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Ocular Hypertension Treatment Study (OHTS) calculator

Estimates 5-year risk of conversion from ocular hypertension to primary open-angle glaucoma.

Ocular Hypertension Treatment Study (OHTS) calculator
Age
Patient age in years.
Mean intraocular pressure
Average of 3 Goldmann applanation tonometry readings per eye, averaged across both eyes.
Mean central corneal thickness
Average of 3 ultrasound pachymetry readings per eye, averaged across both eyes.
Mean vertical cup/disc ratio
By contour estimation, averaged across both eyes.
Mean Humphrey pattern standard deviation
Average of 2 reliable Humphrey visual field tests per eye, averaged across both eyes (use the Octopus loss-variance equivalent if that perimeter was used).
Result0 points

Estimated 5-year risk of developing primary open-angle glaucoma is ≤4 %.

Total points
0
Estimated 5-year risk of POAG
≤4 %

When to use

  • Estimating 5-year probability of conversion to primary open-angle glaucoma in adults with ocular hypertension (elevated IOP, open angles, no glaucomatous optic nerve or visual field damage) to help decide whether to start preventive topical therapy.
  • Risk-stratifying ocular hypertensive patients to set follow-up and testing intervals.

Formula

Point system (0-4 points per factor, summed to a total of 0-20): age, mean IOP, mean central corneal thickness, mean vertical cup/disc ratio, and mean Humphrey pattern standard deviation (or Octopus loss variance) are each banded and scored. Total points are mapped to a banded 5-year POAG risk: 0-6 points ≈≤4%, 7-8 ≈10%, 9-10 ≈15%, 11-12 ≈20%, >12 ≥33%. This is the simplified point-system version of the continuous Cox proportional-hazards model derived from the pooled OHTS observation-group and European Glaucoma Prevention Study placebo-group cohorts.

Pearls and pitfalls

  • Derived and validated in patients with baseline IOP 22-32 mmHg (OHTS eligibility was 24-32 mmHg in at least one eye), open angles, and normal visual fields; extrapolation outside these criteria (e.g. pre-existing field loss) is not validated.
  • A continuous (non-banded) version of the same model gives a more precise individual risk estimate than this simplified 5-point-per-factor system.
  • Central corneal thickness and vertical cup/disc ratio are typically the strongest contributors to risk in this model; thin corneas can lead to under-measurement of true IOP.

References

  1. Gordon MO, Torri V, Miglior S, et al. Validated prediction model for the development of primary open-angle glaucoma in individuals with ocular hypertension. Ophthalmology. 2007;114(1):10-19.
  2. Gordon MO, Beiser JA, Brandt JD, et al. The Ocular Hypertension Treatment Study: baseline factors that predict the onset of primary open-angle glaucoma. Arch Ophthalmol. 2002;120(6):714-720.