Ординатура / Офтальмология / Английские материалы / Moorfields Manual of Ophthalmology_Jackson_2007

Trabeculectomy II: postoperative care

Trabeculectomy II:

Postoperative Care

Background Careful postoperative care is essential to the success of glaucoma surgery. Typically, topical therapy includes: prednisolone acetate 1% 2-hourly for 2 weeks, tapering off over 12 weeks, topical antibiotics for 4 weeks and subconjunctival 5FU ± betnesol if the bleb is failing.

Signs of impending bleb failure Increased bleb vascularity, reduction of conjunctival microcysts, progressive IOP elevation or focal bleb encapsulation (Fig. 7.12).

Subconjunctival 5FU Used to modify postoperative wound healing, following a needling or re-exploration procedure, or to prevent failure after cataract surgery. Use topical amethocaine, povidone-iodine 5% and a lid speculum. Inject one-tenth of 1 mL of 50 mg/mL 5FU in an insulin syringe (integral 29-gauge needle) posterior to the bleb. This may be combined with 1–2 mg Betnesol. Stop before the injection meets the drainage area. Leave the needle in place for a few seconds (this helps to hydrate and seal the injection site). Irrigate any leakage.

Post-trabeculectomy complications

■Shallow/flat anterior chamber: differentiate high and low IOP. High IOP indicates aqueous misdirection (See below, and

p. 317). Low IOP suggests over-drainage. Prevent by suturing the flap tight initially and avoiding early release of scleral flap sutures. Exclude conjunctival wound leaks. Dilate with atropine 1%. Most cases settle without intervention. Hypotony maculopathy requires revision of flap. If there is lens–corneal touch, consider reforming the anterior chamber with gas or viscoelastic.

■Choroidal effusion : treat with atropine and frequent topical steroids. Drain effusions if there is lens–corneal touch with corneal oedema, bleb failure with increasing IOP, marked anterior segment inflammation, or apposition of the effusions (‘kissing choroidals’). Consider other causes of effusions such as scleritis and nanophthalmos.

■Raised intraocular pressure : usually due to inadequate aqueous outflow. Treatment depends on the site of obstruction. Obstruction may occur in several sites at once:

1. Aqueous misdirection (malignant glaucoma): indicated by

(if no contraindication), and aqueous suppressants ± hyperosmotics. Surgical vitrectomy may be necessary.

2. Blockage of fistula : causes include a tight scleral flap, fibrin and blood, and iris/ciliary body/vitreous incarceration in the sclerostomy. Manage with gentle massage at the posterior lip of the scleral flap. Remove releasable sutures, loosen adjustable sutures or perform argon laser suture lysis. Pilocarpine may help. Argon or YAG laser obstructions in the sclerostomy.

3. Cyst or capsule formation : use intensive topical steroids and topical aqueous suppressants. Needling of an encapsulated bleb may only be of temporary benefit.

Fig. 7.12: Inflamed bleb with increased vascular diameter and tortuosity (cork-screw vessels). This appearance suggests a high risk of failure.

GLAUCOMA 7 Chapter

Argon laser trabeculoplasty

Argon Laser Trabeculoplasty

Indications Inadequate IOP control. Specifically, to lower IOP where surgery is contraindicated or to decrease dependency on topical medication (poor compliance, adverse effects).

Contraindications Uveitic glaucoma; angle-closure glaucoma; poor angle visualization; patient unable to sit at laser or maintain a steady gaze.

Consent

■Benefit : reports suggest 65–90% get a 7–10 mmHg drop, with 10% attrition/year.

■Risk : elevated IOP, pain, vasovagal attacks, peripheral anterior synechiae (PAS), visual field loss, iritis, haemorrhage, and corneal burns.

Technique See Box 7.2.

Box 7.2: Argon laser trabeculoplasty

1.Continue all glaucoma medications before and after treatment.

2.Instil G. proxymethacaine 0.5%, G. pilocarpine 2–4%, G. apraclonidine 0.5%.

3.Select a Goldmann model gonioscope.

4.Target the circular aiming beam at the junction of pigmented and nonpigmented meshwork (Fig. 7.13).

5.Use continuous wave laser at 50 microns, 0.1 sec.

6.Increase power in 100 mW increments (maximum 1200 mW), until the meshwork blanches with a tiny bubble. Pigmented meshwork requires less energy.

7.Equally space 50 burns over the superior 180º (inferior 180º for re-treatment).

8.Document the area treated.

9.Prescribe G. prednisolone 0.5% q.d.s. 1 week.

10.Check IOP at 1.5 hours, treat acute pressure spikes.

Trans-scleral cyclodiode laser treatment

Trans-scleral Cyclodiode

Laser Treatment

Background Cyclodiode aims to reduce IOP by cyclodestructive trans-scleral diode laser.

Indications Advanced glaucoma with uncontrolled IOP, often with a poor visual prognosis.

Contraindications Exercise caution if there is low aqueous flow (e.g. uveitic glaucoma, previous cyclodestructive procedures): the risk is hypotony.

Technique See Box 7.3.

Follow–up The full effect takes 4 weeks. Continue glaucoma therapy until reviewed.

Box 7.3: Trans-scleral cyclodiode laser treatment

1.Give a sub-Tenon’s or peribulbar block.

2.Avoid areas of subconjunctival haemorrhage (risk of conjunctival burns).

3.Transilluminate the globe to locate the ciliary body, as its position may be highly variable, especially in eyes with congenital glaucoma or multiple previous operations.

4.Use a diode laser and the appropriate probe. Position the heel of the probe at the anterior border of the ciliary body.

5.Apply two rows of five burns (one slightly posterior to the other) per quadrant. Avoid the long ciliary nerves (3 and 9 o’clock positions).

6.Standard settings are 1.5 Watts for 1.5 seconds. Reduce power if popping occurs.

7.Prescribe G. prednisolone 1% 6–8 times daily and strong analgesia, e.g. coproxamol or ibuprofen, as postoperative pain is common.

Glaucoma Drainage Implants

Indications Uncontrolled IOP, especially after failed trabeculectomy, extensive conjunctival scarring, and as a primary procedure for certain secondary glaucomas.

Surgery A reservoir explant is sutured to the sclera, usually superotemporally. This connects to the anterior chamber by a tube inserted through a tight stab incision (25-gauge) behind the limbus. This should lie just anterior to, and parallel with, the plane of the iris, touching neither the iris nor cornea. The tube is occluded with an external Vicryl ligature to prevent drainage until a fibrous capsule has formed around the explant. An additional intraluminal ‘Supramid’ stent suture (3/0) is often used. The extracameral course of the tube is covered with donor sclera, cornea, or sometimes an autologous scleral flap. Sulcus or pars plana tubes are sometimes used.

Follow-up

■Early complications :

1.Raised IOP: manage medically and avoid early ligature or stent removal

2.Hypotony due to inadequate ligation or oversized entry site

– both require surgery. Tube occlusion with iris indicates a precipitous IOP drop.

■Late complications :

1.Hypotony when the ligature absorbs

2.Tube erosion (Fig. 7.14)

3.Iris or corneal contact.

GLAUCOMA 7 Chapter

Glaucoma drainage implants

A

B

Fig. 7.14: Glaucoma drainage implants with the tube eroded through the conjunctiva (A) and in contact with the iris (B).

Normal Pressure Glaucoma

Background Normal pressure glaucoma (NPG) describes the presence of glaucoma damage with IOP in the statistically ‘normal’ range. An IOP of 21 mmHg is controversially used to define NPG, probably representing the lower end of a spectrum of IOP associated with glaucoma. NPG is usually bilateral, but often asymmetric. Patients are older on average than those with high IOP, with a female preponderance.

Symptoms Typically asymptomatic until advanced visual field loss occurs. May have associated vasospasm.

History Ask specifically for a history of migraine or peripheral vasospasm, e.g. Raynaud’s phenomenon.

Examination

■Slit lamp : normal anterior segment. IOP remains <21 mmHg on phasing (repeated IOP measurement throughout the day).

■Gonioscopy : normal open angle.

■Optic disc : glaucomatous cupping, but focal ischaemic notches and disc haemorrhages are more likely.

Investigations

■Visual field : look for progressive optic nerve head pattern of defects on automated perimetry.

■Optic disc imaging : a baseline photograph or scanning laser ophthalmoscope image is needed to detect change.

■Central corneal thickness : a thin cornea is associated with lower measured IOP.

■Consider ambulatory blood pressure monitoring for nocturnal ‘dips’.

Differential diagnosis Confirm the presence of IOP in the normal range and glaucomatous optic neuropathy. Exclude other causes of optic neuropathy and specifically consider:

■Primary open angle glaucoma (POAG) with high IOP.

■Previous elevated IOP causing stable, nonprogressive signs of optic neuropathy.

■Nonglaucomatous optic neuropathy.

■Other lesions of the visual pathway.

GLAUCOMA 7 Chapter

Normal pressure glaucoma

treatment is progressive disease likely to cause significant loss of vision in the patient’s lifetime.

■Objectives:

1. Lower IOP : with medication, laser trabeculoplasty or trabeculectomy. The ‘target pressure’ or estimated IOP needed to prevent progression will be lower than in POAG.

2. Improve optic nerve head blood flow : prevent nocturnal hypotension (from systemic medication or nocturnal topical beta blockers), treat significant carotid insufficiency, and treat vasospasm (with calcium channel blockers in collaboration with a physician). Carbonic anhydrase inhibitors theoretically improve blood flow.

3. Neuroprotection : currently unproven.

4. Monitor regularly for disc and field progression.