title: Utility of the Tono-Pen in Measuring Intraocular Pressure in Trinidad: A Cross-sectional Study.
abstract: OBJECTIVE
  To determine the sensitivity and specificity of the Reichert™ Tono-Pen AVIA® when used by novice medical students in an ethnically diverse population in Trinidad.
  
  
  METHODS
  Participants were residents of Trinidad between the ages of 20 and 90 years attending the Ophthalmology Clinic at the Eric Williams Medical Sciences Complex (EWMSC). Intraocular pressure (IOP) was measured using the Goldmann applanation tonometer (the gold standard) for ophthalmology clinic patients as part of their routine care. Intraocular pressure measurements were then taken using the Tono-Pen.
  
  
  RESULTS
  One hundred persons participated, consisting of Indo-Trinidadians (55%), Afro-Trinidadians (36%), Mixed (8%) and 1% of Caucasian descent. Fourteen per cent reported a diagnosis of glaucoma, with 70.6% of these being of African descent. One hundred and ninety-eight readings of IOP were taken. At a cut-off point of 21 mmHg, there were nine true positives, four false positives, seven false negatives and 178 true negatives. The sensitivity and specificity were found to be 56.3% (95% CI 33.2, 76.9) and 97.8% (95% CI 94.5, 99.1), respectively. The positive predictive value was calculated as 69.2% (95% CI 42.4, 87.3) while the negative predictive value was 96.2% (95% CI 92.4, 98.2). The prevalence of elevated IOP in this population was 8.1% (95% CI 4.8, 13.0). The likelihood ratio of a positive result was calculated to be 25.6 (95% CI 8.6, 73.9).
  
  
  CONCLUSIONS
  The high specificity and negative predictive value suggests that the Tono-Pen can be used with minimal training, and can prove beneficial at the primary care level in the exclusion of increased IOP in an ethnically diverse high-risk Caribbean population.
authors.affiliation: Medical students, Faculty of Medical Sciences, The University of the West Indies, St Augustine, Trinidad and Tobago.
authors.forename: A
authors.initials: A
authors.lastname: Billy
authors.affiliation: Medical students, Faculty of Medical Sciences, The University of the West Indies, St Augustine, Trinidad and Tobago.
authors.forename: P E
authors.initials: PE
authors.lastname: David
authors.affiliation: Medical students, Faculty of Medical Sciences, The University of the West Indies, St Augustine, Trinidad and Tobago.
authors.forename: A K
authors.initials: AK
authors.lastname: Mahabir
authors.affiliation: Medical students, Faculty of Medical Sciences, The University of the West Indies, St Augustine, Trinidad and Tobago.
authors.forename: C P
authors.initials: CP
authors.lastname: Seerattan
authors.affiliation: Medical students, Faculty of Medical Sciences, The University of the West Indies, St Augustine, Trinidad and Tobago.
authors.forename: J M
authors.initials: JM
authors.lastname: Street
authors.affiliation: Medical students, Faculty of Medical Sciences, The University of the West Indies, St Augustine, Trinidad and Tobago.
authors.forename: V D
authors.initials: VD
authors.lastname: Walcott
authors.affiliation: Medical students, Faculty of Medical Sciences, The University of the West Indies, St Augustine, Trinidad and Tobago.
authors.forename: R J
authors.initials: RJ
authors.lastname: Yarna
authors.affiliation: Department of Surgery, Faculty of Medical Sciences, The University of the West Indies, St Augustine, Trinidad and Tobago.
authors.forename: D C
authors.initials: DC
authors.lastname: Murray
authors.affiliation: Unit of Public Health and Primary Care, Faculty of Medical Sciences, The University of the West Indies, St Augustine, Trinidad and Tobago. rohan.maharaj1@gmail.com.
authors.forename: R G
authors.initials: RG
authors.lastname: Maharaj