How to Evaluate the Optic Nerve (in 3D!)
Grading the optic nerve can be tricky. The optic nerve can be shallow, deep, tilted, oblique, and much much more. It’s not suprising that many studies show tremendous amount of interobserver variability when grading cup to disc ratios both in vivo and via photographs.
This is not limited to new eye doctors and clinicians, it also applied to glaucoma specialist experts! One study in 2009 found that eye doctors and glaucoma specialists. In fact, one study found that in 40% of the cases in which a glaucoma specialist believed the optic disc appeared to have progressed in glaucoma severity, the photograph of the “worse” optic disc was in fact taken at the start of the study!
Are You Good at Evaluating the Optic Nerve?
Enter the wonderful world of optic nerve evaluation and grading. Whether you are a student, resident, optometrist, or ophthalmologist, we were all taught similar basics about how to grade the optic nerve and cup to disc ratio. We always look carefully for rim thinning, notching, vessel baring, peripapillary atrophy, etc, etc, etc.
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I know what you’re thinking (I’m a mind reader in my spare time after all). Right about now you’re thinking something along the lines of “of course I evaluate and grade the optic nerve, but that’s why I have an OCT! What’s more reliable: my eyes or a $50,00 piece of equipment that is designed to assess the retinal nerve fiber layer, capillary plexi, ganglion cell layer, and analyze progression?” Was I close? I bet I was…because I think the same exact thing on a daily basis.
Consider the following:
- How will you know when to run an OCT if you can’t assess the nerve for subtle changes ?
- If you decide to just run it on every patient, who is going to pay for it
- Do you really know when the OCT is misreading the nerve fiber layer and optic nerve (“red disease”) and when it can no longer assess change (“floor” effect).
- And the biggest assumption of all…not every optometrist or ophthalmologist has an OCT in their office!
Grading the Optic Nerve: Beyond OCT
Enter the man, the myth, the legend: Dr. Peter Lalle who served as the chief of optometry at the Baltimore VA Medical Center for over 35 years. Dr. Lalle worked with hundreds of students and residents throughout his career and noticed that with the advent of retinal imaging such as OCT, HRT, and GDx that observational skills in optic nerve evaluation have generally deteriorated.
The solution: Dr. Lalle created an awesome video full of stereoscopic optic nerves gathered over the course of his career. The video contains numerous examples of glaucomatous changes that some of your fancy technology may not be able to detect.
The Mind Reader Returns!
Here comes the mind reader again! “But how am I going to see this in 3D?” you ask. Many people can free fuse the images while viewing on your phone or tablet with only a pair of reading glasses. Alternatively, a cheap pair of virtual reality goggles also works great for those who are not able to free fuse.
Without further ado, please enjoy this informative video on how to grade and evaluate the optic nerve.