Optometry case study: Prescription recheck revealing partial third nerve palsy

By Chelsea Lane, Specsavers Geelong, VIC


Px: 31-year old female
Reason for visit: Prescription recheck. Three weeks prior to most recent presentation, patient collected single vision spectacles after full eye examination and had since begun noticing vague double vision.
GH: New mother. Sleep deprived, but otherwise healthy.
POH / FOH: Nil. Full routine eye examination undertaken three weeks prior found no significant pathology.

Clinical Assessment

Prior to optometric assessment:
Recheck log applied by dispensing staff.

Old Rx: R: -1.75/-0.55×165      L: -2.25/-0.50×13
New Rx: R: -1.50/-0.75×165      L: -2.25/-1.00×10

All dispensing parameters unremarkable. Astigmatic change in prescription identified as likely cause of symptoms.

Optometric assessment:
Patient found “double vision” symptom difficult to articulate. She was sleep deprived and when asked, denied that images appeared side-by-side. Instead, she described a ghosting effect. Her vision “felt strange with her old glasses too” and her complaint was that the new spectacles did not improve this.
Refraction: R: -1.50/-0.50×165 (6/6)      L: -2.50/-1.00×10 (6/6)
BV: >10XP at both distance and near
Ocular motilities: Full and smooth with no pain or double vision
Pupil testing: Left anisocoria greater in bright. R: 2.5mm bright (4mm dim) L: 4mm bright (5mm dim). This was a new sign as pupils were noted as PERRLA at last eye exam.
Gross assessment: Slight left ptosis (similar to that shown in Figure 1). No paralysis noted. Smile and brow movements symmetric. No ocular redness or trauma visible.
Posterior examination: Unremarkable. Optic nerve flat and unchanged.

Figure 1. Similar patient presentation (reproduced from Piña-Garza 2013)1

Diagnosis & Management

Differential diagnosis:

  • Myasthenia gravis
  • Thyroid disease
  • INO
  • CPEO
  • Trauma
  • Mass occupying lesion
  • Third nerve palsy
  • Vasculopathy2,3

Management: Immediate and urgent referral to the local emergency department with referral letter to expedite triage. Patient was advised of the likelihood of neuroimaging. Ophthalmology registrar was briefed prior to patient attending. A stroke call was made for the patient on arrival and a CAT-A scan performed.

Diagnosis: Partial non-pupil sparing third nerve palsy secondary to cavernous sinus aneurysm. At the time of writing, the patient was awaiting neuroendovascular treatment in hospital.


Oculomotor nerve palsies are a rarity in Australian optometry clinics, making up fewer than 0.011% of patient presentations.4 That being said, for this minority, identification may be life-saving. This case report highlights the importance of pupil testing and ocular motility examination in every patient, including upon review, as things can change significantly even over a period of a few weeks.

It is important to avoid assumptions when examining patients. Regardless of age or health status, life-threatening conditions should always be ruled out. In this case, the patient was flagged as needing only a basic prescription recheck; this supposition may misdirect clinical decision-making and test selection.

The role of triage training for front-of-house staff is critical. They should be instructed on pathology red flags, aware of screening questions, and have a basic understanding of the conditions that require prioritisation. Following this patient’s examination, all dispensers were briefed on the importance of flagging new onset double vision as a critical symptom requiring urgent attention.


  1. Eric Piña-Garza, Disorders of Ocular Motility. Fenichel’s Clinical Pediatric Neurology (Seventh Edition), 2013. 2.
  2. Motoyama Y, Nonaka J, Hironaka Y, Park YS, Nakase H. Pupil-sparing oculomotor nerve palsy caused by upward compression of a large posterior communicating artery aneurysm. Case report. Neurol. Med. Chir. 2012; 52(4):202-5.
  3. Scumpia AJ, Serak J, Ritchie KL, et al. Posterior communicating artery aneurysm presenting in a 20-year-old female with Noonan’s West J Emerg Med. 2013;14(2):175–6.
  4. Jeffery R, Young B, Swann P, Lueck C. Unequal pupils: Understanding the eye’s aperture. Australian Journal of General Practice. 2019. 48 (1-2).

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