OHSU

Glaucoma Screening

Glaucoma can be diagnosed with a complete eye examination. This includes measuring vision and eye pressure and having a dilated eye examination to properly evaluate the optic nerve.

If any of these parameters are abnormal (for example, high eye pressure or a suspicious appearing optic nerve), further testing will be done.

Perimetry

A visual field examination to test your peripheral vision. Visual field defects in glaucoma follow specific patterns that correlate with the region of the nerve that has been damaged. Keep in mind that 20-30% of the nerve may be damaged before the visual field is affected, so a normal visual field does not rule out glaucoma.

Gonioscopy

An examination of the "drain" or trabecular meshwork using a special lens called a gonioprism. The trabecular meshwork is located at the internal junction of the cornea and iris, and is part of the drainage angle. This exam allow us to determine if a person has "open angle" or "closed angle" glaucoma, which is important because the treatments can be very different.

Pachymetry

A measurement of the thickness of your cornea. The instrument we use to measure eye pressure, the Goldmann tonometer, is calibrated for an average thickness cornea (540 to 550 microns). If you have a thin cornea, your pressure reading will be falsely low (i.e. – the real pressure is actually higher than measured). If you have a thick cornea, your pressure reading will be falsely high (i.e. – the real pressure is actually lower than measured). We take this information into account when interpreting your pressure reading.

Other Testing

Your doctor may order color pictures of the optic nerves for future comparison, allowing him or her to identify progressive cupping more easily. In addition, scans of the optic nerve like the Heidelberg Retina Tomograph (HRT) and Optical Coherence Tomography (OCT) can measure the thickness of the nerve tissue for future comparison.