Direct Ophthalmoscopy is a skill that seemed nearly impossible a
couple of weeks ago. Do I see a reflex? Do I need more magnification or
less? How close should I get to this patient? Can I hold my breath that
long? Do you even have an optic nerve? Can I go back to retinoscopy?
Give me my schematic eye back!!!! These are only a few of the many
thoughts running through my mind as I continuously “play” doctor
alongside my classmates.
After getting over my mental rant and
numerous failed attempts, I was finally able to get my very first view
of the optic nerve. It was then that I remembered the analogy a fellow
SCO graduate once gave me: think of the cup to disk ratio as a bowl of
spaghetti! An idea that once seemed so obscure finally began to take on a
whole new meaning. Who would’ve thought that my love for spaghetti
would come in handy at optometry school? Not me!
So here is how it
goes: Picture a bowl (disk) with a fixed number of spaghetti strands
(nerves; lets say 10) arranged diagonally so that the strands all have a
common point where they meet, prior to diverting outwards in various
directions till they graze the edges of the bowl and ultimately fall
outwards. The key point to remember is that the number of spaghetti
strands will always remain fixed. However, the bowl of spaghetti may
either increase or decrease, meaning the optic disk will be larger or
smaller, respectively. You then need to add the spaghetti sauce (cup),
which will go in the middle of the bowl. The bigger the bowl, the larger
the amount of sauce that can be added, and therefore, the larger the
cup will be. Similarly, the smaller the bowl, the smaller the amount of
sauce that can be added and therefore, the smaller the cup will be.
Once you can picture this, you can then determine the cup-to-disk
ratio. What percentage of the cup does the disk occupy? Or, what
percentage of the bowl does the sauce occupy? Good news: you can now
predict a C/D ratio!! Bad news: the spaghetti analogy will only get you
so far. It will not help with determining the presence of a spontaneous
venous pulsation or foveal light reflex, nor will it aid in assessing
the vasculature or macula of the eye. You’re on your own there!!
However,
I will give you one last piece of advice, when looking at your
patient's right eye, use your RIGHT eye, and when looking at their left
eye, use your LEFT eye – unless of course, you’re trying to sneak in a
peck on the lips! (Seriously, don’t be THAT person in the middle of a
practical!)
That’s all for now... until next time! Can’t wait to share some post first year wisdom with you all in just a couple weeks!