The medical term for for crows feet–the wrinkles at the lateral or temperal side of the eye, is: Lateral canthal wrinkles.
Lateral canthal wrinkles caused by the contraction of the lateral side of the orbital portion of the obicularis oculi–(the obicularis oculi is the muscle that runs the circumference of the eye.) Squinting, or smiling are called Dynamic lateral canthal wrinkles. These wrinkles are the result of in folding and pleating of the overlying skin which radiate away from the lateral canthus–
(the lateral canthus refers to either of the temporal corners of the eye where the upper and lower eyelids meet.)
These canthal winkles are perpendicular to the direction of the lateral muscle fibers and of the orbital portion of the obicularis oculi which run mostly in a vertical direction around the lateral canthus. These type of wrinkles can be diminished through the use and injection of a neurotoxin (trade name Botox). Botox is also used clinically in small quantities to treat strabismus: Abnormal alignment of one or both eyes, and facial spasms and other neurological disorders characterized by abnormal muscle contractions. In some patients, however, age, thin skin, muscle degeneration, tendon degeneration and, sun damage are the main and contributing factors that produce lateral canthal wrinkles.
When the aforementioned is the cause, these types of wrinkles will always present whether a person is actively animating their face or not, therefore, these types of wrinkles are referred to as: static, Lateral canthal wrinkles.
When the bulk of lateral canthal wrinkles are static, the wrinkles are informally called crow’s feet but more affectionately called laugh lines. The neurotoxin mentioned above, (botox) in this case, is less effective and only through resurfacing, soft tissue filler, or reinforcement at the Lateral Canthus might this help modify static wrinkles of the lateral canthus.
Other more invasive procedures are: Canthoplasty, tarsal strip resuspension, lateral canthal- plication, canthopexy, lateral retinacular suspension and inferior retinacular suspension.
When the bulk of the crows feet are caused caused by hyperactivity, a condition characterized by excessive restlessness and movement of the lateral orbital portion of the obicularis oculi then injections of Botox can play a significant role in reducing the wrinkles.