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IOLs anatomical prerequisites for accommodation?
Ophthalmologists must improve IOL sizing, its position on the optical axis and IOL centration and tilt if they want to achieve accommodation. “These factors are IOL anatomical prerequisites that must be improved to make accommodation possible,” Dr. Philippe Sourdille told delegates.
Dr. Sourdille told the audience that there are many processes involved in accommodation, including the cornea and the pupil, but he said he would focus on the lens, zonular relaxation or tension and ciliary process movements.
He outlined a study he conducted on eye bank eyes that showed, that in capsular bag diameter increases with age, with axial length and with cataract formation. This causes interesting effects on the position of the lens relative to the ciliary ring.
In his study, 80% of had their lens equator on the ciliary ring plane, but in 20% were of the eyes the equator was behind the ciliary ring, mainly in patients who had greater axial length or who had caracterous eyes.
He told the audience that when the lens is placed behind the ciliary ring it has consequences for accommodation. “When that happens, the lens is behind the ciliary apex plane, which means the zonular system is totally distorted.” This is an obstacle to accommodation.
For this reason, accurate lens sizing is crucial. Dr. Sourdille cited a study by Rossella Apolloni from Rome, who studied the postoperative impact on the capsular bag.
It showed in nearly all cases that distance between the ciliary ring and the capsular bag went from 0.52 to almost 0.02. So IOL sizing is very important, said Sourdille. If you enlarge the capsular bag you will have an impact on the ciliary processes, which is not good for accommodation.
The position on the optical axis is also extremely important for accommodation, Because if you are two far or two anterior you will be myopic or hyperopic, he said, So we should consider the position on the visual axis and the ciliary plane as a reference.
Dr. Soudille also showed data from the same study that indicated that tilting was a often problem. In the series more than half were either tilted or posterior 12 months post-op, with 8 or 33% posterior. Centration, too, was a problem, and surgeons should make special efforts to ensure their IOLs are remaining central.
In conclusion, Dr. Sourdille noted that the accommodation problem is not totally solved, but in the meantime the capsular bag should be thoroughly documented and you must use a properly sized IOL.