Mutation of the p53 tumor suppressor gene, induced by UV radiation, has been identified as a crucial step in AK formation. This tumor suppressor gene, located on chromosome 17p132, allows for cell cycle arrest when DNA or RNA is damaged. Dysregulation of the p53 pathway can thus result in unchecked replication of dysplastic keratinocytes, thereby serving as a source of neoplastic growth and the development of AK, as well as possible progression from AK to skin cancer. Other molecular markers that have been associated with the development of AK include the expression of p16ink4, p14, the CD95 ligand, TNF-related apoptosis-inducing ligand (TRAIL) and TRAIL receptors, and loss of heterozygosity.Evidence also suggests that the human papillomavirus (HPV) plays a role in the development of AKs. The HPV virus has been detected in AKs, with measurable HPV viral loads (one HPV-DNA copy per less than 50 cells) measured in 40% of AKs. Similar to UV radiation, higher levels of HPV found in AKs reflect enhanced viral DNA replication. This is suspected to be related to the abnormal keratinocyte proliferation and differentiation in AKs, which facilitate an environment for HPV replication. This in turn may further stimulate the abnormal proliferation that contributes to the development of AKs and carcinogenesis. Ultraviolet radiation
It is thought that ultraviolet (UV) radiation induces mutations in the keratinocytes of the epidermis, promoting the survival and proliferation of these atypical cells. Both UV-A and UV-B radiation have been implicated as causes of AKs.
Duane syndrome is a congenital rare type of strabismus most commonly characterized by the inability of the eye to move outward. The syndrome was first described by ophthalmologists Jakob Stilling (1887) and Siegmund Türk (1896), and subsequently named after Alexander Duane, who discussed the disorder in more detail in 1905.Other names for this condition include: Duanes retraction syndrome, eye retraction syndrome, retraction syndrome, congenital retraction syndrome and Stilling-Türk-Duane syndrome. Presentation
The characteristic features of the syndrome are:

Limitation of abduction (outward movement) of the affected eye. Less marked limitation of adduction (inward movement) of the same eye. Retraction of the eyeball into the socket on adduction, with associated narrowing of the palpebral fissure (eye closing). Widening of the palpebral fissure on attempted abduction. (N. B. Mein and Trimble point out that this is "probably of no significance" as the phenomenon also occurs in other conditions in which abduction is limited.) Poor convergence. A head turn to the side of the affected eye to compensate for the movement limitations of the eye(s) and to maintain binocular vision.While usually isolated to the eye abnormalities, Duane syndrome can be associated with other problems including cervical spine abnormalities Klippel–Feil syndrome, Goldenhar syndrome, heterochromia, and congenital deafness. Causes
Duane syndrome is most probably a miswiring of the eye muscles, causing some eye muscles to contract when they shouldnt and other eye muscles not to contract when they should.