Patient Information

Glaucoma Surgery Information

SLT and surgical techniques are different ways of lowering intraocular pressure. They do not form a compulsory sequence: the choice depends on glaucoma type and severity, target pressure, progression, anatomy, previous treatment, adherence and any coexisting cataract.

This is an educational guide. The indication and expected pressure reduction must be assessed individually.

New · Interactive model

Glaucoma, in 3D

A two-minute visual journey: from the healthy eye to glaucoma, and from glaucoma to laser and surgery.

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Laser and surgical options

Three ways to improve the eye's drainage

The fluid the eye produces has to leave through its natural drain, located in the angle where the cornea and the iris meet. In glaucoma that drain works poorly and pressure rises. What sets each technique apart is where it acts along that pathway.

Cross-section of the anterior segment of the eye with the path of the aqueous humourThe fluid is produced behind the iris, passes through the pupil into the anterior chamber and leaves through the drainage angle, where the cornea and the iris meet. SLT laser and MIGS techniques act on that angle. Filtering surgery creates a new outflow pathway under the conjunctiva. A box in the bottom-right corner shows the eye from the front, with a line marking where this cross-section is taken.CORNEAIRISLENS01SLTimproves the mesh in the angle02MIGSopens or bypasses the angle03FilteringNew pathwayFront viewhow we see it

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  • Natural path of the fluid
  • Outflow pathway created by surgery
  • Filtering bleb under the conjunctiva
The drainage angle appears on both sides of the cross-section: it is the same structure seen from its two ends. Proportions are not to scale.
  • A

    SLT laser

    Selective laser trabeculoplasty

    Where it actsOn the drainage mesh the eye already has, so that it filters better.

    An outpatient procedure with no incision. It can be considered initially in selected open-angle glaucoma or ocular hypertension, or later. The effect varies, may diminish with time and does not always replace drops.

    Setting
    In the clinic
    Recovery
    Usually brief, with individual instructions
    IOP reduction
    Variable
  • B

    MIGS surgery

    Minimally invasive

    Where it actsIn that same angle: they open the natural pathway or bypass it with a microscopic implant.

    A heterogeneous group of procedures, often combined with cataract surgery. They may suit selected mild-to-moderate disease when a modest pressure or medication reduction is sought; they are not the right option for every eye.

    Setting
    Operating room, often alongside cataract surgery
    Recovery
    Depends on the technique and combined surgery
    IOP reduction
    Technique-dependent
  • C

    Filtering surgery

    Non-penetrating deep sclerectomy · trabeculectomy

    Where it actsOutside the natural pathway: it creates a new outflow under the conjunctiva.

    Considered when a lower target pressure or stronger pressure reduction is needed, including some advanced or progressing cases. The balance of effect, risk and postoperative follow-up is discussed individually.

    Setting
    Operating room
    Recovery
    Longer, with close follow-up
    IOP reduction
    Potentially substantial

There is no universal order. None of these techniques restores optic-nerve damage that has already occurred. The aim is to reduce future risk, and the choice is guided by the target pressure and the complete clinical picture.

Frequently asked questions

Anaesthetic drops are used and many patients report little discomfort, although sensations vary. You may notice the contact lens used for treatment, light or brief discomfort. Tell the clinician if you are uncomfortable.

No. MIGS may lower pressure or reduce medication in selected eyes, but the effect varies and follow-up remains necessary. It is not the preferred approach when a very low target pressure or a large pressure reduction is required.

The purpose of glaucoma surgery is to lower pressure and reduce the risk of further damage, not to restore vision already lost. If cataract surgery is performed at the same time, visual change depends on the cataract, optic-nerve damage and other eye conditions.
Editorial transparency

Authorship, medical review and sources

Author and medical reviewer
Dr. Francisco Javier Abellán Martínez
Ophthalmologist · Medical registration no. 282880215
The same specialist currently authors and medically reviews the content; this is not presented as an independent external review.
Last medically reviewed
Sources consulted (3)

General educational content. It does not replace an individual assessment, diagnosis or personalised instructions from your healthcare team.

How these guides are written and reviewed

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A consultation can clarify the target pressure, evidence of progression and whether observation, medication, SLT or a surgical technique should be considered.

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