Ординатура / Офтальмология / Английские материалы / Clinical Ophthalmology A Systematic Approach 7th Edition_Kanski, Bowling_2011

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aViscoelastic is aspirated.

bThe side port incisions may be sealed with a jet of saline.

cCommon anti-infection measures at the end of surgery may include a drop of topical antibiotic, a subconjunctival injection of steroid and antibiotic, and/or an intracameral (anterior chamber) antibiotic.

Fig. 9.11 Preparation. (A) Povidone-iodine 5% is instilled; (B) skin is painted; (C) drapes isolate the eyelids fromthe operating field with insertion of a speculum.

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Fig. 9.12 Four quadrant ('divide and conquer’) phacoemulsification. (A) Corneal incision; (B) capsulorhexis; (C) hydrodissection; (D) nucleus is grooved; (E) nucleus is cracked; (F) each nuclear quadrant is emulsified and aspirated

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Fig. 9.13 Completion of phacoemulsification. (A) Cortical lens matter is pulled centrally and aspirated: (B) injection of viscoelastic into the capsular bag; (C) incision is enlarged; (D) cartridge nozzle with IOL is introduced through the incision; (E) IOL is slowly injected into the eye; (F) IOL is dialled into position if necessary

Small incision manual cataract surgery

Small incision manual cataract surgery is an effective alternative to phacoemulsification in countries where very high volume surgery with inexpensive instrumentation is required. The procedure is fast and has a low rate of complications, and can be performed on a dense cataract. The technique is as follows:

a A self-sealing partial thickness scleral tunnel is dissected and the anterior chamber is entered (Fig. 9.14A).

bCapsulorhexis is performed (Fig. 9.14B).

cHydrodissection is performed and the nucleus is partly prolapsed into the anterior chamber (Fig. 9.14C).

dA small hook is inserted between the posterior capsule and nucleus, and the nucleus extracted (Fig. 9.14D). It is also possible to extract the nucleus with an irrigating vectis.

e The epinucleus and residual cortex are aspirated with a Simcoe cannula (Fig. 9.14E). f The IOL is inserted (Fig. 9.14F).

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Fig. 9.14 Small incision manual cataract surgery. (A) Anterior chamber is entered; (B) capsulorhexis; (C) prolapse of nucleus into anterior chamber; (D) expression of nucleus; (E) cortical cleanup; (F) IOL in place

(Courtesy of A Hennig)

Operative complications

Rupture of the posterior lens capsule

Capsular rupture may be accompanied by vitreous loss, posterior migration of lens material, and rarely expulsive haemorrhage. Sequelae to vitreous loss, particularly if inappropriately managed, include chronic cystoid macular oedema, retinal detachment, endophthalmitis, updrawn pupil, uveitis, vitreous touch, vitreous wick syndrome, glaucoma and posterior dislocation of the IOL.

1Signs

•Sudden deepening or shallowing of the anterior chamber and momentary pupillary dilatation.

•The nucleus falls away and cannot be approached by the phaco tip.

•Vitreous aspirated into the phaco tip often manifests with a marked slowing of lens material aspiration.

•The torn capsule or vitreous gel may be directly visible.

2Management depends on the magnitude of the tear, the size and type of any residual lens material, and the presence or absence of vitreous prolapse. The main principles of management are as follows:

aDispersive viscoelastic such as Viscoat may be injected behind nuclear material with the purpose of expressing it into the anterior chamber and of preventing anterior herniation of additional vitreous. If a complete or nearly-complete nucleus remains, conversion to extracapsular extraction may be considered. A vitrector can be employed at this point (see below) to remove vitreous entangled with nuclear fragments.

bThe incision may be enlarged, if necessary, and a lens glide (Sheets’) may be passed behind the lens fragments to cover the capsular defect (Fig. 9.15), although it is important to confirm that vitreous has first been displaced or removed and will not be put under traction.

cResidual nuclear fragments are carefully removed by phaco with low bottle height and lowAFR, or if large by viscoexpression after extending the main wound.

dOnce nuclear remnants have been removed, the anterior chamber is gently filled with a cohesive viscoelastic and a manual aspiration cannula with irrigation turned off used to gently aspirate residual cortex, topping up the AC with viscoelastic as necessary.

eAll vitreous is removed from the anterior chamber and the wound with a vitrector placed deep to the capsular tear. A bimanual technique, with separate of the infusion and cutting instruments, is viewed as superior by many, as vitreous is not pushed away from the cutter (the position of the infusion cannula is kept high and that of the cutter low). The main practical

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difficulty is visualization of the vitreous gel, and this can be enhanced by the instillation of trypan blue 0.06% (VisionBlue) or 0.1 mL of 40 mg/mL of triamcinolone (shake well before use). The infusion bottle height should be sufficient to keep the anterior chamber maintained without intermittent shallowing.

fA small posterior capsular tear may allow careful in-the-bag implantation of a PC-IOL and it may be possible to convert a small tear into a posterior capsulorhexis.

gEven a large tear will usually allow ciliary sulcus placement of a three piece PC-IOL. The haptics should be placed at 90° to a peripheral tear, and should be angulated posteriorly to maximize iris clearance. If possible, after placing the IOL in the sulcus the optic should be captured within an intact capsulorhexis of slightly smaller diameter by depressing each side of the optic beneath the capsulorhexis in turn. With capsulorhexis capture, the originally planned IOL power, or possibly 0.5 D less, can be used; without capture, the power is reduced by 0.5–1.0 D.

hAcetylcholine (Miochol®) is used to constrict the pupil following implantation of a PC-IOL or prior to inserting an AC-IOL.

iInsufficient capsular support may necessitate implantation of an AC-IOL with the aid of a glide (Fig. 9.16); an iridectomy is needed to prevent pupillary block. AC-IOLs are associated with a higher risk than PC-IOLs of complications including bullous keratopathy, hyphaema, iris tuck and pupillary irregularities. An iris or trans-sclerally sutured posterior chamber IOL is an alternative.

jA suture should be used to secure the wound, even if it seems adequately self-sealed.

Fig. 9.15 Lens glide supporting nuclear fragments following rupture of the posterior capsule

(Courtesy of R Packard)

Fig. 9.16 Insertion of an anterior chamber IOL. (A) Glide is inserted; (B) IOL is coated with viscoelastic; (C) IOL is inserted; (D) incision is sutured

Posterior loss of lens fragments

Dislocation of fragments of lens material into the vitreous cavity after zonular dehiscence or posterior capsule rupture is rare but potentially serious as it may result in glaucoma, chronic uveitis, retinal detachment and chronic cystoid macular oedema. Initially, any uveitis or raised intraocular pressure must be treated. It may be reasonable to adopt a conservative approach for small fragments, but larger fragments,

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certainly a quadrant or more, will virtually always require removal by pars plana vitrectomy.

Posterior dislocation of IOL

Dislocation of an IOL into the vitreous cavity (Fig. 9.17A) is a rare but serious complication particularly if accompanied by loss of lens material (Fig. 9.17B). If the IOL is left in the posterior segment it may lead to vitreous haemorrhage, retinal detachment, uveitis and chronic cystoid macular oedema. Treatment involves pars plana vitrectomy with removal, repositioning or exchange of the IOL depending on the extent of capsular support.

Fig. 9.17 (A) IOL on the retina; (B) IOL and large nuclear fragments in vitreous

(Courtesy of S Milewski)

Suprachoroidal haemorrhage

A suprachoroidal haemorrhage involves a bleed into the suprachoroidal space from a ruptured long or short posterior ciliary artery. If sufficiently severe it may result in extrusion of intraocular contents (‘expulsive’ haemorrhage). It is a dreaded complication, but extremely rare (0.04%) with phacoemulsification. Contributing factors include advanced age, glaucoma, increased axial length, systemic cardiovascular disease, vitreous loss, and conversion from phacoemulsification to ECCE. A high intraoperative index of suspicion is critical, and if there is any suggestion of a suprachoroidal haemorrhage the operation should be terminated and the incision sutured immediately.

1Signs in chronological order

aProgressive shallowing of the anterior chamber, increased intraocular pressure and prolapse of the iris.

bVitreous extrusion, loss or partial obscuration of the red reflex and the appearance of a dark mound behind the pupil.

cIn severe cases, posterior segment contents may be extruded into the anterior chamber and through the incision.

2Immediate treatment

aThe AC is filled with a cohesive viscoelastic and the incision is sutured.

bThe viscoelastic should be left in the eye to raise the intraocular pressure and tamponade the bleeding vessel.

c IOP-lowering medication such as oral acetazolamide is given to address the resultant pressure spike.

d Intravenous mannitol may be given if necessary although reducing the IOP too rapidly should be avoided.

ePostoperatively, topical and systemic steroids should be used aggressively to reduce intraocular inflammation.

3Subsequent treatment, if spontaneous absorption fails to occur, involves drainage of large ‘kissing’ haemorrhages that can be performed 7–14 days later, by which time liquefaction of blood clot has taken place. The visual prognosis for large haemorrhages is

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highly variable; prolonged chorioretinal apposition (>14 days) has a poor prognosis. Pars plana vitrectomy may be considered when the retina appears adherent or detached, though kissing haemorrhages may resolve spontaneously without immediately apparent retinal problems. If appropriate, completion of cataract surgery may be considered after a further 1–2 weeks.

Acute postoperative endophthalmitis

Pathogenesis

The estimated incidence of acute endophthalmitis following cataract surgery is approximately 0.3%. Toxins produced by the infecting bacteria and the host inflammatory responses cause rapid and irreversible photoreceptor damage, and these effects can continue long after the ocular contents have been rendered sterile.

1Possible risk factors include operative complications such as posterior capsule rupture, prolonged procedure time, combined procedure (e.g. with vitrectomy), clear corneal sutureless incision, temporal incision, wound leak on the first day, delaying postoperative topical antibiotics until the day after surgery, topical anaesthesia, adnexal disease and diabetes.

2Pathogens. About 90% of isolates are Gram-positive and 10% Gram-negative. In order of frequency they include:

•Coagulase-negative staphylococci (S. epidermidis).

•Other Gram-positive organisms (S. aureus and Streptococcus spp.).

•Gram-negative organisms (Pseudomonas spp. and Proteus spp.).

3The source of infection usually cannot be identified with certainty. It is thought that the flora of the eyelids and conjunctiva are the most frequent source, including contamination via incisions in the early postoperative stages. Other potential sources include contaminated solutions and instruments, environmental air, and the surgeon and other operating room personnel.

Prophylaxis

Because of the low rate of endophthalmitis it is very difficult to prove that any method of prophylaxis is effective or superior to any other. The following are likely to be beneficial:

1 Instillation of 5%povidone-iodine into the conjunctival fornices and leaving this undisturbed for at least 3 minutes prior to surgery.

2Scrupulous preparation of the surgical site, with re-draping if eyelash coverage is inadequate.

3Treatment of pre-existing infections such as blepharitis, conjunctivitis, chronic dacryocystitis and infection in the contralateral eye or socket.

4Prophylactic antibiotics

•Pre-operative topical fluoroquinolone antibiotics are frequently given in regimens from 1 hour to 3 days before surgery.

•Intracameral cefuroxime (1 mg in 0.1 mL) injected into the AC at the end of surgery.

•Postoperative subconjunctival injection can achieve bactericidal levels in the anterior chamber for at least 1–2 hours.

•Newer-generation quinolones such as moxifloxacin penetrate the eye effectively to give concentrations inhibitory to bacterial growth.

5Early resuturing of leaking wounds rather than observation may be prudent.

6Reviewing personal surgical practice to eliminate potentially risk-prone elements, particularly if a significant rate of endophthalmitis is encountered.

Clinical features

1 Symptoms are pain and visual loss.

2Signs vary according to severity.

•Eyelid swelling, chemosis, conjunctival injection and discharge.

•A relative afferent pupillary defect is common.

•Corneal haze (Fig. 9.18A)

•Fibrinous exudate and hypopyon (Fig. 9.18B).

•Vitritis with an impaired view of the fundus (Fig. 9.18C).

•Severe vitreous inflammation and debris (Fig. 9.18D) with loss of the red reflex.

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Fig. 9.18 Acute bacterial endophthalmitis. (A) Corneal haze; (B) fibrinous exudate and hypopyon; (C) vitreous haze and impaired fundus view; (D) severe vitritis

(Courtesy of S Tuft – figs A, B and D)

Differential diagnosis

If there is any doubt about the diagnosis, treatment should be that of infectious endophthalmitis. Early recognition leads to a better outcome.

1Retained lens material in the anterior chamber or vitreous may precipitate a severe uveitis, corneal oedema and raised intraocular pressure.

2Vitreous haemorrhage, especially if blood in the vitreous is depigmented.

3Postoperative uveitis. A confident diagnosis of infection is not always straightforward. If signs of inflammation are mild a trial of topical steroid therapy and early review (6–24 hours) is appropriate. If there is no substantial improvement management should be that of endophthalmitis.

4Toxic reaction to the use of inappropriate or contaminated irrigating fluid or viscoelastic. An intense fibrinous reaction with corneal oedema may develop although other signs of infectious endophthalmitis are absent. Treatment is with intensive topical steroids combined with cycloplegics. Corneal decompensation may be permanent.

5Complicated or prolonged surgery may result in corneal oedema and uveitis.

Identification of pathogens

Samples for culture should be obtained from aqueous and vitreous to confirm the diagnosis. However, negative culture does not necessarily rule out infection and treatment should be continued. An operating theatre with experienced staff is the best setting, but samples can be taken in a minor procedures operating room if necessary to avoid delay, making sure that all equipment is available prior to starting.

1B-scan ultrasound should be performed prior to vitreous sampling to exclude retinal detachment if there is no clinical view.

2Preparation

•Povidone iodine 5% is instilled.

•Topical and subconjunctival, sub-Tenon's or peribulbar anaesthesia is administered.

•The eye is draped as for cataract surgery, with insertion of a speculum.

3Aqueous samples

•Between 0.1 mL and 0.2 mL of aqueous is aspirated via a limbal paracentesis using a 25-G needle on a tuberculin syringe.

•The syringe is capped and labelled.

4Vitreous samples are more likely to yield a positive culture than aqueous.

•A 2 mL syringe and a 23-G needle may be used, or optimally a disposable vitrector (Fig. 9.19A).

•The distance from the limbus for the scleral incision is measured with callipers and marked (Fig. 9.19B): 3 mm (pseudophakic eye), 4 mm (phakic eye).

•0.2–0.4 mL is aspirated from the mid-vitreous cavity (Fig. 9.19C). If using a disposable vitrector, cap off the tubing securely and place in a specimen bag. Do not disconnect the vitrector from its tubing.

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6Conjunctival swabs may be taken as well, as significant culture may be helpful in the absence of a positive culture from intraocular samples.

7Microbiology. Specimens should be sent to the microbiology laboratory immediately; most prefer to receive a sample in the apparatus used for acquiring the specimen and will divide the specimen for microscopy and culture. Polymerase chain reaction (PCR) can be helpful in identifying unusual organisms, the cause of culture negative disease, and organisms after antibiotic treatment has been started. However, its high sensitivity means that contamination can lead to false positive results.

Fig. 9.19 Management of acute endophthalmitis. (A) Mini-vitrector for obtaining vitreous samples; (B) callipers measuring distance fromlimbus; (C) vitreous samples obtained with vitrector; (D) intravitreal antibiotic injection

Treatment

1Intravitreal antibiotics are the key to management because they achieve levels above the minimum inhibitory concentration of most pathogens, and these are maintained for days. They should be administered immediately after culture specimens have been obtained. Two antibiotics commonly used in combination are ceftazidime, which will kill most Gram-negative organisms (including Pseudomonas aeruginosa) and vancomycin to address coagulase-negative and coagulase-positive cocci (including methicillinresistant S. aureus).

•The concentrations are ceftazidime 2 mg in 0.1 mL and vancomycin 2 mg in 0.1 mL; amikacin 0.4 mg in 0.1 mL can be used as an alternative to ceftazidime in patients allergic to penicillin but is more toxic to the retina. See Table 9.2 for details of preparation.

•The antibiotics are injected slowly into the mid-vitreous cavity using a 25-G needle (Fig. 9.19D).

•After the first injection has been given, the syringe may be disconnected but the needle left inside the vitreous cavity so that the second injection can be given through the same needle. Alternatively, a second needle can be used.

2Periocular antibiotic injections are often given but are of doubtful additional benefit if intravitreal antibiotics have been used. Suggested doses are vancomycin 50 mg and ceftazidime 125 mg (or amikacin 50 mg).

3Topical antibiotics are of limited benefit and are often used only 4–6 times daily in order to protect the fresh wounds from contamination. Vancomycin 5% (50 mg/mL) or ceftazidime 5% (50 mg/mL) applied intensively may penetrate the cornea in therapeutic levels. Third or fourth generation fluoroquinolones achieve effective levels in the aqueous and vitreous, even in uninflamed eyes, and may be considered.

4Oral antibiotics. Fluoroquinolones penetrate the eye well and moxifloxacin 400 mg daily for 10 days is recommended; clarithromycin 500 mg twice daily may be helpful for culture negative infections. Evidence suggests these may attack bacterial biofilm.

5Oral steroids. The rationale for the use of steroids is to limit the destructive complications of the inflammatory process. Prednisolone 1 mg/kg daily should be started in severe cases after 12–24 hours provided fungal infection has been excluded from examination of smears. Beware contraindications, prescribe gastric protection (e.g. lansoprazole 30 mg once daily) and monitor appropriately including baseline blood tests; if necessary request general medical advice.

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6 Periocular steroids. Dexamethasone or triamcinolone should be considered if systemic therapy is contraindicated. 7 Topical dexamethasone 0.1% 2-hourly initially for anterior uveitis.

8Topical mydriatic such as atropine 1% twice daily.

9Intravitreal steroids may reduce inflammation in the short term but they do not influence the final visual outcome; some studies even suggest a detrimental effect. Conversely, improvement in outcome in some bacterial sub-groups has been reported.

10Pars plana vitrectomy. The Endophthalmitis Vitrectomy Study (EVS) showed a benefit for immediate pars plana vitrectomy in eyes with a visual acuity of perception of light (NOT hand movements vision or better) at presentation, with a 50% reduction in severe visual loss. If vitrectomy is not readily available, it is prudent to give intravitreal antibiotics in the interim. The conclusions of the EVS in post-cataract surgery eyes cannot readily be extrapolated to other forms of endophthalmitis.

Table 9.2 -- Preparation of antibiotics for intravitreal injection

Ceftazidime (broad spectrum, including Pseudomonas)

A)Begin with a 500 mg ampoule.

B)Add 10 mL water for injection (WFI) or saline and dissolve thoroughly (for a 250 mg vial add 5 mL WFI or saline, for a 1 g vial add 20 mL WFI or saline).

C)Draw up 1 mL of the solution, containing 50 mg of antibiotic.

D)Add 1.5 mL WFI or saline giving 50 mg in 2.5 mL.

E)Draw up about 0.2 mL (excess to facilitate priming) into a 1 mL syringe. When ready to inject fit the Rycroft cannula or the needle to be used, and discard all but 0.1 mL (contains 2 mg of antibiotic) for injection.

Vancomycin (action primarily against Gram-positive organisms)

Only saline, not WFI, should be used with vancomycin

As A–E above, again preferably starting with a 500 mg ampoule.

Amikacin (alternative to ceftazidime; as carries a higher risk of retinal infarction, use only if well-defined penicillin or cephalosporin allergy); lower intravitreal dose than ceftazidime and vancomycin

Note different dilution procedure to ceftazidime and vancomycin

A)Presentation: vial contains 500 mg of amikacin in 2 mL of solution.

B)Use a 2.5 mL syringe to draw up 1 mL of amikacin solution then 1.5 mL of WFI.

C)Inject 0.4 mL of the solution, containing 40 mg of antibiotic, into a 10 mL syringe and dilute to 10 mL (giving 4 mg per mL).

E)Draw up about 0.2 mL (excess to facilitate priming) into a 1 mL syringe. When ready to inject fit the Rycroft cannula or the needle to be used, and discard all but 0.1 mL (contains 0.4 mg of antibiotic) for injection.

Subsequent management

Subsequent management proceeds according to culture results and clinical findings. Ultrasonography may be useful in assessing response to treatment.

1Signs of improvement include contraction of fibrinous exudate and reduction of anterior chamber cellular activity and hypopyon. In this situation treatment is not modified irrespective of culture results.

2If the clinical signs are worsening after 48 hours antibiotic sensitivities should be reviewed and therapy modified accordingly. Par plana vitrectomy should be considered if not previously performed. Intravitreal antibiotics can be repeated after 2 days; if amikacin has previously been used, repeated administration should probably be avoided to reduce the risk of retinal toxicity.

3The outcome is related to the duration of the infection prior to treatment and the virulence of organisms.

•If visual acuity at presentation is light perception 30% of eyes achieve 6/12 following treatment. If visual acuity is better than light perception this figure increases to 60%.

•Infection with Bacillus cereus and streptococci has a poor visual outcome despite aggressive and appropriate therapy, with 70% and 55%, respectively, achieving a final visual acuity of 6/60 or less. This poor visual outcome may be related to early retinopathy from exotoxins.

4Late problems

aPersistent vitreous opacities. Aggressive and extended topical, periocular and, if necessary, oral steroid treatment will often lead to resolution. Vitrectomy can be considered if unresolving and severe.

bMaculopathy in the form of epimacular membranes, cystoid oedema and ischaemia.

cHypotony. Wound leak should be excluded and persistent inflammation addressed. Choroidal effusions should be identified and drained if necessary. Retinal detachment and anterior vitreous membranes may require vitrectomy.

dOther problems include chronic uveitis, secondary glaucoma, retinal detachment and phthisis.

Delayed-onset postoperative endophthalmitis

Pathogenesis

Delayed-onset endophthalmitis following cataract surgery develops when an organism of low virulence becomes trapped within the capsular bag ('saccular endophthalmitis’). Organisms can become sequestered within macrophages, protected from eradication but with continued expression of bacterial antigen.

It has an onset ranging from 4 weeks to years (mean of 9 months) postoperatively and typically follows uneventful cataract extraction with a posterior chamber intraocular lens. It may rarely be precipitated by Nd:YAG laser capsulotomy, which releases the organism into the vitreous. The infection is caused most frequently by P. acnes and occasionally S. epidermidis, Corynebacterium spp. or Candida parapsilosis.

Diagnosis

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