24 Cataracts

Cataracts are a common finding clinically.  It is, therefore, imperative that you are able to differentiate between different types of cataracts (especially the most commonly encountered ones – nuclear sclerotic, cortical, and posterior sub-capsular cataracts), and be able to counsel your patient appropriately.

To this end, review your notes from V644 – Ocular Disease I, which should have covered much of this material.

Next, have a look at this article, which reviews some common clinical presentations of cataract.

With respect to the clinical examination of a patient with cataract, there are a couple of points to emphasize.

First, a patient history is the most important part of your examination.  Get a good history, and you’ll likely be able to significantly narrow down your differential diagnoses, or at least clearly guide your examination forward in a way that will get you the answers you need.  With respect to cataracts, questions about glare and halos with headlights are critical.  But how you ask is also critical.  If I suspect that a patient has cataracts, I start off by asking, “Do you drive at night?”  If they answer, “yes”, I’ll then ask, “Do you have any problems with night driving?”  If they answer, “yes”, I’ll ask what those problems are.  If they answer “no”, I’ll then introduce the notion of glare and halo with headlights.

If the patient answers, “no”, to my original question, I’ll ask them why they don’t drive at night.  At this point, they will often mention halo and glare with headlights.

Notice that I don’t directly ask questions about “glare” and “halos” with headlights at the onset of this conversation.  If you ask very specific questions of a patient, they will often answer affirmatively.  I generally try to avoid specificity early, but if I don’t get the answer I want, I’ll increase my specificity as the history progress.

Next, if you suspect cataracts, or the patient has a history of cataracts, always perform and record brightness acuity testing (BAT) at the high setting.

After dilation, examine the lens body with an optic section, grading the amount of yellowing of the lens (nuclear sclerosis), and identifying the location of any discrete lens opacities (anterior and posterior cortical, posterior sub-capsular cataracts, etc.).  Also look at the anterior lens capsule for any opacities.  Finally, retro-illumination will help you identify lens opacities.

What follows is a quick look at cataract surgery, in which a cloudy natural lens is replaced with a clear artificial lens.  Note that an A-scan of the eye is performed prior to surgery to determine the axial length of each eye.  This information is combined with other information to help select a power for the clear, artificial lens implant that satisfies patient requirements for quality of life issues (the patient can be set to be plano in the distance, or have a bit of residual myopia to help them read with no glasses, for instance.  The paradigm is not perfect, but works extremely well)