Phakic lens valuable for high ametropia after corneal transplantation

Study shows safety and efficacy in both phakic and pseudophakic or aphakic yes, including complicated cases.

ByMichela Cimberle

STOCKHOLM – The toric Verisyse phakic IOL is a safe and reliable way of correcting refractive errors, particularly high astigmatism, in both phakic and aphakic patients after penetrating keratoplasty or deep anterior lamellar keratoplasty, according to one surgeon.

José L. Güell

“This type of phakic IOL provides good centration, stable fixation and safe distance from the endothelium. We are sure that, in the future, a foldable version of the toric iris claw lens can be implanted through a smaller incision, like we do it for the VeriFlex (Advanced Medical Optics), thus avoiding further induction of astigmatism,” OSN Europe/Asia-Pacific Edition Editorial Board Member José L. Güell, MD, said.

In many cases, post-keratoplasty eyes need a toric implant. Evaluating the reference axis, before and during surgery, is mandatory.

“I use the ophthalmometer, which allows me to fix a reference point at the limbus, but the slit lamp or any other method can be used, provided that a reference axis is clearly marked preoperatively,” Dr. Güell said at the meeting of the European Society of Cataract and Refractive Surgeons.

Even a small misalignment will result in undercorrection or even in an increase of the astigmatic error, he said.

“A deviation of only 4% from the correct axis will lead to an undercorrection of about 14%, a deviation of 10% can lead to an undercorrection of 34%. A 30% misalignment will result in a complete axis change with the same, or even more, astigmatic value. Above 30%, the axis will change and there will be a severe increase of the astigmatism,” Dr. Güell said.

Surgery requires precision and experience, particularly at the enclavation stage, and care in avoiding contact with the endothelium.

“One of the keystones is using a cohesive viscoelastic, like Healon (sodium hyaluronate, AMO), to protect the endothelium. In post-keratoplasty eyes, this is even more important,” he said.

Postoperatively, modern imaging technology, such as the Visante anterior chamber OCT (Carl Zeiss Meditec) provides invaluable support in evaluating the performance of this lens during the follow-up, he said. Central and peripheral anterior chamber depth, as well as the distance of the phakic IOL from the endothelium and from the crystalline lens, should be evaluated with these instruments at least once a year.

Remarkable improvement in phakic eyes

Dr. Güell presented the preliminary retrospective evaluation of 14 phakic and 10 aphakic eyes implanted with the toric Verisyse (AMO) lens. All eyes had previously undergone PK or deep anterior lamellar keratoplasty (DALK). In some eyes, other refractive procedures had been attempted to correct the refractive error that followed corneal grafting.

In the group of 14 phakic eyes (13 patients), nine were post-PK and five post-DALK. Nine eyes were treated for keratoconus, two for irregular astigmatism after LASIK, one for perforating trauma, one for post-LASIK ectasia and one for postoperative endophthalmitis. The mean follow-up period after implantation of the lens was 36 months.

“Mean best corrected vision improved from 20/63 preop to 20/50 postop. A mean uncorrected vision of 20/50 was achieved,” Dr. Güell said.

“Mean spherical equivalent improved from –5 D preop to –0.4 D postop. Mean astigmatism decreased from –3.6 D to –2.75 D.”

The implant proved to be safe in terms of endothelial preservation. The mean endothelial cell density of donor grafts was 2,690 cells/mm². After keratoplasty and before phakic IOL implantation, it was 1,983 cells/mm². At the last control after phakic IOL implantation, it was 1,813 cells/mm².

“These numbers are quite similar to the data of [phakic] IOL implantation in eyes without corneal transplantation,” Dr. Güell noted.

Effective in difficult cases

The five aphakic and five pseudophakic eyes were complicated cases, thus difficult to evaluate and compare with eyes without transplantation, Dr. Güell said.

Five eyes had previously undergone complicated cataract surgery, and one eye underwent retinal detachment surgery. There were also two post-traumatic cases, one herpes case and one Peters’ anomaly. The mean follow-up after implantation of the lens was 15 months.

“Secondary [phakic] IOL implantation proved effective in regaining some useful vision also for these highly compromised eyes,” Dr. Güell said.

Mean BCVA improved from 20/500 to 20/100. Mean UCVA after phakic IOL implantation was 20/160.

Mean spherical equivalent improved from –1.35 D to –0.69 D. Astigmatism was difficult to address in some cases, resulting in a slight increase of the mean cylinder value, from –1.92 D to –3.92 D, with a high standard deviation of 3.45 D.

In terms of endothelial density, results were similar to those of non-keratoplasty eyes, Dr. Güell said. The mean endothelial cell count of donor grafts, which was 2,598 cell/mm² initially, decreased to 1,620 cells/mm² after keratoplasty and was 1,490 cells/mm² at the last control after phakic IOL implantation.

“We need more long-term results to evaluate the safety of this lens, in terms of endothelial survival in post-keratoplasty eyes. On the other hand, we don’t have so much information on the long-term evolution of the endothelium after PK without the IOL,” Dr. Güell noted.

However, results so far suggest that the toric Verisyse lens is a valuable option to improve vision in patients who have undergone corneal transplantation and clearly better from a predictability and stability point of view than corneal refractive surgery in this particular group of post-keratoplasty patients, he said.

“[This IOL is] definitely more appropriate than laser refractive surgery in eyes with residual high ametropia,” Dr. Güell said.

For more information:

José L. Güell, MD, can be reached at IMO c/munner 10, 08022 Barcelona, Spain; +34-93-2531500; fax: +34-93-4171301; e-mail: guell@imo.es. Dr. Güell is a surgical consultant for AMO.

Advanced Medical Optics, distributor of the Verisyse and Veriflex IOLs, can be reached at 1700 E. St. Andrew Place, Santa Ana, CA 92705 U.S.A.; +1-714-247-8200; fax: +1-714-247-8672; Web site: www.amo-inc.com.

Michela Cimberle is an OSN Correspondent based in Treviso, Italy, who covers all aspects of ophthalmology. She focuses geographically on Europe.