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How does too little or too much sunlight affect your eyes?

The sun is a double-edged sword when it comes to eyes. Conscientious daily sun exposure (before 10 am and after 4 pm and with the right protection) helps maintain optimum levels of Vitamin D in our body. Studies estimate that around 1 in 5 people in the UK are deficient. Vitamin D deficiency has been linked to a host of eye diseases, including Dry Eyes and Macular Degeneration (which can cause irreversible sight loss). It has even been connected to Uveitis, a painful inflammation of the front and middle eye. Of course, Vitamin D levels can also be maintained through supplementation – although it is important to do this under a doctor's care, as Vitamin D can be poisonous to the body in excess.

The other main benefit of direct, conscientious sunlight exposure is that it is has been clinically proven to slow down the progression of short-sightedness (myopia) in children. The incidence of myopia is growing very quickly; by 2050, it is estimated that 28 to 56% of us will be short-sighted 2050. Many parents will know that unsettling feeling of going to their child’s regular eye test only to see their glasses prescription creep up and up. Spending 2 hours outdoors every day can slow down this prescription creep, especially when playing a ball sport; think cricket, tennis or football.

Finally, the effects of direct, conscientious sunlight exposure on our sleeping habits are well documented. Sunlight helps boost serotonin levels (the hormone responsible for good moods) during the day. The slow setting of the sun triggers the production of melatonin (the hormone responsible for a good night's sleep). Together these two hormones, largely controlled by the sun, are part of the circadian rhythm, which regulates our moods and routines (a productive working day and a good nights sleep).

On the flip side – we are much more aware of the dangers of sunlight exposure – and these absolutely extend to your eyes. Basal cell carcinomas (cancer of the skin around your eyes) accounts for a mammoth 70% of all skin cancers! While we are all getting better at sun protection, the eyes are often forgotten, which is why this type of skin cancer is so prevalent.

Overexposure to both UV-A and UV-B light wavelengths from the sun can accelerate the development of cataracts (where the middle lens of your eye becomes cloudy to the point of needing surgical replacement). Age-related macular degeneration, where the photoreceptor cells in the back of your eye die, can also be accelerated. It can also promote harmless but irritating growths of the sclera (the white of your eyes) across your iris called a Pinguecula or even across your cornea called a pterygium. Many a skier will also have heard of ‘snow blindness’, but this very painful condition (photokeratitis) can affect anyone exposed to the sun reflecting off snow, ice, sand or water.

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