A 45-year-old woman comes to the clinic due to blurry vision in the left eye. The patient first noticed some decreased visual acuity 2 days ago and thought she may need a new prescription for her glasses. However, the blurriness has progressively worsened. The patient has no eye pain or foreign body sensation and does not wear contact lenses. Temperature is 36.8 C (98.2 F), blood pressure is 110/78 mm Hg, pulse is 76/min, and respirations are 14/min. On examination, visual acuity is moderately reduced in the left eye. The upper and lower eyelids can fully open and close bilaterally. Corneal esthesiometry reveals decreased sensation of the left cornea. Fluorescein examination shows a large, geographic ulceration and several linear, branched defects overlying the cornea. Dysfunction in which of the following nerves is most likely the cause of this patient's impaired corneal sensation?

Question

A 45-year-old woman comes to the clinic due to blurry vision in the left eye.  The patient first noticed some decreased visual acuity 2 days ago and thought she may need a new prescription for her glasses.  However, the blurriness has progressively worsened.  The patient has no eye pain or foreign body sensation and does not wear contact lenses.  Temperature is 36.8 C (98.2 F), blood pressure is 110/78 mm Hg, pulse is 76/min, and respirations are 14/min.  On examination, visual acuity is moderately reduced in the left eye.  The upper and lower eyelids can fully open and close bilaterally.  Corneal esthesiometry reveals decreased sensation of the left cornea.  Fluorescein examination shows a large, geographic ulceration and several linear, branched defects overlying the cornea.  Dysfunction in which of the following nerves is most likely the cause of this patient's impaired corneal sensation?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c010_a7a6_8f63_59060d35de04_MD0005_00 This patient with blurry vision has dendritic (linear, branched) corneal ulcerations on fluorescein examination, findings diagnostic for herpes simplex virus (HSV) keratitis. HSV keratitis is a corneal infection caused by viral reactivation and is the most common cause of corneal blindness in resource-rich countries. corneal ulcerations Classic signs and symptoms of HSV keratitis include eye pain, photophobia, and clear discharge, as well as decreased visual acuity and ciliary flush (ie, conjunctival injection surrounding the cornea). However, some patients may have no significant pain due to decreased corneal sensation and despite the presence of a large ulceration, as in this patient. The pathophysiology of decreased corneal sensation in HSV keratitis involves dysfunction of the trigeminal nerve (CN V). CN V has 3 branches, and the V1 (ophthalmic) branch carries sensory fibers to the upper eyelids, conjunctivae, and corneas, as well as other local structures (eg, scalp, forehead, frontal sinuses). HSV infection of the V1 branch (specifically the nasociliary nerve mediating the afferent limb of the corneal reflex) causes corneal anesthesia. Symptoms typically resolve within 2 weeks of treatment with topical or oral antiviral therapy; however, recurrent episodes can occur. (Choice A) The facial nerve (CN VII) is responsible for facial movement, including eyelid closure, as well as taste in the anterior tongue, lacrimation, and salivation; it does not innervate the cornea. (Choice B) The oculomotor nerve (CN III) is a pure motor nerve responsible for the majority of eye movement, eyelid opening, and pupillary constriction. (Choice C) The optic nerve (CN II) carries visual information to the brain and mediates the afferent limb of the pupillary light reflex. Damage can cause monocular blindness and an afferent pupillary defect, not decreased corneal sensation. (Choice E) The vagus nerve (CN X) does not innervate the cornea. CN X functions include, but are not limited to, swallowing, palate elevation, phonation, and parasympathetic outflow to the thoracoabdominal viscera. Educational objective: Herpes simplex virus keratitis, diagnosed by visualization of dendritic corneal ulcerations, usually presents with eye pain, in addition to other classic findings (eg, blurry vision, tearing, redness), but can occur without pain due to decreased corneal sensation from trigeminal nerve (CN V) involvement. References: Herpes simplex virus-1 KOS-63 strain is virulent and causes titer-dependent corneal nerve damage and keratitis. (http://www.ncbi.nlm.nih.gov/pubmed/33608598) Corneal sub-basal nerve changes in patients with herpetic keratitis during acute phase and after 6 months. (http://www.ncbi.nlm.nih.gov/pubmed/31137905)

A 45-Year-Old Woman Comes to the Clinic Due to Blurry