Glaucoma monitoring: target IOP, OCT / visual field and reports

What it is

Public education on long-term glaucoma monitoring: teaching figures for target pressure, how structure (OCT) and function (visual field) are read together, and what colour maps on reports mean. This page does not score your report and does not teach DIY dose changes or stopping drops. Disease types (open-angle, normal-tension, ocular hypertension, angle closure) are on the glaucoma overview; five pressure-lowering drop classes are on the glaucoma drops page.

Why monitor

Lost nerve fibres and field usually do not return. In the spirit of the Early Manifest Glaucoma Trial (EMGT), lowering IOP may slow progression in some people — not a cure and not a personal guarantee. Monitoring usually includes IOP, structure (OCT RNFL / ganglion-cell–related measures) and function (Humphrey-class automated perimetry). Follow-up density follows risk and speed of change — not one timetable for everyone.

Target IOP (teaching)

Literature often discusses relative pressure drops: normal-tension glaucoma (CNTGS) commonly discusses a further drop of about 30%; ocular hypertension (OHTS) commonly discusses about 20%. Actual millimetre-of-mercury targets and percentage drops are decided only by an ophthalmologist; this page is not a visit.

Educational factors that may shape a target (a list, not a DIY score): optic-nerve damage, visual field, speed of change, age, thin cornea, disc haemorrhage, family history.

Structure and function: OCT / visual field

OCT colour maps are usually compared with that machine’s age norms: green often within a common statistical range, yellow borderline, red uncommon — statistical hints, not a verdict and not “already blind”. Macular / ganglion-cell complex (GCC and similar) is more sensitive to central-pattern loss. Humphrey-class field: mean deviation (MD) more negative usually means lower overall sensitivity; pattern standard deviation (PSD) reflects focal loss; glaucoma hemifield test (GHT) compares upper and lower halves. First tests often show a learning effect — repeat to build a baseline.

If OCT already shows clear thinning while the field is still relatively preserved, that is a time to discuss stronger IOP lowering to slow worsening — not a vision-preservation guarantee.

Worsening clues (education only — not self-diagnosis)

• Structure (OCT): larger cup–disc ratio, rim notches, disc haemorrhage, progressive RNFL / ganglion-cell–related thinning
• Function (visual field): clear MD worsening, new scotomas or central encroachment, progression analysis suggesting change (doctor interprets)
• IOP: persistently above target, or large swings — still combine with structure and function; one reading is not enough

What reports look like

• Green / yellow / red are often statistical colours vs that machine’s norms — not a court verdict
• Thickness numbers from different brands are usually not directly cross-comparable
• Red ≠ blind; false positives, poor fixation, cataract and small pupils all matter
• One bad field often needs a repeat before it means much
• Do not send report photos to non-treating clinicians as a formal reading
• This site will not score your report — bring the printout to follow-up

Go to A&E now (if you cannot get there: call 999)

• Acute angle-closure attack: severe red painful eye, headache and vomiting, rainbows, sudden vision drop — A&E now; if you cannot travel: call 999 (see urgent, glaucoma overview, hyperopia / shallow-chamber page)
• Sudden vision drop or sudden blindness

Same-day / scheduled follow-up

• If already diagnosed: keep the pressure / OCT / field schedule the doctor set — do not invent your own denser or looser plan
• New sense of field loss or tunnel vision without A&E red flags: see an ophthalmologist as soon as possible
• Do not stop, change doses or lend leftover drops yourself — see the glaucoma drops page