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Glaucoma implants (also called aqueous shunt devices or glaucoma drainage devices) are used in the surgical management of refractory or advanced glaucoma, especially when conventional filtering surgery (e.g., trabeculectomy) fails or is unlikely to succeed.

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They work by shunting aqueous humor from the anterior chamber to a reservoir plate implanted in the subconjunctival space, thereby lowering intraocular pressure (IOP).

Indications

Types of Glaucoma Implants

Glaucoma implants are broadly classified based on:

A. Presence of Flow Restriction Mechanism

![a-1 The Ahmed® Glaucoma Valve showing its components and valve mechanism, where Section A represents the larger inlet port of the integrated Venturi chamber, and Section B represents the smaller outlet port of the Venturi chamber. a-2 Silicone models of the Ahmed® Glaucoma Valve: (2i) Ahmed® Glaucoma Valve Model FP7; (2ii) Ahmed® Glaucoma Valve Model FX1; (2iii) Ahmed® Glaucoma Valve Model FP8; and (2iv) Ahmed® Glaucoma Valve Model PC7—Ahmed® FP7 with Pars Plana Clip [41]. b The Ahmed® ClearPath Glaucoma Drainage Device: (i) model CP350; and (ii) model CP250 [60]. “SA” stands for surface area of the end plate.

Pereira, I.C.F., van de Wijdeven, R., Wyss, H.M. et al. Conventional glaucoma implants and the new MIGS devices: a comprehensive review of current options and future directions. Eye 35, 3202–3221 (2021). https://doi.org/10.1038/s41433-021-01595-x](attachment:0dd0c990-3b5c-4092-a37c-cd0f80aad5ca:41433_2021_1595_Fig3_HTML.webp)

a-1 The Ahmed® Glaucoma Valve showing its components and valve mechanism, where Section A represents the larger inlet port of the integrated Venturi chamber, and Section B represents the smaller outlet port of the Venturi chamber. a-2 Silicone models of the Ahmed® Glaucoma Valve: (2i) Ahmed® Glaucoma Valve Model FP7; (2ii) Ahmed® Glaucoma Valve Model FX1; (2iii) Ahmed® Glaucoma Valve Model FP8; and (2iv) Ahmed® Glaucoma Valve Model PC7—Ahmed® FP7 with Pars Plana Clip [41]. b The Ahmed® ClearPath Glaucoma Drainage Device: (i) model CP350; and (ii) model CP250 [60]. “SA” stands for surface area of the end plate.

Pereira, I.C.F., van de Wijdeven, R., Wyss, H.M. et al. Conventional glaucoma implants and the new MIGS devices: a comprehensive review of current options and future directions. Eye 35, 3202–3221 (2021). https://doi.org/10.1038/s41433-021-01595-x

![a The Molteno® implants: (i) Molteno® single plate implant S1, the original Molteno® glaucoma implant; (ii) Molteno® double plate implant, available in right eye (R2) and left eye (L2) configurations; (iii) Molteno® pressure ridge single plate implant D1; (iv) Molteno® pressure ridge double plate implant, available in right eye (DR) and left eye (DL) configurations; (v) Molteno3® S-series, with the end plate available in two different sizes: 185 mm2 (SS, left side) and 245 mm2 (SL, right side); and (vi) Molteno® microphthalmic implant P1 [39]; images courtesy of Molteno Ophthalmic Ltd. b The Baerveldt® implants: (i) Baerveldt® BG 101–350; (ii) Baerveldt® BG 103–250; and (iii) Baerveldt® Pars Plana BG 102–350, showing its Hoffman elbow that allows positioning the tube into the vitreous cavity; images reproduced with permission from [25] and [135]. c The PAUL® Glaucoma Implant, showing the dimensions of the end plate [38, 136]; left image courtesy of Advanced Ophthalmic Innovations, and right image reproduced with permission from [38]. “SA” stands for surface area of the end plate.

Pereira, I.C.F., van de Wijdeven, R., Wyss, H.M. et al. Conventional glaucoma implants and the new MIGS devices: a comprehensive review of current options and future directions. Eye 35, 3202–3221 (2021). https://doi.org/10.1038/s41433-021-01595-x](attachment:44778460-54a1-4a7d-9cac-a2652c6ea861:41433_2021_1595_Fig2_HTML.webp)

a The Molteno® implants: (i) Molteno® single plate implant S1, the original Molteno® glaucoma implant; (ii) Molteno® double plate implant, available in right eye (R2) and left eye (L2) configurations; (iii) Molteno® pressure ridge single plate implant D1; (iv) Molteno® pressure ridge double plate implant, available in right eye (DR) and left eye (DL) configurations; (v) Molteno3® S-series, with the end plate available in two different sizes: 185 mm2 (SS, left side) and 245 mm2 (SL, right side); and (vi) Molteno® microphthalmic implant P1 [39]; images courtesy of Molteno Ophthalmic Ltd. b The Baerveldt® implants: (i) Baerveldt® BG 101–350; (ii) Baerveldt® BG 103–250; and (iii) Baerveldt® Pars Plana BG 102–350, showing its Hoffman elbow that allows positioning the tube into the vitreous cavity; images reproduced with permission from [25] and [135]. c The PAUL® Glaucoma Implant, showing the dimensions of the end plate [38, 136]; left image courtesy of Advanced Ophthalmic Innovations, and right image reproduced with permission from [38]. “SA” stands for surface area of the end plate.

Pereira, I.C.F., van de Wijdeven, R., Wyss, H.M. et al. Conventional glaucoma implants and the new MIGS devices: a comprehensive review of current options and future directions. Eye 35, 3202–3221 (2021). https://doi.org/10.1038/s41433-021-01595-x

Examples of Common Implants

Surgical Technique (General Steps)

1. Implant plate is sutured to the sclera 8–10 mm posterior to the limbus.
2. Tube is inserted into the anterior chamber, sulcus, or pars plana (depending on context).
3. Patch graft (pericardium, sclera, or cornea) covers the tube.
4. Conjunctiva and Tenon’s capsule are closed over the device.

Postoperative complications