What Is Ocular Surface Disease?
Ocular surface disease is a very common condition that can impact the stability of your tear film, as well as the quality or quantity (or both) of your tears.
Ocular surface disease (OSD) is an overarching term for a variety of conditions that disrupt the health of the cornea, the surface of the eye. It encompasses several subsets like dry eye, meibomian gland dysfunction, and blepharitis. Dry eye disease (DED), is the most common form of OSD and it is the main reason patients visit an eye care provider.
DED can range from being mildly irritating to debilitating. It is the corneal surface’s response to a break down in the natural layer of tears that coat the front of the eye, the tear film. Normally, this layer acts as protection for the eye against exposure to the environment and it is the first refracting surface of the eye, meaning clear and stable vision also depends on the tear film’s health.
The symptoms of DED are numerous; one of the most common and confusing to patients is the tendency to have increased tearing. This happens when an unhealthy tear film and the subsequent irritation stimulates the brain to produce reflex of tears in response to the irritation. The tear film in its unstable state, however, will not do its job properly. Other symptoms include:
- Blurry or fluctuating vision (made worse when reading, computer, watching television, driving, or playing video games)
- Sandy or gritty feeling
- Matting or caking of the eyelashes (usually worse upon waking)
- Sensitivity to light
- Eye pain and/or headache
- Heavy eye lids
- Scratchy or foreign-body sensation
- Frequent blinking
- Eye fatigue
Healthy tears are the key to eye comfort and good vision. There are three components of healthy tears that all service a function and are all important: lipid or the oil component, aqueous or the water component, and a mucin or mucous-like component. Lipids enhance lubrication and help keep the tear film from evaporating too quickly and the mucin helps spread tears across the surface of the eye.
Each of these types of tears is produced by a different gland: meibomian glands in the eyelids make oil, lacrimal glands behind the upper eyelid make the water, and goblet cells in the conjunctiva make mucin.
DED falls into different categories based on which component of the tear film is affected. The oil component, also called meibum, is produced by the meibomian glands. If this process is not working effectively and the tear film evaporates too quickly, this is referred to as “evaporative dry eye” and meibomian gland disease is the cause. If the lacrimal glands for not produce enough watery fluid, the condition is called “aqueous deficiency dry eye.”
When diagnosing DED, eye care providers will conduct a comprehensive examination, use certain tests to determine the underlying cause of DED and base their treatment on these findings. Diagnosis and treatment of DED will be discussed in future blog posts in this series.