The first generation Crystalens accommodating intraocular lens (IOL) (eyeonics) was approved by the FDA in November 2003 and
has since undergone two revisions. The first involved modification of the lens optic to a "square" rather than smooth edge
in order to reduce the incidence of asymmetric capsular fibrosis, which could cause capsular contraction and IOL tilt (AT-45).
The second revision involved enlarging the lens optic to 5 mm, modifying the haptic plates to a more square shape, for increased
capsular support, and increasing the arc length of the haptics for greater stability (Five-0). Each of these revisions provided
greater stability and predictability.
In order to increase functional near vision with this lens, a third revision was made and the ensuing lens is known as the
Crystalens HD. In lab testing, this lens provided greater depth of field than the parent AT-45 lens and better contrast as
measured by modulation transfer function, an objective measure of contrast, than ReSTOR (Alcon) or ReZoom (AMO) implants.
We were involved in a FDA multicentre study, the purpose of which was to determine surgical outcomes with this new fourth-generation
lens and to establish whether it would degrade contrast acuity in human subjects.
Who's in and who's out
After Institutional Review Board (IRB) approval of the study protocol, a total of 125 primary eyes were implanted with the
Crystalens HD. Inclusion criteria included patients aged 18 years or over, presence of a visually significant cataract, less
than 1 D of corneal astigmatism and the potential for best corrected visual acuity (BCVA) of 20/25 or better in both eyes.
Surgery was performed using standard phacoemulsification techniques and the lens was implanted using an injector system. Postoperatively,
patients were evaluated at one day, seven to 14 days, one to two months, and four to six months.
For analysis of uncorrected and distance-corrected visual acuity VA, we selected patients who achieved a target refraction
within 0.5 D of the intended target. We also conducted a comparison of monocular uncorrected and distance-corrected near VA
with results of a randomly selected, similar sized group of patients from prior studies of the parent lens, AT-45, and the
third-generation Crystalens Five-0.
Facts and figures
Sixty eyes remained in follow-up by the four to six month mark and were within 0.5 D of intended target. Mesopic contrast
sensitivity testing with and without glare (Figures 1 & 2) revealed no significant difference between Crystalens HD eyes and eyes tested previously with the AT-45 parent lens. A monocular
uncorrected distance VA (UCDVA) of 20/40 was achieved by 100% of patients, 20/32 by 86.6%, 20/25 by 61.6% and 20/20 by 41.6%
of patients. Monocular uncorrected intermediate VA (UCIVA) of 20/40 was achieved in 100% of patients, 20/32 by 96.6%, 20/25
by 93.3% and 20/20 by 80% of patients. Monocular uncorrected near VA (UCNVA) of J3 was achieved by 100% of patients, J2 by
80% and J1 by 55% of patients.