Aqueous Dynamics and Glaucoma Surgeries

The Effect of Glaucoma Surgery on Aqueous Dynamics in Patients With Glaucoma or Ocular Hypertension: An Observational Study

There are currently many surgical options for patients with glaucoma and ocular hypertension (OHT), including the Hydrus Microstent implant, HiFU (High intensity Focused ultrasound), STAR flo, Kahook Dual Blade, Diode laser, trabeculectomy and the Baerveldt implant, but little is known about how these different surgical techniques used to treat glaucoma affect the flow of fluid through and out of the eye (aqueous dynamics).

Study Overview

• Status: Unknown
• Conditions: Ocular Hypertension; Glaucoma
• Intervention / Treatment: Device: HiFU; Device: Baerveldt implant; Device: Ahmed implant; Device: STARflo; Device: Hydrus Microstent implant; Device: iStent implant; Device: Kahook Dual Blade

Detailed Description

Trial objectives

Main outcome measures: The following aqueous dynamics parameters will be measured: IOP, aqueous flow rate, trabecular outflow facility and uveoscleral outflow. These parameters will be measured pre-treatment (up to 2 months before glaucoma surgery) and repeated 3 months and 12 months post-surgery. Measures will be taken from the operated eye and the contra lateral non-operated eye which will be used as the control.

Trial design

This is a prospective observational study with the contra lateral untreated eye being used as control. Baseline measures will be conducted at a routine clinic visit up to 2 months before glaucoma surgery after 4 weeks of treatment washout.

Post-treatment follow-up measurements of the main outcomes will be conducted 3 months and 12 months after surgery, again, after 4 weeks wash out. A number of additional eye tests will also be performed to collect data for the study at the pre-operative appointment when the baseline measurements are taken and at the post-operative follow-up appointments 3 months and 12 months after the surgery. Other data will be collected from eye tests that are routinely performed pre-operatively and at the post-operative follow-up appointments 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months after their surgery.

Study participants will be recruited from patients attending the Ophthalmology Department Outpatients Clinic at St Thomas' Hospital, London, United Kingdom who have a diagnosis of glaucoma or OHT (ocular hypertension) requiring glaucoma drainage surgery. One hundred patients with glaucoma or OHT and where a clinical decision has been made that they need glaucoma surgery will be included in the study such that 100 eyes undergoing surgery will be included together with the contra-lateral untreated eyes that will be used as controls for comparison with the treated eyes.

Data will be collected for the study at the following routine appointments that patients undergoing glaucoma surgery are asked to attend: a pre-operative appointment, surgery, and follow-up assessments 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months after surgery. Baseline measurements will be taken up to 2 months before glaucoma surgery.

At the baseline assessment demographic information will be collected

Details of participants' relevant past medical history will be collected at the baseline pre-operative assessment and at 12 months post-surgery.

All tests will be performed on both eyes as the contra-lateral non-operated eye will be used as control.

Aqueous parameters

• Aqueous flow rate: Participants will be asked to self-administer 3 to 6 drops (depending on their age) of fluorescein sodium 2% topically into both eyes at 5 minute intervals on the night before the fluorophotometric scans. Fluorophotometry will be performed using a scanning ocular fluorophotometer from 9:00 am -12:00 midday. Four sets of triplicate scans will be collected at 1 hour intervals to determine the aqueous flow rate (Ft). The 3 scans are done in quick succession, taking approximately 2 seconds in total to complete the set. Following each set of scans, IOP will be measured using pneumatonometry. and rebound tonometry. IOP will be recorded as the mean of a total of 12 measurements per eye: 3 measurements every hour alternating between eyes.

Patients who have had previous cataract surgeries or iridotomy/iridectomy will be excluded from this aspect of the measurements as fluorophotometry is inaccurate in these eyes.

• Outflow facility: Tonographic outflow facility (C) measurement will be performed using an electronic Schiøtz tonographer (Model 720, Berkeley Bioengineering Inc, USA) between 9:00 am -12:00 midday. The facility of outflow will be measured from the rate of decay of IOP in the supine position during application of a recording Schiøtz tonometer over a period of 4 minutes with a standard 5.5 gram weight. The "R" values of the curve at every 30-second time point will be manually entered into the McLaren tonography computer program. The program fits a second-degree polynomial by least squares to the nine data points and determines the best-fit values for time 0 and time 4 minutes by extrapolation.
• Intraocular pressure (IOP): Pneumatonometry and rebound tonometry will be used to measure IOP for patients undergoing fluorophotometry. The IOP measurements will be recorded at 1 hour intervals between the hours of 9:00 am -12:00 midday following each set of fluorophotometric scans.
• Uveoscleral outflow: There are currently no reliable clinical methods of measuring uveoscleral outflow (Fu) and episcleral venous pressure (Pv). Fu will be therefore calculated using the Goldmann equation (see below) with an assumed episcleral venous pressure of 8-11 mmHg:

Ft = C(IOP - Pv) +Fu Where:

Ft = Measured aqueous flow rate Fu = Ft - C(IOP - Pv) Fu = Calculated uveoscleral outflow C = Tonographic outflow facility (value computed by the measurement device) IOP = Mean morning intraocular pressure as measured by pneumatonometry Pv = Episcleral venous pressure (8-11 mmHg, exact value calculated based on patient parameters)

Routine tests

At the pre-operative visit when baseline measurements are taken and at each routine post-operative follow-up visit (1 day, 1 week, 1 month, 3 months, 6 months, and 12 months after surgery) patients will undergo a clinical ophthalmological examination including the following tests and examinations:

• Visual acuity measurement (Snellen and ETDRS charts will be used. Best Corrected Distance Visual Acuity (BCVA) and Non Corrected Distance Visual Acuity (NCVA) will be measured using ETDRS (early treatment diabetic retinopathy study) charts. Best Corrected Near Visual Acuity (BCVA) will be measured using a standard near vision chart).
• Slit lamp examination
• Visual fields
• IOP (intraocular pressure) measurement (Goldmann applanation tonometry will be used to measure IOP, except when there is irregular corneal astigmatism or other corneal problems which may preclude accurate reading. The IOP measurement will be done after application of topical anesthetic (eye drop) with fluorescein)
• Gonioscopy
• Dilated fundoscopy
• Anterior chamber depth and axial length
• Central corneal thickness
• Refraction (routine at baseline only)

Description of the surgical interventions

There are potentially four types of operation that patients may have as part of their glaucoma care in the department:

• Trans-trabecular meshwork implants (Hydrus implant or iStent implant)
• Ciliary Ablation Treatment (Diode laser or HiFu ultrasound treatment)
• External (sub-conjunctival) Drainage Surgery (Trabeculectomy, Baerveldt implant or Ahmed Implant)
• Suprachoroidal Shunt Surgery (STARflo)

• Study Type: Observational
• Enrollment (Anticipated): 100

Contacts and Locations

• Study Contact: Name: Stephanie Jones, BA; Phone Number: 02071884885; Email: stephanie.jones@gstt.nhs.uk

Study Locations

• United Kingdom
  • London, United Kingdom, SE1 7EH
    • Recruiting
    • St Thomas Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 90 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

One hundred patients with glaucoma or OHT and where a clinical decision has been made that they need glaucoma surgery will be included in the study such that 100 eyes undergoing surgery will be included together with the contralateral untreated eyes that will be used as controls for comparison with the treated eyes

Description

Inclusion Criteria:

• Males or females between the ages of 18 and 90 (inclusive).
• Able to understand the study and give informed consent.
• Willing, able and available to participate in all aspects of the study.
• Diagnosis of glaucoma or OHT which requires glaucoma surgery. (Defined as primary or secondary glaucoma; all types of secondary glaucoma may be included. Glaucoma will be diagnosed based on abnormal visual field testing and corresponding disc changes once seen by a glaucoma specialist.)
• Able to undergo accurate fluorophotometry and tonography.

Exclusion Criteria:

• Mental impairment conflicting with informed consent or follow-up.
• Allergy to fluorescein.
• Current use of any investigational drug or device or current participation in an interventional clinical trial.
• Patients who might not adequately understand written information given in English or verbal explanations in English will not be included as participants in the study must be able to understand English to complete some of the tests.
• Any inclusion criteria not met

Study Plan

How is the study designed?

Design Details

• Observational Models: Cohort
• Time Perspectives: Prospective

Number of groups / cohorts

7

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
HiFu (ultrasound); Manufacturer Name Eyehope Principle intended use Surgical treatment of uncontrolled glaucoma and OHT The device is currently routinely used in the department for the treatment of uncontrolled glaucoma and OHT, and will be used in accordance with usual clinical practice. It is not anticipated that there will be any changes to the device or its usage during the course of the study.	Device: HiFU; Ciliary Ablation Treatment ( HiFu ultrasound treatment)
Baerveldt implant; Manufacturer Name Abbott Medical Optics Inc., Abbott Laboratories Inc., Abbott Park, Illinois, USA. Principle intended use Surgical treatment of uncontrolled glaucoma and OHT The device is currently routinely used in the department for the treatment of uncontrolled glaucoma and OHT, and will be used in accordance with usual clinical practice. It is not anticipated that there will be any changes to the device or its usage during the course of the study.	Device: Baerveldt implant; External (sub-conjunctival) Drainage Surgery (Baerveldt implant)
Ahmed Implant; Manufacturer Name New World Medical, Inc., 10763 Edison Court, Rancho Cucamonga, CA 91730, USA. Principle intended use Surgical treatment of uncontrolled glaucoma and OHT The device is currently routinely used in the department for the treatment of uncontrolled glaucoma and OHT, and will be used in accordance with usual clinical practice. It is not anticipated that there will be any changes to the device or its usage during the course of the study.	Device: Ahmed implant; External (sub-conjunctival) Drainage Surgery (Ahmed Implant)
STARflo; Manufacturer Name iSTAR Medical SA, Parc Créalys, Rue Phocas Lejeune, Bâtiment Regain 25/3, 5032 Isnes, Belgium. Principle intended use Surgical treatment of uncontrolled glaucoma and OHT The device is currently routinely used in the department for the treatment of uncontrolled glaucoma and OHT, and will be used in accordance with usual clinical practice. It is not anticipated that there will be any changes to the device or its usage during the course of the study.	Device: STARflo; Suprachoroidal Shunt Surgery (STARflo)
Hydrus Microstent implant; Manufacturer Name Ivantis, Inc., 38 Discovery, Suite 150, Irvine, CA 92618, USA. Principle intended use Surgical treatment of uncontrolled glaucoma and OHT The device is currently routinely used in the department for the treatment of uncontrolled glaucoma and OHT, and will be used in accordance with usual clinical practice. It is not anticipated that there will be any changes to the device or its usage during the course of the study.	Device: Hydrus Microstent implant; Trans-trabecular meshwork implants (Hydrus Microstent implant).
iStent implant; Manufacturer Name Glaukos Corporation, 26051 Merit Circle, Suite 103, Laguna Hills, CA 92653, USA. Principle intended use Surgical treatment of uncontrolled glaucoma and OHT The device is currently routinely used in the department for the treatment of uncontrolled glaucoma and OHT, and will be used in accordance with usual clinical practice. It is not anticipated that there will be any changes to the device or its usage during the course of the study.	Device: iStent implant; Trans-trabecular meshwork implants (iStent implant).
Kahook Dual Blade; Manufacturer: New World Medical. Inc. Single use, ophthalmic blade Utilizes ab interno approach through a clear cornea micro incision Dual blades positioned for precise parallel incisions of the trabecular meshwork with minimal residual leaflets Maintains natural physiologic outflow pathways	Device: Kahook Dual Blade; It removes part of the trabecular meshwork

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change from baseline of Intraocular pressure at 12 months	It would be measured by Goldmann tonometer, iCare and pneumatonometer. The unit of measurement for all of these devices is the same. It is mmHg	baseline and 12 months
Change from baseline of aqueous flow at 12 months	This parameter is measured by fluorophotometry	baseline and12 months
Change from baseline of uveoscleral outflow at 12 months	It would be calculated by Goldmann's equation	baseline and 12 months
Change from baseline of trabecular outflow facility at 12 months	It will be measured by Electronic Schiotz tonography	baseline and 12 months

Collaborators and Investigators

• Sponsor: Guy's and St Thomas' NHS Foundation Trust

Publications and helpful links

General Publications

• Ho H, Daas A, Ho J, Alaghband P, Galvis EA, de Antonio Ramirez A, Grassi P, Lim R, Lim KS. Intraocular pressure changes following topical ocular hypotensive medications washout. Br J Ophthalmol. 2021 Feb;105(2):205-209. doi: 10.1136/bjophthalmol-2019-315778. Epub 2020 Apr 10.

Study record dates

Study Major Dates

• Study Start: July 1, 2016
• Primary Completion (Anticipated): December 1, 2017
• Study Completion (Anticipated): December 1, 2017

Study Registration Dates

• First Submitted: June 28, 2016
• First Submitted That Met QC Criteria: July 18, 2016
• First Posted (Estimate): July 21, 2016

Study Record Updates

• Last Update Posted (Estimate): July 21, 2016
• Last Update Submitted That Met QC Criteria: July 18, 2016
• Last Verified: July 1, 2016

More Information

Terms related to this study

• Keywords: Ocular hypertension; Glaucoma; Aqueous dynamics
• Additional Relevant MeSH Terms: Cardiovascular Diseases; Vascular Diseases; Eye Diseases; Glaucoma; Ocular Hypertension; Hypertension
• Other Study ID Numbers: 163050; 15/LO/1809 (Other Identifier: Research Ethics Committee)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: No
• IPD Plan Description: There is no plan to share individual participant data (IPD)