Aqueous Humor Dynamics Changes and Predictors of IOP Response to Latanoprost in Healthy Subjects.

Conclusions: In our study of the factors predictive of latanoprost response, we found that normotensive subjects with higher intraocular pressure, lower uveoscleral outflow, and higher body mass index had a greater response to 1-week treatment.

Objective: To evaluate relationships between variable intraocular pressure (IOP) responses to latanoprost and participant characteristics, baseline values and changes in aqueous humor dynamics (AHD) parameters.

Methods: We assessed 226 eyes from 113 healthy participants. AHD parameters measured at baseline and after 1-week treatment with latanoprost included: IOP by pneumatonometry, episcleral venous pressure (EVP) by venomanometry, aqueous humor flow rate by fluorophotometry, outflow facility by 2-minute pneumatonography, and uveoscleral outflow calculated using the modified Goldmann equation. IOP responses were categorized into 4 groups: non-responders (<10% reduction), all-responders (≥10% reduction), medium-responders (10-20% reduction), and high-responders (≥20% reduction). Generalized estimating equation models were used to analyze treatment effects and compare groups.

Results: Baseline IOP was higher in high-responders than medium-responders and non-responders (P=0.007 and P<0.001, respectively). Body mass index (BMI) was significantly higher in high-responders and all-responders compared to non-responders (P=0.02 and P=0.03, respectively). Responders had lower baseline uveoscleral outflow (P=0.03). There were no significant differences in other baseline characteristics including EVP, outflow facility, and aqueous flow rate between the 4 groups. IOP decreased while outflow facility and uveoscleral outflow increased after latanoprost treatment in all responder groups but did not change in non-responders. EVP and aqueous flow rate did not change significantly in any group. The change in uveoscleral outflow was greater in high-responders than in non-responders (P=0.004).

Conclusions: In healthy subjects, higher baseline IOP, lower uveoscleral outflow and higher BMI are predictors of a greater IOP reduction by latanoprost. A greater increase in uveoscleral outflow is responsible for this larger response.