The utility of the monocular trial: data from the ocular hypertension treatment study.
OBJECTIVE
To determine whether adjusting the intraocular pressure (IOP) change of the trial eye for the IOP change of the fellow eye (i.e., monocular trial) is a better assessment of medication response than testing each eye independently.


METHODS
Analysis of data from a prospective, randomized, clinical trial.


METHODS
Two hundred six participants with ocular hypertension randomized to the observation group and later started on a topical prostaglandin analog (PGA).


METHODS
Participants were started on a topical PGA in 1 eye and returned in approximately 1 month to determine medication response. The IOP response of the trial eye was determined by the IOP change between baseline and 1 month in the trial eye alone (unadjusted method) and by adjusting for the IOP change in the fellow eye between the same visits (adjusted method). Our "gold standard" for medication response was the IOP change in the trial eye between up to 3 pre- and 3 posttreatment visits on the same medication. Pearson correlation was used to compare the gold standard with the unadjusted and adjusted methods. In addition, symmetry of IOP response between trial and fellow eyes to the same medication was determined by correlating the trial eye IOP change between up to 3 pre- and 3 posttreatment visits to the fellow eye IOP change between the same visits.


METHODS
Correlations of IOP change of the trial eye using the gold standard to the IOP change of the trial eye using the unadjusted and adjusted methods.


RESULTS
The correlations of IOP change using the gold standard to the IOP change using the unadjusted and adjusted methods were r = 0.40 and r = 0.41, respectively. The correlation of IOP change of both eyes between the same pre- and posttreatment visits was r = 0.81.


CONCLUSIONS
The monocular trial (i.e., adjusted method) appears equivalent to testing each eye independently (i.e., unadjusted method); however, neither method is adequate to determine medication response to topical PGAs. Both eyes have a similar IOP response to the same PGA. Further studies to understand IOP fluctuation are necessary to improve current methods of assessing medication response.


BACKGROUND
Proprietary or commercial disclosure may be found after the references.
Bhorade
Anjali M
AM
Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, USA.
Wilson
Bradley S
BS
Gordon
Mae O
MO
Palmberg
Paul
P
Weinreb
Robert N
RN
Miller
Eydie
E
Chang
Robert T
RT
Kass
Michael A
MA
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000959:Antihypertensive Agents / Q000008:administration & dosage*; D002986:Clinical Trials as Topic; D005260:Female; D005902:Glaucoma, Open-Angle / Q000517:prevention & control*; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000188:drug therapy*; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies; D011461:Prostaglandins F, Synthetic / Q000008:administration & dosage*; D014065:Tonometry, Ocular; D016896:Treatment Outcome
D000959:Antihypertensive Agents; D011461:Prostaglandins F, Synthetic