Intraocular Lens Update

Educational Objectives

The goal of this program is to improve the use of and patient selection for intraocular lenses (IOLs). After hearing and assimilating this program, the participant will be better able to:

1.   Compare and contrast the advantages and challenges of currently available IOLs.

2.   Summarize the features of different IOL designs, such as ease of use, visual acuity at different distances, and predictability of the refractive end point.

3.   Describe how patient characteristics such as astigmatism and pupil size influence the performance of different IOLs.

4.   Practice techniques that minimize complications associated with implantation of IOLs.

5.   Choose the appropriate patients and IOLs for correction of presbyopia.

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. Hamilton reported receiving honoraria from Alcon, Allergan, and Reichert, Inc. Dr. Serafano reported a consulting agreement with Alcon Surgical and presents in­formation in his lecture that is related to off-label or investigational use of a therapy, product, or device. The planning com­mittee reported nothing to disclose.

Acknowledgements

Dr. Hamilton spoke at the 30th Annual Scientific Meeting, held February 27, 2009, in Salt Lake City, UT, presented by the Utah Ophthalmology Society. Dr. Serafano presented at the 2009 Annual Meeting – Current Trends and Ad­vances in Ophthalmology, held March 26-27, 2009, in Seattle WA, and presented by the Washington Academy of Eye Physicians and Surgeons.  The Audio-Digest Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.

Conquering Challenges of Refractive Cataract Surgery

D. Rex Hamilton, MD, MS, Assistant Professor of Ophthalmology, and Director, UCLA Laser Refractive Cen­ter, Jules Stein Eye Institute, University of California, Los Angeles

Background: 80 million people born between 1946 and 1964 (“baby boomers”) soon to reach 65 yr of age; »50% of individuals >65 yr of age have significant cataracts; »20 million such patients today growing to 30 million in slightly  >10 yr

Crystalens: first intraocular lens (IOL) approved (5 yr ago); 5-mm silicone optic; accommodative mechanism thought to involve forward movement resulting from ciliary muscle contraction and decrease of volume available at vitreous space; change of curvature may augment depth of focus; lenses  —  most recent model (HD) available in different lengths (500 and 520); alteration in center adds negative spherical aberration that improves depth of focus, but may reduce stigmatic nature of focal point; some physicians implant Model 5.0 in distance eye and HD in near eye; lower power lenses 0.5 mm longer to give better filling of capsular bag (generally larger in patients with myo­pia)

ReSTOR: approved 3 yr ago; combined refractive-diffractive lens that splits light to form distance and near images (separated to minimize blurring); design  —  aspheric platform with 2 add powers; diffractive and aspheric surface on front; aspheric lenses counteract positive spherical aberration of cornea to focus all light rays to retina; wide di­optic range available with higher A constant; designed for placement through small incision available with Intrepid System on Infinity (important for patients with astigmatism)

ReZoom: refractive multifocal lens with central distance, midperipheral near zones, and another distance zone out­side

Crystalens

Advantages: monofocal lens that gives good quality of night vision; 20/25 and J3 visual acuities (VAs) achieved if used in mini-monovision fashion, targeting small amount of myopia in nondominant eye

Challenges: refractive end point variable because of inability to measure capsular bag size before surgery; myopic surprise occurs at rate of 10% to 15%; Crystalsert injector requires smaller incision; lens’ greater sensitivity to capsular contraction can lead to myopic shift or tilting of lens (rare)

Refractive end point: one-quarter-diopter steps available but not very helpful because of unpredictability of end­point; if capsular bag smaller, lens sits farther back to give hyperoptic result; if capsular bag larger, lens sits ante­riorly and produces myopic result; A constant value of 119; with shorter axial lengths, manufacturer recommends targeting to achieve a little myopia; among all patients in clinical trial, only 50% achieved VA 20/25 or better

Capsular contraction: ideal rhexis size larger than optic and symmetric; speaker recommends using 6.5-mm inked trephine centered on visual axis as guideline for rhexis at 6 mm inside eye; Z syndrome treated with yttium-alu­minum-garnet (YAG) capsulotomy, but induces astigmatism and decreases best corrected vision; asymmetric rhexis can cause asymmetric overlap of haptics, and asymmetric capsular contraction can occur; seen more often in younger patients, possibly because of inflammation; use longer course of steroids and minimize retained cor­tex; if Z syndrome present, YAG performed across fibrosis behind anterior haptic and in center; speaker recom­mends cystoid macular edema (CME) prophylaxis

Tecnis Multifocal Lens

Characteristics: diffractive optic extends to edge; available in silicone and acrylic versions; diffractive optic leads to some loss of light to scatter and loss of contrast; theoretically, better night distance vision obtained with ReSTOR and better dim-light near vision with Tecnis; large add power lens; diffractive pattern on posterior surface; aspheric anterior surface; equal distribution of light between distance and near across all pupil diameters; near vision possi­bly better with large pupil, but distance vision possibly inferior; custom matching of ReZooM lens in one eye (for intermediate vision) and Tecnis in other (for near and distance) marketed in Europe

Light distribution comparison: highly variable amount of light going to near and distance vision in ReZooM lens because of dependence on pupil size; light evenly distributed in Tecnis; more light contributes to distance focus with larger pupils in ReSTOR lens

ReSTOR

Advantages: easy to use; requires small incision; predictable refractive end point; appropriate for any size pupil

Challenges: because of multifocal properties, lower quality of vision than with monofocal lens under dim light, al­though now improved with aspheric design; with higher add power, intermediate vision problematic, but improved with lower add power (D1) lens; good eye health required for multifocal lens; presence of diabetic retinopathy, macular degeneration, or epiretinal membranes reduces performance; threshold for obtaining preoperative op­tical coherence tomography (OCT) lower than with other lenses; small posterior capsule opacifications (PCOs) or folds can disrupt optics

Study: in 36 eyes of 18 patients implanted with ReSTOR aspheric lenses, nearly 80% had VA of 20/25 or better at 3 mo

Lower add power version: D1 has add power of 2.5 at spectacle plane; apodization (different heights and distances between diffractive steps) becomes closer together and smaller, allowing separation of focal points; similar energy balance; with larger pupils, more light goes to distance image in both higher and lower add power lenses

Intermediate range: higher add power version achieves VA of only »20/40; D1 provides broader range of high acu­ity

Study: compared +3 (D1) and +4 in 300 patients implanted bilaterally; similar performance for uncorrected distance vision; D1 performed better at intermediate range, and slightly better at near; patients with D1 held reading mate­rial at 15 in; with higher add power, few patients achieved 20/20 or better at all levels of distance because interme­diate VA only 20/40; with D1 lens, patients achieved better performance at all levels of vision; quality of vision comparable, but slightly more glare with D1

ReZooM

Advantages: provides high level of independence from spectacles and predictable refractive end point; good near vi­sion; may not perform as well as D1 for intermediate vision

Challenges: nighttime glare and pupil size–dependent performance; many elderly patients have small pupils and do not achieve good near vision

Patient selection factors: patient’s desire for independence from spectacles; patient’s understanding and acceptance of compromises associated with lens choice

Surgical Issues

Astigmatism: mandatory to evaluate topography; »25% of patients have >1.5 diopters (D) of cylinder; types  —  with the rule, steep at 90°; against the rule, steep at 180°; irregular keratoconic eye; possible to correct somewhat by placing incision on axis; study showed size of incision mattered; astigmatic keratotomies (AKs) and limbal relax­ing incisions (LRIs) useful at same time as cataract surgery; speaker uses micrometer blade set at 80% of peripheral corneal thickness; results from AKs variable; refractive cataract surgery not appropriate for patients with >1.5 D

Toric lens: appropriate for patients with astigmatism, especially those satisfied with monovision contact lenses; place reference axis marks with patient sitting upright before surgery; place axis marks and rotate lens into position; re­move any residual viscoelastic behind lens; clean cortex well to prevent rotation; currently available in 1.0, 1.5, and 2.0 at cornea plane; rotational stability  —  3.3% of astigmatism correction lost for every degree of off-axis rotation; study of rotational stability compared 200 toric lenses with standard lenses and found mean rotation of <4°; no lenses rotated >15°; important to perform Orbscan topography before and after implantation to estimate average in­duced astigmatism; wider range, including 0.5 D, available in future

Surgery: speaker recommends performing on-axis incision to manage lower amounts of astigmatism, using LRIs and AKs up to 1.0 D, and using toric lenses for 1.0 to 2.5 D; possible to couple toric lens with AK to correct slightly higher astigmatism; at 2.5 to 3.0 D, consider 2 separate procedures; multifocal lenses appropriate for astigmatism <0.5 D; monofocal appropriate for £ 0.75 D when targeting distance vision in patient who does not want spectacles

Case report: patient with 3 D of astigmatism; placed toric T5 lens and performed superior and inferior AKs; antici­pated 1 D residual astigmatism; after surgery, patient had 0.7 D and 20/25 VA

IOLs in patients after refractive surgery: corneas behave differently; speaker does not recommend performing AK because of variability of outcome; prefers to wait and do refractive correction later with laser assisted in-situ ker­atomileusis (LASIK); consider Crystalens over multifocal IOLs because spherical aberration compromises optics; avoid using multifocal IOL in patients after radial keratotomy (RKI) because of diurnal variability; wait for postop­erative refractions to stabilize before performing enhancements

Problems After Surgery

Distance vision: ask patients about night vision and any change in postoperative refraction: examine posterior cap­sule and macula for epiretinal membrane or CME

Cystoid macular edema: endophthalmitis most serious complication, but CME most frequent cause of decline in vi­sion after uncomplicated cataract surgery; treat with nonsteroidal medication prophylactically several days before surgery and continue for 1 mo after (longer in patients at higher risk); study  — compared treatments with steroids alone to steroids plus nonsteroidal agents in patients with monofocal lenses; 5 eyes (2%) in steroid-alone group de­veloped CME vs zero eyes in the combination group; rate possibly higher for multifocal lenses because subtle thickening of macula less well-tolerated

IOL Asphericity and Presbyopia Correction

Donald N. Serafano, MD, Associate Professor of Ophthalmology, University of Southern California, Los Ange­les, CA, and Private Practice, Los Alamitos, CA

Patient selection: speaker offers presbyopia-correcting IOLs to all candidates, depending on health of cornea, astigmatism (including surgically induced), and personality of patient; presbyopia-correcting types of lenses include refractive, refractive-diffractive, accommodating, and astigmatism-correcting; speaker uses auto-kera­tometer results and steep axis; aims for <0.75 D residual astigmatism for patients receiving ReSTOR; uses toric cal­culator for toric and ReSTOR lenses and corrects for astigmatism with LRI or laser correction; informs patients that they can go without glasses 80% to 90% of time, but may need glasses for particular tasks; presbyopic-correcting IOLs best for patients strongly motivated to avoid glasses

Lens types: refractive-diffractive lenses not dependent on pupil size; astigmatism-correcting lens  —  steep axis very important; Alcon toric lens had <4° rotation; appropriate for patients needing better distance and near vision

Other issues: surgically induced astigmatism  —  important to use keratometer and calculate values before and at £3 mo after surgery for »50 cases having incisions of similar size and location; enter this number in toric calculator to obtain individualized surgically induced corneal astigmatism for that incision size and location; LRI  — perform LRI if patient wants ReSTOR, and residual astigmatism estimated at >0.75; if estimated residual astigmatism higher, second procedure necessary; PCO  —  important for presbyopic-correcting IOLs (more sensitive); speaker performs YAG capsulotomies slightly earlier on patients with ReSTOR; bilateral use  —  speaker prefers patients to use lens for both eyes

Poor outcomes: causes of poor performance in multifocal lenses similar to those for monofocal lens; neuroadaptation  —  real phenomenon because patient sees new image; VA and satisfaction improve over time; reading distance too close  —  reading and computer distance improved with ReSTOR +3 version, which has +250 reader and fewer rings; equivalent apodized (3.5 mm across) and refractive sections, zones, and lengths; not appro­priate for sulcus; ReSTOR has 3-piece version that can be used for sulcus with 0.5 D difference in IOL power; LRI necessary for toric lens

Asphericity: allows focus on a single point; no complaints of too close reading distance

Suggested Reading

Amesbury EC, Miller KM: Correction of astigmatism at the time of cataract surgery. Cur Opin Ophthalmol 20:19, 2009; Al­fonso JF et al: Visual function after implantation of an aspheric bifocal intraocular lens. J Cataract Refract Surg 35:885, 2009; Awasthi N et al: Posterior capsular opacification: a problem reduced but not yet eradicated. Arch Ophthalmol 127:555, 2009; Blaylock JF et al: Intermediate optimization of vision with bilateral nonaspheric multifocal intraocular lens implantation. J Cataract Refract Surg 35:303, 2009; Buel W, Findle O: Effect of intraocular lens design on posterior capsule opacification. J Cataract Refract Surg 34:1976, 2008; Buznego C, Trattler WB: Presbyopia-correcting intraocular lenses. Curr Opin Oph­thalmol 20:13, 2009; Cillino S et al: One-year outcomes with new-generation multifocal intraocular lenses. Ophthalmology 115:1508, 2008; Dick HB: Recent developments in aspheric intraocular lenses. Curr Opin Ophthalmol 20:25, 2009; Fuchs HA et al: Multiple component intraocular lens: first human implantation. J Refract Surg 25:390, 2009; Hermans EA et al: Development of a ciliary muscle-driven accommodating intraocular lens. J Cataract Refract Surg 34:2133, 2008; Ishii Y, et al: Mesopic contrast sensitivity and ocular higher-order aberrations in eyes with conventional spherical intraocular lenses. Am J Ophthalmol May 6, 2009, [Epub ahead of print]; Kohnen T: Multifocal IOL technology: a successful step on the journey to­ward presbyopia treatment. J Cataract Refract Surg 34:2005, 2008; Maxwell WA et al: Performance of presbyopia-correcting intraocular lenses in distance optical bench tests. J Cataract Refract Surg 35:166, 2009; Mendicute J et al: Toric intraocular lens versus opposite clear corneal incisions to correct astigmatism in eyes having cataract surgery. J Cataract Refract Surg 35:451, 2008; Montes-Micro R, et al: Analysis of the possible benefits of aspheric intraocular lenses: review of the literature. J Cataract Refract Surg 35:172, 2009; Ohtani S et al: Intraindividual comparison of aspherical and spherical intraocular lenses of same material and platform. Ophthalmology 116:896, 2009; Pepose JS: Maximizing satisfaction with presbyopia-correcting intraocular lenses: the missing links. Am J Ophthalmol 146:641, 2008; Trueb PR et al: Visual acuity and contrast sensitivity in eyes implanted with aspheric and spherical intraocular lenses. Ophthalmology 116:890, 2009; Wilkiins MR et al: Spectacle use after routine cataract surgery. Br J Ophthalmol May 7, 2009 [Epub ahead of print].