Aqueous Humor Dynamic Components That Determine Intraocular Pressure Variance

This proposal responded to PA-18-351 "Human Subjects Mechanistic and Minimal Risk Studies" and qualifies as a clinical trial. The central hypothesis is that variations in IOP response to glaucoma drugs and IOP fluctuation can be predicted by the aqueous humor dynamic (AHD) factors that regulate IOP. This hypothesis will be tested in up to 200 participants with ocular hypertension (OHT) or open-angle glaucoma (OAG). This hypothesis will be tested in two aims: Aim 1, Test the hypothesis that AHD factors predict the IOP drug response; Aim 2, Test the hypothesis that aqueous flow and outflow facility predict IOP fluctuation.

The objective is to determine which AHD factors predict a participant's IOP drug response and IOP fluctuation. The scientific rationale is that AHD parameters (aqueous flow, outflow facility, episcleral venous pressure, and uveoscleral flow) determine drug response and IOP fluctuation.

The primary endpoint is IOP response to glaucoma drugs. Exploratory outcome measures include IOP fluctuation and the AHD measures.

The study population includes participants who have either OHT or OAG. The inclusion and exclusion criteria described in 5.3, Study Population. The goal is to recruit 150-200 participants over 4 years.

All drugs and instruments used in this study have been FDA approved.

Three sites will enroll participants: Mayo Clinic, The Ohio State University, and University of Nebraska Medical Center. All sites have experience and expertise with AHD studies in humans. These study team members have productive collaborations during AHD studies in controls during the prior NIH funding period. There are no sites outside of the United States.

The experimental design is a prospective, open-label, clinical trial with randomized cross over treatment using the topical glaucoma medications, timolol 0.5% and latanoprost 0.005%. Timolol 0.5% is a beta-blocker and will be dosed as one drop two times a day. Latanoprost 0.005% is a prostaglandin analogue and will be dosed as one drop daily in the evening. The treatment order will depend on randomization.

AHD measurements are performed at baseline without glaucoma medications. The AHD measurements include IOP, aqueous humor flow, outflow facility, and episcleral venous pressure. Uveoscleral outflow is calculated. Some participants who are already taking glaucoma medications will be washed out in order to assess baseline AHD measurements. An IOP safety check will be scheduled for those who are washed out of their glaucoma Rx. After baseline AHD measurements, the AHD measurements are repeated after each of the 7-day drug interventions to determine the effect of the drug treatment on AHD variables.

There are six study visits, Visits 1 - 6, that include clinical testing, surveys, and AHD procedures (see 1.2 Schema). Participants will be trained to use the Icare® HOME tonometer to measure IOP outside of clinic to assess IOP fluctuation.

The study design is a prospective, open-label, randomized order of 7-days treatments with timolol 0.5% (1 drop two times daily) followed by a washout period and then with latanoprost 0.005% (1 drop daily in the evening) or vice versa. These are referred to as Tx 1 and Tx 2. IOP safety checks during washout are included for those already taking glaucoma Rx upon entering the study. IOP response will be determined to each of these medications. AHD factors will be determined for both study treatments using tonometry, fluorophotometry, tonography, and episcleral venomanometry. IOP fluctuation will be assessed using the FDA-approved Icare® HOME tonometer. All test procedures and drugs are FDA approved. There are no experimental tests or agents.

Sample sizes and power calculations provide rigor to test the hypothesis.

A REDCap database is populated from data on case report forms (CRF), surveys, and the Icare® HOME tonometer. Data will be analyzed using descriptive statistics of central tendencies and dispersion, and regression methods in order to understand the individual data in the distribution of the cohort.