In order to understand what the ocular surface disease index is, first we need to understand a little more about what an ocular surface disease is.
What is OSD?
An ocular surface disease indicates some sort of damage to the front or surface layers of the eyes. The surface layers are called the cornea and the conjunctiva. The list of what might cause ocular surface disease, hereafter referred to as OSD, is quite long. In this article we will only be looking at the most common cause of OSD, and that is ‘dry eye syndrome’.
What is dry eye syndrome?
Dry eye syndrome can be classified as a disease which causes the eyes to become dry and remain irritable for extended periods of time. Dry eye syndrome also causes nagging discomfort throughout the day and when performing daily activities.
Types of dry eye syndrome
There are two types of dry eye syndrome
- Tear deficiency dry eye syndrome – As the name implies is just a case of the eyes not generating enough moisture to keep the eyes moist. Usually tear eye deficiency is resolved with the use of artificial tears.
- Evaporative tear deficiency – With this OSD a deficient tear film lipid layer will increase tear evaporation which leaves the eyes dry.
Causes of dry eye syndrome
Dry eye syndrome can be caused by a variety of reasons and depending on the type of dry eye syndrome these causes might be environmental or biological.
Most causes of dry eye syndrome is due to a disruption of the healthy tear film. Causes include:
- Previous existing medical conditions such as: allergic eye disease, scleroderma and lupus
- Corneal nerve desensitivity caused by wearing of contact lenses
- Parkinsons disease
- Posterior blepharitis
- Environmental factors such as pollution, wind or smoke
- Vitamin A deficiency
What is OSDI
Now that we understand what an ocular surface disease is and how it is caused, we will look at the OSDI or, ocular surface disease index. The OSDI is a questionnaire that was created to provide a quick and easy assessment of the symptoms related to ocular surface diseases like dry eye syndrome, and the impact that these symptoms have on your vision.
How does it work?
The ocular surface disease index is a 12 item questionnaire that is presented to patients during various intervals of procedure. It can be before procedures, during, or after. These questionnaires take into consideration various categories of daily function including: reading, accuity, and ability to maintain lifestyle. These questions are used to determine the level of discomfort of a patient. If a patient was completely comfortable they would indicate a 0 and if they were extremely uncomfortable they would indicate a 4.
Is it accurate?
When using the OSDI as a test for determining OSDI and also the level of severity of OSDI, it has been found to be quite accurate with results at 0.83 for specificity, and 0.60 for sensitivity. (Grubbs JR, Tolleson-Rinehart S, Huynh K, Davis RM. A Review of Quality of Life Measures in Dry Eye Questionnaires. Cornea. 2014;33(2):215-218.)
What are the alternatives?
In order to ensure accurate diagnoses of OSDI more advanced methods can also be employed in order to ascertain the level and severity of OSDI. These include:
- Tear Lab