Ocular Blood Flow in Early Glaucoma Patients Before and After Treatment With Dorzolamide

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT00152932
Recruitment Status : Unknown
Verified September 2005 by University Health Network, Toronto.
Recruitment status was:  Recruiting
First Posted : September 9, 2005
Last Update Posted : July 25, 2007
Merck Frosst Canada Ltd.
Information provided by:
University Health Network, Toronto

September 8, 2005
September 9, 2005
July 25, 2007
May 2005
Not Provided
Ocular blood flow measurements
Same as current
Complete list of historical versions of study NCT00152932 on Archive Site
Intraocular pressure reduction
Same as current
Not Provided
Not Provided
Ocular Blood Flow in Early Glaucoma Patients Before and After Treatment With Dorzolamide
Ocular Blood Flow Measured by HRF and CLBF in Newly Diagnosed and Early Glaucoma Patients Before and After Instillation of Dorzolamide 2%

Impaired ocular blood flow is an important risk factor in the pathogenesis of primary open angle glaucoma (POAG). A few studies suggest that topical dorzolamide 2% may increase optic nerve perfusion. The objectives of this study are to learn the effects of dorzolamide on the retinal and optic nerve blood flow of glaucoma patients.

The present study is a prospective, randomized, double-masked, crossover design study of newly diagnosed or already treated patients with early glaucoma.

The investigators will check ocular blood flow parameters using the Canon Laser Blood Flowmeter (CLBF), used to evaluate retinal arteriole blood flow, and the Heidelberg retinal flowmeter (HRF), which measures blood flow through capillary beds in the retina and optic nerve head.

Any demonstrated improvements to retinal and optic nerve blood flow with dorzolamide, will mean that the drug may protect against ischaemic nerve and retinal damage. Any documented improvement in flow could lead to a major change in the management of glaucoma patients as well as other retinal ischemic diseases such as diabetic retinopathy and central retinal vein occlusion.

High intraocular pressure (IOP) is the major risk factor for glaucoma. Lowering intraocular pressure is still the only accepted form of treatment for glaucoma.

Over the past decade, epidemiological and experimental evidence suggested that impaired ocular blood flow is an important risk factor with an important role in the pathogenesis of primary open angle glaucoma (POAG). Several studies suggest that ischemia-promoting vascular factors may contribute to glaucomatous damage including vasospasm, impaired ocular perfusion pressure and general vascular disorders such as low blood pressure, especially dips in blood pressure at night.

Different techniques are employed to assess vascular dysfunction in the eye. As the methodology of ocular blood flow assessment is complex and differs in various aspects (e.g. target tissue and physiological parameters), comparative studies are required in order to enhance the interpretation of these measurements.

Our laboratory has state of the art equipment to assess ocular blood flow. One study done by us suggested that one drop of Dorzolamide 2% does not improve retinal blood flow in normal eyes. In the present study we plan to extend this study to 2 weeks of treatment in patients with POAG.

Dorzolamide hydrochloride 2% is a topical carbonic anhydrase inhibitor which reduces intraocular pressure (IOP) by decreasing the production of aqueous humour. Pharmacological studies on volunteers and glaucoma patients, using Color Doppler Imaging (measuring the retrobulbar blood flow) and Scanning laser Ophthalmoscopy (measuring arteriovenous passage time), indicate that topically applied Dorzolamide may increase perfusion of the optic nerve and peripapillary retina.

Not Applicable
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single
Primary Purpose: Diagnostic
  • Drug: Dorzolamide 2% drops
  • Device: HRF and CLBF
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*   Includes publications given by the data provider as well as publications identified by Identifier (NCT Number) in Medline.
Unknown status
Same as current
June 2006
Not Provided

Inclusion Criteria:

  1. Males or females 20-80 years of age.
  2. Presence of typical early glaucomatous optic disc changes (cup/disc ratio ≤ 0.75) and/or early glaucomatous visual field defects (mean deviation less than 5dB and outside of 10° from fixation) in the study eye at the baseline visit.
  3. Best corrected visual acuity of at least 20/40.
  4. Signed informed consent from the subject
  5. The subject should be able to understand the instructions and perform the HRF and CLBF tests as well as be willing and able to comply with the study schedule and treatment.

Exclusion Criteria:

  1. Pregnant women or nursing mothers.
  2. Any other active ocular disease (ocular infections, Uveitis, etc.)
  3. Known allergy or sensitivity to the study medications.
  4. Functionally significant visual field loss (mean deviation greater than 5dB) or cup/disc ratio greater than 0.75 or evidence of progressive visual field loss within the last 6 months.
  5. Required chronic use of other ocular or systemic hypotensive medications during the study, other than the study medication (e.g. beta-blockers, Ca-channel blockers)
  6. Vascular occlusive disease affecting the ocular circulation such as: diabetic retinopathy, central retinal vein occlusion, central retinal artery occlusion, or non-arteritic ischemic optic neuropathy.
  7. Previous intraocular surgery or ocular traumas.
  8. Any past history of serious systemic condition affecting cerebral circulation including: hypertension, diabetes, cerebral vascular accident (CVA), or coronary artery bypass graft (CABG).
Sexes Eligible for Study: All
20 Years to 80 Years   (Adult, Senior)
Contact information is only displayed when the study is recruiting subjects
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University Health Network, Toronto
Merck Frosst Canada Ltd.
Principal Investigator: Graham E Trope, MB, FRCSC University of Toronto, Department of Ophthalmology
Study Chair: Chris Hudson, PhD Department of Ophthalmology, Toronto Western Hospital, Toronto
Study Chair: John Flanagan, PhD Department of Ophthalmology, Toronto Western Hospital, Toronto
Study Chair: Yvonne M Buys, MD, FRCSC University of Toronto, Department of Ophthalmology, Toronto Western Hospital, Toronto
University Health Network, Toronto
September 2005

ICMJE     Data element required by the International Committee of Medical Journal Editors and the World Health Organization ICTRP