Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001

R E F E R E N C E S

1. Amigo A, Giebel AW, Muiños JA: Astigmatic keratotomy effect of single-hinge, clear corneal incisions using various preincision lengths. J Cataract Refract Surg 24:765-71, 1998.

2. Vass C, Menapace R, Amon M et al: Batch-by-batch analysis of topographic changes induced

4. Ernst PH, Fenzl R, Lavery KT et al: Relative stability of clear corneal incisions in a cadaver model.

J Cataract Refract Surg 21:39-42, 1995.

5. Lyle WA, Jin G: Prospective evaluation of early visual and refractive effects with small clear corneal incision for cataract surgery. J Cataract Refract Surg 22:1456-60, 1996.

6. Masket S, Tennen DG: Astigmatic stabilization of 3.0 mm temporal clear corneal cataract incisions.

J Cataract Refract Surg 22:1451-55, 1996.

7. Gills J: Limbal Relaxing Incisions. ASCRS Seattle, WA, 1996.

8. Lu LW, Contreras C: Incidence of astigmatism in the cataract population. XIX PanAmerican Congress of Ophthalmology Caracas, Venezuela, 1993.

9. Grabow HB: Six steps to sphericity—An astigmatism management system for temporal, clearcorneal cataract surgery. ACES Ft. Lauderdale, 1997.

10.Trindade F, Oliveira A, Frasson M: Benefit of against-the-rule astigmatism to uncorrected near acuity. J Cataract Refract Surg 23:82-85, 1997.

11.Nichamin LD: Peripheral arcuate astigmatic keratotomy and modern clear corneal phaco surgery— a perfect match. ASCRS Seattle, WA, 1997.

12.Lu LW, Hollis S: Phacoemulsification in patients with high astigmatism. In: Lu LW, Fine IH (Eds):

Phacoemulsification in Difficult and Challenging Cases. Thieme: New York, 33-39, 1999.

13.Langermann DW: Architectural design of a self-sealing corneal tunnel, single-hinge incision. J Cataract Refract Surg 20:84-88, 1994.

14.Fenzl RE: Relaxing incisions and wedge resection in astigmatism surgery. OSN Symposium, New York, 1997.

15.Thornton SP: Graded nonintersecting transverse incisions for the correction of idiopathic astigmatism. In Sanders DR (Ed): Radial Keratotomy: Surgical Techniques. Slack: Thorofare, 103-16, 1985.

16.Lindstrom RL, Lindquist TD. Surgical correction of postoperative astigmatism. Cornea 7:138-48, 1988.

17.Sanders DR, Grabow HB, Shepherd J et al: STAAR AA 4203T toric silicone IOL. In Martin RG, Gills JP, Sanders DR (Eds): Foldable Intraocular Lenses. Slack: Thorofare, 237-50, 1993.

18.Susuki A, Maeda N, Watanabe H et al: Using a reference point and videokeratography for intraoperative identification of astigmatism axis. J Cataract Refract Surg 23:1491-95, 1997.

19.Koch DD: Pearls in performing peripheral corneal relaxing incisions. Vision News 6:2, 1999.

20.Kershner RM: Keratolenticuloplasty—arcuate keratotomy for cataract suregery and astigmatism.

J Cataract Refract Surg 21:274-77, 1995.

Enrique Chipont

Jorge L Alio

INTRODUCTION

The indications for proceeding with cataract surgery are more demanding in eyes with uveitis. The reported incidence of cataract in uveitic patients varies between series but it approaches 50 percent in juvenile rheumatoid arthritis1 and other forms of posterior uveitis2 and up to 75 percent in chronic anterior uveitis.3 Also complications of this surgery are higher in these patients than in no uveitic patients. Uncontrolled inflammation, hypotony, phthisis bulbi, among others are important challenges to the postoperative period in uveitic patients.4 The time of surgery has to be justified on eyes with slightly decrease in visual acuity, but in functional vision that are not in danger of visual loss, but on the other hand we cannot delay the surgery so long that treatable problems worsen progressively the status of the eye.

The improvement in surgical techniques and preand postoperative control of inflammation thanks to new and safer small incision surgeries and the usage of corticosteroids preand postoperatively have lead to better results of surgery in patients with uveitis. This has increased the tendency to operate these eyes earlier and earlier to prevent more important complications.

Surgery should be performed when the inflammation of the eyes is quiet. However, in some patients, it is impossible to clear every cell from the anterior chamber or vitreous. Furthermore, in patients with dense cataracts and primarily vitreoretinal inflammation, it is impossible to assess the activity of the disease behind the cataract.

Clinical Presentation

Complaints in those patients associated with the development of cataract will depend on age, the type of uveitis and mostly the type of cataract. Decrease of visual acuity

is the most important symptom of the development of cataract in patients with uveitis. Glare, and sometimes halo symptoms can be described by the patient as the first complaint. Glare can be associated with subcapsular posterior cataract, anterior Tyndall effect, intermediate uveitis or glaucoma that must be ruled out in such patients.

The control of the intraocular inflammation is needed prior to the surgical procedure. This preoperative control may require the use of topical or systemic steroids or immunosuppressive drugs. The treatment should be aimed at achieving a reduction in cellularity in the anterior chamber as well as little or no vitreous activity. The inflammatory activity should be assessed—by the presence of cells

in the anterior chamber and not—by the amount of flare presence.5

Cataract surgery is sometimes complicated by the presence of iris atrophy, sclerosis of the pupillary sphincter, cyclitic membranes, posterior synechiae, anterior capsular sclerosis, and possible hemorrhage from the iris and angle neovascularization. A precise and delicate surgery is mandatory. Keep in mind that surgery can exacerbate the underlying inflammatory process by the release of lens material and by the surgical trauma itself. It is then very important that the surgery should be performed in an undisturbed eye with an inflammatory reaction that has been controlled for at least three months prior to surgery.

The firm control of the postoperative inflammation is imperative. The necessary use of topical and in most cases, periocular and systemic steroids can give rise to problems as steroids dependent ocular hypertension and even problems related to the progressive and full withdrawal of them. The use of NSAIDs is a step forward in the postoperative control of inflammation.

Surgical Indications

There are two main indications for cataract surgery in patients with uveitis: (i) visually significant cataract if prospects for substantial improvement in visual acuity are good, and (ii) cataract that impairs fundus assessment in a patient with suspected fundus pathology.

Visually Significant Cataract

Cataract is not a reversible disease, so a detected decrease in visual acuity due to cataract precludes a subsequent decrease in few years. Techniques to estimate postoperative visual acuity can be used in patients where standard acuity scales are not sufficient and the health of the macula is unclear. Potential acuity meter (PAM) and Laser Interferometry are the most reliable techniques in these patients

Glare

Sometimes a 20/20 visual acuity is present in a patient with uveitis that complaint of blurred vision. Explanation of the potential risks and benefits must be carefully given including the fact that cataract is not reversible and that those symptoms will augment with time.

CATARACTS IN PATIENTS WITH UVEITIS 355

Improvement of Posterior Pole Visualization

Those situations associated with visualization of the posterior pole either to a given disease—diagnose or to observe and assess its evolution (e.g. posterior uveitis, vasculitis, macular edema) or the response to a treatment (systemic steroids or immunosuppressants). Such observations can be hindered by the presence of a dense cataract or even a wide posterior subcapsular cataract.

Preoperative Management

The single most important sign of inflammation is presence or absence of inflammatory cells in the anterior chamber or vitreous. Aqueous flare in anterior chronic uveitis simply denotes vascular incompetence of the iris and ciliary body, a consequence of vascular damage from recurrent uveitis. Therefore flare should in general not be used as a guidepost for inflammatory quiescence.

Our approach includes that patients will be divided into two groups: complicated cases and noncomplicated cases.6

Complicated patients are those in whom systemic or periocular therapy is necessary to maintain uveitis in a quiescent state or those in which surgery itself is expected to be difficult by the surgeon.

Noncomplicated patients are those on topical steroids and in those in whom surgery is expected to be easy.

The therapeutic approach will begin one week before surgery. Each subject will be given a topical corticosteroid (prednisolone acetate 1% or dexamethasone phosphate 0.5%) one drop four times daily. All subjects classified as “complicated” cases will also receive 1 mg/kg/day of oral predisone. After the operation treatment will be continued in each group in the way that will be described in the forward “postoperative treatment”.

Surgical Technique

Intracapsular surgery is reserved for the situations in which an important phacoinduced component is revealed in prior contralateral surgery. In case a chronic macular edema, a combined anterior and posterior procedure should be performed. Most surgeons opt for conventional pars plana vitrectomy techniques.5

Cataract surgery is sometimes complicated by the presence of iris atrophy, sclerosis of the pupillary sphincter, cyclitic membranes, posterior synechiae, anterior capsular sclerosis, and possible hemorrhage from the iris and angle neovascularization. A precise and delicate surgery is mandatory.

Phacoemulsification allows a small wound, causes minimal trauma and may therefore minimize postoperative inflammation. Young patients and patients on high doses of corticosteroids are at an advantage with this technique. General anesthesia is not necessary (though many patients are young requiring general anesthesia locoregional anesthesia by retrobulbar or peribulbar block are preferred. Topical anesthesia is not contraindicated but we do not use it in these cases.7

has some advantages over scleral tunnels such as the absence of postoperative hyphemas, filtering blebs and need for cautery among others. This is our favored approach if no lens or a foldable lens is implanted. If the implantation of a rigid PMMA lens is planned a limbal approach with a short scleral tunnel is performed. Viscoelastic substances are routinely used to release adhesions and aid mydriasis. Combinations of hyaluronic acid and chondroitin sulfate (Viscoat R) are preferred,

and high viscosity viscoelastics can be used (Healon GV R, Amvisc plus R). Many patients with uveitis have sclerosis of the dilator muscle of the pupil or intense posterior synechiae. In such cases, under viscoelastic aid synechiolysis is performed with an iris spatula. If further mydriasis is desired we use four De Juan hooks placed at each quadrant through four small corneal incisions. Continuous circular capsulotomy (capsulorrhexis) is always performed, even in intumescent cataracts, and if this is not possible a can-opener capsulotomy is opted for, but phacoemulsification is performed with caution.

The phacoemulsification procedure is accomplished by the most suitable technique for each case, with chop techniques if hardness of the nucleus is high. In general the nucleus is soft in young patients and phacoemulsification can be performed without any complications. Intensive cortical cleaning is mandatory to eliminate one of the sources of postoperative inflammatory reaction. The posterior surface of the anterior capsule must be aspirated with a low vacuum to eliminate proliferative cells and to remove one of the sources of posterior and possibly anterior capsule opacification. Bimanual techniques give excellent results in anterior cortical cleaning.

Where there is extensive membrane formation in the vitreous especially in the anterior part, vitrectomy after posterior central capsulorrhexis must be considered. If the vitreous cavity shows extensive fibrosis and exudate formation, transscleral pars plana vitrectomy may be indicated.8

INTRAOCULAR LENSES

Several researches have suggested that inserting a posterior chamber lens into the capsular bag poses no additional threat to ocular morbidity in selective uveitis cases, providing proper perioperative treatment for inflammation is given.9,10

Surface-modified IOLs such as the heparin-coated models have been introduced. The heparin surface-modified IOL is created by inducing electrostatic absorption of heparin onto the surface of a PMMA IOL. Heparin-coated IOLs are recommended for patients with uveitis as they decrease the number and severity of deposits on the surface of the IOL.11

Limited information is available regarding small incision phacoemulsification and foldable IOL implantation in patients with chronic uveitis. Several controlled studies comparing flexible IOL implantation through a 3.2 mm incision and conventional PMMA IOL implantation through 5.5 mm or larger incisions have been reported. Postoperative inflammation has been significantly less with smaller incisions.

CATARACTS IN PATIENTS WITH UVEITIS 357

Polymethylmethacrylate (PMMA) is the most commonly used IOL material. It has proved to be inert and stable. Design and manufacture have been optimized over decades.12 New materials like silicone and hydrogel have been progressively accepted for intraocular implants in humans because phacoemulsification is becoming

PB THE ART OF PHACOEMULSIFICATION

more popular. The interest for these materials is based on their mechanical properties, which allow them to be folded and inserted through a small incision. New technology applied to PMMA lenses has enabled the development of a new generation of acrylic foldable lenses for small incision surgery.13

Silicone lenses have displayed greater inflammatory reaction after ECs in nonuveitic patients when compared with other types of lenses (PMMA, heparin-modified, hydrogel). After phacoemulsification procedures a number of complications have been described such as intense inflammatory reactions in the anterior chamber, the total closure of the capsulorrhexis14 and an increase in posterior capsule opacification when compared with PMMA implants. The use of this material in patients whose blood-aqueous barrier is affected is not accepted by many authors. Nevertheless few reports of the use of silicone IOLs in patients with uveitis have been published. A 13 mm silicone IOL with 6 mm optic was implanted through a 3.2 mm incision in a woman with sarcoidosis uveitis; this case revealed perioperative tolerance to the silicone implant and rapid visual rehabilitation compared with the fellow eye which received a rigid PMMA lens. Few reports about the use of this material are available, though a prospective study may be able to establish some indications as to this silicone IOL.

The issues surrounding IOL placement in uveitic eyes after cataract extraction remains a key concern in management of the uveitic patient. Many features unique to a uveitic eye must be considered, including different types of uveitis and their diagnoses, preoperative inflammation and treatment, postoperative inflammation and specific complications. With newer techniques and modern posterior chamber lenses, IOLs are being implanted with fewer complications. These IOLs are well tolerated in selected patients, especially when the lens is placed in the capsular bag. Many questions remain unanswered regarding the uveitic eye in conjunction with IOL biocompatibility and inflammation. Valuable information can be gained through more experience with IOL use in these eyes.

Because the heterogeneity and the scarce number of patients, multicentric studies are needed to determine which, if any, IOL material is better tolerated in a uveitic patient by evaluating postoperative responses in the operative eye. This will be accomplished by descriptively comparing the postoperative outcomes of these eyes when implanted with IOLs made of various materials. Outcomes will be determined by measuring visual acuities and postoperative parameters such as posterior capsule opacification, inflammatory responses and endothelial cell counts.

COMBINED SURGERIES Glaucoma

Glaucoma associated with uveitis is one of the most serious complications of intraocular inflammation. It occurs in various syndromes and it may be difficult to manage. Most patients respond poorly to surgery. It is of primary importance to determine the severity of the inflammation and if possible, the syndrome associated with it. Management includes treatment of the underlying inflammation and of the glaucoma itself. Various mechanisms produce secondary glaucoma, and it is important to identify them to institute the appropriate therapy. Special considerations should be given to the management of acute or chronic intraocular inflammation and to make it certain that corticosteroids are not the cause of the elevated pressure. Pharmacologic intervention is the first step in the treatment of uveitic glaucoma. Corticosteroids, acetazolamide, beta-blockers, cycloplegics, etc.

In general the results of the surgery for glaucoma in uveitic patients is not as good as it is for glaucoma in patients without uveitis. The following procedures can be performed: laser iridectomy, surgical iridectomy, trabeculodialisis, trabeculectomy, trabeculectomy with wound modulation therapy, ab interno laser sclerostomy, drainage implantation, cycloablation therapy.

Cataract-Vitrectomy

Combined phacoemulsification and pars plana vitrectomy technique has displayed many advantages over other techniques.15,16 A small incision (even 3.00 mm) guarantees minimal corneal distortion and manipulation. These incisions are water-tight so they allow perfect closure during the vitrectomy portion of the operation. Lens density is not a main problem for phacoemulsification and allows the posterior capsule to remain intact, enabling endocapsular fixation of a posterior chamber lens. Delaying the IOL implantation until completion of vitrectomy, if required, allows fast visual rehabilitation and functional unaided vision in patients who are considered poor candidates for aphakic contact lens wear. If a limbal approach to the cataract and posterior pars plana vitrectomy is intended, the scleral incisions for the vitrectomy should be made first. The upper sclerotomies are occluded with scleral plugs. The advantage of this procedure lies in preserving part of the posterior capsule for the secondary implant of an IOL. We prefer this approach whenever possible, first performing phacoemulsification of the crystalline lens followed by pars plana vitrectomy.

PB THE ART OF PHACOEMULSIFICATION

A capsulotomy or posterior capsulorrhexis must be performed on completion of the vitrectomy due to the fast opacification occurring and because it allows the decompartmentalization of the eye, facilitating the access of anti-inflammatory drugs in the postoperative stage.

Postoperative Inflammation

The clinical consequence of inflammation is represented by a transient or permanent blood-aqueous barrier rupture. This is a common phenomenon that usually appears associated to the postoperative surgical inflammation. This is mostly subclinical and difficult to detect by biomicroscopy. Clinically it is very difficult to establish if that inflammation has vanished definitively. This subclinical inflammation can only be measured with most modern procedures like fluorophotometry and the laser flare cell meter. This technique can explain some clinical events such as late endothelial

decompensation, not explained by clinical reasons.

The common clinical features of postoperative inflammation include the presence of cells, leukocites and proteins flare in the anterior chamber and engorgement of the iris and conjunctival vessels. In clinical practice, it is standard to monitor the resolution of postoperative inflammation by observing the level of cells and flare in the anterior chamber for four to six weeks postoperatively. Slit lamp biomicroscopy is used to detect and aid the physician in assessing the extent of anterior chamber inflammation and engorgement of the conjunctival vasculature.

In human clinical studies of post-surgical inflammation the primary clinical variable examined to assess is the degree of postoperative intraocular inflammation. The presence of cells and flare in the anterior chamber are mandatory. It is measured with the laser flare cell meter, fluorophotometry, or an inflammation severity score, i.e. uveitic scoring system (USS).17 Secondary measures of treatment efficacy include the degree of ocular discomfort, bulbar conjunctival hyperemia, ciliary flush, corneal edema, an even anterior vitreous reaction. In addition, the frequency of treatment failures and the follow-up impression of inflammatory response must be assessed.

Measuring the degree of blood-aqueous barrier (BAB) disruption was difficult in the 1970s. With development of the fluorophotometer and the laser flare cell meter, however, the task has been simplified, allowing the BAB function to be used as a physiological, clinical parameter. The laser flare meter has been especially useful because it is noninvasive and easy to perform.

Recent studies suggest that capsule opacification is a form of postoperative inflammatory reaction. Because the lens capsule is primarily composed of collagen type IV, Miyake et al18 performed an experimental study to compare PMMA IOLs with collagen type IV mediators implanted inside the lens capsule. They found that eyes receiving the collagen type IV mediators had less severe postoperative inflammation and less anterior capsule opacification.18

Topically applied steroids have become the standard of care during the immediate postoperative period to reduce the morbidity associated with ocular inflammation, to prevent structural damage to the eye, and to reduce patient’s discomfort.19 Their potential side effects limit their clinical effectiveness in some settings. This is

particularly true for steroids that have a predilection for elevating IOP. A current strategy underlying the development of new steroidal compounds for ocular use is therefore, to identify drugs that exhibit marked antiinflammatory activity while decreasing the propensity to raise IOP or induce other side effects.

In emergency cases, no strict guidelines are available. When a previous uveitis is present a severe postsurgical exacerbation of preexisting inflammation should be expected. Depending on the severity of the case one week prior to surgery topical

or systemic corticosteroids should be administered. At the time of surgery a sub- conjunctival corticosteroid should be injected subconjunctivally far from any ocular

wounds. During the postoperative period both topical and systemic corticosteroids may be tapered based on the severity of ocular inflammation. In the most severe cases moderate to high doses of oral prednisone from 1 to 1.5 mg/kg/day, and intensive once per hour topical corticosteroids drops should be given prior to and tapered after surgery. In cases of steroid-induced glaucoma, the management may be much more difficult. In these cases temporary immunosuppressive therapy may need to be substituted to control inflammation in the very operative period. These guidelines may be applied for all intraocular procedures in uveitis eyes.

Several recent studies have assessed the effectiveness of NSAIDs to treat ocular inflammation. Most NSAIDs used today act by inhibiting the enzyme cyclo-oxygenase and thereby decreasing the formation of prostaglandins which play a major role in ocular inflammation by producing and maintaining the rupture blood-aqueous barrier. Diclofenac drops were shown to reduce inflammation after argon laser trabeculoplasty,20 and after cataract surgery.21 We cannot offer these drugs as an alternative to corticosteroids or even as an adjunct to treatment in uveitis patients with cataract.

FOLLOW-UP

Generally a low inflammatory reaction is observed after IOL implantation in patient with chronic anterior uveitis if preoperative and postoperative antiinflammatory measures are undertaken. Complications associated with these patients in the followup are linked with the following.

Posterior capsule opacification This complication has been described in some series at least in 50% of cases.22

Membranes The appearance of fibrous membranes mostly in pars planitis patients has been described.23

Decreased visual acuity The major causes of decreased visual acuity in these patients are cystic macular edema (CME),5 Epiretinal membrane,24 and glaucomatous optic nerve damage.5 Nevertheless a proper visual acuity was achieved in the majority of patients in the most important series of patients published.24,25 Visual acuities better than 20/40 can be achieved in 20 to 75 percent of patients.26,27