Optometry case study: Optic neuritis

1880
Figure 1. DRS image of LE showing swollen inferior optic nerve head

by Haydn Williams, Specsavers Charlestown, NSW

History

Px: 22-year-old female
Reason for visit: Flashing lights from left side and generally blurred vision (mild). No specs used. LEE 2-3 years elsewhere
GH: Good
Meds: Nil
POH: Mentions previous period of similar symptoms. Sought no advice, received no treatment
FOH: Nil

Clinical Findings

Vision: 6/6 OU
Rx: -025 DS OU and VA 6/5 OU
IOL: 12 R / 13 L
Motility: Full and smooth
Pupils: Normal PERRL, no RAPD

Ocular health:
Anterior – Clear and quiet OU
Posterior – Swelling of the left optic nerve head; swelling more prominent in the inferior half (Figures 1 and 2)

Additional tests: Visual fields were performed and a depression of the superior field was seen in the LE (Figure 3)

Figure 3. Visual field of the LE

Diagnosis & Management

Differential diagnosis:

  • Optic neurits
  • Optic disc drusen
  • Papilleodema

Management: An urgent referral was made to the local ophthalmologist for further assessment

Diagnosis: Left optic neuritis

Prognosis: As visual acuity was still intact at 6/6, no initial treatment was required. However, if VA was to drop to 6/18 or worse, a steroid such as IV Methylprednisolone could be indicated. Further investigation could involve an MRI to rule out underlying pathology such as multiple sclerosis (MS) and also blood investigations to look for autoimmune and infective causes. No permanent impacts to vision were expected, but recovery could take several weeks / months.

Discussion

Optic neuritis is an inflammatory, infective or demyelinating process affecting the optic nerve.

Clinical classification is as below:

  1. Retrobulbar – The disc appearance is usually normal because the optic nerve head is not involved. This is the most common type of optic neuritis in adults and is frequently associated with MS.
  2. Papillitis – Characterised by variable hyperaemia and oedema of the optic disc, which can be associated with parapapillary flame-shaped haemorrhages. This is the most common form of optic neuritis in children, although it can also affect adults.
  3. Neuroretinitis – Characterised by papillitis in association with inflammation of the retinal nerve fibre layer. A macular star may present after a few days or weeks and will become more prominent as disc swelling resolves. This is the least common type of optic neuritis and is frequently associated with viral infections.

Aetiological classification is as below:

  • Demyelinating
  • Parainfectious
  • Infectious
  • Autoimmune.

Demyelinating is the most common type of optic neuritis. It is a pathological process by which normally myelinated nerve fibres lose their insulating myelin layer, resulting in disruption of nervous conduction within the white matter tracts of the brain, brain stem and spinal cord. The most common underlying disease is MS.

It is worth noting that although some patients with optic neuritis have no clinically demonstrable associated systemic disease, there is a strong association between optic neuritis and MS. Patients who develop optic neuritis but have normal brain MRI have a 16% probability of developing MS within 5 years. Evidence of optic neuritis may be found in 70% of established cases of MS.

Print