title: Monocular trial of intraocular pressure-lowering medication: a prospective study.
abstract: OBJECTIVE
  To investigate the validity of the monocular therapeutic trial of therapy in patients commencing topical glaucoma treatment.
  
  
  METHODS
  Prospective intention-to-treat cohort study of untreated patients presenting with open-angle glaucoma or ocular hypertension.
  
  
  METHODS
  We included 30 treatment-naïve subjects.
  
  
  METHODS
  All subjects had 8 visits at which intraocular pressure (IOP) was measured by masked Goldmann tonometry. After the recruitment visit, IOP was measured in both eyes at 11 am for 7 consecutive weeks. At week 3, travaprost (0.001%) was commenced in the eye with the higher IOP and at week 4 travaprost was also commenced in the fellow eye.
  
  
  METHODS
  Three IOP outcomes were measured for the trial eye: (1) Unadjusted IOP-lowering effect (difference between recruitment IOP and first IOP on treatment); (2) adjusted IOP-lowering effect (unadjusted effect - [difference between IOPs at the same visits in the fellow eye]); and (3) true therapeutic effect (mean difference between 3 baseline pretreatment IOPs and 3 IOPs on treatment).
  
  
  RESULTS
  Mean recruitment IOPs were 28.2 and 26.0 mmHg in the trial and fellow eyes, respectively. The mean baseline IOPs were 25.8 and 22.7 mmHg in the trial and fellow eyes, respectively, indicating that regression to the mean was responsible for 2.4 and 3.3 mmHg, respectively, in the trial and fellow eyes. The unadjusted treatment effect (11.7 mmHg) overestimated the true effect (8.6 mmHg) by a mean of 3.1 mmHg, whereas the mean adjusted IOP was almost identical to the true effect. The correlation between the unadjusted effect of treatment and the true effect was 0.55, whereas the effect when adjusted by the monocular trial was 0.72.
  
  
  CONCLUSIONS
  In our cohort of patients with bilateral IOPs >21 mmHg at baseline, the monocular trial provides a significantly more accurate estimate of the therapeutic response when initiating prostaglandin monotherapy in untreated eyes. It is particularly helpful in avoiding overestimation of effectiveness and so reducing the number of patients on inadequate treatment.
  
  
  BACKGROUND
  The authors have no proprietary or commercial interest in any of the materials discussed in this article.
authors: Queen's Medical Centre, Nottingham, UK. anthony.king@nuh.nhs.uk
authors: Anthony J
authors: AJ
authors: King
authors: Samreen
authors: S
authors: Uppal
authors: Alan P
authors: AP
authors: Rotchford
authors: Arun
authors: A
authors: Lakshumanan
authors: Asiya
authors: A
authors: Abedin
authors: Emer
authors: E
authors: Henry
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D003008:Cloprostenol / Q000031:analogs & derivatives* / Q000627:therapeutic use; D005260:Female; D005902:Glaucoma, Open-Angle / Q000188:drug therapy*; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000188:drug therapy; D009883:Ophthalmic Solutions / Q000627:therapeutic use; D011446:Prospective Studies; D014065:Tonometry, Ocular; D000069557:Travoprost; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology
chemical_list: D000959:Antihypertensive Agents; D009883:Ophthalmic Solutions; D003008:Cloprostenol; D000069557:Travoprost