Table 2

Model data (natural history, efficacy and diagnostic accuracy/agreement)

DescriptionMean (years)Probability distribution* (mean, variance)Source
Glaucoma progression
Time of progression from early glaucoma to moderate glaucoma4Normal (4, 2)Untreated. Variance based on assumption14
Time of progression from moderate to severe glaucoma9Normal (9, 2)Untreated. Variance based on assumption14
Time of progression from severe glaucoma to visual impairment10Normal (10, 2)Untreated. Variance based on assumption14
Mean IOP reduction (%)Source
Treatment efficacy
BB vs no treatment12Developed based on weighted mean differences in NICE guideline6
PGA vs BB5Developed based on weighted mean differences in NICE guideline6
PGA+BB vs PGA1.5Developed based on weighted mean differences in NICE guideline6
Treatment effectiveness (risk of glaucoma or progressive glaucoma)
Reduction in risk of progression from any medical treatment (HR)
 Ocular hypertension0.56Maier et al15
 Glaucoma0.65Maier et al15
Glaucoma surgery
Proportion (of those converting to glaucoma) requiring trabeculectomy over 20 years8.50%Burr et al16
Proportion with successful trabeculectomy (success defined as no need for additional laser or surgery)88% at 1 year and 79% at year 4Burr et al16
Measurement precision and accuracy of glaucoma detection
Ophthalmologist
 IOP measurement error (mm Hg)‡1Based on regression model in Burr et al.8 Sampled from a normal distribution (mean, 0; variance, 0.036)
 Sensitivity1Assumption
 Specificity1Assumption
Primary care (optometrist or glaucoma specialist general practitioner)
 IOP measurement error (mm Hg)§0Cook et al.12 Sampled from a normal distribution (mean 0; variance 5.76)
 Sensitivity0.76Azuara-Blanco et al17
 Specificity0.93Azuara-Blanco et al17
  • *Probability distributions are used to simulate a hypothetical cohort of people with ocular hypertension; details are described in the text below.

  • †Monocular visual field loss, mean deviation (MD in decibels (dB)). Mild glaucoma, 0.01 to −6.00 dB; moderate glaucoma, −6.01 to −12.0 dB; severe glaucoma, −12.01 to −20.00 dB; visual impairment, −20.01 dB to worse.18

  • ‡Error term used in the model to reflect variability in IOP based on cohort data.8

  • §Error term used in the model to reflect interobserver error in tonometry.8 ,12

  • BB, beta blocker; IOP, intraocular pressure; NICE, National Institute for Health and Care Excellence; PGA, prostaglandin analogue.