OCT

Optical Coherence Tomography

OCT Macula (Mac for short)

Clinical Pearls

An OCT Mac is a high- resolution image of the Macula. It is done via a low- intensity laser and penetrates the retina so we can see all the tissue layers
There is no radiation involved with this, and there is no risk to the patients that have to get this test done repeatedly

It is imperative that you center the image directly over the Macula, otherwise the image will likely have to be repeated. This is a huge inconvenience for both the patient, as well as our providers. Please be sure to constantly remind the patient to look at the center of the star. The image is not useful if it is not over the macula.
If their vision is so bad to the point they can't see the star, try to get them to look straight ahead and manually move the grid over where the macula should be. Do not be afraid to ask for help with this if needed.
Be sure the patient's forehead and chin are always on the forehead and chinrest at all times. When moving the patient closer to the machine, remind them of this as they can have a tendency to move away from the rest as they are being moved around and positioned properly.
The chinrest will move around as well, so remind the patient to move with it. Essentially, we move the eye up and down by moving the chinrest up & down, left & right
There is no reason the hold the shift button while doing an OCT! Please refrain form doing this as it serves no purpose........

This is a normal Macula, but note that they come in all shapes and sizes
Sometimes a macula can be completely flat, or have edema and they will look volcano- shaped (see following images)

We always take 2 images per Macula on different settings. Pictured here is the Macular Cube 200 X 200 setting
From above, you can see the macula looks like a donut
You want every OCT to be dead- centered in the middle of this donut as best as possible (as seen in the red circles)
You also want the cross- sections of the macula in the middle of the image
Always save OCT Macs in black & white!

This is an example of an OCT that is off- centered
Notice the macula (circled in red) is completely below the crosshairs
This will be of little (if any) diagnostic value to our providers and it would have to be repeated!
Imagine if the patient is 90 years old and in a walker, having to go back to the OCT and go through the process all over again.........

Another off- centered OCT
The macula (circled in red) should be dead- centered in the middle of the image!

Additionally, you want the OCT image in the middle of the image
Although the OCT is centered properly, the cross- section is too low on the image as seen here
If the OCT is too low or high, the provider cannot see vital areas, such as the basement membrane

This is Vitreomacular Traction (VMT)
When a PVD is incomplete and doesn't completely separate from the retina, the bit that is left over can pull on the retina

This is Dry AMD

This is Wet AMD

This is a Retinal Detachment (Macula On)

Clinical Pearls

RNFL: Retinal Nerve Fiber Layer
To get OD, have the patient look to the left, which will bring the optic nerve straight back so the laser can hit it (this video get's this wrong as it states have the patient look to the right for OD. For OD, the patient will look to the left)
To get OS, have the patient look to the right

This is what an OCT Nerve (RNFL) looks like
It measures the C/D ratio, the nerve thickness, as well as the symmetry between OU
Save these in color

Retinal ganglion cell analysis is great for early detection of damage from glaucoma when compared with changes to the optic nerve or visual fields
It is a simple test. Just do a normal 200 X 200 OCT, but analyze it under the GCA OU setting!
Save these in color and leave the overlay on the scan

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