The Response of Intraocular Pressure to Systemic Hypercapnia and Hyperoxia
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ClinicalTrials.gov Identifier: NCT01325285 |
Recruitment Status
: Unknown
Verified November 2010 by University of Toronto.
Recruitment status was: Not yet recruiting
First Posted
: March 29, 2011
Last Update Posted
: August 18, 2011
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Condition or disease | Intervention/treatment |
---|---|
Intraocular Pressure | Device: RespirAct |
In response to changes in the composition of inhaled gases, blood vessels will dilate or constrict. As a result, hypercapnia or hyperoxia may affect the production and drainage of aqueous humour in the anterior chamber of the eye. The balance between the production and drainage of the aqueous humour determines the intraocular pressure. As this system is hydrodynamic, it is expected that any increase or decrease in the production of aqueous humour due to dilation or constriction of the capillaries within the ciliary body will be compensated by increased or decreased drainage at the trabecular meshwork. Therefore intraocular pressure is not expected to show a response to hypercapnia or hyperoxia, but this supposition needs to be tested in a stably controlled manner of inducing inhaled gas provocations. This study will measure the intraocular pressure at varying levels of hypercapnia and hyperoxia using a sequential rebreathing circuit and automated gas blender. This will allow the precise targeting and stable control of end-tidal partial pressure values of carbon dioxide and oxygen.
In this study, intraocular pressure will be measured at seven different inhaled gas stages. The seven stages are as follows:
- Baseline, measured in eye A (PETCO2=38mmHg and PETO2=100mmHg)
- 10% hypercapnic increase, measured in eye A (PETCO2=42mmHg and PETO2=100mmHg)
- 20% hypercapnic increase, measured in eye A (PETCO2=46mmHg and PETO2=100mmHg)
- Baseline, measured in both eyes (PETCO2=38mmHg and PETO2=100mmHg)
- 250% hyperoxic increase, measured in eye B (PETCO2=38mmHg and PETO2=250mmHg)
- 500% hyperoxic increase, measured in eye B (PETCO2=38mmHg and PETO2=500mmHg)
- Baseline, measured in eye B (PETCO2=38mmHg and PETO2=100mmHg)
Study Type : | Observational |
Estimated Enrollment : | 14 participants |
Observational Model: | Case-Only |
Time Perspective: | Cross-Sectional |
Official Title: | The Response of Intraocular Pressure to Systemic Hypercapnia and Hyperoxia |
Study Start Date : | August 2011 |
Estimated Primary Completion Date : | September 2011 |
Estimated Study Completion Date : | September 2011 |
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Device: RespirAct
- Baseline, measured in eye A (PETCO2=38mmHg and PETO2=100mmHg)
- 10% hypercapnic increase, measured in eye A (PETCO2=42mmHg and PETO2=100mmHg)
- 20% hypercapnic increase, measured in eye A (PETCO2=46mmHg and PETO2=100mmHg)
- Baseline, measured in both eyes (PETCO2=38mmHg and PETO2=100mmHg)
- 250% hyperoxic increase, measured in eye B (PETCO2=38mmHg and PETO2=250mmHg)
- 500% hyperoxic increase, measured in eye B (PETCO2=38mmHg and PETO2=500mmHg)
- Baseline, measured in eye B (PETCO2=38mmHg and PETO2=100mmHg)
Participants will breathe through a mask connected to a sequential rebreathing circuit and gas blender. The following seven gas stages will be targeted for about 10 minutes each:
- Intraocular pressure [ Time Frame: Intraocular pressure will be measured during the study visit, ten minutes into each of the seven inhaled gas provocation stages ]Intraocular pressure will be measured using Goldmann applanation tonometry.
- Retinal blood flow [ Time Frame: Retinal blood flow will be measured during the second (optional) study visit, ten minutes into each of the seven inhaled gas provocation stages ]Retinal blood flow will be measured using the Canon Laser Blood Flowmeter in a subset of participants asked to return for a second visit. This will demonstrate that retinal blood flow behaves as the study claims that it does.

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Ages Eligible for Study: | 18 Years to 30 Years (Adult) |
Sexes Eligible for Study: | All |
Accepts Healthy Volunteers: | Yes |
Sampling Method: | Non-Probability Sample |
Inclusion Criteria:
- Age range 18-30 years old
- Visual acuity of 20/20 or better
Exclusion Criteria:
- Refractive error >±6.00 DS and/or ± 2.00 DC
- History or presence of ocular disease
- Family history of diabetes or glaucoma
- History of intraocular or refractive surgery
- Nursing or pregnant women
- History of clinically diagnosed endocrine disease
- History of vascular disease, cardiovascular disease, or any treated respiratory disorders (seasonal asthma excluded from this so long as subject not taking Rx at the time)
- History of systemic hypertension
- Habitual smoking
- Use of medications that affect blood flow

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT01325285
Contact: Alanna Adleman, BSc | 416-603-5694 | aadleman@uhnresearch.ca | |
Contact: Tien Wong, BSc | 416-603-5694 | twong@uhnresearch.ca |
Canada, Ontario | |
Toronto Western Hospital | Not yet recruiting |
Toronto, Ontario, Canada | |
Contact: Alanna Adleman, BSc 416-603-5694 aadleman@uhnresearch.ca | |
Contact: Tien Wong, BSc 416-603-5694 twong@uhnresearch.ca | |
Principal Investigator: Christopher Hudson, PhD | |
Sub-Investigator: Joseph Fisher, FRCPC, MD | |
Sub-Investigator: Richard Cheng, BSc |
Principal Investigator: | Christopher Hudson, PhD | University of Toronto |
Publications:
Responsible Party: | Dr. Christopher Hudson, University of Toronto, University of Waterloo, and Toronto Western Research Institute |
ClinicalTrials.gov Identifier: | NCT01325285 History of Changes |
Other Study ID Numbers: |
10-0655 |
First Posted: | March 29, 2011 Key Record Dates |
Last Update Posted: | August 18, 2011 |
Last Verified: | November 2010 |
Keywords provided by University of Toronto:
Intraocular pressure Hypercapnia Hyperoxia Rebreathing circuit |
Additional relevant MeSH terms:
Hypercapnia Hyperoxia Signs and Symptoms, Respiratory Signs and Symptoms |