Double Whammy

Optic neuritis involves an acute, painful loss of vision (in 90% of cases) caused by underlying inflammation and demyelination of the optic nerve that predominantly affects young females.^1-4 Typically unilateral with the possibility of recurrences, this disorder can have a plethora of underlying etiologies, such as infectious, inflammatory, and genetic.⁴

THE EXAMINATION

A stepwise approach is key to avoid breezing over important findings, as one may make the diagnosis.

A natural first step that is often overlooked is listening to your patient. Always verify a case history by having a direct, pointed conversation with your patient. Their symptom presentation likely did not come on gradually. Typically, these patients can tell us the exact moment they noticed the change in their vision.² They will likely describe it as new or sudden, with gradual worsening since onset.

Secondly, and most obviously, a detailed visual acuity must be taken. Patients with optic neuritis can have an entering VA from 20/20 to no light perception.¹ Visual acuity, when normal, can provide a false sense of security and should not be solely relied on to exclude optic neuritis as a possibility. Visual field defects are also often seen with optic neuritis, so it is important to perform a formal visual field assessment if a patient complains of acute vision loss—particularly if their vision remains 20/20.

A detailed pupillary assessment should always be performed with the swinging flashlight test. The presence of an afferent pupillary defect (APD), at times, may be the only finding that is proof of a pathologic etiology. It is important to note, however, that an APD may be absent if the fellow eye previously had optic neuritis or other significant optic nerve damage.

Color vision should also be checked. This can be done by formal assessment, such as Ishihara color plates or a simple red cap desaturation test. For the latter, the patient looks at a bright red cap (phenylephrine bottle caps work great for this) with their uninvolved eye and compares the brightness with what they see with their involved eye. In optic neuritis, the involved eye will see a darker or paler color.² As for funduscopic changes, the optic disc oftentimes appears normal; in two-thirds of cases, the inflammation is retrobulbar. This is why optic neuritis is often missed at early stages. A detailed description, as well as funduscopic photos and a baseline optic nerve OCT, are warranted.

CASE NO. 1

A 28-year-old female presented to the ED with concerns of vision loss in her left eye. She stated that she woke up the previous day with dark vision in her left eye. She endorsed a history of migraines that are usually stress-related but denied any other ocular symptoms. The ED consulted ophthalmology and neurology to examine the patient. Upon arrival, she was 20/20 OD and 20/30 OS with full-to-finger-counting confrontation visual fields. At that time, no APD was noted, and funduscopic examination was unremarkable. It was deemed the patient was having a nonspecific visual disturbance, likely migraine-related, and follow-up with formal visual field testing was recommended.

The patient presented to the triage clinic 4 days later. Vision in the involved eye had progressed from 20/30 to counting fingers, and an APD was now noted. A complete superior visual field defect was found with Humphrey visual field testing (Figure 1). The optic nerve OCT was normal and symmetric (Figures 2 and 3). Funduscopic examination continued to be unremarkable without evidence of swelling, elevation, or edema. The patient was diagnosed with retrobulbar optic neuritis and was sent back to the ED for a thorough workup, including brain MRI with and without contrast.

The brain MRI showed “hyperintense lesions in the periventricular and deep white matter of both cerebral hemispheres with a short segment contrast enhancement within the orbital segment of the left optic nerve” (Figure 4). The patient was given 1 g methylprednisolone and was admitted to neurology for further evaluation and management.

She returned 2 weeks later with no residual visual issues. Her vision had returned to 20/20, and the severe visual field defect had completely resolved (Figure 5). She was followed by neurology with a working diagnosis of multiple sclerosis (MS).

CASE NO. 2

A 22-year-old female presented to the general clinic with concern over sudden vision loss in her right eye, which was sore to the touch. Entering VA was 20/25 OD and 20/20 OS. All testing was normal with no color desaturation, no APD, and normal optic nerve appearance funduscopically. Her optic nerve OCT was borderline when assessing the retinal nerve fiber layer thickness, but overall symmetric between her eyes (Figure 6). She had a mild superior altitudinal defect superiorly OD. This, too, was diagnosed as a visual disturbance, but it was documented that the patient had some concerning features of optic neuritis, including pain with eye movement, so she was followed closely with a return visit planned for 1 week later.

After 1 week, the patient returned with progression of symptoms, including worsening of vision and a pressure-like sensation of pulling against the nose in the involved eye. Her VA was 20/50 OD, and the visual field defect was now a complete superior defect (Figure 7). There was also a notable APD in the involved eye. The patient was sent to the ED for further workup, including brain MRI, which showed “multiple white matter lesions with an appearance and pattern consistent with demyelinating disease” (Figure 8). With this, the patient was admitted and started on a 3-day course of intravitreal 1 g/day methylprednisolone.

The patient returned 2 weeks later with resolved symptoms. She was once again 20/20 in the involved eye, and the previously noted visual field defect had resolved. She was subsequently diagnosed with MS and is now taking a once-monthly injection of ofatumumab for relapsing forms of MS.

MULTIPLE SCLEROSIS

MS is an inflammatory autoimmune condition that results in demyelination and subsequent neurodegeneration of the central nervous system.^3-6 Typically diagnosed between the ages of 20 to 30 years old, its progression can result in physical, visual, and/or cognitive decline.⁶ The underlying cause remains unclear, but genetic and environmental factors, such as low vitamin D levels, exposure to Epstein-Barr virus, UV light exposure, obesity, and smoking, may play a role.^5,6 Affecting women at a 3:1 ratio, MS can be widespread and develop subacutely over hours to days before stabilizing and then slowly improving.⁵ It can present as unilateral optic neuritis, myelitis (weakness or loss of sensation of the extremities from spinal cord inflammation), or brain stem syndromes (intranuclear ophthalmoplegia, vertigo, hearing loss).^5,6 Treatment of MS is multifaceted and involves disease-modifying therapies, symptom control, lifestyle changes, and psychological support.^5,6

In one-fifth of MS cases, optic neuritis is the initial manifestation of the disease.⁷ The probability of a patient developing MS after optic neuritis is 50% within 15 years.⁷ When lesions are found on subsequent brain MRI, the probability escalates to more than 70%.⁷ Although it does not improve the visual endpoint, evidence shows that a 3-day course of intravitreal methylprednisolone sodium succinate followed by 2 weeks of oral prednisone (1 mg/kg/day) speeds up visual recovery.⁸

THE TAKEAWAY

Although there are a multitude of other possible causes of optic neuritis, the visual, systemic, and life-long implications associated with MS make it a diagnosis you don’t want to miss. By communicating with your patient and conducting a thorough examination, you can expedite the diagnosis and speed up visual recovery, leading to a better quality of life for the patient during a difficult time in their life.