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

342 THE ART OF PHACOEMULSIFICATION

after a bleb revision procedure is less predictable than in primary filtration surgery. Potential complications include flat anterior chamber, hyphema, choroidal effusion, wound leaks, bleb failure, bleb infection, and endophthalmitis.

Hypotony Maculopathy

The prevalence of postfiltration hypotony maculopathy continues to increase as a result of more widespread use of mitomycin-C and longer patient follow-up. The tendency for cataract surgery to influence bleb function adversely has generated interest in the concept of utilizing cataract surgery to treat postfiltration hypotony maculopathy. Although some authors have advocated this mode of therapy, it has not been demonstrated to be reliable or predictable in resolving hypotony and its complications.3,32,33

S U G G E S T I O N S

•Carefully evaluate the function of the preexisting filtering bleb preoperatively.

•Determine whether mechanical pupillary dilation will be required at the time of surgery and weigh the pros and cons of iris manipulation against the potential for an increased rate of bleb failure.

•Defer cataract surgery for at least six months or more after the establishment of a functional filter to improve long-term IOP control.

•The preferred incision is in temporal clear cornea and just large enough to allow insertion of a foldable IOL.

•Avoid bleb trauma related to manipulation, instrumentation and high infusion pressures.

• If bleb survival is in doubt, consider a concurrent bleb revision procedure.

•Suture the incision if the eye is soft or digital massage is anticipated postoperatively.

•Use topical corticosteroids generously in the early postoperative period and consider an adjunctive topical nonsteroidal agent.

•Consider postoperative 5-FU injections following combined internal revision and cataract surgery.

•Intracameral tPA may salvage bleb function in the event of an early severe postoperative pressure spike unresponsive to standard therapy.

R E F E R E N C E S

1. Caprioli J, Park HJ, Kwon YH et al: Temporal corneal phacoemulsification in filtered glaucoma patients (discussion). Trans Am Ophthalmol Soc 95:153-67, 1997.

2. Davison JA: Phacoemulsification in glaucomatous eyes. In: Thomas JV (Ed): Glaucoma Surgery (1st ed) CV Mosby: St. Louis, 295-314, 1992.

3. Chen PP, Weaver YK, Budenz DL et al: Trabeculectomy function after cataract extraction.

Ophthalmology 105:1928-35, 1998.

4. Seah SKL, Jap A, Prata JA Jr et al: Cataract surgery after trabeculectomy. Ophthalmic Surg Lasers 27:587-94, 1996.

5. Dickens MA, Cashwell LF: Long-term effect of cataract extraction on the function of an established filtering bleb. Ophthalmic Surg Lasers 27:9-14, 1996.

6. Wygnanski-Jaffe T, Barak A, Melamed S et al: Ophthalmic Surg Lasers 28:657-61, 1997.

7. Zaltas M, Schuman J, Shingleton B et al: Cataract extraction following filtering surgery. Invest Ophthalmol Vis Sci 35(ARVO suppl): 1420, 1994.

8. Foster RE, Lowder CY, Meisler DM et al: Extracapsular cataract extraction and posterior chamber intraocular lens implantation in uveitis patients. Ophthalmology 99:1234-41, 1992.

9. Shields ML: Combined cataract extraction and guarded sclerectomy—reevaluation in the extracapsular era. Ophthalmology 93:366-70, 1986.

10.Shields MB: Textbook of glaucoma (4th ed). Williams & Wilkins: Baltimore, 566, 1998.

11.Ferguson VMG, Spalton DJ: Continued breakdown of the blood aqueous barrier following cataract surgery. Br J Ophthalmol 76:453-56, 1992.

12.Lesser GR, Osher RH, Whipple D et al: Treatment of anterior chamber fibrin following cataract surgery with tissue plasminogen activator. J Cataract Refract Surg 19:301-05, 1992.

13.Ortiz JR, Walker SD, McManus PE et al: Filtering bleb thrombolysis with tissue plasminogen activator. [letter] Am J Ophthalmol 106:624-25, 1988.

14.Apple DJ, Solomon KD, Tetz MR et al: Posterior capsule opacification. Surv Ophthalmol 37(2): 73-116, 1992.

15.Naveh N, Kottas R, Glovinsky J et al: The long-term effect on intraocular pressure of a procedure combining trabeculectomy and cataract surgery, as compared with trabeculectomy alone. Ophthalmic Surg 21:339-45, 1990.

16.Murchison JF, Shields MB: An evaluation of three surgical approaches for coexisting cataract and glaucoma. Ophthalmic Surg 20:393-98, 1989.

17.Simmons ST, David L, Nichols DA et al: Extracapsular cataract extraction and posterior chamber intraocular lens implantation combined with trabeculectomy in patients with glaucoma. Am J Ophthalmol 104:465-70, 1987.

18.Kasahara N, Sibayan SA, Montenegro MH et al: Corneal incision phacoemulsification and internal bleb revision. Ophthalmic Surg Lasers 27:361-66, 1996.

19.Sofinski SJ, Thomas JV, Simmons RJ: Filtering bleb revision techniques. In: Thomas JV (ed): Glaucoma Surgery (1st ed). St. Louis, MO: Mosby; 75-82, 1992.

20.Wyse T, Meyer M, Ruderman JM et al: Combined trabeculectomy and phacoemulsification: a onesite vs a two-site approach. Am J Ophthalmol 125:334-39, 1998.

21.Warwar RE, Bullock JD, Ballal D: Cystoid macular edema and anterior uveitis associated with latanoprost use. Ophthalmology 105:263-68, 1998.

22.Dirscherl M, Straub W: Prophylaxis of cystoid macular edema after cataract surgery. Observation of an application of Chibro-Amuno. Ophthalmologica 200:142-49, 1990.

23.Flach AJ, Stegman RC, Graham J et al: Prophylaxis of cystoid macular edema without corticosteroids.

A paired-comparison, placebo-controlled double-masked study. Ophthalmology 97:1253-58, 1990.

24.Ernest P, Tipperman R, Eagle R et al: Is there a difference in incision healing based on location?

J Cataract Refract Surg 24:482-86, 1998.

25.Shingleton BJ (Ed): Surgical management of coexisting cataract and glaucoma. Boston, Ophthalmology Interactive,1996.

26.Hayashi K, Hayashi H, Nakao F et al Reduction in the area of the anterior capsule opening after polymethylmethacrylate, silicone, and soft acrylic intraocular lens implantation [see comments].

Am J Ophthalmol 123:441-47, 1997.

27.Hollick EJ, Spalton DJ, Ursell PG et al: Biocompatibility of polymethylmethacrylate, silicone, and AcrySof intraocular lenses: randomized comparison of the cellular reaction on the anterior lens surface. J Cataract Refract Surg 24:361-66, 1998.

28.Hollick EJ, Spalton DJ, Ursell PG et al: The effect of polymethylmethacrylate, silicone, and polyacrylic intraocular lenses on posterior capsular opacification 3 years after cataract surgery (discussion). Ophthalmology 106:49-54, 54-55, 1999.

29.Lundy DC, Sidoti P, Winarko T et al: Intracameral tissue plasminogen activator after glaucoma surgery. Indications, effectiveness and complications. Ophthalmology 103:274-82, 1996.

30.Savage JA, Condon GP, Lytle RA et al: Laser suture lysis after trabeculectomy. Ophthalmology 95:1631-38, 1988.

31.Shingleton BJ, Richter CU, Bellows AR et al: Management of encapsulated filtration blebs.

Ophthalmology 97:63, 1990.

32.Sibayan SAB, Igarashi S, Kasahara N et al: Cataract extraction as a means of treating postfiltration hypotony maculopathy [case reports]. Ophthalmic Surg Lasers 28:241-43, 1997.

33.Allingham RR: Treatment of hypotonous maculopathy. In Epstein DL, Allingham RR, Schuman JS (Eds): Chandler and Grant’s Glaucoma (4th ed). Williams & Wilkins: Baltimore, 549, 1997.

improvements in foldable intraocular lens (IOL) implantation delivery systems, implantation may now be routinely performed through incisions of 3.0 to 3.2 mm.

Well-documented studies now support the clinical impression that incisions of this size behave in an essentially astigmatically neutral fashion.5,6 Thus, an incision may be easily and reproducibly crafted that yields all of the wonderful benefits of the clear corneal approach, yet is astigmatically neutral. If a patient has enough

preexisting astigmatism to warrant reduction, modern astigmatic keratotomy (AK) may then be conservatively added to arrive at the desired cylindrical outcome.

Admittedly, this approach may result in a greater number of incisions placed onto the cornea. However, use of peripheral (intralimbal) arcuate astigmatic relaxing incisions has proven to be extremely safe and reliable.7 In the setting of concomitant cataract surgery, our data indicates that this technique provides for more predictable astigmatic outcomes as compared to the use of conventional (smaller) AK optical zones, and yields more consistent results than when relying solely upon a “tailored” phaco incision.

Our use of limbal relaxing incisions (LRIs) originated from the work of Stephen Hollis. With refinement of his nomogram, we found this approach to astigmatic keratotomy to be considerably more forgiving with less induced shift of resultant cylinder axis and greater predictability. This heightened safety level makes the technique most appropriate for the cataract-aged population where overcorrection should generally be avoided. Furthermore, this form of intralimbal keratotomy seems to logically dovetail with the trend toward clear corneal phaco incisions. Thus, we start with the amazingly simple but elegant single-plane, beveled (neutral) clear corneal phaco incision, and then add to it the necessary nonbeveled (perpendicular to the corneal surface) limbal arcuate relaxing incisions. This makes for a facile, logical and esthetic approach to astigmatism management.

Correcting the Spherical Component

Third-generation formulas are preferred for calculating the IOL power. In our experience the SRK/T formula appears to be the most accurate for patients with myopia and an axial length of 26.0 mm or longer. The third-generation Holladay 1 formula is indicated for eyes with an axial length between 24.5 and 26.0 mm. Hoffer Q and Holladay 2 formulas are preferred for those with less than 22.0 mm, and the average of the SRK/T, Holladay 1 and Hoffer Q for eyes between 22.0 and 24.5 mm. At present the IOL power calculations are based on the Hoffer 2.0 and Holladay 2 software.

Correcting the Astigmatism Component

About 5 percent of the patients seen for cataract surgery have astigmatism of less than 0.5D. In the remaining 95 percent, 75 percent have astigmatism of less than 1.25D.8 In our experience about 25 to 35 percent of cataract patients will be candidates for surgical correction of the astigmatism as an addition to their cataract surgery.

It is generally agreed that mild residual with-the-rule (WTR) astigmatism might be desirable (when using monofocal IOLs), overcorrection (axis shift of 180 degrees) is undesirable, and that the refractive plan must take into account the status of the fellow eye.9 Some authors suggest a mild against-the-rule (ATR) astigmatism as the desirable outcome after cataract surgery.10

With this in mind, surgery is planned according to the nomogram (Table 32.1) as illustrated.11 Unfortunately, preoperative measurements – keratometry, refraction, and topography – do not always agree. We have found that keratometry provides the most accurate determination of axis, and refraction provides a more reliable indicator of the quantity of cylinder. Topography is helpful when measurements

do vary and in complex cases, but is not a prerequisite for this technique. Phacoemulsification is performed through a 2.5- to 2.8-mm incision, depending

upon the tip and sleeve combination, and is then enlarged to 3.0 to 3.5 mm to accommodate the particular fordable IOL. This single plane, paracentesis-style temporal incision is placed at or just anterior to the vascular arcade. If a larger incision is to be used (to accommodate a particular IOL), increased against-the- wound drift (with-the-rule, given temporal incision location) must be anticipated and factored into the amount of cylinder to be corrected. As seen in the nomogram (Table 32.1), for patients with minimal preexisting astigmatism (+0.75×90 to 0.50×180), a single plane phaco incision is employed (Fig. 32.1). A 3.2 mm temporal clear corneal incision will induce 0.37 D of against-the-wound astigmatism.12 For patients with mild ATR astigmatism (+0.75 to +1.25D), the surgeon will have the option of a two-step grooved incision (300-600 microns groove) which can correct up to 0.75D,13 or a nasal peripheral arcuate relaxing incision placed opposite to the temporal clear cornea phaco incision leading to a nice, symmetrical corneal flattening (Figs 32.2 and 3).

For moderate levels of ATR astigmatism (1.5 to 2.75D), a temporal arcuate incision is placed along with the nasal incision. This temporal cut, in essence, becomes a deep groove such that the incision architecture resembles the Langerman hinge (with the extent or length of the groove determined by the nomogram).

For WTR astigmatism, the surgeon has two choices. There is varying opinion regarding the use of superior clear corneal incisions. Many leading surgeons fully advocate their use. We believe that it is acceptable to use a superior clear corneal incision provided that the patient has at least 2 diopters of WTR cylinder and good globe exposure. This most commonly occurs in young, myopic patients. One must keep in mind that these superior incisions will drift against the wound more than temporal incisions, as noted by Harry Grabow and others. In most cases of WTR astigmatism, we personally prefer to keep the phaco tunnel situated temporally, maintain an incision size of 3.5 mm or less for neutrality, and apply astigmatic keratotomy incisions over the steep axis (Figs 32.4 and 5). In our experience, this approach has yielded more consistent results with less corneal edema, particularly in those patients who have short eyes with small corneal diameters, are deeply set, or those who have compromised endothelium. A final

PHACOEMULSIFICATION IN PATIENTS WITH SIGNIFICANT ASTIGMATISM 347

Table 32.1: Nomogram for clear corneal phaco surgery

•ASTIGMATIC STATUS = “SPHERICAL”: (+0.75 × 90o ↔ + 0.5 × 180o)

Incision Design = “neutral” temporal clear corneal incision (3.5 mm or less, single plane, just anterior to vascular arcade)

•ASTIGMATIC STATUS = “AGAINST-THE-RULE”: Steep axis 0-30/150-180o

Intraoperative keratoscopy determines exact incision location

degrees of arc to be incised

* The temporal incision is made first by creating a two-plane, grooved phaco incision (600 µ depth), which is then extended to the appropriate arc length at the conclusion of surgery.

•ASTIGMATIC STATUS = “WITH-THE-RULE”: Steep axis 60-120o

Intraoperative keratoscopy determines exact incision location Incision Design = “Neutral” temporal clear corneal along with the Following peripheral arcuate incisions

•Acknowledgement is given to Dr Stephen Hollis whose original work provided the platform for this technique, and to Dr Spencer Thornton who has contributed so much to astigmatism surgery and whose modifiers are incorporated into this current nomogram. Drs David Dillman and William Maloney have also shared in the evolution of this nomogram.

PHACOEMULSIFICATION IN PATIENTS WITH SIGNIFICANT ASTIGMATISM 349

planning note for patients who have WTR astigmatism, the side port incision location may need to be adjusted so as not to interfere with the intralimbal relaxing incision.

Depending upon age, intralimbal relaxing incisions can address up to 3.5 diopters of astigmatism. For higher levels, corneal relaxing incisions placed at smaller optical zones become necessary (Figs 32.6 to 8). Well-established nomograms such as that of Dr Spencer Thornton or Richard Lindstrom may be used.14-16

Toric IOLs represent another option. Currently only one model is available in the US, but is available in two cylinder powers: 2.00 D or 3.5 D, which treat 1.00D to 1.25D or 2.00D to 2.5D of cylinder, respectively. The STAARR Toric IOL (AA4203TF) is designed for those cataract patients with 1.0 to 2.5 diopters of regular preexisting astigmatism. That is, symmetrical, “bow -tie” or “wedge” patterns. The anterior surface is a spherocylindrical refracting element and the posterior surface is a spherical lens to create a biconvex toric optic 6 mm in diameter. To ensure the power of the cylindrical correction is maximized, the surgeon is asked to use the two markings indicating the axis of the cylindrical correction of the lens and align them with the steep corneal meridian. The lens can be used in combination with LRIs to achieve the correction of high degrees of astigmatism.17

Excimer Laser Correction of Astigmatism

In cases where a high degree of correction is desired, Excimer ablation is another option. The decision as to when to perform the refractive correction will depend as several factors such wound healing, size of the cataract incision, time until refractive stability, and presence and extent of previous limbal or corneal relaxing incisions. As in the case of LASIK, wound gape can be encountered upon the application of the suction ring. If further surgical correction is anticipated, consider creating a corneal flap that may be prepared prior to cataract surgery.

The astigmatic incisions are placed just inside of the limbus at an empiric depth of 600 microns. Prior studies employing pachymetry and adjusted blade settings yielded negligible benefit in this older population, as opposed to younger refractive surgery patients where variable blade depth is justified. Diamond blade style and configuration may require an adjustment in depth settings; in our experience a triple-edged 15 degree Thornton arcuate diamond blade and the Katena 15 degrees diamond blade set at this depth have yielded excellent results with no

perforations. A new diamond blade solely dedicated to this technique is now available from Mastel. A single footplate may improve visibility and the diamond

extends to the appropriate (600 micron) preset depth.

The extent of arc to be incised may be demarcated in several different ways. One of our preferred method makes use of a modified Mendez ring (Lu-Mendez fixation ring/degree gauge) that both fixates the globe and allows one to delineate the extent of arc by visually extrapolating from the limbus to the adjacent marker (Katena K3-6158). A similar method may be employed through the use of a specially designed Fine-Thornton fixation ring (Nichamin fixation ring and gauge by Mastel Precision and Rhein Medical) in which each incremental mark is 10 degrees apart, and bold marks 180 degrees apart serve to align with the steep axis. This approach avoids inking and marking of the cornea. If desired, a two-cut RK marker may be lightly inked and used to mark the exact extent of arc to be incised in conjunction with the fixation ring/gauge. Alternatively, a Thornton-Nichamin arcuate marker utilizing a 10-mm OZ may be used to mark the cornea (Moria).

Interestingly, one of the most common patient complaints following contemporary phacoemulsification is that of a foreign body sensation. Intralimbal relaxing incisions, as compared to more central corneal incisions (smaller optical zones), definitely improve patient comfort. With the addition of a postoperative topical nonsteroidal antiinflammatory drugs (NSAIDs), this problem is virtually eliminated. Upon examination, these incisions appear to heal quickly and are nearly unidentifiable within several days.

Potential complications related to LRIs/CRIs include infection, perforation, wound gaping, and clinically significant overcorrection. In over 10 years of performing CRIs and 5 years of LRIs, we have never seen a case of infection or perforation with this technique. Isolated cases of wound gape have been described. The present Nichamin’s nomogram is designed to avoid overcorrections.

C O NC LU SI O N

This approach to astigmatism management has been evolving for the past five years, and parallels the development of several techniques such as keratolenticuloplasty (Kershner)20 and Gills’ use of Limbal relaxing incisions.7 Through these techniques both patient and surgeon may enjoy the great benefit of clear corneal surgery performed through an enlarged phacoemulsification incision, in concert with a safe and reproducible means to correct preexisting astigmatism.