A 30-year-old myopic woman is found to have IOP of 24 mmHg by Goldmann applanation tonometry. Central corneal thickness measured by pachymetry is 480 microns. How does this finding alter the estimated true intraocular pressure?
- A True IOP is higher than measured; the reading underestimates actual pressure
- B True IOP is lower than measured; the reading overestimates actual pressure ✓
- C True IOP equals measured IOP; corneal thickness does not affect Goldmann readings
- D True IOP cannot be estimated from pachymetry
Correct answer: B. True IOP is lower than measured; the reading overestimates actual pressure
Explanation
Thinner corneas (below the Goldmann assumed 520 microns) offer less resistance during applanation, causing the tonometer to underestimate the true IOP. B cornea of 480 microns means the actual IOP is higher than 24 mmHg. Conversely, thick corneas overestimate IOP. The OHTS used CCT correction: thinner CCT is a strong independent risk factor for glaucoma conversion.
Reference: Ocular Hypertension Treatment Study (OHTS) Group, Archives of Ophthalmology, 2002 ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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