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A Study of Isosorbide Mononitrate for Patients with Normal Tension Glaucoma to Improve Blood Flow to the Optic Nerve

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study examines normal tension glaucoma, which is a type of eye disease where the nerve that carries visual information from the eye to the brain becomes damaged even though the pressure inside the eye is not elevated. In this condition, the field of vision gradually becomes smaller, and the layer of nerve fibers at the back of the eye becomes thinner over time. The study will use Ismox 20 mg tablets, which contain the active ingredient isosorbide 5 mononitrate, a medication that belongs to a group of medicines called nitrates that help improve blood flow. This medication will be given in addition to the regular eye drops that patients are already using for their glaucoma treatment. Some participants will receive a placebo instead of the active medication.

The purpose of the study is to find out whether taking this long-acting nitrate medication by mouth can improve blood circulation to the optic nerve head, which is the part of the nerve at the back of the eye where damage occurs in glaucoma, and whether it can help slow down the progression of the disease when used together with other glaucoma treatments. The study will also examine how the medication affects the structure and function of the eye using various imaging and testing methods.

During the study, participants will attend regular visits where the thickness of the nerve fiber layer at the back of the eye will be measured using a special imaging technique called optical coherence tomography, which uses light waves to take detailed pictures of the eye structures. Visual field testing will also be performed to measure how well participants can see in different areas of their vision. The study will last for 18 months, with measurements taken at the beginning and at 6, 12, and 18 months to track any changes over time. The main focus will be on measuring changes in nerve fiber thickness and visual field measurements to determine whether the medication helps slow down disease progression compared to placebo.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial assessment and treatment start

    At the beginning of the trial, your optic nerve fiber layer thickness will be measured using optical coherence tomography, which is an imaging method that creates detailed pictures of the eye.

    A visual field test will be performed to assess your peripheral and central vision.

    You will be assigned to receive either the study medication or a placebo. The study medication is isosorbide 5-mononitrate (brand name Ismox), a long-acting nitrate tablet taken by mouth. The dosage is 20 mg.

    You will continue taking your current eye drop medications for glaucoma alongside the study medication.

  2. Step 2

    Treatment period

    You will take the assigned medication (either the study drug or placebo) regularly throughout the trial period.

    The medication is taken orally in tablet form.

    You will keep a symptom diary to record any side effects or symptoms you experience during the treatment.

  3. Step 3

    6-month evaluation

    After 6 months of treatment, you will attend a follow-up visit.

    Your optic nerve fiber layer thickness will be measured again using optical coherence tomography.

    A visual field test will be performed to check for any changes in your vision.

    The results from this visit serve as an intermediate checkpoint, not as a final outcome measure.

  4. Step 4

    12-month evaluation

    After 12 months of treatment, you will attend another follow-up visit.

    Your optic nerve fiber layer thickness will be measured using optical coherence tomography.

    A visual field test will be performed.

    The results from this visit serve as an intermediate checkpoint, not as a final outcome measure.

  5. Step 5

    Final evaluation at 18 months

    After 18 months of treatment, you will attend the final study visit.

    Your optic nerve fiber layer thickness will be measured using optical coherence tomography.

    A visual field test will be performed.

    The primary outcome will be assessed by comparing the rate of change in your optic nerve fiber layer thickness from the start of treatment to this final visit.

    Secondary outcomes will include changes in your visual field mean defect values, whether your glaucoma eye drop treatment needed to be intensified, whether you required selective laser trabeculoplasty (a laser procedure for glaucoma) or glaucoma surgery during the follow-up period, and the tolerability of the treatment based on your symptom diary.

Who can join the trial?

8 criteria

  • You must have been previously diagnosed with normal tension glaucoma, which is a type of eye condition affecting the optic nerve despite normal eye pressure
  • You must be between 50 and 90 years old
  • You must not have previously used nitrate medications for heart conditions
  • You must have had at least two previous imaging tests of the optic nerve head using a special scanning technique called optical coherence tomography, which takes detailed pictures of the layers at the back of your eye
  • You must have had at least two previous visual field tests, which are examinations that check your side vision and detect blind spots
  • You must be using at least two different active ingredients in eye drop form to treat your glaucoma
  • Your eye tests must show specific changes: either your average nerve fiber layer thickness (the layer of nerve cells measured at 3.5 mm diameter) is less than 75 micrometers, or two sections show thinning compared to reference data, and your visual field test shows a mean defect value of at least 5 dB, which indicates vision loss
  • Your follow-up tests must show that your normal tension glaucoma is progressing, meaning it is getting worse over time based on the imaging scans of your optic nerve or visual field test results

Who cannot join the trial?

1 criterion

  • The exclusion criteria for this clinical trial have not been specified in the provided information.
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Investigated drugs

Isosorbide mononitrate is a long-acting nitrate medication taken by mouth. In this trial, it is being studied to see if it can improve blood flow to the optic nerve head in people with normal tension glaucoma. The medication is also being tested to find out if it helps treat normal tension glaucoma when used together with other eye medications that patients are already using.

What is already known about the treatment

Ismox – Ismox is a long-acting oral medication containing isosorbide-5-mononitrate, which belongs to a group of drugs called nitrates that work by relaxing and widening blood vessels to improve blood flow. In this clinical trial, it is being studied as an experimental treatment for normal tension glaucoma, a condition where the optic nerve is damaged despite normal eye pressure. The medication is taken by mouth in a 20 mg dose and is being investigated to see if it can enhance blood circulation to the optic nerve head and potentially help protect vision when used alongside standard eye drop treatments. The study aims to evaluate both the structural and functional effects on the optic nerve using advanced imaging techniques and visual field testing.

Investigated diseases

Normal Tension Glaucoma – Normal tension glaucoma is a form of glaucoma where damage to the optic nerve occurs even though the pressure inside the eye remains within the normal range. The condition leads to progressive loss of nerve fibers in the optic nerve head, which can be detected through specialized imaging techniques. As the disease advances, it causes gradual deterioration of the visual field, meaning the person's peripheral vision slowly diminishes. The damage occurs despite eye pressure measurements that would typically be considered safe or normal. Blood flow problems to the optic nerve are thought to play a role in how this condition develops. The progression is typically slow and may affect both eyes, though not always at the same rate.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-522059-24-00Estimated enrolment100 patientsSponsorUniversity Of Helsinki

sourced from the EU Clinical Trials Register and site verification

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).