gas permeable and soft. The hard contacts are the original if you will. They are small just covering the iris portion of your eye, are not flexible and do not let gas pass through the lens. Many people find these irritating to wear and difficult to put in and remove. One common problem is it is possible to get a fleck of dust between the lens and the cornea Since there is no exchange of air through the lens users cannot wear them for long periods of time. They must be removed before going to sleep or you can become hypoxic. That is the eye is not getting enough oxygen. Hard contacts are not as common as they were a few years ago, as advancements in gas permeable lenses have made them more popular.
Gas permeable lenses allow some air to pass through the lenses and are a bit larger than the hard lenses. They are also more flexible. They can be worn for a number of days. These lenses do take some time for a user to get used to. There are two concerns about diving with gas permeable lenses and hard lenses. Their size makes it likely that you can lose a contact if your mask floods. With hard contacts it is almost certain, gas permeable lenses could stay in if you get your eyelids partially closed fast enough.
The next issue concerns ascending and mostly applies to hard contacts but can also apply to gas permeable lenses that have a slower rate of allowing gas to pass. The cornea is a fast tissue meaning it will absorb nitrogen under pressure rapidly. It will also release it rapidly as the pressure decreases. The problem can occur when the diver ascends at a rate faster than the air can pass around the contact. It can have an air bubble form between the cornea and the lens. That bubble can push against the cornea causing an indent. A number of these indents will cause a distortion that will produce blurred vision. It could take more than 30 minutes before the diver regains his normal sight.
Soft contacts are the contact of choice for divers. These contacts are the largest of the three types. The eyelids of most people with overlap the edge of the lenses. This will make them more secure if the mask floods or is lost. Also in exposed conditions, the size tends to keep the contact against the eye. Soft contacts will not allow a build-up of gas between the eye and the lens. So you do not have the risk of blurred vision as with the hard lenses. There are a few concerns that need to be addressed. The soft lens will absorb liquids. If your mask floods, it will absorb some of the water. If you are in the ocean that means salt water. The saltwater and the underwater pressure will press the lens against your eye. The salt can make the lens stick to the eyeball. Also once you surface, the residual salt can dry out the lens. Most contact wearers have experienced a time where the lens has dried out some. It can feel scratchy and irritating. The solution to both the dried out contact and it sticking to the eyeball is a solution. A few drops of a Lubricant Eye Drops solution will loosen the contact from the eyeball and restore the moisture. After your day of diving, you should remove your contacts and clean them. If you are wearing soft contacts you also need to be careful with what you use to defog your mask. The contact can absorb that as well and it might cause irritation to your eye.
Prescription Mask, Your Other Alternative
No discussion about diving with contact lenses would be complete without at least mentioning the alternative. That alternative is prescription lenses in a dive mask. We have a couple of different ways to accomplish using a mask to restore your vision underwater for those needing corrective lenses. The best quality is to have a lens custom made to exactly fit your prescription for eyeglasses. All the measurements that are required to make your eyeglasses are needed to make your custom lenses. The lenses can be made for single vision, bifocals or readers. For those of us who take off their glasses to read you can even get a see under style. A set of custom lenses may be as much as $400 plus the mask. Most companies that make these lenses will have the option of you sending in your mask or purchasing one from their stock. Surprisingly the companies often prefer you send in your own mask. This eliminates some guesswork on their part if you are getting bifocals and ensures you get a mask that fits you properly. Custom made lenses can be made to fit any good quality dive mask.
The second type of mask I call the drop-ins. These are masks that have been designed to accept interchangeable lenses. You buy your lenses based on your diopter reading. Then you simply insert the prescription lens in place of the original lens. You can get a good quality mask with corrective lenses for around $100. Most of the major mask manufacturers have a mask with these features. There are some trade-offs getting one of these masks as opposed to the custom-made lenses. First prescriptions are in .25 diopter measurements, while most of these lenses are sold in .50 diopter measurements. So if your prescription is -1.75, then you will have to get -2. Will you notice the difference, not likely and especially underwater where the property of the water will modify what reaches your eyes anyway. Custom lenses will take in the secondary factors of your vision correction, such as the distance between pupils and the center point of each pupil. These are important to get the best focus for your eyes and to reduce eyestrain. However, most recreational divers do not stay underwater often enough to appreciate the difference. These drop-in lenses can distort peripheral vision a little, while the custom-made will not.
There is a third method that is a possibility with those who just have problems with reading their gauges. A small lens is attached to the inside of your mask. It creates an effect similar to bifocals. The majority of your lens is normal, but when you look at your gauges using the attached lens it acts like a magnifying glass making it easier to read.
Contacts or Prescription Mask?
It is mostly a personal choice. If you normally wear soft contacts than you can dive with any mask that fits you. There is no extra cost involved. Soft contacts seem to allow greater peripheral vision. Also when you finish your dive, you can take off your mask and not have to search for your eyeglasses. If someone sits a dive cylinder down on your mask, you can just take theirs for the next dive.
A prescription mask is the only option for those who can not or will not wear contacts. Contact users who use monovision might be more comfortable diving with a bifocal prescription mask or a mask with one lens with a small lens attached. Monovision is where one eye is correct for distance and the other eye is corrected to see near. Many divers who do not use contacts daily feel more comfortable using a prescription mask. While the possibility of losing a contact is small, it is still possible.