Presbyopia Correction/Astigmatism

From the 2009 Ophthalmology Symposium: Cataract, presented by Kaiser Permanente

Educational Objectives

The goal of this program is to improve the management of astigmatism and presbyopia with intraocular lenses (IOLs). After hearing and assimilating this program, the participant will be better able to:

1.   Describe the benefits and requirements of multifocal IOLs for treatment of cataracts.

2.   Select appropriate patients for implantation of multifocal lenses.

3.   Summarize the advantages and limitations of the Crystalens accommodative presbyopia-correcting IOL and apply surgical techniques to maximize the outcome of implantation.

4. Review techniques for maximizing refractive outcome after lens implantation by lens exchange or keratorefrac­tive procedure.

5.   Choose the best surgical approach for the correction of mild, moderate, and severe astigmatism.

Faculty Disclosure

In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the planning committee to disclose relevant financial relationships within the past 12 months that might create any per­sonal conflicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. For this program, Dr. Colvard reported serving as a consultant for Bausch and Lomb. Dr. Miller and the planning committee reported nothing to disclose.

Acknowledgements

Drs. Miller and Colvard were recorded at 2009 Ophthalmology Symposium: Cataract, held July 18, 2009, in Ana­heim, CA, and presented by Kaiser Permanente. The Audio-Digest Foundation thanks the speakers and Kaiser Per­manente for their cooperation in the production of this program.

Multifocal Presbyopia-Correcting Intraocular Lenses

Kevin M. Miller, MD, Kolokotrones Professor of Clinical Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles

Current multifocal lenses: (ReZOOM, ReSTOR, and TECNIS) allow distance and near vision simultaneously in same eye; technologies include refractive and diffractive designs; both split light to give 2 simultaneous points of focus

Refractive cataract surgery: goals  —  remove cataract and achieve patient’s desired postoperative spherical correc­tion (emmetropia or mild myopia); requirements  —  excellent biometry, reduction or elimination of preoperative astigmatism, and addressing presbyopia

Biometry: speaker recommends immersion A-scan or partial coherence interferometry; available instruments include IOLMaster and Haag-Streit LenStar LS900

AcrySof ReSTOR lens: approved by United States Food and Drug Administration (FDA) in 2005 and Centers for Medicare and Medicaid Services (CMS) in 2007; +3.00 diopter (D) SN6AD1 recently launched; clinical trial of ReSTOR vs monofocal lens showed similar distance vision achieved, but significantly more patients achieved Jae­ger score of 1 or better for near vision with ReSTOR; amplitude of functional vision curve showed trough at 20/25 for +3.00 D lens (ie, excellent computer-distance vision); 80% of patients in trial independent of spectacles (»90% in speaker’s practice); disadvantages  —  difficulty with night vision, glare, and halos significantly more common with multifocal than with monofocal lenses; speaker finds »25% of patients bothered by halos, but not to extent that explantation desired; apodized diffractive lens with central 3.6-mm split for distance and near; original lens had +4.00 D at plane of intraocular lens (IOL; 3.20 D at spectacle plane); light going through near portion of lens defo­cused on retina with considerable spread, and light coming from distance sharply in focus; when superimposed, im­age loses contrast minimally; aspheric lenses (improved quality) have front surface with negative spherical aberration

Patient selection: speaker uses multifocals only when bilateral implantation possible; excludes any patient with other vision-limiting problems (eg, pseudophakic in one eye [»10%] or with comorbidities such as epiretinal membrane, diabetic maculopathy, or moderate to high astigmatism); among »40% of patients who remain eligible (more pa­tients eligible for Crystalens than multifocal), »50% choose multifocal (20% of patients in speaker’s practice)

Postoperative management: achieve patient satisfaction with first eye before performing second implant; do not mix IOL types; if final uncorrected near and distance visions good, check posterior capsule in 1 yr

Refraction: very important to achieve postoperative astigmatism <0.75 D; vision declines more rapidly with multifo­cal lens if comorbidity exists (eg, dry eye, map-dot-fingerprint, posterior capsule opacification [PCO], or epiretinal membrane)

Managing patient dissatisfaction: hold -3.00 lens in front of each eye for +4.00 D version (or -2.25 if patient re­ceived the +3.00 D) to demonstrate effect on near vision if lens replaced with monofocal lens; patients usually de­cide to keep multifocal lens; patients who have problems with multifocal require slightly more counseling after surgery; implantation in both eyes necessary to obtain best reading result; »50% of speaker’s patients with +3.00 D and most with +1.00 D can read computer screen without glasses

Patients who have had refractive surgery: speaker advises against using presbyopia-correcting IOLs; too problem­atic; difficulties compounded by aberration profile of patients who have had radial keratotomy or photorefractive keratectotomy

Accommodative Presbyopia-Correcting
Intraocular Lenses

D. Michael Colvard, MD, Clinical Professor of Ophthalmology, Keck School of Medicine, University of South­ern California, Los Angeles

Background: 3 categories of accommodative lenses; 1) flexible haptic lenses have fixed optic power designed to move forward with accommodative effort; 2) lenses in which optic power changes with accommodative effort; 3) dual optic lenses (eg, Synchrony) use positive and negative lenses, which separate with accommodative effort to produce magnified image

Stages of development: Crystalens available clinically; TetraFlex lens by Lenstec and Synchrony lens in trials; lenses in which optic power changes in preclinical development

Crystalens

Background: advantages  —  improved range of visual function without reduced visual quality; no splitting of light (ie, 100% for distance, intermediate, and near vision) provides more consistent patient response and high level of independence from spectacles; limitations  —  cannot provide 6.00 D of accommodation (need realistic expecta­tions); success depends on meeting refractive goals

Patient criteria: good candidates  —  have visually significant cataracts and age >55 yr; easier to provide hyperopic patients with satisfactory result, but procedure effective for patients with any refractive status without significant cylinder; poor candidates  —  myopic patients who can read without glasses; Crystalens provides only 1.50 D ac­commodation effect; patients who use monovision lenses successfully should receive single-focus lenses; younger patients who still have useful accommodation (5.00-6.00 D); “neurotic” patients, although adjustment to lens rela­tively easy; patients taking tamsulosin (Flomax) because good visualization of capsule margin needed to achieve perfect implantation within capsular bag and to avoid development of Z configuration; strongly contraindicated in patients with pseudoexfoliation; patients with ocular comorbidities (eg, maculopathy)

Preoperative evaluation: determine ocular dominance (speaker performs mini-monovision by making nondominant eye -0.5 D); pupil size less important, but eliminate patients with widely dilating pupils in low illumination (likely to experience glare at night); if cylinder >1.25 D, offer standard monofocal or toric lens; if <1.25 D, offer monofo­cal IOL or Crystalens, except in good candidates for multifocal IOL (eg, less active older patients with good macu­lar function)

Counseling patients: important to explain that procedure involves lens exchange; monofocal lens provides good dis­tance vision without glasses; glasses needed for intermediate and near vision; monofocal lens covered by insurance and provides good optics; Crystalens provides distance vision equal to monofocal lens; helps with intermediate vi­sion (eg, to read watch, cellular phone, or computer screen without glasses); helps somewhat with reading vision, but 1.50 D magnifiers necessary for small print; Crystalens much more expensive

Surgical tips: managing astigmatism  —  if cylinder <1.25 D, evaluate topography and make careful preoperative drawings (if <75 D, use K readings from IOLMaster; if >75 D, obtain topography); make drawing of surgical plan for all patients, regardless of cylinder, which shows exact location of incision; operating on steep axis always di­minishes cylinder; show exact location and size of limbal relaxing incision; mark patients in sitting position (as for AcrySof toric lenses) because cyclotorsion (20° of temporal downward rotation) occurs in nearly all patients when they lie down with one eye covered; limbal relaxing incisions forgiving, but only effective if placed in correct loca­tion; speaker uses axis indicator, marks exact axis for incision location according to drawing, and marks sites for limbal relaxing incisions; Crystalens intolerant of any shallowing of anterior chamber during postoperative period; although most square clear corneal incisions do not leak extensively or create hypotony, some leak slightly; can cause shallowing of chamber and make Crystalens vault forward slightly, thereby inducing myopic shift; to avoid this, either place suture in clear corneal incision or perform scleral tunnel incision (speaker’s preference); easy to mistakenly implant Crystalens upside-down; haptic designed with round end on right side and oval end on left; af­ter haptics in place, confirm round knob on right; if not, rotate 180° to ensure lens implanted in correct orientation;  place distal haptics within capsular bag and proximal haptic on iris in anterior chamber; lift lens and tuck optic into capsular bag (“lift and fold,” rather than push)

Refractive outcome: »10% of patients with presbyopic lenses not completely satisfied; if patient has simple spheri­cal error, consider IOL exchange early (easy if done within 2 to 3 wk); after 6 to 8 wk, lenses “set up”, polyimide haptics stick into capsule, and keratorefractive procedure or piggyback becomes necessary; piggyback IOL less predictable than exchange and may reduce accommodative effect; if patient has residual astigmatic error, keratore­fractive procedure necessary; PRK better option for older patients

IOL exchange: to determine correct lens, plot IOL powers along abscissa and predicted refractive outcomes along ordinate from original biometry; choose IOL power to achieve desired correction

Postoperative instructions: speaker uses steroids and nonsteroidal anti-inflammatory drugs to reduce risk for cys­toid macular edema (CME); asks patients to use reading glasses for first 2 wk to avoid inducing myopia with lenses (not clinically proven); after 2 wk, encourages patients to read without glasses; timing of recovery  —  distance vi­sion good after 1 day, computer reading very good by 2 wk, and reading vision improves more slowly (eg, within 8 mo)

Surgical Control of Astigmatism

Dr. Miller

Requirements for achieving good distance vision: good macula, biometry, and astigmatic results

Biometry: partial coherence interferometry (gold standard) or immersion A-scan

Approaches: cataract surgeons focus on corneal astigmatism; if topographically measured corneal astigmatism <1.00 D (80% of patients), speaker performs phacoemulsification on steep axis; for 1.00 to 1.50 D, speaker prefers relax­ing incisions (toric lenses possible); for 1.50 to 2.50 D, uses toric lenses; for >2.50 D, uses combined peripheral corneal relaxing incisions plus toric IOL and can achieve £5.00 D correction; toric lenses available for £12.00 D of correction in Europe

Phacoemulsification: 3-mm incision flattens corneal meridian by 0.50 D (90% confidence interval of 0.40 to 0.60 D)

Peripheral corneal relaxing incisions: limbus not really cut; evaluate corneal topography and assess symmetry of “bow tie”; if symmetrical, speaker makes paired incisions in peripheral cornea, just inside limbus; cuts through ves­sels if necessary; makes paired incisions as long in clock hours as cornea is steep in diopters; tension in cornea ex­ists mostly in anterior half, therefore depth of more than halfway through cornea appropriate for incision; speaker uses blades from 450 to 600 m; use paired incisions with maximum length of 3 clock hours each (gives 3 D of astig­matism correction); longer incisions create risk of gaping and corneal anesthesia; speaker makes incisions at begin­ning, when intraocular pressure (IOP) consistent (helps keep blade depth consistent) with Mastel 3-step diamond knife (select diamond knives on basis of smoothness of footplate to avoid binding on conjunctiva); one clock hour easy to visualize (equivalent to 30° or »3 mm in 12-mm globe); make phaco incision through relaxing incision

Toric lenses: STAAR Surgical Toric IOL  —  approved by FDA in 1998; early model tended to rotate, but TL lenses with longer haptic do not; Alcon toric lens  —  approved in 2005 by FDA and 2007 by CMS; do not rotate; aspheric toric lens  —  launched 2009; all yellow; study of 494 patients with 211 AcrySof toric lenses vs 210 control lenses; no other correction of astigmatism allowed; toric lens outperformed control lens at all levels of acuity and produced lower residual cylinder; 60% of patients with toric lens implanted in single eye achieved spectacle independence for distance vision (»40% with control lens); 97% with bilateral toric lenses achieved spectacle independence for distance vision

Combined relaxing incisions with toric IOL: possible to achieve £5.00 D (more when IOLs with higher powers be­come available)

Integrating premium lenses into practice: Medicare allows patients to pay for premium services; physicians need business plan for premium services (ie, astigmatism management) regardless of type of lens implanted; speaker does not implant multifocal or toric lens in patients who do not opt for astigmatism management service; patient pays hospital for premium lens if desired, and speaker does not advocate premium lenses more strongly; patients with ³1.00 D residual astigmatism after phaco incision qualify for AcrySof toric lens; 3 powers of toric lenses available (1.50, 2.25, and 3.00 D), equivalent to 1.00, 1.50, and 2.00 D in corneal plane; Alcon and STAAR surgical provide online toric calculators

Future developments: Alcon expecting to launch T2 and T6 through T9 (4.00 D of correction) by 2010 and Re­STOR toric lens by 2011; STAAR Surgical expects toric lens by 2010

Suggested Reading

Aimsbury EC, Miller KM: Correction of astigmatism at the time of cataract surgery. Curr Opin Ophthalmol 20:52, 2009; Buznego C, Trattler WB: Presbyopia-correcting intraocular lenses. Curr Opin Ophthalmol 20:13, 2009; Cionne RJ et al: Clinical outcomes and functional visual performance: comparison of the ReSTOR apodized diffractive intraocular lens to a monofocal control. Br J Ophthalmol 93:1215, 2009; Cristobal JA et al: Effect of limbal relaxing incisions during phacoemul­sification surgery based on nomogram review and numerical simulation. Cornea Aug 29, 2009 [Epub ahead of print]; Gra­ether JM: Simplified system of marking the cornea for a toric intraocular lens. J Cataract Refract Surg 35:1498, 2009; Hagan JC 3rd, Kutryb MJ: Cataract and intraocular implant surgery concerns and comments posted at two internet eye care forums. Mo Med 106:117, 2009; Ito M, Shimizu K: Reading ability with pseudophakic monovision and with refractive multifocal in­traocular lenses: comparative study. J Cataract Refract Surg 35:150, 2009; Karamaounas N et al: Surgical techniques for small-incision intraocular lens exchange. J Cataract Refract Surg 35:1146, 2009; Landers J, Goggin M: Comparison of re­fractive outcomes using immersion ultrasound biometry and IOLMaster biometry. Clin Experiment Ophthalmol 37:566, 2009; Langenbucher A et al: Toric intraocular lenses—theory, matrix calculations, and clinical practice. J Refract Surg 25:611, 2009; Maxwell WA, et al: Performance of presbyopia-correcting intraocular lenses in distance optical bench tests. J Cataract Refract Surg 35:166, 2009; Maxwell WA et al: A United States cost-benefit comparison of an apodized, diffractive, presby­opia-correcting, multifocal intraocular lens and a conventional monofocal lens. J Cataract Refract Surg 24:1855, 2008; Pepose JS: Maximizing satisfaction with presbyopia-correcting intraocular lenses: the missing links. Am J Ophthalmol 146:641, 2008; Reeves SW: Advances in cataract surgery and intraocular lenses. Minn Med 92:38, 2009; Wilkins MR et al: Spectacle use af­ter routine cataract surgery. Br J Ophthalmol May 7, 2009 [Epub ahead of print]; Yuen L et al: Two cases of Z syndrome with the Crystalens after uneventful cataract surgery. J Cataract Refract Surg 34:1986, 2008.