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

248 CHAPTER 9 Lens

Table 9.8 PCIOL materials

Design

•Square-edged vs. rounded: IOL optics with square posterior edges appear to reduce posterior capsular opacification by reducing migration of lens epithelial cells.

•Toric vs. spherical: toric IOLs can correct for preoperative astigmatism but may cause problems or be ineffective if not perfectly positioned.

•Short-wavelength filtration: some recent IOLs filter out shortwavelength blue light as this may be linked to accelerated age-related macular changes in pseudophakic patients.

•Pseudoaccommodative lenses are multifocals that may be diffractive or refractive in nature. They are attended by a loss of contrast sensitivity and are not always tolerated.

•Accommodative IOLs alter their focal length by anteroposterior movement within the capsular bag.

Anterior chamber intraocular lens (ACIOL)

ACIOL use is mainly associated with intracapsular cataract extraction but may still be of use where there is innate or acquired loss of capsular support. These may be angle supported or iris supported. Angle-supported lenses are sized to the anterior chamber (measure “white to white”).

In earlier designs, sizing was critical: too large and they would cause inflammation and local destruction; too small and they would be unstable and again cause irritation.

Modern one-piece lenses with threeor four-point fixation are much better tolerated and sizing is less critical. ACIOLs may be introduced by means of a glide. A peripheral iridectomy should be performed at the time of surgery to avoid iris bombe from pupillary block.

CATARACT SURGERY AND CONCURRENT EYE DISEASE 249

Cataract surgery and concurrent eye disease

Intraoperative floppy iris syndrome (IFIS)

Hypotonic iris smooth muscle results from ischemia, inflammation, or most commonly use of tamsulosin (i.e., Flomax) or other systemic A1-blocker.

Iris smooth muscle atrophy results in varying degrees of IFIS, most commonly manifesting as mild to severe miosis and iris prolapse through corneal incisions. Consider use of a combination of preoperative mydriatics, intracameral epinephrine, mechanical dilators such as iris hooks or the Malyugin ring, and/or a highly cohesive viscoeleastic (Healon 5).

Pupil stretching can exacerbate iris floppiness and should be avoided.

Diabetes

•Complications: fibrinous anterior uveitis, posterior capsular opacification (PCO), progression of retinopathy, and macular edema. Risk of complications increases with degree of retinopathy.

•Preoperative: if severe nonproliferative (NPDR) or proliferative diabetic retinopathy (PDR), treat patient (PRP or anti-VEGF agent, i.e., bevacizumab) prior to surgery when possible. Treat CSME (focal, grid laser, bevacizumab, triamcinolone) before surgery.

•Postoperative: consider topical NSAID (e.g., ketorolac 0.3% 3x/day for

1 month). An extended course of topical steroids may be required. See patient at 1 day, 1 week, and then 6 weeks to monitor for CME or anterior segment neovascularization.

Glaucoma

•Complications: postoperative pressure spike, progression of field loss, failure of previous trabeculectomy

•Preoperative: stabilize IOP control, identify degree of vision loss due to glaucomatous field loss, consider combining cataract surgery with IOP-lowering procedure (e.g., trabeculectomy).

•Consider clear corneal wound to prevent scarring of conjunctiva, thereby facilitating future drainage surgery. Meticulous removal of viscoelastic is needed to prevent postoperative IOP spike.

•Postoperative: consider extended use of postoperative acetazolamide or topical IOP-lowering agents to minimize postoperative pressure spikes (and risk of “wipe-out” to a vulnerable optic nerve). Although there have been concerns about CME, the continuation of

prostaglandin analogues postoperatively is probably safe. In the short eye, watch for aqueous misdirection syndrome. See patient at 1 day, 1 week, and then 6 weeks.

250 CHAPTER 9 Lens

Uveitis

•Complications: exacerbation of inflammation, fibrinous anterior uveitis, synechiae, raised IOP, CME, PCO.

•Preoperative: control inflammation and IOP as much as possible. In well-controlled anterior uveitis, consider intensive topical steroids for 2 weeks prior to surgery (e.g., dexamethasone 0.1% q2h). In patients with chronic uveitis, consider 500 mg IV methylprednisolone 1 hour before surgery, or prednisolone 40 mg PO for 1 week prior to surgery.

•Intraoperative: ensure adequate pupillary access (synechialysis, iris hooks, iris stretching) but avoid unnecessary iris manipulation.

Ensure meticulous cortical clearance. Perform a well-centered 5–6 mm capsulorhexis (to reduce postoperative capsular phimosis, iris-capsule synechiae). Give subconjunctival or intravitreal steroid

(e.g., betamethasone 4 mg).

•Postoperative: frequent potent topical steroids (e.g., dexamethasone 0.1% q2h) and taper slowly; if oral steroids were started or increased preoperatively, these should be tapered slowly to zero or maintenance dose. Consider mydriatic (e.g., cyclopentolate 1%). In persistent fibrinous uveitis, consider intracameral recombinant tissue plasminogen activator (rtPA). See patient at 1 day, 1 week, and as necessary.

Postvitrectomy

•Complications: PCO, retinal (re)detachment, vitreous hemorrhage.

•Preoperative: silicone oil slows sound transmission (estimated at 987 m/sec), and this must be incorporated when calculating axial length from an A-scan. Additionally, the axial length may not be stable within a year of scleral buckling procedures and may be unpredictable after macular surgery.

•Intraoperative: use clear corneal incision (rather than scleral tunnel). Poor mydriasis may require iris hooks or stretching. Fluctuation of AC depth and the risk to the flaccid PC may be minimized by wellconstructed wounds, lower bottle height, reduced vacuum, and lifting of the iris with a second instrument. Minimize nucleus manipulation to protect damaged zonules. Use acrylic or PMMA lenses (not silicone), placing in the bag or sulcus.

•Postoperative: warn patient about retinal detachment, dilate at follow-up review.

CATARACT SURGERY: COMPLICATIONS 251

Cataract surgery: complications

Intraoperative

Posterior capsule rupture without vitreous loss (approximately 3% of surgeries)

The main goals when confronted with a PC tear (without vitreous loss) are to avoid vitreous traction or loss and maintain as much capsule and zonular support as possible. To prevent vitreous prolapse, the anterior chamber should remain pressurized by maintaining irrigation and using a viscoelastic to tamponade the vitreous posteriorly prior to withdrawing instruments.

If the PC tear is small and well defined, a PCIOL may still be placed in the bag either at the time of surgery or as a secondary procedure. However, with larger, poorly defined PC tears, it is safer to place the lens in the sulcus provided that sufficient anterior capsule remains to stabilize the IOC.

Assuming equal A-constants, a sulcus-fixated lens should be about 0.5D lower power than that calculated for placement in the capsular bag.

Posterior capsule rupture with vitreous loss (approximately 1% of surgeries)

Clear the wound and AC of vitreous with manual (sponge or scissors) and/or automated vitrectomy while maintaining as much posterior capsule as possible. Dilute triamcinolone in the anterior chamber can stain vitreous, thereby enabling more efficient and complete vitreous removal.

If sufficient anterior capsule remains, place the lens in the sulcus (see note above); otherwise, consider an ACIOL with a peripheral iridotomy or suture fixate a PCIOL.

Anterior capsule problems

The capsulorhexis has a tendency to run out in a number of situations: shallow AC, positive posterior pressure, young patients, and intumescent cataracts. Stabilize the AC with a more cohesive viscolelastic (e.g., Healon 5). Decompress intumescent cataracts by puncturing the AC and aspirating lens matter.

If unable to bring the capsulorhexis back in, options include returning to the start and attempting a second tear in the opposite direction with use of capsulorhexis scissors and switching to a can-opener technique. Depending on the security of the resulting capsulorhexis, either continue with cautious phacoemulsification or convert to ECCE.

Zonular dehiscence

Consider stabilizing the capsule with iris hooks (secure the capsule in the area of dialysis) or a capsular tension ring (stabilizes the bag and redistributes forces away from individual zonules). Partially subluxed lenses may be more safely removed via phacoemulsification with the use of capsular tension rings with or without fixation loops (FDA approved) or with capsular tension segments (not FDA approved, but available through compassionate use).

254 CHAPTER 9 Lens

Postoperative endophthalmitis

Acute postoperative endophthalmitis

This is a sight-threatening emergency requiring rapid assessment and treatment. Onset is usually 1–7 days after surgery. The most common organisms are Staphylococcus epidermidis, Staphylococcus aureus, and Streptococcus species.

Historically, acute postoperative endophthalmitis after cataract surgery occurred at a rate of 1.79 per 1000 cases, but recent reports suggest the rate has increased to 2.47 per 1000 cases, possibly because of poorly constructed clear corneal and temporal corneal incisions.

Suspect

Suspect this if the patient has pain, worsening vision, disproportionate or increasing postoperative inflammation (including hypopyon), posterior segment inflammation, and lid swelling. An RAPD and inaccurate light projection suggest a poor prognosis.

Risk factors include patient flora (blepharitis, conjunctivitis, nasolacrimal disease), comorbidity (diabetes), and complicated surgery (PC rupture with vitreous loss, ACIOL, prolonged surgery).

Diagnosis

Perform an AC tap and vitreous biopsy (with simultaneous intravitreal antibiotics); use automated vitrector to perform a vitreous biopsy. Consider B-scan ultrasound to indicate the degree of vitritis and integrity of retina.

Treatment

Consider hospital admission if the patient is incapacitated by the condition.

•Intravitreal antibiotics: consider vancomycin 1 mg in 0.1 mL (grampositive coverage) combined with either amikacin 0.4 mg in 0.1 mL or ceftazidime 2 mg in 0.1 mL (gram-negative coverage). Ceftazidime can precipitate with vancomycin and so requires a different syringe.

•Vitrectomy: if VA is LP or worse (the Early Vitrectomy Study found a significant, threefold improvement in attaining 20/40 for this group; in diabetics, there was a trend toward benefit whatever the baseline VA).

Consider

•Oral moxifloxacin or gatifloxacin have broad antibiotic coverage and excellent intraocular penetration.

•Topical antibiotics: possibilities include hourly fourth-generation fluoroquinolones (moxifloxacin or gatifloxacin) or fortified vancomycin (50 mg/mL), amikacin (20 mg/mL), or ceftazidime (100 mg/mL) with a view to increasing anterior-segment concentration of the intravitreal drugs. There is no evidence of clinical benefit.

•Corticosteroids may be topical (e.g., dexamethasone 0.1% hourly), intravitreal (dexamethasone 0.4 mg in 0.1 mL), or systemic (prednisone PO 1 week). While steroids reduce inflammation and some sequelae of endophthalmitis, there is no evidence that it improves VA.

POSTOPERATIVE ENDOPHTHALMITIS 255

If failure to respond at 24 hours

Consider repeating AC tap, vitreous biopsy, and intravitreal antibiotics.

Chronic postoperative endophthalmitis

Onset is usually 1 week to several months after surgery. The most common organisms are Propionobacterium acnes, partially treated S. epidermidis, and fungi.

Suspect

Suspect this if there is chronic postoperative inflammation, which flares up whenever steroid treatment is reduced. A white plaque on the posterior capsule suggests P. acnes infection.

Diagnosis

Perform an AC tap and vitreous biopsy and consider removal of posterior capsule. Send sample for smears (Gram, Giemsa, and methenamine-silver stain) and culture (blood, chocolate, Sabouraud’s, thioglycolate broth, and solid anaerobic medium; the last is especially important for P. acnes). PCR may also be helpful.

Treatment

For P. acnes or low-grade S. epidermidis, consider vitrectomy and posterior capsulectomy, intravitreal vancomycin, and, if necessary, IOL removal. For suspected fungal infection, consider vitrectomy with or without IOL removal, intravitreal amphotericin B (5–10 μg), and subsequent systemic antifungals according to sensitivity (see also Box 9.2).

American Academy of Ophthalmology recommendations for endophthalmitis prophylaxis

•Preoperative treatment of blepharitis and other lid pathology.

•5% povidine iodine prep in the conjunctival fornices and 10% povidine iodine prep of the lids.

•Special attention to achieving a watertight closure of incisions.

•Other measures, including preoperative antibiotics, intracameral antibiotics, or subconjunctival antibiotics, are left to the surgeon’s preference.