(May 16, 2013 - Insidermedicine)
Hi I am Dr. Sanjay Sharma and I am an ophthalmologist and epidemiologist at Queen’s University. Today I want to talk about the importance of having your patients receive periodic eye assessments for glaucoma detection.
This video is based on our systematic review of the leading glaucoma literature, and was published as part of the rational clinical exam series in JAMA.
Open angle glaucoma is a leading cause of visual loss, but because it begins by affecting the far periphery of vision, most patients don’t know that they have it until the disease progresses and begins to destroy their central vision. Nearly half of those with glaucoma remain undetected and 50% of those diagnosed have very advanced disease on presentation. This is why it is so critical that at-risk patients be regularly screened for glaucoma.
All eyes have pressure in them so that refraction can properly take place and the eye’s internal structures can be bathed in nutrients. The eye’s pressure is maintained because of the continuous creation and flow of aqueous humor. This fluid, which is secreted by the ciliary body, flows through the pupil and leaves the eye through its drainage system called the trabecular meshwork.
There are two types of glaucoma: open angle and closed angle defined by the state of the angle at the junction between the iris and the cornea. In closed angle glaucoma the iris is pushed forward such that it obstructs the trabecular meshwork, whereas in open angle glaucoma the iris remains posterior and the trabecular meshwork remains open but degenerates over time.
While glaucoma caused by a closed angle is very rare – its presentation is dramatic and it is a true medical emergency as vision can be lost within a matter of hours.
Open angle glaucoma accounts for the vast majority of cases. In these patients chronically elevated pressure can destroy the optic nerve over a period of many years. However with drops, laser treatment or surgery – disease progression can be halted.
Our analysis based on a synthesis of 50 peer reviewed articles shows that 2.6% of the overall population has glaucoma.
We also found a higher risk of glaucoma in:
1. those over the age of 80
2. those who are nearsighted
3. those with a positive family history, and
4. those who are African-American
The analysis also showed that certain physical findings detected through high quality periodic screening are strongly associated with open angle glaucoma. These include:
1. an increased cup to disc ratio
2. a cup disc asymmetry between the two eyes
3. the presence of a disc hemorrhage, and
4. an eye pressure that is greater than 21 mmHg.
Because diagnosing glaucoma requires specialized testing including measuring visual fields and retinal nerve fibre layer thickness, it is essential that generalist physicians direct any patient over the age of 45 to be periodically screened for glaucoma typically every 2 to 4 years. As patients age, or if they have more than one risk factor as listed previously, patients should be screened more regularly, up to once every 1 or 2 years
It is our sincere hope that if generalist physicians adopt this practice and regularly refer their patients for high quality periodic eye examinations, glaucoma can be detected at an early stage and proactively managed before it causes significant visual loss and blindness.