Posterior chamber phakic lens treats high myopia in the long term

The hydrophobic silicone implant significantly improved uncorrected and corrected distance visual acuity, reduced spherical equivalent and yielded few complications.

Issue: April 25, 2012

A posterior chamber phakic lens treated high myopia for up to 6 years, a study found.

Results of the study, which was conducted at the Institute of Vision and Optics at the University of Crete under primary investigator Ioannis Pallikaris, MD, also showed high predictability and stability.

“The most significant findings from the study were the stability of refraction during the long-term follow-up period and the low rate of complications in our patient series,” Dimitra M. Portaliou, MD, the corresponding author, said in an email interview. “These two findings confirm the stability and safety of the PRL implantation technique for the management of high myopia.”

The researchers investigated outcomes and the safety profile of the Phakic Refractive Lens (PRL, Carl Zeiss Meditec), a posterior chamber lens made of thin, highly refractive silicone.

Study results were published in the Journal of Refractive Surgery.

Advantages of phakic IOL

“The silicone used in the PRL lens offers great advantages and plays an important role in the safety of the procedure,” Dr. Portaliou said. “Silicone provides higher biocompatibility so as to avoid chronic inflammation and significant endothelial cell loss. Silicone has a higher refractive index which is preferable because it produces thinner implants that can be linked with an easier implantation procedure and fewer complications.”

In addition, the silicone material facilitates implantation through small incisions of 2.5 mm to 3 mm and does not need to be sutured, Dr. Portaliou said.

Posterior chamber PRL implantation minimizes long-term endothelial cell loss, offers ease of implantation, and reduces the risk of pupil ovalization, halos and glare. Additionally, the smaller incision minimizes postoperative astigmatism, the study authors said.

The lens is not supported in the sulcus angle. Contact with the crystalline lens is discouraged because of the implant’s hydrophobic material and aqueous fluid dynamics, they said.

Patients and parameters

The retrospective study included 143 eyes of 82 patients who received the PRL for high myopia. Mean patient age was 28.7 years.

Preoperatively, patients underwent evaluation of cycloplegic refraction, spherical equivalent, logMAR uncorrected and corrected distance visual acuity, IOP, slit lamp microscopy, scotopic pupil size, white-to-white corneal diameter, dilated funduscopy and A-scan ultrasonography.

Patients younger than 18 years and those with previous intraocular surgery, anterior chamber depth less than 3 mm, glaucoma, cataract or active ocular infection were excluded from the study.

“Patient selection is extremely important so as to ensure a successful result,” Dr. Portaliou said. “Along with appropriate patient selection, another important factor that plays a key role to a favorable outcome is accurate lens calculation.”

Lens power calculations were based on preoperative cycloplegic spherical equivalent, average keratometric power, anterior chamber depth measured with A-scan ultrasonography, target postoperative refraction and the manufacturer’s nomogram, Dr. Portaliou said.

All implantations were performed by Dr. Pallikaris at the University of Crete. Mean postoperative follow-up was 3.8 years. Ninety-eight eyes (68.5%) underwent at least 2 years of follow-up.

Results and conclusions

“The most important factor of our study was that 6 years after the treatment, efficacy, safety, stability and predictability of the PRL implantation were adequately proven,” Dr. Portaliou said.

Study results showed that mean logMAR uncorrected distance visual acuity improved from counting fingers preoperatively to 0.13 at 2-year follow-up and 0.17 at 6-year follow-up (P < .001).

At final follow-up, 82 eyes (57.3%) gained one to four lines of corrected distance visual acuity. About 8% of eyes lost one or two lines of corrected distance visual acuity at final follow-up.

Data showed that cycloplegic spherical equivalent refraction diminished from –14.08 D before lens implantation to –0.45 D after implantation (P < .001).

At 6 years, 23 eyes (67.6%) were within 0.50 D of targeted refraction and 31 eyes (91.2%) were within 1 D of the target.

Complications included anterior capsule damage in three eyes, temporary IOP increase in 14 eyes, pigment dispersion in one eye and lens decentration in one eye. No eyes showed evidence of developing cataract at 6-year follow-up, the researchers said. – by Matt Hasson

Reference:

Portaliou DM, Kymionis GD, Panagopoulou SI, Kalyvianaki MI, Grentzelos MA, Pallikaris IG. Long-term results of phakic refractive lens implantation in eyes with high myopia. J Refract Surg. 2011;27(11):787-791.

For more information:

Dimitra M. Portaliou, MD, can be reached at Institute of Vision and Optics, University of Crete, Medical School, 71003 Heraklion, Crete, Greece; 30-2810-371800; fax: 30-2810-394653; email: mimi24279@gmail.com.
Disclosure: Dr. Portaliou has no relevant financial disclosures.