New research into accommodating intraocular lenses indicates that many patients who get these implants will enjoy good distance and near vision. The first hint that intraocular lens implants could accommodate came back in 1986, when Spencer Thornton, M.D., used A-scan biometry to report on anterior movement of a three-piece loop IOL.1 He found that this forward movement allowed some patients to have good uncorrected distance and near vision simultaneously. At the time, few understood the mechanism that caused this forward movement, but since then research has given us new insight into IOL movement. 

Laying the Groundwork
In 1986 J. Coleman reported that during accommodation, the ciliary body applies pressure to the vitreous as it contracts. This pressure, in combination with the increasing laxity of the zonules during accommodation, caused the natural lens to move forward.2

This may explain Dr. Thorntons observation in a pseudophakic eye. As a patient accommodates, the ciliary muscle contracts, applying pressure to the vitreous body and increasing laxity of the zonules. This causes the IOL to move forward, increasing its relative power approximately 0.15D to 0.20D for each 0.1mm of forward movement. Thus, 1mm of forward movement can result in 1.50D of pseudo-accommodative amplitude. 

In 1989 J. Stuart Cumming, M.D., observed a similar forward movement in plate haptic intraocular lenses. Utilizing A-scans on 10 patients, he demonstrated an average movement of 0.7mm. A more recent study confirmed these findings with magnetic resonance imaging.3

Building on this important observation, Dr. Cumming and German researcher Jochen Kammann, M.D., developed seven prototype IOLs in an attempt to achieve a reproducible pseudo-accommodative amplitude utilizing the vitreous pressure model.4












The CrystaLens accommodating IOL (inset and upon insertion) has had good results in carefully screened presbyopes.
Clinical Experience
From the beginning, pseudo-accommodative amplitudes were demonstrated with enhanced uncorrected reading vision, but several of these lenses subluxated into the anterior chamber. Eventually, they developed a design utilizing a 4.5mm optic, which is hinged with polyimide haptics. This allows forward movement, but prevents subluxation. This lens, called the C & C Vision CrystaLens AT-45 IOL, is in FDA trials and has been studied in other countries as well.

Ophthalmologists Howard Fine, Richard Hoffman and Mark Packer have reported on their clinical experience with this lens, having evaluated 82 patients with more than one month of follow-up. Their surgical technique has been to target
-0.50D in the first eye and plano in the second. Theyve used a 3.5mm clear corneal incision, a 4mm diameter round centered capsulorhexis, and implant the lens without an injector.

They instilled atropine 1% at the end of surgery to let the lens fixate as far posterior as possible in an accommodation-relaxed environment. Theyve evaluated distance-corrected near vision (i.e., reading at 6 inches through distance correction); distance-corrected intermediate vision (reading at 32 inches through distance correction); and uncorrected distance, intermediate and near vision.
Looking at the monocular results, 37% of subjects achieved 20/20 vision at distance without correction and 85% achieved 20/40 or better. At near, 29.6% were J1 or better, and 92.5% were J3 or better.5

The Most Telling Data
An appropriate historical comparison appears in the publications by Richard L. Lindstrom, M.D., and Roger Steinert, M.D., in the FDA-controlled clinical trials of multifocal IOLs. In these studies 37-48% of monofocal intraocular lenses resulted in J3 or better distance-corrected near acuity.6

Binocular results provide the most telling data. Utilizing two eyes, 71% of patients achieved 20/25 or better at near and distance, 96% were J1 or better at intermediate, and 75% were J1 or better at near without correction when using both eyes. Fully 100% were 20/32 or better at distance, and J3 or better at intermediate or nearwhich allows for comfortable reading of a newspaper and legal driving without correction.

This result is far superior to results with monofocal and multifocal intraocular lenses, which achieved 20/20 and J1 in only 18% of patients and 20/30 and J3 in about 60% of patients.6

Additionally, contrast-sensitivity testing in these patients demonstrated neither loss of contrast nor loss of lines of best-corrected visual acuity. Further, these patients did not note glare and haloes, visual side effects commonly associated with multifocal IOLs.

Accommodating IOLs are showing extraordinary promise for treatment of the cataract patient as well as for select cases of refractive lensectomy, especially in the hyperopic presbyope. This technology, now available outside the United States, may achieve FDA approval in late 2003. Accommodating IOLs will be a welcome addition as a surgical alternative for treating both the cataract patient as well as the patient with a refractive error and presbyopia. 

Dr. Karpecki is director of research for the Moyes Eye Center in Kansas City, Mo. He has no financial interest in any of the products he mentions.
Richard L. Lindstrom, M.D., contributed to this article.

1. Thornton S. Lens implantation with restored accommodation. Curr Canadian Ophthalmic Prac 1986;4:60-62.
2. Coleman J. On the hydraulic suspension theory of accommodation. Trans Am Ophthalmol Soc 1986;846-868.
3. Strenk SA, Semmlow JL, Strenk LM, et al. Age-related changes in human ciliary muscle and lens: a magnetic resonance imaging study. Invest Ophthalmol Vis Sci 1999;40(6):1162-1169)
4. Cumming JS, Kammann J. Experience with an accommodating IOL. J Cataract Refract Surg 1996 Oct;22(8):1001.
5. Breen MJ, Cumming JS, Kramsky PS. White paper for international surgeons: The C&C Vision CrystaLens Model AT45 silicone multipiece intraocular lens. C&C Web site:
www.candcvision.com.
6. Steinert RF, Post CT Jr, Brint SF, et al. A retrospective, randomized, double-masked comparison of a zonal-progressive multifocal intraocular lens and a monofocal intraocular lens. Ophthalmology 1992 Jun;99(6):853-60.

Vol. No: 139:12Issue: 12/15/02