Ординатура / Офтальмология / Английские материалы / Oxford American Handbook of Ophthalmology_Tsai, Denniston, Murray_2011

296 CHAPTER 10 Glaucoma

Micropulse laser trabeculoplasty (MLT, 810 nm) uses bursts of short diode laser pulses, which theoretically prevent thermal injury. In addition, the same system that powers MLT can be used for photocoagulation, increasing the utility of the machine.

Indications

•Open-angle glaucoma—commonly POAG, PXF glaucoma, or PDS glaucoma.

•Medical and surgical options are undesirable or ineffective.

Method

•Consent: explain what the procedure does and possible complications, including failure (short and long term), bleeding, inflammation, or PAS.

•Instill apraclonidine 1% (to prevent IOP spike; alternatively give 250 mg acetazolamide 30 min beforehand) + topical anesthetic (e.g., proparacaine).

•Argon: #80–100 spots (360*), 50 μm spot size, 0.1 sec duration, 500–1000 mW power (start low, increase as required to obtain light blanching of pigmented TM).

•Diode: 100 μm spot size, 0.1–0.2 sec duration, 800–1200 mW power.

•SLT: #80–100 spots (360*), 400 μm spot size, 0.8–1.1 mJ titrate to obtain fine “champagne bubbles.”

•TLT: #100, 30–120 mJ, 200 μm spot size.

•MLT: #65–130 spots, 2 mW, 300 μm spot size, 2 ms micropulse (0.3 ms on, 1.7 ms off).

•Position goniolens (antireflective laser lens).

•Identify trabeculoplasty site: aim for the anterior border of the pigmented trabecular meshwork.

•Focus and fire laser: the ideal reaction is a mild blanching or small bubble; the more pigmented the angle, the less power is usually required. In these cases, consider placing only 50 equally spaced shots over 180*.

•If patient is currently using maximum tolerated medical therapy, consider dividing treatment into two 180*sessions to prevent IOP spike.

Post-procedure

•Topical steroid (e.g., prednisolone qid) and all usual glaucoma medication.

•Check IOP 1 hour later and observe until IOP plateaus.

•Review in 1–2 weeks: if there is an inadequate IOP response, consider laser trabeculoplasty on the remaining 180*.

•Complications: bleeding (stops with maintained pressure on lens), anterior inflammation (usually mild), peripheral anterior synechiae, pressure spike.

Laser iridoplasty

Most commonly used for plateau iris syndrome, the laser shrinks the peripheral iris to widen the angular approach. Iridoplasty may also be used to pull the iris tissue away from a drainage implant tube lumen or trabeculectomy fistula. A contact lens (e.g., Abraham or Goldmann [central part rather than mirrors]) is used to direct the argon laser to the most peripheral iris.

LASER PROCEDURES FOR GLAUCOMA 297

Typical applications are 20–50 burns over 360* (with 2 spot sizes between burns) of 200–500 μm spot size, 0.2–0.5 sec duration, and 200– 400 mW power.

Post-laser inflammation may promote formation of PAS.

Transscleral cyclophotocoagulation (cyclodiode)

Indications

These include intractable increased IOP, e.g., in rubeotic or synechial angle closure where other treatment modalities have failed, low visual potential, or a poor surgical candidate.

Method

•Consent: explain what the procedure does and the possible complications, including failure of treatment or need for retreatment, hypotony, inflammation, bleeding, vision loss, and sympathetic ophthalmia.

•Set laser (varies according to model)—commonly 2500 mW power, 2000 ms duration.

•Identify ciliary body 0.5–2 mm from limbus. Transillumination helps to identify the dark ciliary body. Place the contact G-probe (of the diode laser) in an anteroposterior manner against the globe, with the heel to the limbus.

•Fire laser: aim to treat up to three quadrants or 360*, using 6–7 shots per quadrant. If laser burn is audible (“pop”), decrease power.

Post-procedure

•Topical steroid (e.g., dexamethasone 0.1% 4x/day until inflammation abates) and all usual glaucoma medication except prostaglandin. Review in 1–2 weeks.

•Complications: vision loss, anterior inflammation (may get hypopyon or hyphema), hypotony, scleral thinning, cataract, phthisis, sympathetic ophthalmia.

Alternative

Endoscopic cyclophotocoagulation (requiring surgical incision) is a viable alternative to the external, nonincisional cyclodiode treatment.

FILTRATION SURGERY: TRABECULECTOMY 299

Filtration surgery: trabeculectomy

The Collaborative Initial Glaucoma Treatment Study (CIGTS) compared the safety and efficacy of medical therapy and trabeculectomy and generally found similar outcomes, although patients who presented with more advanced glaucoma maintained more vision with earlier surgery.

Indication

•When to operate: this surgery may be first line if there is a high risk of progression or the patient aims to be drop-free; more commonly it is reserved for when medical and/or laser therapy is proven to be inadequate.

•Which operation: assess risks of operation failure (e.g., from scarring) against the increased risk of complications from antimetabolite augmentation or tube procedures (see Table 10.8).

Method

The standard trabeculectomy with fornix-based flap is described here.

•Consent: explain what the operation does and possible complications, including scarring with return to high IOP, hypotony, hemorrhage, worsened vision, and risk of acute postoperative infection as well as late-onset endophthalmitis.

•Preoperative: consider stopping aqueous suppressants a couple of days before surgery.

•Prep with 5% povidone iodine and drape.

•Place corneal traction suture.

•Form fornix based: incise at limbus (5 to 8 mm length) (Table 10.9).

•Form scleral flap (rectangular/square/triangular): incise outline of the flap to a depth of 1/2 to ¾ scleral thickness, before anterior lamellar dissection anteriorly into the clear cornea, and free the posterior and lateral aspects of the flap.

•Place a paracentesis obliquely in the temporal cornea.

•Form sclerectomy under scleral flap: make a perpendicular incision at the sclerolimbal junction to form the anterior margin of the sclerectomy. Complete sclerectomy posteriorly by removing a block of sclerolimbal tissue with the punch (e.g., Kelly) or blade or scissors (e.g., Vannas).

•Perform peripheral iridectomy: this should be broad-based but short and peripheral. This stage is primarily to prevent iris blockage of the trabeculectomy, although it will also relieve any coincident pupillary block.

•Suture scleral flap: sutures can either be fixed, releasable (leave access via a corneal groove), or adjustable (can be loosened by massaging posterior aspect of scleral flap). Assess flap by injecting balanced salt solution via the paracentesis.

•Close conjunctiva securely to prevent retraction and consequent leak. This can be achieved with two lateral interrupted and a central mattress suture or a continuous running suture.

•Postoperative: subconjunctival steroid (e.g., dexamethasone), antibiotic (e.g., cefazolin).

FILTRATION SURGERY: ANTIMETABOLITES 303

Box 10.4 Potential complications of antimetabolites

•Epithelial erosions

•Wound leak

•Bleb leak

•Hypotony

•Blebitis

•Endophthalmitis

•Scleritis

FILTRATION SURGERY: COMPLICATIONS (1) 305

Wound leak

In milder cases where antimetabolites have not been used, resolution is likely within 48 hours. In the interim, a bandage contact lens may be applied. However, other cases (particularly with antimetabolites) usually require surgical intervention (i.e., suture wound).

Overfiltration

In milder cases, observation, a scleral shell, or autologous blood injection may be sufficient. However, more severe cases (e.g., hypotony maculopathy) may need surgical intervention (partial/temporary closure of overdraining bleb).

High IOP

Pupillary block: PI is either incomplete or blocked by inflammatory debris.

•Perform a new Nd-YAG PI (or complete old iridectomy); then give topical mydriatic + steroids.

Malignant glaucoma: aqueous misdirection may occur especially in short eyes (p. 290).

Filtration failure: obstruction of the sclerostomy and scleral flap may be internal (incarceration of iris, ciliary processes, or vitreous), scleral (fibrin, blood), or external (overly tight scleral flap sutures).

•Consider bleb massage, removal of releasable suture(s), loosening of adjustable suture(s), and argon laser lysis of fixed suture(s).

Infection

Blebitis: presents as a painful red eye, possibly with mucus discharge and photophobia (see Fig. 10.1). The bleb is milky with loculations of pus, conjunctival injection (especially around the bleb), and increasing IOP. Occasionally there is AC activity (cells/flare ± hypopyon).

•Identify organism with culture/swab of bleb.

•Treat with intensive topical antibiotics (e.g., moxifloxacin qh) and systemic antibiotic (e.g., moxifloxacin 400 mg PO qd); adjust according to response and organism identified (commonly staphylococci if early and streptococci and Haemophilus if late). Consider addition of topical steroids after 24 hours and add mydriatic if AC activity is present.

Endophthalmitis: clinical features are the same as for blebitis but are more severe, with decreased VA and vitritis.

•Investigate and treat as for other postoperative endophthalmitis. However, endophthalmitis occurring after trabeculectomy tends to run a more aggressive course with a worse prognosis than after cataract surgery.

Visual loss

Wipe-out of the remaining field may occur in the presence of a vulnerable optic nerve (associated with increased IOP or hypotony) or hypotonous changes may lead to reduced acuity (e.g., from maculopathy).