Dare to dilate: Evaluation of acute visual loss in the emergency department

Why don't we dilate in the emergency department?

• Dilation can induce acute angle closure glaucoma. Emergency medicine texts are riddled with warnings against precipitating acute angle closure glaucoma via pharmacologic dilation in patients with shallow anterior chambers. This is an incredibly rare phenomena, estimated at 3 in 10,000, an incidence which can be further lowered by using a penlight to estimate the patients AC depth prior to dilation[1, 2]. It is important to note that dilation does not cause a shallow anterior chamber but simply unmasks its presence, an event which could actually be sight-saving for the patient. In fact, historically ophthalmologists have attempted (and failed) to identify a provocative test for angle closure in order to preemptively provide therapy. Therefore, we should not fear this complication, but instead be aware of the possibility of this event  as well as its therapy.

• Dilation takes time. Application of a few drops while seeing another patient, performing tonometry or slit lamp exam, should not unduly interfere with patient flow.

Why should we dilate?

• Direct funduscopy is difficult and we probably aren't very good at it. Even in the dilated eye, less than half of graduating medical students feel comfortable examining and identifying key pathology[3, 4]. This is reflected by the fact that emergency physicians frequently do not perform funduscopy, even when the patient’s chief complaint likely warrants it. When we do, our exam is insensitive to relevant findings[5]. For learners, it is particularly important to dilate while learning to recognize normal and abnormal retinas.

When should we dilate?

• Highest yield is likely painless monocular visual loss: Here's a case:

• 60 year old male, sudden, painless vision loss in his right eye 1o minutes ago. Physical exam reveals an normal appearing external eye. Intraocular pressure is 16 on the right and 12 on the left. He can intermittently count fingers if held a foot from the right eye with the left eye covered.

• You ask yourself: Do I need an ophthalmologist right now? Is there anything I can do to treat this now? Do I need further imaging? A dilated eye exam can help you answer these questions as well as your patient's, "Will I ever see again?"

• When not to dilate:
  • If you are concerned about elevated intracranial pressure. Dilation obscures your ability to do repeat neurologic examinations and evidence of impending herniation.
  • Active angle closure glaucoma (patients with a history of angle closure glaucoma are likely post-iridectomy and dilation should not pose a threat to them).

• How to dilate:
  • Pearl: All mydriatic solutions have RED caps. (Red = STOP, therefore these paralyze the muscles of the iris).
  • Apply phenylephrine (Neo-Synephrine) 2.5%, which lasts a total of 3 hours , this agent alone may be enough to facilitate your exam and has the benefit of not affecting the patient’s vision.
  • If you are not satisfied with phenylephrine alone you may also apply tropicamide (Mydriacyl) 1%, which lasts a total of four hours.
    • Always counsel your patients that they will be sensitive to light and have fuzzy vision for several hours before applying tropicamide.
  • Patients with lighter iris colors are more sensitive to cycloplegic agents.
  • Check back in 10-15 minutes. The pupil should now be dilated.

• Take home message:
  • Direct funduscopy is a challenging skill even in the best of circumstances.
  • It is essential for resident physicians to build this skill, ideally with the help of dilation when necessary.
  • Dilation is safe, easy, and should not be time consuming.
  • Dilation of the eye should be a tool in every emergency physician’s arsenal, best applied in patients presenting with painless, monocular visual loss.

References:

1. Wolfs, R.C., et al., Risk of acute angle-closure glaucoma after diagnostic mydriasis in nonselected subjects: the Rotterdam Study. Investigative ophthalmology & visual science, 1997. 38(12): p. 2683-7.
2. Patel, K.H., et al., Incidence of acute angle-closure glaucoma after pharmacologic mydriasis. American journal of ophthalmology, 1995. 120(6): p. 709-17.
3. Schulz, C. and P. Hodgkins, Factors associated with confidence in fundoscopy. The clinical teacher, 2014. 11(6): p. 431-5.
4. Roberts, E., et al., Funduscopy: a forgotten art? Postgraduate medical journal, 1999. 75(883): p. 282-4.
5. Bruce, B.B., et al., Diagnostic Accuracy and Use of Nonmydriatic Ocular Fundus Photography by Emergency Physicians: Phase II of the FOTO-ED Study. Annals of Emergency Medicine, 2013. 62(1): p. 28-33.e1.
6. Adam T. Gerstenblith, M.P.R., Wills Eye Manual, The: Office and Emergency Room Diagnosis and Treatment of Eye Disease, 2012. Source of images.

Reviewed by Daniel Cabrera, M.D.