Mar 24, 2016

Seeing Sunlight as a Positive Agent

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By Joseph Zikry, BS and Lance Chapman, MD, MBA

Our lives are unavoidably affected by the cyclic nature of the sun. It marks the beginning of each new day, an unspoken promise by the universe to mankind. It is essential to life on earth. While humans have found innumerable ways to utilize the sun and its energy throughout history, the sun has garnered somewhat of a negative reputation in the field of dermatology and ophthalmology. Beware of excessive sunshine, avoid the midday sun, don’t get a sunburn, shun a tan. Ultraviolet light has been indisputably linked to the majority of skin malignancies and also to cataracts. But are there no benefits to sunshine?

Absolutely! Seasonal affective disorder, a common condition in which the sufferers become lethargic and depressed during the wintertime, tends to improve in the summertime. Vitamin D deficiency is a common problem which can be helped, in part, by exposing oneself to sunlight (though taking Vitamin D tablets is much easier!). Patients with the skin condition psoriasis are sent by some UK health centers to hangout abroad in sunny climates because their skin tends to clear up after a few weeks soaking up the rays.

Physicians become quite passionate about the need to avoid or conversely enjoy the sunshine. It’s confusing to the public when we physicians say on the one hand that sun rays are bad for you, and on the other that we actually prescribe sunlight for the treatment of many skin conditions.  Thus, there needs to be a clear understanding of the balance between the Yin and the Yang of sunlight.

In 1999, the Food and Drug Administration approved photodynamic therapy (PDT) for treatment of pre-malignant actinic keratosis (AK).  Patients with multiples lesions seem to be the best candidates. The instructions are simple: one applies a topical photosensitizing agent and undergoes blue light treatment for a specified amount of time in order for the medication to become active. Even more recently however, PDT has been shown to be successful with just natural daylight.1 But what about its efficacy in comparison to traditional modes of treatment such as freezing (cryotherapy)? An extensive meta-analysis in 2014 showed that it is 14% more effective than cryotherapy in clearing AK on the face and scalp, and doing so with superior cosmetic results.2 Nevertheless, it still is not considered a first line treatment for AK, and not widely used by dermatologists. Still, this should not be a point of discouragement as such advances in medical science can be the spark of a revolutionary change in the way we utilize the sun.

Another condition, keratoconus, is an eye problem seen more often in patients with eczema, and is characterized by progressive corneal thinning, causing the cornea to take on a coned shape, thus distorting vision. Currently, the only treatment is corneal transplantation. However, a novel surgical procedure called Collagen Corneal Cross-linking (CXL) in phase III clinical trials, works by applying drops of the dye riboflavin onto the surface of the patient’s eye after surgical disruption of the corneal epithelial layer, and then treating the cornea with UV-A light for 30 minutes. This causes the corneal collagen fibers to cross-link, thereby increasing corneal strength and halting the progression of the disease. That sure beats a corneal transplant. The future of medicine sure seems bright.

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Blue-Light and PDT
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