Accommodation allows the eye to change its refractive status to produce a clear image at near. In classic theory, Helmholtz1 showed that accommodation is achieved when the ciliary muscle contracts. As this muscle contracts, the release of circumferential tension on the zonules leads to a curvature change of the crystalline lens, resulting in a dioptric power change in the eye. Loss of accommodative amplitude (ie, presbyopia) usually occurs after 40 years of age.
The Synchrony Dual Optic lens (Visiogen, Irvine, California) (Figure 1) is a single-piece silicone IOL with a high plus anterior optic—always 32.00 D—coupled with a negative posterior optic. For distance vision, the two optics rest close together. When the patient focuses on a near target, forward movement of the front optic causes an increase in effective IOL power. As the ciliary body relaxes, capsular bag tension brings the front optic back to the resting state, thus restoring emmetropic distance focus. We have proved this with ultrasound biomicroscopy testing (Figure 2). We have also proved that this IOL kept functioning with adequate movement of the optics during accommodation, in patients implanted more than 1 year ago.2
INCLUSION, EXCLUSION CRITERIA
We have implanted the Synchrony IOL after conventional phacoemulsification in more than 100 patients. Thirty-two patients were implanted binocularly. Inclusion criteria were (1) aged 40 or more years, (2) the presence of cataracts, (3) fewer than 2.00 D of preoperative astigmatism, and (4) the ability to comply with follow-up visits. Exclusion criteria were (1) a patient having only one eye with potentially good vision, (2) a significant ocular pathology, (3) history of intraocular surgery, (4) diabetes, or (5) use of systemic medications that affect accommodation.
The surgery consisted of conventional clear-cornea phacoemulsification and complete cortical clean-up with anterior capsule polishing. The lens was implanted with Synchrony's preloaded injector, through a 3.6 mm to 3.8 mm incision. The injector delivers the lens into the bag in one easy and controlled step. A standard regimen of antibiotics-steroids was given after surgery. Follow-up visits were scheduled at 1, 3, 6, and 12 months after surgery. Early Treatment of Diabetic Retinopathy Study charts for distance, intermediate (80 cm), and near (40 cm) vision were used for visual acuity testing. Retroillumination photographs were taken at each visit to evaluate IOL centration and capsular bag opacification. Reading speed was also assessed in a subgroup of patients.
RESULTS
From the 32 binocular patients evaluated, 65% were female. Mean follow-up was 10.4 months, and the mean age was 61 years (range, 41 years to 74 years). The mean visual acuities were outstanding: Average UCVA was 0.02 logMAR (20/21 Snellen); uncorrected intermediate visual acuity was -0.10 logMAR (20/16 Snellen); and uncorrected near visual was 0.1 logMAR (20/25 Snellen). After correcting these patients for distance, best corrected distance visual acuity was -0.08 logMAR (20/17 Snellen). Distance corrected intermediate visual acuity and distance corrected near visual acuity remained unchanged (Figure 3).
Nintey-one percent of the patients achieved this 20/40 for distance, 97% for intermediate, and 84% for near vision. With distance correction in place, the percentage of patients achieving 20/40 or better improved to 100% for intermediate and 87% for near.
COMPARED WITH THE ACRYSOF
We performed reading speed in a subset of patients (n=25) and compared it with a cohort of 15 patients matched for age, who were binocularly implanted with the AcrySof IOL (Alcon Laboratories, Inc., Fort Worth, Texas). This test was performed with full distance correction in place, and without near add power. Reading acuity was better with the Synchrony IOL (logRAD 0.17 [Snellen 20/30]) versus the AcrySof IOL (logRAD 0.51 [Snellen 20/65]), and this difference was statistically significant (P<0.001). At newspaper print size (logRAD 0.4), the average reading speed for Synchrony was 160 words/minute versus 23 words/minute for the control (P<0.001), with 88% of Synchrony patients reading at least 80 words/minute (ie, the lower reading speed threshold) versus 13% of control patients.
We have worked with this lens for more than 2 years and found that it combines the advantages of a monofocal IOL (ie, quality of vision, excellent contrast sensitivity) with improved near and intermediate function, without inducing photopic phenomena (ie, halos and glare). It is worthy to note that our first concern with this lens was not its performance, but the possibility of interlenticular opacification (ie, Elshnig pearls and fibrosis between the two optics). Our initial cohort of patients have been implanted with this lens for more than 2 years, and we have not seen one case of this disease. The capsular bag remains clean and functional, which we believe is due to continuous aqueous exchange between the bag and the anterior chamber that keeps the lens epithelial cells quiet.
SECOND-GENERATION IOLs
Presbyopia correction has been a challenge for the ophthalmic community for many years. Second-generation accommodative IOLs, including the Synchrony, are a promising alternative for pseudophakic presbyopia. This dual optic accommodating IOL provides very good UCVA, and with distance correction in place, maintains or improves near and intermediate vision. The Synchrony also demonstrated good reading performance. It shows potential advantages over multifocal IOLs, because intermediate vision for activities including computer work, dashboard viewing, cell phone dialing, and grocery shopping is excellent.
Ricardo Alarcon, MD, is from the Department of Ophthalmology at Servioftalmos, in Bogotá, Colombia. Dr. Alarcón states that he is a paid consultant to Visiogen. He may be reached at ralarconji@msn.com.
Victor Bohórquez MD, is from the Department of Ophthalmology at Servioftalmos, in Bogotá, Colombia. Dr. Bohórquez states that he is a paid consultant to Visiogen. He may be reached at vibo4@hotmail.com.
Up Front | Jan 2007
Functional Vision With a Dual Optic Accommodating IOL
The high plus anterior optic of the Synchrony Dual Optic IOL provides excellent vision at all distances.
Ricardo Alarcon, MD, and Victor Bohórquez MD
