All cataract patients have some artifact or light-scattering phenomenon after IOL implantation, regardless of implant style, size, or material. Surgeons see this in many forms, characterized as either TCS (temporal crescent syndrome), dysphotopsia, edge glare, or other monikers.
In our clinic, we have seen this for over 20 years. It does not discriminate between lens manufacturers. The patient describes the phenomenon at the one-day post-op visit, is told it is “normal” and will go away, or that “you will get used to it”. After 3 months or so, most patients do accept it, although it is generally still there.
Indeed, in my own early experience, I asked my technician (who is still with me) to document any artifact with pictures or drawings in our post-op charts and after several weeks discovered it occurred in almost all patients. I asked her to stop since it was such a common occurrence in order to save time
Lens manufacturers struggle with this issue for several reasons. The industry standard for incision size is 3.0mm in order to minimize post-op astigmatism. Since 1991, when the first two manufacturers had FDA-approved foldable IOLs (AMO and STAAR), there has been a constant “race” to get to the “smallest possible wound.
Manufacturers have used several methods to enable their injector/lens combinations to get through smaller and smaller wounds, but, generally, have done this by making the lenses smaller and thinner.
The ALCON Acrysof IOL platform uses a hydrophobic acrylic material with a refractive index of 1.55, the thinnest in the industry. This lens gets most of the attention for artifact, but this may also be due to its 56% US Market share. The properties of the lens, particularly its thinness, enable it to go through its smaller injector (2.4mm). However, because the material is so rigid, the 6.0mm optic must have three (3) different-sized cartridges as the power-scale is ascended and the IOL becomes thicker.
All other manufacturers face similar issues, but generally, the larger or thicker the optic, the larger the incision. Astigmatism control is more important to the surgeon than potential artifact that “goes away”.
Oval optics have been around since 1989 and the introduction of 5.0mm optics and the 5.0mm x 6.0mm Clayman lens. These PMMA optics were introduced to minimize loss of market share to the budding foldable lens industry. As surgeons discovered they could minimize astigmatism by using the smaller foldable lens incision of 4.0mm with a 6.0mm optic, the shift to foldables crowded out these smaller PMMA lenses.
Before PMMA lost favor, there was a similar race to eliminate artifact. IOLAB and Intermedics, the two leaders for most of the 1980’s, had started with 5.0mm optics early, and escalated from the original 5.0mm to 7.0mm and were discussing 7.5mm lenses with 14.5mm-wide loops. At this point, the principal lens controversy was over sulcus or bag placement and sulcus proponents saw no need to limit optic size since it covered a multitude of “sins” (centration, tilt, and artifact among them).
In the 90’s as foldables grew, the retina surgeons gained power as they begandealing with more and more post-op IOL patients. Concerns about material and overall length arose, but the biggest issue was optic size. Retina surgeons would prefer to work on patients with the largest possible optic. Alcon now has a large Acrysof( 6.5mm) for “special” patients, although it requires a larger incision.
The most popular sub-6.0mm IOLs currently in use are the B&L Crystalens (5.0mm) and the Softec Series from Lenstec (5.75mm). Neither company reports debilitating artifact with either lens, although there are some reports in the literature on the Crystalens.
Minimizing or eliminating artifact in our cataract patients would be a major step in improving one-day VAs. The ideal product would need to:
Maintain a smaller incision size (sub-3.0) and, ultimately, be capable of going through a 2.4mm wound or smaller.
Not be susceptible to tilt or decentration.
Have the widest possible temporal “window”.
Utilize existing cartridges and injectors.
Have the least-burdensome regulatory pathway.
An Oval Softec HD would allow for a 5.75mm x 6.25mm optic with a 12.5mm overall length, and would cover the needs of expressed above. If proven, it would minimize artifact, give the retinal surgeon a larger window, and improve early VAs.