Case 7:
This month’s Eyes of the Month is about an elderly woman experiencing intermittent flickering in her right eye for serval months, eventually leading to a diagnosis of NAION.
Patient Visit:
A 77-year-old woman was referred to Queensland Eye and Retina Specialists by her GP, due to changes in peripheral vision. The patient had been aware of intermittent flickering in the vision of her right eye for several months, but this had changed recently to a dark patch in the same spot. She had not experienced any pain or headaches.
Her previous ocular history included uncomplicated bilateral cataract surgery two years prior and a family history of retinal detachment. She had mild blepharitis, for which her optometrist had prescribed NovaTears, FML, Hycor ointment and Systane Wipes, which she had been using for over a year. General medical history was unremarkable and she was currently only taking medications for hypertension (Irbesartan) and for reflux (Pantoprazole). She smoked for 10 years in her 20’s.
Ocular exam revealed the following:
Best Corrected Visual Acuity:
RE: -2.00/-0.75 x 80 (6/6=) LE: -0.50/-1.50 x 70 (6/6=)
Intraocular Pressure (iCare):
RE: 23mmHg LE: 22mmHg
Pupils: EA, DCN No RAPD
External examination with slit lamp was within normal limits for her age. Both IOLs were well positioned within the capsular bag.
Examination of the posterior pole revealed a swollen right optic nerve, more noticeably so in the superior portion. The nerve appeared hyperemic when compared with the fellow eye and a small peripapillary splinter hemorrhage was seen at the nasal edge (Fig1). Dilated fundus examination showed no evidence of retinal tear or detachment through 360degrees. Although inconsequential, peripheral or geographic drusen was noted bilaterally.
Figure 1: Fundus photograph of the right eye, demonstrating hyperaemic oedematous
optic nerve with raised superior edge and haemorrhage on the nasal side.
OCT imaging (Fig2) confirmed swelling of the optic nerve head in the RE. Clear asymmetry between the right and left eye can be seen in both neuro-retinal rim and retinal nerve fibre layer thickness.
Figure 2: OCT imaging of right and left eyes. The thickness map of the right eye illustrates the diffuse ONH swelling, more so in the superior portion of the nerve.
Visual field testing (Humphrey 30-2) (Fig3) confirmed the inferior field loss that the patient was noticing.
Figure 3: Inferior visual field loss in the RE.
Diagnosis and Discussion
Diagnosis:
RE Non-arteritic anterior ischemic optic neuropathy (NAION)
Differential diagnosis:
Arteritic anterior ischemic optic neuropathy (AAION) – secondary to Giant Cell Arteritis
Optic neuritis
Discussion:
NAION is the most common cause of acute optic neuropathy over the age of 50, affecting roughly 5 people per 100,000 per year. Males and females are represented equally, and interestingly over 95% of cases occur in those with Caucasian background.
At present there is no one definitive causative mechanism for NAION. The portion of the nerve affected in NAION is the most anterior 1mm segment of the optic nerve head, referred to as the optic disc. This area is supplied by the short posterior ciliary arteries. Currently it is thought that NAION results from circulatory insufficiency in the optic disc. The oedema seen in the acute phase appears to be caused by axonal swelling and resultant apoptotic ganglion cell death.
After initial presentation it is common to see vision deteriorate in the first two weeks, before stabilising around the 2-month mark.
Treatment:
There is currently no known effective treatment for NAION. The vision loss is considered to be irreversible. A number of different treatments have been trialled, to see if they can limit vision loss. Although there is no evidence to suggest commencing corticosteroids, anti-platelet or anticoagulants improves final visual acuity or visual field, it is still necessary to investigate and optimise patients cardiovascular risk factors if a diagnosis of NAION is made.
It is also vital to question patients further regarding any symptoms which may point towards an arteritic anterior ischemic optic neuropathy (AAION). These may include persistent severe head pain most often in the temple area, scalp tenderness, jaw or tongue claudication (i.e. pain and tiredness) or weight loss. Presence of any of these symptoms may prompt laboratory testing including c-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) and also temporal artery biopsy to rule out giant cell arteritis (GCA). In some atypical cases an MRI may also be ordered to exclude causes of nerve swelling such as optic neuritis or multiple sclerosis.
Follow-Up:
At review one week later, the patient felt that the blurry patch in her inferior visual field had increased in size. Her visual acuity was stable, but when reading the Snellen chart, she felt the blur patch was intermittently encroaching over the letters. Below is the visual field result from her second visit (Fig4). All her lab work has returned normal results.
If your patient is experiencing vision issues such as intermittent flickering, refer them to QERS for specialised care and treatment.
Figure 4: Extended inferior visual field loss in the RE one week later.
Have any questions about patient eye care?
Contact Queensland Eye & Retina Specialists for more information.