A 35-year-old woman underwent uneventful LASIK for -8 dioptres of myopia five years ago. She now has progressive cupping and field loss, yet Goldmann applanation repeatedly records 14 mmHg bilaterally. What best explains this discrepancy?
- A The ablated cornea is thinner and softer, so applanation underestimates the true intraocular pressure ✓
- B Goldmann tonometry systematically overreads eyes after refractive surgery
- C Her glaucoma is normotensive and unrelated to pressure measurement error
- D Topical anaesthetic used in applanation artificially lowers the recorded pressure
Correct answer: A. The ablated cornea is thinner and softer, so applanation underestimates the true intraocular pressure
Explanation
Goldmann applanation assumes a central corneal thickness near 520 microns. Myopic LASIK thins and alters the biomechanical stiffness of the cornea, so less force is needed to flatten it and the device reads falsely low, sometimes by several mmHg per 100 microns of deviation. Progressive cupping despite low readings should prompt correction for corneal parameters or alternative tonometry. Normotension cannot explain advancing structural damage combined with a systematic measurement bias.
Reference: American Academy of Ophthalmology, BCSC Section 10: Glaucoma, 2023 ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.