A Case That Breaks the Rules

A 28-year-old woman presented with a complaint of blurry vision at distance and near in both eyes. She had been wearing outdated prescription glasses for several years. She also reported transient episodes of vision loss in her right eye, particularly when she bent forward. She endorsed experiencing daily migraines, for which she had been prescribed multiple medications. Despite consistent use, she found these medications ineffective.

The patient’s medical history was notable for a heart murmur, and she denied any significant ocular history. At the time of presentation, her blood pressure was 128/87 mm Hg.

FINDINGS

The patient’s BCVA was 20/30 OD and 20/20 OS. Her IOP was 20 mm Hg OD and 19 mm Hg OS. Pupillary assessment revealed a reverse relative afferent pupillary defect (RAPD) in the left eye. Confrontational visual fields and extraocular motility were normal in each eye. A slit-lamp examination was unremarkable bilaterally.

A posterior segment evaluation revealed significant findings. There was asymmetric papilledema: grade 5 OD and grade 2 OS (Figure 1). This was accompanied by flame-shaped hemorrhages in the right eye, predominantly in the superior temporal and inferior nasal quadrants. The pronounced asymmetry and presence of hemorrhages prompted concern for possible elevated intracranial pressure or compressive optic neuropathy. This asymmetry explained the presence of a reverse RAPD in the left eye, indicating the more affected right eye was not transmitting light stimuli as well, despite showing more overt structural damage.

OUTCOMES

The patient was educated on the urgency of the findings and advised to proceed to the emergency department for neuroimaging and a lumbar puncture to evaluate her for potential intracranial tumors, hemorrhage, or other space-occupying lesions. A CT scan and MRI of the brain and orbits both returned normal results. However, the lumbar puncture opening pressure was 25 cm H₂O (abnormally elevated cerebrospinal fluid [CSF] pressure), confirming a diagnosis of idiopathic intracranial hypertension (IIH).

Lumbar puncture is essential in assessing suspected IIH. Normally, CSF opening pressure falls between 10 and 20 cm H₂O. Measuring it directly helps confirm or rule out IIH, which is associated with a pressure of 25 cm H₂O or higher. Patients often present with headaches, visual changes such as blurred or double vision, papilledema, pulsatile tinnitus, dizziness, or neck and back pain. Beyond confirming the diagnosis, lumbar puncture provides valuable information for ruling out infection, inflammation, or cancer. Brain imaging by CT and MRI must be done before lumbar puncture to ensure there is not a mass lesion, which could make lumbar puncture dangerous. Recording the initial pressure also provides a baseline to monitor the effectiveness of treatment and help determine whether new headaches are due to medication side effects or ongoing high pressure. Performing the test before starting acetazolamide is critical because the drug reduces CSF production and may mask elevated pressure, resulting in a false negative. Skipping the procedure risks delayed or missed diagnoses, inappropriate treatment, and serious consequences such as permanent vision loss.

The patient was started on oral acetazolamide at a higher-than-typical dosage of 1,500 mg twice daily owing to her weight and level of swelling. She was also referred to a neuro-ophthalmologist for further evaluation and continued management. Remarkably, after the emergency intervention and initiation of treatment, the patient reported complete resolution of her migraines, and she was able to discontinue her prior migraine medications.

Visual field testing was performed every 2 weeks (Figure 2), and OCT of the retinal nerve fiber layer (RNFL) was performed biweekly to monitor the optic nerve swelling. Two weeks after treatment, the right eye showed an RNFL thickness of 260 µm, macular volume of 9.17 mm³, and segmented ganglion cell layer (GCL) volume of 1.13 mm³. The left eye had an RNFL thickness of 197 µm, macular volume of 9.66 mm³, and GCL volume of 1.10 mm³. One month later, follow-up testing indicated improved optic nerve swelling bilaterally. RNFL thickness and macular volume decreased in the right eye to 174 µm and 8.8 mm³, respectively, while GCL volume remained stable at 1.13 mm³. RNFL thickness and macular volume also decreased in the left eye to 127 µm and 8.63 mm³, respectively, and there was a slight increase in GCL volume to 1.12 mm³.

UNUSUAL BUT POSSIBLE

Although IIH typically presents with bilateral symmetric papilledema, this case was unusual due to the asymmetry in disc swelling and a reverse RAPD. These findings can easily be mistaken for unilateral optic neuropathies or other serious intracranial conditions, underscoring the need for urgent and a thorough neuro-ophthalmic investigation.