What Happens During a Glaucoma Test? Tests, Preparation and Follow-Up

A glaucoma assessment usually combines several tests rather than one pass-or-fail check. The team may measure eye pressure, examine the optic nerve, test your visual field and take images. The combination and order depend on why you were referred and what is already known about your eyes.

Information checked October 15, 2026. This general preparation guide uses U.S. National Eye Institute and UK NHS clinical patient information. It does not apply UK appointment arrangements or insurance rules to U.S. readers, and it is not an individualized examination plan or a medical professional’s review.

Before the appointment: confirm the plan with the clinic

Ask which tests are planned, whether dilation is likely and how long to allow, including waiting time. There is no reliable universal 60-to-90-minute total. A short pressure review and an initial assessment involving several tests can require very different amounts of time.

• Bring your glasses, including reading glasses, and your current medication list or bottles.
• Tell the practice about allergies, previous eye procedures and other medical conditions.
• Bring sunglasses and arrange help getting home if dilation is expected.
• Ask in advance about accessibility, an interpreter or help with positioning.
• Follow the clinic’s preparation instructions. Do not stop glaucoma drops or change prescribed medicines to try to improve a test result.

Write down the main reason for your visit and any new symptoms. If you are being treated elsewhere, ask whether the clinic needs previous scans, visual field results or a visit summary.

Common parts of a glaucoma assessment

The Manchester Royal Eye Hospital leaflet explains these basic tests. Its July 2026 review date has passed, so confirm current arrangements with your clinic.

Eye pressure: tonometry

This measures pressure inside the eye. Some devices use a puff of air; others briefly contact the eye with appropriate preparation. Tell the examiner if you find it difficult to hold your position. Do not squeeze, hold your breath or try to influence the number; follow the instructions you are given.

A pressure number alone does not settle a glaucoma diagnosis. Ask how it fits with the rest of your examination rather than comparing it with a single online cut-off.

Slit-lamp examination

A microscope and light help the clinician examine eye structures. Tell the team if positioning is uncomfortable.

Corneal thickness: pachymetry

Corneal thickness helps put pressure readings in context. It may not need repeating at every visit. Ask what it means for your assessment.

Drainage-angle examination: gonioscopy

After numbing drops, the clinician uses a small lens on the eye to inspect drainage structures. Ask for an explanation before starting.

Optic-nerve examination and imaging

Optic-nerve examination, photographs and scans can support comparisons over time. If OCT is planned, ask what is being scanned and how the result is interpreted.

During a visual field test: respond to what you actually see

In a common automated test, you look at a central target and press a button when you see a light. The Guy’s and St Thomas’ visual field guide, reviewed February 2026, explains that lights vary in brightness and that it is normal not to see one every time.

• Keep looking at the central target rather than looking around for lights.
• Press when you see a light; do not guess just to keep the test moving.
• Blink normally and tell the examiner if instructions or lights are unclear.
• Ask for help if you feel tired, uncomfortable or unable to concentrate.

The NHS guide gives about five to ten minutes per eye for a Humphrey test, while other methods can take longer. That estimate is for the test itself, not the whole appointment. A repeat may improve reliability or help monitor change. Needing a repeat does not by itself establish either a diagnosis or a harmless result.

Dilation: plan your journey before the drops

Dilating drops widen the pupils to help the clinician see inside the eyes. The National Eye Institute’s dilated-exam guide explains that blurred vision and light sensitivity can last for a few hours and advises arranging someone to drive you home. Sunglasses can help with light sensitivity.

Do not treat four or six hours as a guaranteed point at which driving becomes safe. Follow your clinic’s advice and do not drive while your vision is affected. Ask whom to call if the effects seem different from what the team told you to expect.

Before you leave: results, follow-up and costs

Ask: “What did today’s tests show, what is still uncertain, and what happens next?” If the clinician recommends monitoring or treatment, ask why and obtain the actual follow-up date. Do not choose observation or treatment yourself from an online decision card or a fixed repeat-test interval.

Useful questions include:

• Was a result reliable enough to interpret, and does anything need repeating?
• Are you comparing with previous tests or establishing a starting point?
• Should I keep my current medicines unchanged?
• Which symptoms should make me contact you sooner?
• Who will send the results, and who should I contact if I do not receive them?

If you have another eye condition or several specialists, use the 11 questions for a coordinated glaucoma care plan to clarify who is responsible for each part of follow-up.

Ask for an actual estimate instead of a generic price table

Ask the practice for the planned test names, whether examination and imaging are billed separately and what an estimate includes. If you have insurance, confirm the applicable provider network, referral or authorization requirements and expected cost-sharing with the practice and insurer. These depend on your location and plan.

There is no standard “Tier 1 to Tier 5” ladder for a glaucoma workup. A website’s self-pay range cannot establish what you will owe. In an NHS pathway, ask your service about local arrangements; in private or U.S. care, request the relevant written estimate and plan-specific explanation. Do not delay urgent care while obtaining a routine quote.

A short preparation checklist

Confirm the likely tests and time needed, gather glasses and medicines, plan transport if you may be dilated, and write down your most important question. During testing, follow the examiner’s instructions and ask for help when needed. Leave with a clear next step and contact details.