Diplopia - ED evaluation

Primary eye disorders or systemic diseases presenting as ophthalmologic complaints may present to the Emergency Department especially when symptoms are acute in onset. Diplopia is one such complaint which we might come across in ED. 

Key Questions when evaluating diplopia:
1. Is it Monocular or Binocular Diplopia?

• Monocular Diplopia - Eye Problem (cataract irregularities, lens displacement, or primary problems with the corneal curvature such as keratoconus.)
• Binocular Diplopia (Common) - Likely Neuro Problem (3,4,6 Nerve lesions, Grave's eye Disease, Myasthenia gravis, Orbital Myositis)

2.  Does the degree of diplopia change with direction of gaze and/or head position?  (Determines whether deficit related to cranial nerve innervation)

3. Is the diplopia horizontal or vertical?  

(Horizontal diplopia suggests cranial nerve III or VI deficit (i.e. lateral gaze function); vertical diplopia suggests cranial nerve IV deficit (i.e. elevator/depressor gaze function).

4. Associated pain? (Suggests possible foreign body or extraocular muscle entrapment).

5. Associated trauma? (Blow-out fractures can be associated with diplopia).

6. Associated weakness, headache, confusion, or dizziness?  (Imaging usually indicated to rule out intracranial processes such as stroke or increased intracranial pressure).

3rd Nerve palsy

• Supplies most of the EOM
• Lesion results in Down and out deviation of eyeball, Ptosis due to levator palpebrae paralysis and Ptosis due to damage to parasympathetic pupil-constrictor fibers from the Edinger-Westphal nucleus

Most third nerve palsies are caused by ischemic events due to hypertension or diabetes. 

Pupillary involvement is a crucial diagnostic sign -- compressive lesions tend to involve the pupil, while vascular lesions might actually spare it! This is due to the fact that the parasympathetic nerves course along the surface of the oculomotor nerve making them susceptible to compressive lesions from the outside whereas ischemic lesions occur deeper within the oculomotor nerve and thus spare the superficial parasympathetic fibers.


4th Nerve Palsy

• Difficult to diagnose
• Innervates Superior Oblique muscle
• These patients have an upward deviation of the affected eye with a tilt their head away from the lesion
• Possible Causes include Trauma, ischemia, congenital lesions, malignancy

6th Nerve Palsy

• Supplies the lateral rectus muscle
• Loss of function renders the eye unable to abduct (turn out). 
• Patients go cross-eyed, so to compensate they may turn their head to avoid double vision.
• Susceptible to high intracranial pressures.e.g. pseudotumor cerebri 

Table from Rosen's EM Textbook - Causes of Diplopia

Take Home

• Differentiate betweekn monocular and binocular diplopia is the key
• Think compressive causes e.g. P Comm Aneurysm with a dilated pupil (3N palsy)

Posted by:

              

     Lakshay Chanana

     

     ST4 Trainee

     Royal Infirmary of Edinburgh

     Department of Emergency Medicine

     Edinburgh

     Scotland

     @EMDidactic

Corneal Abrasions - Eye emergencies

Cornea

The cornea is a transparent layer over the anterior part of the eye that serves as a  protective coat, aids refraction, and filtration of some UV light. Cornea has no blood vessels and receives nutrients through tears as well as from the aqueous humor. It is innervated primarily by the ophthalmic division of the trigeminal nerve and the oculomotor nerve.

https://www.allaboutvision.com/resources/cornea.htm

Corneal Abrasion

Corneal abrasion is the most common form of eye trauma presenting to the emergency department. Abrasions may result from contact lens wear, foreign objects blown into eyes or other trivial trauma. Patients present with a feeling of foreign body sensation, photophobia, and tearing. It is important to enquire about the work circumstances and the mechanism of injury because injuries with the use of high-speed machine are associated with corneal laceration and globe perforation. 

Examination (Evert the eyelids to look for a foreign body)

• Exam reveals conjunctival injection, tearing, and lid swelling. 
• Blepharospasm may accompany due to severe pain (may require a topical anesthetic to do the examination). Relief of pain with topical anesthesia is virtually diagnostic of corneal abrasion. 
• Photophobia 
• Decreased visual acuity (if the abrasion is in the central visual axis or if there is an associated iritis)
• Use Seidel's test to check for open globe injury 

The corneal abrasion is often visible to the naked eye as an irregular area of light reflection off the cornea

• Slit lamp examination: Shows a flare and cells from iritis if the abrasion is large and >24 hours old. It is crucial to check the entire thickness of the cornea for a full-thickness laceration, and the Seidel test should be negative. The abrasion usually appears as a superficial, irregular corneal defect appearing bright green under the cobalt blue light after instillation of fluorescein.

A series of small, fine-lined vertical/linear corneal abrasions seen with fluorescein staining suggests the presence of a foreign body embedded in the tarsal conjunctiva of the upper lid

Treatment

Majority of corneal abrasions heal spontaneously and thus treatment is aimed at relieving pain and preventing infection. 

Cycloplegics - Believed to relax the ciliary body and relieve pain from spasm (However, no good evidence exists in the literature to support the common practice of using cycloplegics/mydriatics for the treatment of routine corneal abrasions)

Pain Relief: Traditionally, these agents have never been prescribed for home use, because they may cause a secondary keratitis, compromise epithelial wound healing, and block effective corneal protective reflexes and sensation. Topical NSAIDs provide pain relief and do not impair healing in patients with corneal abrasions. 

Antibiotics
Topical antibiotics ointment are usually prescribed

• Non-contact lens wearers: erythromycin ointment.
• Contact lens wearers: cover for Pseudomonas species (ophthalmic ciprofloxacin, ofloxacin, etc.)

Antibiotic drops are more comfortable than ointments but must be administered every 2-3 hours. Ointments that retain their antibacterial effect longer can be used less often (every 4-6 h) but are more uncomfortable due to visual blurring.

Patching no longer recommended for abrasions involving < 50% of the cornea. A meta-analysis of 7 trials in patients with corneal abrasion showed similar healing rates between patching and no patching. Patching the eye does not promote healing. Abrasions from fingernails, vegetable matter, or a contact lens should not be patched, as they are at higher risk of infection.

Tetanus prophylaxis

Consult Ophthalmology in ED for:

• Large abrasions (involving > 50% of the cornea)
• Findings suggestive of corneal ulceration.
• Inability to remove retained FB.
• Hypopion

Smaller abrasions should be checked in 48 to 72 hours. 

Further Reading:

• Flynn CA, D'Amico F, Smith G. Should we patch corneal abrasions? A meta-analysis. J Fam Pract. 1998 Oct. 47(4):264-70.
• http://rebelem.com/topical-pain-control-for-corneal-abrasions/
• https://anatomyforemergencymedicine.wordpress.com/2015/05/03/031-eye-anatomy-part-2/

Posted by:

              

     Lakshay Chanana

     

     ST4 Trainee

     Royal Infirmary of Edinburgh

     Department of Emergency Medicine

     Edinburgh

     Scotland

     @EMDidactic