# Open-Angle Glaucoma

Manage open-angle glaucoma by confirming open-angle optic neuropathy, establishing a patient-specific pressure-reduction target, and selecting drops, selective laser trabeculoplasty, or surgery according to disease severity, baseline IOP, tolerance, adherence, and documented structural or functional progression.

**Clinical question:** How should clinicians confirm, risk-stratify, treat, and monitor open-angle glaucoma to prevent progressive visual field loss?

Updated: 2026-08-24T16:10:57.517698+00:00

## What matters in practice
- Confirm the phenotype with tonometry, gonioscopy, optic nerve assessment or imaging, and standard automated perimetry; IOP alone neither establishes nor excludes glaucoma. [8][11][18]
- Set treatment intensity against baseline IOP, optic nerve and visual-field damage, and evidence of progression; a 30% reduction from baseline is a cited target framework for normal-tension glaucoma. [5]
- SLT is an effective first-line option for open-angle glaucoma and ocular hypertension, has pressure-lowering efficacy similar to prostaglandin analogues at 9 to 12 months, and is repeatable. [3][4]
- Expect a larger pressure reduction after SLT when pretreatment IOP is higher; low baseline IOP limits the absolute reduction achievable with trabecular interventions. [3][23]
- Escalate when target IOP is not achieved or structural or functional progression continues despite treatment; trabeculectomy with mitomycin and tube shunt surgery are established pressure-lowering options. [1][16]

## Confirm glaucomatous optic neuropathy and an open angle

Do not equate ocular hypertension with glaucoma or normal IOP with absence of disease.

At the diagnostic visit, document IOP by tonometry, anterior-chamber angle anatomy by gonioscopy, optic nerve head appearance by dilated examination, and baseline structural and functional damage with optic nerve imaging and standard automated perimetry. Open-angle glaucoma is defined clinically by progressive optic nerve rim and retinal nerve fiber layer loss with a compatible open-angle anatomy; IOP is the principal modifiable risk factor but is not itself diagnostic. [8][10][11][18]

Use central corneal thickness as an interpretive modifier for applanation IOP and risk assessment rather than as a stand-alone treatment threshold. The core distinction is ocular hypertension—elevated IOP without established glaucomatous structural or field injury—versus definite glaucoma, in which optic nerve or retinal nerve fiber layer loss and/or reproducible visual-field loss establishes the disease phenotype. [8][18][21]

In suspected or established disease, obtain a reliable baseline visual field using a central threshold automated perimetry strategy and retain the same strategy for subsequent tests when a defect has been detected. Repeat optic nerve head examination or imaging when clinically indicated, because progression may be structural, functional, or both. [17]
- Perform gonioscopy before selecting trabecular laser therapy; SLT is intended for eyes with adequately visualized open-angle trabecular structures. [11][22]
- Interpret an IOP of more than 21 mm Hg as ocular hypertension only after excluding glaucomatous damage; epidemiologic work commonly defines ocular hypertension at this threshold. [21]
- Do not dismiss glaucomatous damage when measured IOP is within a statistically normal range; normal-tension glaucoma requires a pressure-reduction strategy despite lower baseline values. [5]

*Diagnostic branches that change the next management step. [5][8][11][17][18]*

| Clinical pattern | Required discriminators | Immediate management implication |
| --- | --- | --- |
| Ocular hypertension | Elevated IOP without established optic nerve, retinal nerve fiber layer, or visual-field damage; assess CCT and obtain baseline imaging and perimetry. [8][17][21] | Risk-stratify for observation versus IOP lowering; do not label as glaucoma solely from IOP. [8][18] |
| Primary open-angle glaucoma | Open angle on gonioscopy plus glaucomatous optic nerve or retinal nerve fiber layer loss and/or compatible field defect. [11][18] | Set a target IOP and begin pressure-lowering treatment with longitudinal structural and functional surveillance. [17][18] |
| Normal-tension glaucoma | Glaucomatous damage despite IOP not exceeding the conventional ocular-hypertension threshold. [5][21] | Aim for substantial relative IOP lowering; a 30% reduction from baseline is a cited target approach. [5] |
| Secondary open-angle mechanism | Open angle with pigment dispersion or pseudoexfoliation features, medication exposure, or other identifiable cause on history and examination. [19][23] | Treat the IOP and address the identified driver; assess whether a higher baseline IOP or more rapid progression warrants earlier escalation. [19][23] |

## Set a target IOP and define failure by progression

A target is a management tool, not a single universally safe pressure.

Set the initial target as a relative and absolute IOP objective based on untreated or pretreatment IOP, current optic nerve and field damage, and subsequent rate of progression. European guidance cites a peak IOP of 8 to 15 mm Hg on a diurnal curve or approximately 30% reduction from baseline in most normal-tension glaucoma cases; the appropriate target should be lowered further if damage progresses at the achieved IOP. [5]

Measure treatment success against both pressure and disease course. A pressure value that meets the initial target is inadequate if serial OCT or optic nerve assessment shows progressive retinal nerve fiber layer loss or if reproducible visual-field decline continues. Conversely, isolated IOP elevation without documented damage should prompt confirmation, risk assessment, and an individualized decision rather than automatic assignment of a glaucoma diagnosis. [8][17][18]

Recognize that IOP fluctuates over short and long time periods. When office values and progression appear discordant, repeat IOP measurements at different times or obtain a diurnal assessment before declaring a regimen effective or ineffective. [5][10]
- Lower the target when there is advanced baseline damage, central field threat, or progression despite apparent target attainment. The trigger is documented progression, not a fixed interval alone. [17][18]
- Use the same perimetric strategy for follow-up after a visual-field defect is identified, reducing apparent change caused by switching test methods. [17]
- Higher pretreatment IOP predicts a greater absolute response to SLT, which should shape expectations when considering laser for lower-pressure disease. [3][23]

*Treatment-response assessment after IOP lowering. [3][5][10][17][18][23]*

| Follow-up finding | Interpretation | Next action |
| --- | --- | --- |
| IOP reaches target and OCT/field remain stable | Current treatment is achieving the pressure objective without documented progression. [17][18] | Continue the regimen and repeat IOP, optic nerve assessment or imaging, and perimetry according to clinical risk. [17] |
| IOP remains above target | Pressure reduction is insufficient; confirm adherence, dosing technique, and measurement consistency. [10][18] | Add or change pressure-lowering therapy, offer SLT if the angle is suitable, or plan surgery when adequate target reduction is unlikely medically. [3][4][16] |
| Target IOP achieved but OCT or field progresses | The target is too high for that eye or measured IOP does not reflect clinically relevant exposure. [5][10][17] | Lower the target, reassess IOP at additional times, and intensify treatment. [5][10] |
| Minimal response after SLT | Low baseline IOP is one recognized reason for limited absolute IOP reduction; individual responses vary. [3][23] | Do not repeatedly defer escalation when progression or target failure persists; use drops or surgical intervention according to needed pressure reduction. [16][18] |

## Choose drops or selective laser trabeculoplasty

For a suitable open angle, choose the modality most likely to achieve target IOP sustainably.

Initial treatment for primary open-angle glaucoma or ocular hypertension can be topical pressure-lowering medication or SLT when the angle is open and trabecular meshwork is adequately visualized. SLT was safe and effective as first-line therapy in the LiGHT trial, and guideline evidence indicates IOP reduction comparable to prostaglandin analogues at 9 to 12 months. [3][4]

Favor SLT when avoiding long-term drop burden, adherence dependence, ocular-surface exposure, or medication cost is important, provided the anticipated pressure reduction is sufficient. SLT is repeatable, but its effect is variable and generally greater when baseline IOP is higher. [3][13][23]

Favor or retain topical therapy when laser access is delayed, the angle cannot be treated adequately, the required pressure reduction exceeds the expected laser response, or a patient prefers medication. Pharmacologic classes used in glaucoma include prostaglandin analogues, beta-blockers, alpha agonists, and topical carbonic anhydrase inhibitors; select agents based on achieved IOP reduction and tolerance rather than assuming equivalence across patients. [13][24]

Reserve systemic carbonic anhydrase inhibition for situations in which topical therapy does not sufficiently reduce IOP or when urgent pressure lowering is needed, recognizing that systemic agents have renal effects including urinary alkalinization and kidney-stone risk. In open-angle glaucoma, systemic therapy is generally a bridge or adjunct when topical, laser, or procedural control is inadequate. [24]
- Before SLT, exclude peripheral anterior synechiae that prevent adequate trabecular treatment and document pretreatment IOP for response assessment. [22][23]
- Assess early post-laser IOP and anterior-segment findings; published SLT outcome studies record IOP at 1 hour, day 1, and 1 week after treatment. [23]
- Counsel that serious SLT complications are uncommon but include angle bleeding at approximately 2 per 1,000 treatments, hyphema at 0.7 per 1,000 treatments, and corneal edema or Descemet membrane folds in approximately 0.1% of treatments. [12]

### Practical selection of SLT

SLT is particularly useful when a patient requires pressure reduction but cannot reliably use drops or wishes to reduce medication exposure. It is not a substitute for surveillance: compare post-treatment IOP with the pre-laser baseline and continue OCT, optic nerve, and visual-field monitoring to determine whether the achieved reduction protects against progression. [3][4][17]
- Expect greater likelihood of meaningful IOP reduction with higher pre-SLT IOP. [3][23]
- Consider repeat SLT when a prior response wanes and the angle remains suitable; repeatability is supported in guideline evidence. [3]
- Escalate rather than observe when SLT fails to reach target and progression is documented. [16][17][18]

*Selection framework for initial pressure-lowering treatment. [3][4][12][13][16][23][24]*

| Option | Best-fit clinical situation | Key limitation or monitoring need |
| --- | --- | --- |
| Topical therapy | Immediate nonprocedural treatment is preferred or laser is unsuitable; choose an effective, tolerated regimen that reaches target IOP. [5][13] | Adherence, local and systemic tolerability, and measured IOP response determine durability. [5][13] |
| Selective laser trabeculoplasty | Open-angle glaucoma or ocular hypertension with visible angle structures, especially when drop burden or adherence is problematic. [4][22][23] | Response is variable and baseline-IOP dependent; assess IOP response and rare anterior-segment complications. [3][12][23] |
| Systemic carbonic anhydrase inhibitor | Topical therapy is insufficient or urgent additional pressure reduction is required. [24] | Systemic adverse effects and renal consequences limit chronic routine use. [24] |
| Incisional glaucoma surgery | Target IOP remains unattained or disease progresses despite feasible medication and laser treatment. [1][16][18] | Procedure selection depends on prior surgery, needed IOP reduction, and surgeon assessment. [1][16] |

## Proceed to surgery when nonincisional treatment cannot protect the nerve

The operative indication is inadequate disease control, not medication count alone.

Refer for incisional glaucoma surgery when IOP remains above the individualized target despite tolerated medical therapy and/or SLT, or when structural or field progression continues at the achieved IOP. Available procedural pathways include trabeculectomy with mitomycin, tube shunt surgery, trabecular stent bypass procedures, ab interno trabeculotomy, canaloplasty, and subconjunctival gelatin-stent approaches. [1][16]

When a very low target pressure is required, trabeculectomy with mitomycin remains a central filtering procedure; comparative evidence in primary open-angle glaucoma indicates that trabeculectomy with mitomycin may provide IOP lowering similar to tube shunt surgery. Procedure choice should therefore incorporate prior ocular surgery, conjunctival status, disease severity, complication tolerance, and the magnitude of pressure reduction needed. [1]

Do not use a microinvasive procedure merely to postpone adequate pressure reduction in a progressing eye. The required target, trajectory of visual-field loss, and prior response to medications or SLT should determine whether a trabecular procedure, filtering operation, or tube procedure is appropriate. [16][17][18]
- Document preoperative IOP, medications, optic nerve imaging, and visual-field status so that postoperative pressure goals are linked to a measurable baseline. [17][18]
- After surgery, continue functional and structural surveillance; pressure lowering is the intervention, while visual-field and optic nerve stability are the outcomes that justify it. [17][18]
- Reassess treatment intensity promptly when progression occurs rather than waiting for a predefined number of abnormal tests if the defect is reproducible and clinically meaningful. [17][18]

*Escalation triggers in open-angle glaucoma. [1][16][17][18]*

| Trigger | Interpretation | Action |
| --- | --- | --- |
| Persistent IOP above individualized target on tolerated therapy | Current treatment is not delivering the pressure reduction required for the eye. [5][18] | Optimize medication or SLT when appropriate; move to surgical planning if the anticipated reduction remains inadequate. [3][16] |
| Reproducible field decline or structural loss despite target attainment | The existing target is not protective. [5][17][18] | Lower the target and intensify treatment, including consideration of filtering or tube surgery. [1][16] |
| Medication intolerance or inability to sustain adherence | Nominally effective pharmacotherapy may be ineffective in practice. [4][13] | Offer SLT for an eligible angle or proceed to surgical discussion when lower target pressures are needed. [3][4][16] |

## Monitor IOP, structure, and function with a consistent testing strategy

Longitudinal progression, rather than a single IOP value, determines whether treatment is adequate.

At follow-up, measure IOP and compare it with the individual target; repeat optic nerve head examination or imaging and automated perimetry when clinically indicated. In eyes with a prior visual-field defect, use the same perimetric measurement strategy at each assessment to make serial change interpretable. [17]

Treat discordance as a signal for reassessment. Progression on OCT or visual fields despite apparently controlled IOP requires a lower target and more intensive therapy; an IOP increase without confirmed structural or functional change requires confirmation of measurement, assessment of adherence or treatment delivery, and reassessment of risk. [5][10][17][18]

For treated ocular hypertension or suspected glaucoma without demonstrated damage, repeat visual-field testing when clinically indicated and reassess optic nerve status. If glaucoma is no longer suspected or ocular hypertension does not require treatment, discharge to primary eye care with ongoing routine surveillance may be appropriate. [17]
- After SLT, include slit-lamp assessment and early IOP monitoring because hyphema, angle bleeding, corneal edema, and Descemet membrane folds have been reported, albeit rarely. [12][23]
- When progression is suspected, seek reproducibility on visual-field testing and compare with optic nerve imaging rather than escalating from one equivocal field alone. [17]
- Use serial evidence of progression to individualize the target IOP; normal-tension glaucoma may require approximately 30% lowering from baseline. [5]

*Follow-up components and their management purpose. [5][10][12][17][18][23]*

| Monitoring domain | What to document | Management consequence |
| --- | --- | --- |
| IOP | Current IOP, relation to target, treatment exposure, and time-of-day context when values are discordant. [5][10] | Above-target values or concerning fluctuation prompt treatment intensification or additional pressure assessment. [10][18] |
| Optic nerve and OCT | Optic nerve head examination and imaging when clinically indicated. [17] | Progressive structural loss lowers the acceptable target IOP even if office IOP appears controlled. [5][17] |
| Automated perimetry | Use a central threshold strategy at baseline and the same strategy after a defect is established. [17] | Reproducible functional decline warrants intensified IOP lowering. [17][18] |
| Post-SLT anterior segment | Early IOP plus slit-lamp findings, including bleeding, hyphema, or corneal change. [12][23] | Identify and manage procedure-related complications while determining whether laser achieved the needed IOP reduction. [12][23] |

## References
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## Editorial note

Prepared from cited clinical literature using Astra's research workflow. Verify recommendations against current guidance and patient-specific factors.