The Art of the OCT

If an ophthalmologist wants to look at the inside of a patient’s eye, the doctor will order an OCT (Optical Coherence Topography). The OCT will scan a patient’s macula (where his/her central vision is located) and the optic nerve. It uses a near-infrared light source to illuminate either the optic nerve or the macula.

“Look at the Blue Light”

In order to perform an OCT scan, the technician will tell the patient to look at the blue light inside of the machine. When looking at the blue light, the technician will have a good view of either the macula or the optic nerve.

The easier patients will look at the blue light with no hesitation. However, the more challenging ones are the patients who cannot even see the blue light. These are the patients where you will need to redirect the patient’s vision. If the patient is unable to see the blue light inside of the machine, I usually tell them to look at my nose. Because of COVID-19 and the need to wear a mask, the sassier patients will tell me that “they can’t see my nose” since it is underneath my mask. I try not to roll my eyes. I simply tell them,”use your imagination.”

Two Types of OCTs

The first OCT that we will talk about is the RNFL. I know, there are a lot of acronyms in ophthalmology. RNFL stands for Retinal Neural Fiber Layer. Generally, the RNFL OCT is used by glaucoma specialists as a way to diagnose patients. This type of OCT will measure the thickness of the retinal neural fiber layer. If there is evidence of the RNFL thinning on the OCT scan, the doctor may deduce that this happened because of glaucoma. For a full glaucoma evaluation, the ophthalmologist will order both a Humphrey Visual Field test along with an RNFL scan

The next type of OCT is the MAC OCT. For the most part, the MAC OCT is used by retina specialists. MAC stands for macula. Like I stated above, the macula is the center of a patient’s vision. The MAC OCT will show the doctor any irregularities that are happening within the retina. This type of OCT has revolutionized the retina field. Due to its quick timing, the OCT provides a clear image of the patient’s macula painlessly and efficiently.

Your turn. Match the two types of OCTs!