Laser and Surgical Glaucoma Management
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Direct answer
Laser and incisional surgery enter when drops fail or are not tolerated, or when the angle is anatomically closed. Nd:YAG laser peripheral iridotomy is the definitive treatment of pupillary block angle closure and is performed prophylactically in the fellow eye; selective laser trabeculoplasty augments outflow in open-angle disease and, unlike argon laser trabeculoplasty, is repeatable. The filtration standard is trabeculectomy — a guarded fistula from anterior chamber to subconjunctival space, modulated with mitomycin C or 5-fluorouracil — while drainage implants (Ahmed, Baerveldt) serve refractory glaucomas and trans-scleral cyclophotocoagulation palliates painful blind eyes.
What you must remember
- Nd:YAG peripheral iridotomy: indicated in primary angle closure and after an acute attack once the cornea clears and pressure is controlled; complications are transient pressure spike, hyphaema, uveitis and late closure of the iridotomy; the fellow eye of every angle-closure patient receives a prophylactic iridotomy.
- Laser trabeculoplasty (argon or selective): for open angles; selective laser trabeculoplasty spares the trabecular meshwork and can be repeated; pressure spikes after treatment are prevented with prophylactic drops.
- Trabeculectomy: a partial-thickness scleral flap over a fistula, usually fornix-based conjunctival flap; antimetabolites — mitomycin C 0.2–0.4 mg/mL for 2–3 minutes or 5-fluorouracil — raise success in young patients, secondary glaucomas and re-operations.
- Early postoperative complications: hypotony, shallow or flat anterior chamber, choroidal detachment, hyphaema and wound leak; persistent hypotony causes hypotonic maculopathy and, at worst, phthisis bulbi.
- Late complications: encapsulated or failing bleb, late bleb leak, blebitis and bleb-related endophthalmitis (avascular thin blebs leak and infect), and cataract progression.
- A failing or encapsulated bleb is managed with needling plus 5-fluorouracil injections, or surgical bleb revision; antimetabolite use is exactly what makes blebs thin and infection-prone.
- Glaucoma drainage devices: Ahmed (flow-restrictive valve) and Baerveldt or Molteno (non-valved); reserved for refractory disease — neovascular, uveitic, paediatric, post-keratoplasty and failed-trabeculectomy eyes.
- Trans-scleral diode cyclophotocoagulation destroys ciliary processes to lower secretion; reserved for end-stage sightless painful eyes or multiple-surgery-failure patients, with hypotony and phthisis as risks.
Choosing the procedure for the eye in front of you
Run three consultations in your head. The first is a woman one week after an acute angle-closure attack, pressure now 18 mmHg on timolol, cornea clear: her definitive treatment is Nd:YAG peripheral iridotomy — not trabeculectomy — because the mechanism is pupillary block; the fellow eye gets its prophylactic iridotomy the same sitting, halving its lifetime attack risk. The second is a man with open-angle glaucoma failing three drops: offer either selective laser trabeculoplasty as an intermediate step or proceed to trabeculectomy; at surgery, mitomycin C 0.2–0.4 mg/mL is applied for two to three minutes because Indian young conjunctiva heals aggressively, and he is warned about the week of shallow-chamber risk and the lifelong bleb-care advice — no rubbing, and red painful vision loss means an emergency (blebitis or endophthalmitis). The third is a young diabetic with neovascular glaucoma at 45 mmHg: this eye needs panretinal photocoagulation for the ischaemic drive, maximal medical therapy, and likely an Ahmed valve rather than a plain trabeculectomy, because neovascular tissue scars a filter shut; if the eye is already blind and painful, cyclophotocoagulation controls pain without the morbidity of a major operation.
How the exam frames it
The highest-yield single fact is that the definitive treatment of primary angle closure after medical control of the acute attack is laser iridotomy — examinees keep choosing trabeculectomy and lose the mark. Mitomycin C questions come as a double-edged stem: it prevents scarring (higher success) but produces thin avascular blebs that leak and infect. Match-the-following items pair Ahmed valve with refractory glaucoma, cyclophotocoagulation with the blind painful eye, and selective laser trabeculoplasty with repeatability.
Frequently asked questions
What is the definitive treatment of pupillary block angle closure?
Nd:YAG laser peripheral iridotomy, performed once the acute attack is controlled medically, with prophylactic iridotomy in the fellow eye.
Why is mitomycin C used in trabeculectomy, and at what exposure?
It inhibits fibroblast proliferation and postoperative scarring of the filtration bleb, applied at 0.2–0.4 mg/mL for two to three minutes — at the price of thin, leak-prone, infection-prone blebs.
Name the early and late complications of trabeculectomy.
Early: hypotony, flat anterior chamber, choroidal detachment, hyphaema and wound leak. Late: bleb encapsulation or failure, bleb leak, blebitis and endophthalmitis, and cataract.
When is a glaucoma drainage device preferred over trabeculectomy?
In refractory glaucomas — neovascular, uveitic, paediatric, post-keratoplasty — and after failed filtration surgery; the Ahmed valve is flow-restrictive, Baerveldt and Molteno are non-valved.
What is cyclophotocoagulation used for?
Trans-scleral diode destruction of ciliary processes to reduce aqueous secretion, mainly for painful blind eyes or after multiple failed surgeries; risks are hypotony and phthisis bulbi.
Which laser trabeculoplasty can be repeated, and why?
Selective laser trabeculoplasty — it selectively targets pigmented trabecular cells with minimal thermal damage, sparing the meshwork for repeat treatments, unlike argon laser trabeculoplasty.