Assessing Ocular Hemodynamic Response to Surgical Intervention in Glaucoma

Purpose: Glaucoma is the leading cause of irreversible blindness worldwide and the third
leading cause of vision loss in the United States. It is estimated that greater than 4.3
million Americans will have glaucoma in 2030. The treatment options are topical medications,
laser surgery, and incisional surgery. The goal of therapy is to lower intraocular pressure
(IOP). Despite adequate lowering of IOP, many patients continue to lose vision due to
progressive glaucomatous optic atrophy. This is likely related to the poor understanding of
glaucoma pathogenesis. There are two theories which explain the mechanism of primary open
angle glaucoma (POAG). The mechanical theory posits that intraocular pressure (IOP) can
produce optic nerve damage through biomechanical or structural factors. All current
therapeutic interventions are aimed at this particular mechanism. The vascular theory
suggests that compromise of the optic nerve microvasculature induces glaucomatous optic nerve
damage. There is a significant body of literature supporting the role of ocular hemodynamic
(OHD) changes in the development and progression of glaucoma. However, there have been
limited investigations of the effect of surgical interventions on OHD. This is primarily due
to a lack of non-invasive, cost-effective methods of assessing OHD factors. Today, the
technology exists to assess these factors in such a manner. Thus, the purpose of this study
is to assess the response of OHD factors to surgical intervention in glaucoma patients.
Participants: Seventy-five participants with varying degrees of open angle glaucoma (OAG)
that meet clinical criteria for cataract or glaucoma surgery will be recruited from the
glaucoma clinics at the University of North Carolina (UNC) Kittner Eye Center. Once they have
been determined to be eligible, they will be assigned to one of three groups based upon
surgical indication. Group 1 is cataract surgery only. Group 2 is cataract surgery with
iStent (Glaukos Corp., Laguna Hills, CA) implantation. Group 3 is implantation of a glaucoma
drainage device. Each procedure will be completed in a standardized fashion with
standardization of the post-operative medications. An effort will be made to gender and age
match each surgical group as well as provide reasonable racial and ethnic diversity.
Procedures (methods): Participants will undergo assessment of 24 hour IOP and ocular
perfusion pressure (OPP), retinal oxygen saturation (RSO2), and optic nerve blood flow
(ONBF), within 10 days of their assigned surgical procedure and again 6-8 weeks
post-operatively. Ambulatory IOP and OPP: IOP will be measured using the Triggerfish®
(Sensimed AG, Lausanne, Switzerland) contact lens sensor (CLS) every five minutes. Blood
pressure (BP) will be measured with an ambulatory BP measure (ABPM) every 30 minutes during
the day and every hour overnight. Participants will have the CLS and ABPM placed by study
personnel, wear them for 24 hours assuming their typical daily activity and sleep regimen,
then return to clinic the following day to have the devices removed. Optic Nerve Blood Flow
and Retinal Oximetry: Prior to placement of the CLS and ABPM participants will undergo
assessment of the ONBF using Doppler spectral domain optical coherence tomography (SD-OCT)
and RSO2 using the Oxymap T1 (Oxymap, Reykjavik, Iceland) retinal oximeter.

Inclusion Criteria:

- Participants meeting the following surgical indications for glaucoma:

1. Open angle glaucoma with uncontrolled intraocular pressure on maximum tolerated
medical therapy at risk of glaucomatous vision loss, documented visual field
progression, severe visual field defects threatening or involving fixation with
preserved visual acuity

2. Phacomorphic angle closure with clinical symptoms and/or Visual Field/Optical
Coherence Tomography defects

3. Other appropriate indication

- Participants willing to complete the written informed consent

- Participants willing to complete a screening visit and subsequent study visits

Exclusion Criteria:

- Children and adolescents

- Patients with non-phacomorphic angle closure or secondary glaucoma diagnosis

- Prior retinal or glaucoma laser or incisional surgeries

- Non-glaucomatous optic neuropathy

- Any intraocular surgery within the preceding 90 days

- Active ocular infection or inflammation

- Ocular abnormalities that preclude the necessary study related measurements and
assessments

- Pre-existing medical conditions that are associated with blood pressure (BP)
instability

- Medications that confound BP assessment

- Symptomatic dry eye disease

- Allergy to silicone, adhesives, diagnostic and post-surgical topical ocular
medications

- Skin irritation, eczema, or other indication against wearing patches

- Vulnerable populations