Professor Parel discusses assessment of accomodation preservation after cataract surgery
It is difficult to assess the extent of accommodation preservation in patients after cataract surgery, according to Professor J.M. Parel from the Bascom Palmer Eye Institute, Miami, Florida, USA, speaking at the Croma symposium during last year's ESCRS meeting in Paris.
The aetiology of presbyopia
As previously reported in OTEurope,1 presbyopia is clinically manifested when the near point of a patient becomes more remote than their usual near working distance. It has also been noted that the equatorial lens diameter directly influences accommodation as a result of its increase in size over time. As the equatorial lens diameter increases the amount of tension on the ciliary muscle decreases causing a decrease in the baseline ciliary muscle length resulting in the decline of accommodative amplitude.
History of restoring accommodation
The restoration of accommodation has been researched for a long time and it was Dr Tsumotu Hara in 1990 who conceived the idea of double optic, accommodative IOLs.2
Today, two accommodative IOLs are currently marketed in Europe: the Crystalens (Bausch + Lomb), which only offers 1 D of accommodation at best, and the Synchrony (Visiogen, AMO), which might produce 2.2 D of accommodation.
A major problem in cataract surgery, however, is posterior capsule opacification (PCO) which, if uncontrolled, can completely eradicate the restored accommodation. Previous examples of this can be seen in several studies one of which demonstrated how lens tilting can occur when there is excess new tissue growth.3,4
"We see the same issues during lens refilling surgery,5 " commented Prof. Parel. "In performing the surgery," he continued, "we encounter the very same problem of PCO during patient follow-up. In a rabbit the rate at which PCO occurs is extremely fast, but in a monkey it is more like that of a child and not a 50-year old person."6
Prof. Parel went on to discuss the world clinical cataract status, asserting, "Currently, 20??000 cataracts are being removed every day, which means there is an equal amount of potential PCO instances. Of course, surgeons can perform a YAG capsulotomy but there are complications associated with this, it costs money and prevents restoration of accommodation. So, how can we assess PCO in the patient?"