Modifications of haptic design yields benefits
Despite the high standard of modern cataract surgery, posterior capsular opacification (PCO) still remains the most frequent longterm complication. Several new foldable multi- or single piece IOLs with sharp optic edge design have been developed to prevent PCO. Previous studies depict that the presence of a sharp posterior optic edge is crucial for PCO prevention, whereas the IOL material and haptic design may be of less importance.
Due to refinements in phacoemulsification technology, cataract can be removed through incisions smaller than 2 mm in a procedure called microincision cataract surgery (MICS). The benefits of MICS are reduced surgically induced astigmatism, rapid visual rehabilitation and more stable wound construction. The early MICS intraocular lenses showed higher PCO incidence, probably due to hydrophilic acrylic material and deviation from the common 3-piece or 1-piece open-loop haptic designs. Recently hydrophobic acrylic 1-piece and 3-piece IOLs are finally commercially available for microincision cataract surgery.
In a present study, recently published in the British Journal of Ophthalmology,1 we compared the development of PCO as well as the clinical outcome between a 1-piece and a 3-piece MICS IOL. Here we discuss the study, highlighting the benefits of modifying the haptic design of a MICS IOL.
Our prospective randomized patient and examiner-masked clinical trial with intraindividual comparison was performed at the Department of Ophthalmology at the Hietzing Hospital (Vienna, Austria). Forty patients (80 eyes) were recruited consecutively.
Each patient received a 1-piece AF-1 iMICS NY-60 IOL (Hoya, Japan) in 1 eye and a 3-piece AF-1 Y-60H MICS IOL (Hoya) in the contralateral eye to allow intraindividual comparison. In 20 cases, the 1-piece IOL was implanted in the right eye and in 20 cases in the left eye.
Surgery was performed by 1 of 5 experienced surgeons, where the same surgeon operated both eyes of a patient. Cataract surgery was performed as a standardized procedure. In all cases, there was a rhexis-overlap with the IOL optic along the entire circumference at the end of the surgery.
A postoperative examination was performed 1 year after surgery. Uncorrected (UCVA) and best spectacle corrected distance visual acuity (BCVA) were measured using ETDRS charts. Using a standardized evaluation form, the following parameters were assessed subjectively: IOL position and centration, and rhexis-IOL overlap. The amount of anterior capsular opacification (ACO) and of posterior fibrosis (fibrotic PCO) were graded by subjective scale from 0 to 3 (0 = clear capsule, 3 = severe fibrotic opacification). Digital retroillumination photographs were obtained with a digital camera mounted on a modified slitlamp (Carl Zeiss Meditec AG, Jena, Germany) with an external flashlight source, which provides coaxial illumination from the flash pack through a fibreoptic cable to the camera. An automated image analysis software, Automated Quantification of After-Cataract (AQUA), for objective PCO evaluation was used. The program detects the capsulorhexis edge semiautomatically (computer aided). The AQUA software calculates the grade of disorder (entropy) of a bitmap. This value is converted to a score between 0 and 10 (0 = clear capsule, 10 = exceptionally severe PCO).