Ординатура / Офтальмология / Английские материалы / Moorfields Manual of Ophthalmology_Jackson_2007

Bleb-Related Infection

Background Bleb related infection is a potentially blinding, late complication of glaucoma filtering surgery. It refers to a spectrum of disease ranging from blebitis (isolated bleb infection) to blebrelated endophthalmitis (BRE). The organisms usually responsible for BRE (Streptococcus and Haemophilus spp.) are different to, and more virulent than, those of early postoperative endophthalmitis. Thin-walled, cystic, leaking blebs are at risk.

Early and aggressive antimicrobial therapy often permits retention of functional VA and a filtering bleb.

Symptoms Redness, photophobia, pain, reduced VA, and discharge.

Signs Bleb opalescence or mucopurulent infiltrate with surrounding conjunctival injection (‘white on red’), ±bleb leak, and intraocular inflammation and purulent discharge (Fig. 7.21).

History and examination Ask about the duration and severity of symptoms (prodrome of a few days suggests blebitis; sudden onset with rapid progression suggests BRE), ocular trauma (accidental or iatrogenic, e.g. bleb needling), contact lens use, and risk factors such as blepharitis, trichiasis, and dry eyes. Record VA and test for the presence of a bleb leak using 2% fluorescein (Seidel’s test).

Differential diagnosis Bleb leak alone may produce mild ocular discomfort and AC activity. Recent corticosteroid withdrawal or rapid tapering may result in rebound inflammation. In both these cases the bleb is clear, the AC reaction mild, and VA unchanged.

Investigations Blebitis associated with ≥1+ AC cells is considered as BRE, even in the absence of vitritis. BRE requires anterior chamber tap plus vitreous biopsy. A conjunctival swab is not indicated as cultures often correlate poorly with intraocular cultures. A B-scan is indicated if vitritis cannot be excluded or the fundal view is inadequate.

Treatment See Box 7.6.

Follow–up Following an episode of bleb-related infection, surgery is advisable but its risks and benefits must be evaluated for each patient. Surgical revision of the bleb usually involves bleb excision with conjunctival advancement. If present, scleral thinning or a defect must also be repaired with a scleral or Tenon’s graft to avoid the recurrence of cystic blebs. Treat chronic blepharitis, ocular surface, and lid disorders. Prophylactic topical antibiotics are not advised.

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Bleb-related infection

Box 7.6: Treatment of bleb-related infection

■Instil povidon-iodine 5% into the conjunctival sac.

■G. ofloxacin hourly and G. cefuroxime hourly (day and night) for at least 24 hours, reducing frequency as clinically indicated.

■Ciprofloxacin 750 mg b.d. p.o. and co-amoxiclav 625 mg t.d.s. p.o.

(azithromycin 500 mgs b.d. p.o. if penicillin allergy) for

7 days.

■Review patients with blebitis or bleb-related infection within 6 hours to exclude progression to bleb-related endophthalmitis (BRE).

■Intravitreal vancomycin 2 mg and either amikacin 0.4 mg or ceftazidime 2 mg in cases of BRE.

■G. prednisolone 1% q.d.s. (once the course of infection is clear in blebitis).

■ Prednisolone 1 mg/kg p.o. commenced 12 hours after admission.

■Consider intravitreal dexamethasone 0.4 mg to minimize inflammation-related retinal toxicity in cases of BRE.

Fig. 7.21: Bleb-related endophthalmitis.

Primary Angle Closure

Background Angle closure is contact between the iris and trabecular meshwork accompanied by a significant impairment of aqueous outflow. It may be primary (PAC) or secondary, with 75% of primary cases due to pupil block. Frequently associated with glaucomatous optic neuropathy. The symptomatic form (‘acute’ angle closure) is a common ophthalmic emergency.

Classification The traditional classification of acute, intermittent, chronic, and latent phases fails to identify the disease stage and mechanism of closure. Classify as follows:

■Stage.

1. Narrow angles (angle closure suspect).

2. Primary angle closure: a narrow angle with either high IOP or peripheral anterior synechiae (PAS).

3. Angle closure with glaucomatous optic neuropathy (PACG).

■Mechanism of angle closure.

1. Pupil block.

2. Anterior, non-pupil-block (includes plateau iris).

3.Lens induced.

4.Causes behind the lens.

Nuclear sclerosis is almost invariably present. This is part of the primary disease and distinct from phakolytic/phakomorphic glaucoma (p. 311).

Symptoms Blurring of vision sometimes accompanied by halos around lights, redness and periocular or hemicranial pain. There may be nausea and vomiting. However, angle closure is often asymptomatic, especially in Asian people.

Signs Signs mirror symptoms in acute disease; VA is reduced, there is circum-limbal injection with corneal oedema, raised IOP, and an immobile pupil. Refraction is often (but not always) hypermetropic.

History and examination A positive family history is common. Dynamic gonioscopy is essential to make the diagnosis. Record the estimated geometric angle width, angle structures visible, iris profile (steep, regular, or plateau), iris pigment on the trabecular meshwork, and extent of PAS. Asymmetry between the two eyes suggests a secondary cause.

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The presence of >6 clock hours of PAS extending across the trabecular meshwork and glaucomatous optic neuropathy both suggest that laser and medical treatment are unlikely to control IOP satisfactorily. A trabeculectomy will frequently be needed. Because of the poor success rate, trabeculectomy should be avoided soon after an acute attack, unless absolutely necessary.

Follow–up Once IOP is controlled, review patients at one week, 1 month, then annually.

Box 7.7: YAG laser iridotomy

This is the cornerstone of management

1.Premedicate with G. apraclonidine 0.5% and pilocarpine 2% (4% for dark brown irises) 30 minutes and 5 minutes before.

2.Use a Wise or Abraham’s lens. Try to treat in the base of an iris crypt (Fig. 7.22).

3.Create an iridotomy that will be covered by the upper lid. Avoid treating in an area under the marginal tear strip; this may cause glare.

4.If bleeding occurs, a little pressure with the contact lens helps to stop this.

5.Argon pretreatment is useful in patients with thick brown irises: 10–40 shots, 0.05–0.1 s, 50 microns, 200 to 1000 mW power. Avoid charring.

6.YAG laser energy varies with the machine and patient, typically 1–3 mJ, 10–20 shots.

7.Iridotomies should be ≈200 microns in diameter.

8.Check IOP 2 hours post laser. Prescribe G. prednisolone 1%

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Optometry and General

Practice Guidelines

General comments

Cases of suspected open angle glaucoma require routine referral for assessment by an ophthalmologist, or preferably a glaucoma specialist. Acute angle closure and bleb-related infections are emergencies that require prompt action and immediate ophthalmology review.

Optometrists

Glaucoma is a progressive optic neuropathy in which the optic nerve head has characteristic changes and there is typically a corresponding visual field loss. Intraocular pressure (IOP) and age are the major risk factors but IOP on its own is not a good predictor of glaucoma (5% of the normal population have IOPs >21 mmHg and about one-third of those with open angle glaucoma have IOPs <22 mmHg). Other risk factors are ethnicity (Afro-Caribbean) and family history (a first-degree relative with glaucoma).

Consider the cup-to-disc ratio (CDR) in relation to the disc size (a large CDR may be normal if the disc is also large; see p. 279) and look for notches and variations from the normal distribution of rim thickness (see Jonas’ ISNT rule, p. 279). An IOP consistently >24 mmHg caries a 9% risk of progressing to glaucomatous optic neuropathy. A modest (20%) reduction of the IOP reduces this risk to 4%. Refer on a routine basis, or manage in line with local protocols.

General practice

The optometry guidelines also apply. Headaches and eye pain are not generally associated with glaucoma, unless the IOP is very high. If unable to assess disc and fields effectively, recommend review by an optometrist. Topical beta blockers are contraindicated in people with asthma and chronic airways disease. Note that steroids, both systemic and topical (eye, nose, skin), have the potential to generate a steroid-induced increase in IOP. People using these agents regularly for more than 6 weeks should have their IOP monitored. In general, steroid eyedrops are for shortto medium-term use, but with some exceptions, including blind painful eyes, some chronic corneal diseases, and chronic uveitis.

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Optometry and general practice guidelines

The following guide to referral urgency is not prescriptive, as clinical situations vary.

Immediate

History and examination

chorioretinal scars; retinal detachment (rhegmatogenous, serous, and tractional).

■ If VA is worse than 6/9 a cause must be sought.