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Eyes, ears, nose, and throat




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USMLE® Step 1 questions

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High Yield Notes

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USMLE® Step 1 style questions USMLE

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A 56-year-old man presents to the emergency department with severe left eye pain that started while he was at work. The patient is a radiologist and spends most of the day in a dark room reading films. Past medical history is noncontributory, and he does not take any medications. Physical examination of the left eye is shown below. Intraocular pressure is 39 mmHg in the left eye and 18 mmHg in the right eye. Which of the following pharmacologic agents is contraindicated in the treatment of this patient’s condition?

Image reproduced from Wikimedia Commons

External References

First Aid









glaucoma treatment p. 572

β -blockers p. 247

glaucoma treatment p. 572

Carbachol p. 241

glaucoma p. 573

Cholinomimetic agents p. 241

glaucoma treatment p. 572

Closed-angle glaucoma p. 555

pilocarpine for p. 241

Diabetes mellitus p. 352-360

glaucoma and p. 555


glaucoma treatment p. 572


glaucoma p. 573

Eye disorders

glaucoma p. 555

Glaucoma p. 555

acetazolamide for p. 632

atropine p. 242

β -blockers for p. 247

carbachol for p. 241

diabetes mellitus and p. 352

diagnosing p. 241

drugs for p. 572

epinephrine for p. 243

pilocarpine for p. 241

Sturge-Weber syndrome p. 543

Headache p. 536

glaucoma p. 555

Open-angle glaucoma p. 555

carbachol for p. 241

epinephrine for p. 243

pilocarpine for p. 241


glaucoma p. 573

Pilocarpine p. 241

glaucoma p. 573


glaucoma treatment p. 572


Glaucoma is actually a group of eye diseases that are usually due to intraocular hypertension, or increased pressure in the eye, which damages the optic nerve and if left untreated can lead to blindness.

Taking a closer look at this cross section of the eye, you can see that it’s split up into different chambers: The anterior chamber includes the area from the cornea to the iris, the posterior chamber is this really narrow space between the iris and the lens.

And then this larger vitreous chamber includes the space between the lens and the back of the eye.

Not to be too confusing, but both the anterior and posterior chambers are located in the anterior segment of the eye, while the vitreous chamber is part of the posterior segment of the eye.

Typically all of the chambers in the eye are filled with fluid.

The chambers in the anterior section are filled with a liquid called aqueous humor, and the posterior section is filled with vitreous humor.

The aqueous humor is a transparent, watery fluid that is secreted by the ciliary epithelium, which in addition to secreting aqueous humor and providing nutrients to the lens and cornea, it provides structural support and helps to keep the shape of the eye.

So that fluid’s secreted into the posterior chamber, and then flows through a narrow space between the front of the lens and the back of the iris through the pupil to the anterior chamber.

From there the fluid flows out of the eye through the trabecular meshwork, which is a spongy tissue that acts like a drain, and this allows the fluid to go down into a circular channel called the canal of Schlemm and finally into aqueous veins that are part of the episcleral venous system—the veins around the sclera of the eye.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Effects of Prostaglandin Analogues on Aqueous Humor Outflow Pathways" Journal of Ocular Pharmacology and Therapeutics (2014)
  6. "Glaucoma" Primary Care: Clinics in Office Practice (2015)
  7. "The current research status of normal tension glaucoma" Clinical Interventions in Aging (2014)

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