NEW PHAKIC IOL MODEL HAS GOOD RESULTS

A new model of the Staar Surgical Visian ICL™ produced good short-term results in a small series of myopic patients, reported Erik Mertens MD, FEBOphth, Medipolis Eye Centre, Antwerp, Belgium, at the 16th Winter Meeting of the ESCRS. The new lens has a small hole in the centre of its optic to allow the passage of aqueous and eliminate the need for iridectomy in patients receiving the lens. “We all know that when we perform an iridectomy it is bothersome for the patient. Furthermore, iridectomies can result in pigment dispersion in the eye and bleeding, which are two things you want to avoid during surgery. The new version of the lens makes the implantation procedure more like a LASIK procedure,†said Dr Mertens.

He said that in 48 eyes of 24 patients who underwent implantation of the lens, uncorrected distance visual acuity and best corrected distance visual acuity was 1.1 and all eyes were within 0.5 D of emmetropia at one month’s follow-up. Moreover, there was no postoperative elevation of IOP in any eyes and the holes in the implant did not appear to produce any perceptible effect on vision. Preoperatively the patients’ spherical refraction had a mean value of -6.0 D, and ranged from -3.5 D to -8.75 D. In addition, none of the eyes had more than 0.75 D of cylinder, their mean anterior chamber depth was 3.28mm, and their mean IOP was 15.0 mmHg, with values ranging from 10.0 mmHg to 20.0 mmHg. At one month’s follow-up, all eyes were within half a dioptre of the intended refraction and 80 per cent of eyes gained one line or more of best-corrected visual acuity. The efficacy index of the lens was 1.17 and its safety index was 1.07. In addition, IOP values remained low with a mean value of 11.0 mmHg and a range from 9.0 mmHg to 14 mmHg, Dr Mertens said. The new Visian 4C posterior chamber phakic IOL is identical to the previous 4B model of the ICL except for a small hole, or aquaport, 360 microns in diameter in the centre of the optic, Dr Mertens noted. Like the 4B model, the new version of the ICL is a foldable phakic IOL composed of a collagen polymer material and has a plate haptic that rests in the ciliary sulcus, he said.

“The aquaport is designed to restore a more natural aqueous flow around the natural crystalline lens and through the port in the ICL. In this way it eliminates the need for iridectomies or iridotomies,†Dr Mertens said. He noted that, out of concern, that the hole might induce photic phenomena like glare and haloes under night driving and similar conditions; his first two patients implanted with the lens received the new 4C version in one eye and the older 4B version without the aquaport in the other eye, but were not told which eye had which type of IOL. Postoperatively, they could not tell which eye had the new ICL design, Dr Mertens said.

Viscoelastic material

An additional advantage of the new lens is that it makes it much easier to remove viscoelastic material following implantation, Dr Mertens said. He noted that he uses methylcellulose in all of his ICL implantation procedures, and he provided a video demonstration of the technique he uses to remove it at the conclusion of surgery. “I will direct my irrigation port through the aquaport giving it a push; it pushes the methylcellulose out from the posterior surface of the ICL. So people using hyaluronic acid, where it is extremely important to remove all of it, can do a better job and it is much easier to push that from behind the ICL into the anterior chamber where it can be easily aspirated,†he said. Dr Mertens said that when he assesses eyes for the sizing of the ICL he measures the sulcus-to-sulcus diameter with a Quantel or Sonomed UBM device, which provides an average of 10 measurements, and he then compares them to white-to-white measurements obtained with the Orbscan. In addition, he always makes sure that there is a vault of at least 200 microns between the posterior surface of the IOL’s optic and the crystalline lens. That way, even if the vault varies by 100.0 microns as a result of accommodation and other factors, eyes with the implant will still remain within the safety zone. “In our experience to date with the new ICL with an aquaport we haven't seen any IOP elevation and have had very good predictability and our patients have reported no side effects,†he concluded.