In case you were wondering, controlling a potential sight threatening condition is much easier to manage in the early stages as opposed to waiting for noticeable vision loss. Keep in mind an OCT is not recommended for everyone and if it is recommended by your eye doctor there is a reason – and it likely has to do with preserving your vision.
How does an OCT work?
An OCT is essentially an ultrasound that uses light waves instead of sound waves to give detailed information about ocular tissue. So instead of using an ultrasound so see an unborn infant, your optometrist can visualize distinct retinal layers with an OCT. Fun fact: the retina is made up of several thin layers. Looking into the eye, or taking a retinal photograph, only looks at the outermost layer and cannot evaluate the depth of tissue like an OCT.
Why is it important to see retinal layers?
Each layer of the retina has a unique function that relates to vision. Etiology found at varying retinal layers can confirm the diagnosis, which influences treatments and prognosis. Not all diseases of the retinal affect the outermost layer. Certain diseases affect the deeper layers of the retina and therefor are not easily viewed by your eye doctor (or a photograph) – enter the OCT.
Can systemic conditions warrant further investigation with OCT?
Absolutely, did you know that conditions such as diabetes and hypertension can cause vision loss? One of the most common causes of vision loss associated with diabetes is clinically significant macular edema (CSME). CSME is thickening of the retinal tissue because the blood retinal barrier has broken down. To determine if retinal thickening has occurred, an OCT should be performed. Early diagnosis of CSME may help with earlier treatment to help prevent further vision loss. An interesting fact about CSME is that it can occur during any stage of diabetes, it is not directly associated with severe retinopathy.
Also important to mention is that certain systemic medications can cause toxic maculopathy. Toxic maculopathy is most commonly related to Hydroxychloroquine (Plaquenil) usage. Initially patients with toxic maculopathy are asymptomatic and do not develop symptoms until further damage is more severe. Symptoms can include decreased visual acuity, difficulty with night driving, and peripheral vision loss. When starting this medication establishing a baseline and undergoing repeat testing is important to catch early changes.
Another medication that is showing it can have visual complications is Topomax, a medication used to treat seizures and migraines. Further investigation and testing is indicated for Topomax use. It is important to note this blog is not advocating for discontinuing any systemic medication, it is informing you that it is important to work with an eye care professional who will communicate with your primary care physician if any ocular changes occur.
My parents have glaucoma and macular degeneration, do I need to undergo OCT testing?
Not necessarily. While a positive family history of glaucoma or macular degeneration is a risk factor for developing the condition, it does not directly warrant further testing. Your optometrist will evaluate other aspects of your ocular health to determine if testing is indicated. However, regardless of symptomology if recommended it is important to undergo testing.
Glaucoma is a condition that does not have symptoms until changes are severe. It is a painless loss of peripheral vision that is caused by damage to the optic nerve head. During examination your optometrist might mention that your optic nerve looks suspicious an OCT may be warranted. The OCT takes cross sectional views of the optic nerve head and the tissue surrounding the optic nerve. This information can actually help detect sub-clinical changes early in the process. While glaucoma does not currently have a cure, it does have great treatment options to prevent further damage.
Macular degeneration is one of the most common causes of vision loss in patients over the age of 50. It presents as decreased central vision and can have bleeding and edema within the retinal layers. Again, early diagnosis and intervention are important to prevent further vision loss or damage. OCT testing is important to determine if there is bleeding causing vision loss and, if so, which layer of the retina is being affected.
Optical Coherence Tomography is a unique instrument that allows eye care providers to evaluate the eye more in-depth without being invasive. It can also be utilized for many conditions and allows for early diagnosis and intervention.