Abstract
Purpose::
To assess the use of a monocular trial in predicting intraocular pressure (IOP) response in the fellow eye and to determine if this response is associated with inter-ocular symmetry of IOP fluctuation.
Methods::
Setting: Subspecialist glaucoma clinic. Study population: All glaucoma patients who were initiated on a monocular therapeutic trial between 1/1/1996 to 12/31/1998 and subsequently used the same medication in the fellow eye. Measures: IOP reduction in the trial eye vs. the second eye was measured and the degree of correlation was assessed using the coefficient of correlation (r). The inter-visit fluctuation in IOP was compared between the two eyes over four subsequent visits and patients were classified as symmetric (average of <3mmHg difference in fluctuation between the eyes across all visits) or asymmetric (3mmHg or more).
Results::
Ninety-three patients underwent monocular therapeutic trial and 61 (66%) had symmetric and 32 (33%) had asymmetric IOP fluctuation. The difference in IOP reduction between the trial and second eye was 4.8 ± 4.4 mmHg for the study population and 4.0 ± 3.6 and 6.2 ± 5.4 mmHg in the symmetric and asymmetric IOP fluctuation groups, respectively (P = 0.046). The coefficient of correlation for IOP reduction is 0.2 for the study population and 0.33 and 0.07 for the symmetric and asymmetric IOP fluctuation groups, respectively.
Conclusions::
Limited correlation was seen between IOP reductions in the trial compared to the second eye in this study population. The correlation is moderate in patients with symmetric IOP fluctuation and minimal in patients with asymmetric IOP fluctuation. Patients with asymmetric IOP fluctuation account for 33% of this group of glaucoma patients. Noting the symmetry of IOP fluctuation in a given patient may be clinically useful when using monocular therapeutic trials in assessing the efficacy of glaucoma medications.
Keywords: intraocular pressure