Opening our eyes whilst under water is difficult for some. Chlorine and sea water can irritate sensitive eyes and make it almost impossible for vision underwater.

But it’s not only the sensitivity of our eyes which can cause problems; when the human eye is in contact with water the light entering the eye is refracted and sent off in a different direction and the eye is left unable to focus.

Diving Masks And Pressure

Angle of light

Light bends when there are two materials it must travel through, and the amount it bends depends on the substance. The human eye can only focus on one angle, which is when light travels through the air to our eye. When travelling through water, the human eye cannot focus and vision is blurred.

Goggles are the obvious choice for underwater activity. They keep the water out and provide clear vision for users as the space between the eye and the goggles is air. A tempered and strong glass plate is held together with sealed rubber, creating a watertight seal to the face. For free divers (who use no scuba equipment) the masks need to be low volume in order to minimise the change in pressure as the diver descends further into the water, and the lens can instead be made of hard-wearing plastic.

Divers with prescription glasses can opt for goggles which have two lenses, allowing a prescription to be fitted for each eye.

Special goggles

Normal swim goggles cannot be used for divers as the mask must cover the nose. This is for comfort and allows the wearer to empty water from a leaky mask and stop water entering his nose, which would otherwise make for a very uncomfortable dive.

Another incredibly important feature is that a mask covering the nose allows the diver to equalise the air pressure inside the mask as the diver descends further into the water. Without pressure equalisation, the mask could cause suction on the face and in very extreme cases could suck the eyeballs out depending on the depth of the dive.

Steaming and fogging goggles is something that often happens, and it can ruin a dive. However, there are various tricks and steps that can prevent it. Toothpaste, potatoes and baby shampoo are tried and tested ways of reducing fogging when rubbed into and washed off of the inside of goggles.

It is important to keep our eyes healthy. Follow the above guidelines when undertaking any underwater activity for healthy eyes.

Amy is a blogger for one of the leading suppliers of prescription and non prescription glasses online, Direct