EXCELLENT question. Consider these freebies on boards so please do not mess these up! I'm going to try to explain this UW style and throw in some pics/diagrams since ophtho is very visual (ha!)...
Cataracts - there are actually several types of cataracts but for boards purposes know that the decrease in vision or blurring is GRADUAL (months to years) and often associated with AGE. So the vignette may say "70 yr old p/w gradual visual BLURRING and GLARE over the past several years. Glasses does not help. Funduscopic exam is difficult due to a blurry view of the retina." Clearly, the blurry view is due to the OPACIFIED cataract obstructing your view when you look into the eye.
Short story: GRADUAL BLURRINESS, GLARE, AGE, AND OPACIFICATION OF LENS.
Macular degeneration - there are 2 types but for boards purposes know that it is generally a disease of the elderly (> 50), visual loss can be gradual or sudden BUT the patient experiences DISTORTION OF STRAIGHT LINES/EDGES and often has a CENTRAL BLIND SPOT. On funduscopic exam you see MACULAR DRUSEN. Here's what macular drusen looks like:
http://www.macula.org/images/retina_drusen.jpg
Short story: AGE, DISTORTION OF STRAIGHT LINES/EDGES, CENTRAL BLIND SPOT and perhaps a picture of MACULAR DRUSEN.
Glaucoma - there are several types. Two are most important for boards purposes. The most common type is
POAG (Primary OPEN-Angle Glaucoma) and is associated with ELEVATED EYE PRESSURE (normal is around 10-20mm Hg so elevated is anything > 22mm Hg!) and most common in AFRICAN AMERICANS. Visual loss is once again GRADUAL but there is LOSS OF PERIPHERAL VISION -- which is demonstrated by visual field test (with a machine called the Humphrey, not the wiggle your fingers in a bowl crap you learned in med school). Here's an example of a right eye with a superior arcuate defect on visual field testing most likely due to POAG:
http://smtp1.jobsoned.com/emailimages/op/0806_ogs/case_3a.gif
Here's an EXCELLENT pic with description of the increased "cup to disc" ratio that you see in glaucoma:
http://www.revoptom.com/osc/3146/Analysis.jpg
Short story: AFRICAN AMERICAN, ELEVATED EYE PRESSURE (painless), GRADUAL LOSS OF PERIPHERAL VISION AND INCREASED CUP TO DISC RATIO.
The 2nd type of glaucoma is an ophthalmic emergency, hence why they always ask it on Step 1, 2 and 3! In
Acute angle-CLOSURE glaucoma the patient p/w UNILATERAL PAIN, MARKEDLY ELEVATED EYE PRESSURES (> 40mm Hg...I've even seen a pt with an eye pressure of > 70mm Hg! Ouch!), BLURRED VISION, REDNESS, HEADACHE AND NAUSEA AND VOMITING! If you don't remember anything else I said up to this point, please remember this type of glaucoma as it is likely to show up on your exam and you may see it in practice. Time is of the essense in this scenario! (similar to an MI). Early intervention is critical b/c at eye pressures that high (> 40mm Hg) the pt's optic nerve fibers are taking a beating and dying quick! And once they lose their vision, it's gone forever. Not good guys. Here's a schematic that describes the concept of "angle-closure":
http://www.merckfrosst.ca/images/en/patients/diseases/glaucoma/glauc_closed.jpg
Short story: UNILATERAL PAIN, BLURRED VISION, MARKEDLY ELEVATED EYE PRESSURES (> 40mm Hg), REDNESS, HEADACHE, NAUSEA AND VOMITING. A true ophthalmic emergency! Otherwise, don't wake me up when I'm on-call. j/k!
Hope that clears things up a bit. G'luck on Step 1 guys.
