Assessment of Optic Nerve Radiation in Patients With Glaucoma and Ocular Hypertension by 7 Tesla Diffusion Tensor Imaging

Assessment of Optic Nerve Radiation in Patients With Glaucoma and Ocular Hypertension by 7 Tesla Diffusion Tensor Imaging

Glaucoma is among the leading causes for blindness in the western world. Elevated intraocular pressure (IOP) has been identified as the most important risk factor. However, some patients progress despite adequate IOP lowering while some subjects with elevated IOP never develop glaucoma. Other patients develop glaucoma although IOP measurements were always in the normal range. Therefore, other factors must be involved. In the last years, studies using MRI have been performed and evidence has accumulated that also changes in retrobulbar structures are present, in particular in the lateral geniculate nucleus and the visual cortex. However, these studies were limited by the low spatial resolution of the MRI instruments used.

The investigators propose to overcome this problem by using an ultrahigh-field Magnetom 7T whole-body MR scanner (Siemens Medical, Germany) installed at the MR Centre of Excellence at the Medical University of Vienna. This scanner is equipped with a 32-channel head coil and the SC72 high-performance gradient system and is thus perfectly suited for structural and functional imaging. The aim of the present study is to investigate whether structural and functional parameters are altered in patients with primary open angle glaucoma (POAG), normal tension glaucoma (NTG), ocular hypertension (OHT) compared to healthy control subjects. The exact topographical survey of intracranial structures such as the LGN and the assessment of neuronal structures by DTI may allow for the better assessment of therapeutic responses to new neuroprotective agents.

Inclusion Criteria:

Healthy controls

• Men and women aged over 18 years
• Normal findings in the medical history unless the investigator considers an abnormality to be clinically irrelevant
• Normal ophthalmic findings

Patients with ocular hypertension

• Men and women aged over 18 years
• Normal findings in the medical history unless the investigator considers an abnormality to be clinically irrelevant
• Normal ophthalmic findings except presence of ocular hypertension (defined as untreated IOP ≥ 21 mmHg on at least three measurements in the medical history, no signs of glaucomatous damage in the optic disc or the glaucoma hemifield test)

Patients with primary open angle glaucoma

• Men and women aged over 18 years
• Normal findings in the medical history unless the investigator considers an abnormality to be clinically irrelevant
• Diagnosis of manifest primary open angle glaucoma (defined as pathological optic disc appearance, glaucoma hemifield test outside normal limits and untreated IOP > 20 mmHg on at least three measurements in the medical history)
• Mean Deviation in the visual field test ≥ 10dB

Patients with normal-tension glaucoma

• Men and women aged over 18 years
• Normal findings in the medical history unless the investigator considers an abnormality to be clinically irrelevant
• Diagnosis of normal-tension glaucoma (defined as pathological optic disc appearance, glaucoma hemifield test outside normal limits and untreated IOP ≤ 20 mmHg on at least three measurements in the medical history)
• Mean Deviation in the visual field test ≥ 10dB

Exclusion Criteria:

• Symptoms of a clinically relevant illness in the 3 weeks before the first study day
• Presence or history of a severe medical condition as judged by the clinical investigator
• Abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study
• Exfoliation glaucoma, pigmentary glaucoma, history of acute angle closure
• Intraocular surgery within the last 6 months
• Ocular inflammation or infection within the last 3 months
• Pregnancy, planned pregnancy or lactating
• Any metallic, electric, electronic or magnetic device or object not removable except dental fillings
• Claustrophobia