We’ve learned in ophthalmic optics that a minus lens (concave) will minify images, while plus lenses do the opposite. I have been taught by several ophthalmologists to note the size of a patient’s eye through the glasses they’re wearing. If it looks big, then they’re hyperopic. Small = myopia. Easy, right?
Wrong.
In some cases, it is obvious that someone is myopic by the disproportionate size of the eye. To me, most of the cases are not obvious at all.
Years ago when I was still a medical student, Harry Knopf, one of the private attendings at WashU had told me to look at the temples, not the eyes. The refractive error can be estimated by looking at the temple border. Read more…
The AAO (American Academy of Ophthalmology) has a public awareness website, GetEyeSmart.org, that overviews common eye problems.
I direct my English-speaking patients as well as my non-medical friends here for self-education. Helps me to avoid stupid questions (and creates other ill-considered medical questions).
I wrote about my feelings of receiving inappropriate consults on a previous post. Since then, I tallied an additional list of observations I’ve noted in consultation requests. Some of these are absurd:
Me: This is ophthalmology returning a page.
Consultee: You have to see this consult…
Others are even more direct:
Me: This is ophthalmology returning a page.
Consultee: Five-One-One-Eight… [reading medical record number of presumed patient needing consult]
On other occasions, the interaction becomes insulting:
Consultee: (At 3 am) Sorry to wake you. This isn’t an official consult yet, but can I borrow your Tonopen? (Device to check eye pressure). This guy with a history of glaucoma fell and hit his head last night….
I suppose that direct blow to the eye could cause an eye pressure spike, but there are a few other incongruities in this consult request (We take home-call).
The ultimate insult:
Me: Can I borrow your stethoscope?
Consultee: Do you even know how to use one? (I was one year senior to this guy in medical school, and I taught him about renal failure in a review group)
Retinoscopy is one of the more difficult exams to master in ophthalmology. It allows us to obtain one’s refractive error objectively. This is useful in children who are too young to be tested subjectively on an eye chart, or in those who are not verbal.
The optics behind retinoscopy is elegant. In a perfectly round cornea without refractive error, light entering the eye is focused directly onto the retina. The reflection of light appears as a homogeneous red reflex to the examiner. In a hyperopic eye, the cornea is underpowered–light becomes focused behind the retina. As the examiner streaks the light through the pupils, the retinal reflex moves in the same direction as the light beam from the retinoscope–this appearance is dubbed “with motion”. With-motion is created from uncrossed light rays traversing the surface of the retina.
Conversely, myopic eyes focus light in front of the retina. Light rays on the retina are crossed, and produce a red reflex that moves in the opposite direction of the the streak (against motion).
For many people, against motion is difficult to discern, especially if there is with motion in another axis. I have probably overlooked this finding in dozens of kids with small amounts of myopic astigmatism, hopefully without dire consequences.
Last week, however, I successfully identified myopia through retinoscopy in a 5 year-old. The refraction was -1.00 + 4.50 x 085 in the right eye.
A celebration for this momentous event is in hand…
