OCT

Optical Coherence Tomography

OCT Macula (OCT 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. This is a universal concept that will need to be used for every machine we use and for the slit lamp exam we do in the exam rooms. 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! If it makes you feel better, go ahead, but please refrain form doing this as it serves no purpose........

This is the star that patients see (resembles the Walmart logo)
Please always remind them to look into the center of this star if their macula is not visible or dead- centered

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 (refer to the abnormal OCTs section)

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

You will notice this box at the bottom left
The green cross (red circle) is where the fixation target is located for the patient to look at
The purple/blue cross (green circle) is where you are actually taking the picture!
For macular scans, you want these two crosses right on top on one another

By clicking the arrow at the bottom left (red circle), this will align both crosses on top of each other and result in am image that is centered perfectly over the macula (provided the patient is looking dead- centered in the middle of the star)

With the HD Cross, again, you want the green cross directly in the center of the grid
Achieve this by clicking the bottom left arrow (red circle)

This is a Posterior Vitreous Detachment (PVD)
The vitreous cortex pulls away from the retina
It is a common finding as it is part of normal aging, but can an lead to abnormal pathologies

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 also Wet AMD!

This is a Retinal Detachment (Macula On)

Red is bad on an OCT! This means the retina is raised off due to swelling, bleeding, or a detachment!

Another Macula off detachment

Cataracts will interfere with many images, especially OCTs and fundus photos as the light hits the dense areas and cannot pass beyond to the retina
More advanced cataracts can make imaging of the retina difficult, if not impossible!

Note

It goes both ways. Patients can't see out of the eye well, and our providers can't see into the eye well (proportionally)

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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