Dry eye is a complicated, multifactorial, ocular condition affecting millions of patients. Conservatively, it is estimated to affect 10% of the world population over the age of 40; as much as 15% of the population in the United States suffers from dry eye symptoms. Based on current lifestyles and aging population, this condition is likely to increase. With over 1 billion dollars spent annually worldwide, dry eye is second only to glaucoma in the cost of treatment. Aging populations will produce an increase in this cost in the coming years. Dry eye is also prevalent in wearers of contact lens where tear film stability is commonly compromised, leading to irritation and lens dropout.

 

The microenvironment of the cornea plays a critical role in the health and function of the eye. The pathological condition of dry eye syndrome results in altered production of tear film components and is often linked to autoimmunity. The presence of a contact lens in the eye complicates the corneal microenvironment by potentially altering factors such oxygen diffusivity and the friction forces exerted by the blinking action. For example, contact lenses decrease the normal surface cell exfoliation rate (apoptosis), independent of transmissibility. Additionally, contact lenses can cause abrasions to the corneal epithelium, the layer of cells covering the front of the cornea. These cells are capable of responding to this type of mechanical stimulus by rapidly regenerating (proliferating). Together, the environmental conditions and the response of the cornea, eyelid tissues, and contact lens surfaces to the environment and mechanical action act to establish the friction profile in the human blinking action.