title: Correlation of pupil sizes measured with a mesopic infrared pupillometer and a photopic topographer.
abstract: OBJECTIVE
  To determine if videokeratography-based pupil measurements are an accurate method of estimating pupil size under mesopic conditions.
  
  
  METHODS
  Sixty patients who had a preoperative work-up for refractive surgery participated in the study. A single observer obtained detailed pupil measurements with the Colvard pupillometer under standardized lighting conditions. The same observer recorded pupil size measurements obtained automatically when corneal topographic analysis was performed with Humphrey videokeratography.
  
  
  RESULTS
  The Colvard pupillometry low light group was statistically different (P < .0001) from the Humphrey videokeratography automatic pupil measurement group. We calculated the value at which the Humphrey pupil measurements can accurately predict which patients would have pupil diameters > or = 6.5 mm under low mesopic conditions. By adding a constant of 2.6 mm to the Humphrey videokeratography pupil measurement, 100% of patients with a pupil diameter > or = 6.5 mm under low mesopic conditions were detected (sensitivity 100%). However, the ability to correctly reject those patients who do not have pupil diameters > 6.5 mm under low mesopic conditions was lower at 55% (specificity).
  
  
  CONCLUSIONS
  Videokeratography units can be used as a rapid, simple, and accurate method of predicting pupil size under mesopic conditions for potential refractive surgery patients and can provide a permanent record of pupil size. Care should be taken when relying on topography pupil sizes and more accurate measurements of mesopic and scotopic pupil sizes should be obtained.
mesh_terms: D000328:Adult; D000368:Aged; D003315:Cornea / Q000473:pathology / Q000601:surgery; D019781:Corneal Topography / Q000379:methods*; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D007498:Iris / Q000033:anatomy & histology*; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D018903:Photorefractive Keratectomy; D011446:Prospective Studies; D011680:Pupil; D012030:Refractive Errors / Q000473:pathology; D054140:Refractive Surgical Procedures; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity