Technique, sizing can minimize potential phakic IOL complications

March 15, 2006

Chicago?Cataract and glaucoma can occur in eyes with phakic IOLs, but the risk of those complications can often be minimized by careful surgical technique and IOL sizing, said Antonio Marinho, MD, PhD, at the refractive surgery subspecialty day meeting sponsored by the International Society of Refractive Surgery of the American Academy of Ophthalmology.

Chicago-Cataract and glaucoma can occur in eyes with phakic IOLs, but the risk of those complications can often be minimized by careful surgical technique and IOL sizing, said Antonio Marinho, MD, PhD, at the refractive surgery subspecialty day meeting sponsored by the International Society of Refractive Surgery of the American Academy of Ophthalmology.

Dr. Marinho reviewed the mechanisms and management for cataracts and glaucoma that develop in eyes with phakic IOLs. For cataracts, the risk is much greater for posterior chamber versus anterior chamber (angle-and iris-supported) IOLs, he said.

"The explanation for the difference is very logical considering that the posterior chamber implants are much closer to the crystalline lens than the anterior chamber models," said Dr. Marinho, professor of ophthalmology, University of Porto, Portugal.

"These changes tend to be non-progressive, do not reduce visual acuity, and can be avoided with careful surgical technique," Dr. Marinho said.

IOL-related cataracts occur if there is inadequate vault (space between the posterior chamber phakic IOL and the natural lens) or if the implant size chosen is too short. Higher myopia (>15 D) and age (>45 years) are also risk factors.

It is thought that these cataracts are metabolic in origin, arising because contact between the IOL and crystalline lens impedes aqueous humor circulation to the anterior surface of the natural lens. They appear as an anterior subcapsular opacification with a central location, usually 6 to 18 months after surgery. In contrast to the surgeon-related cataracts, these opacifications are usually progressive and go on to affect vision.

"At the beginning, patients will experience glare, but then visual acuity becomes reduced, and phakic IOL removal for phacoemulsification may be necessary," Dr. Marinho said.

Among posterior chamber phakic IOLs, the Visian ICL (STAAR Surgical) has been associated most often with the IOL-related type of cataracts. Proper sizing is still a difficult issue, although problems associated with inadequate vault have been addressed with a series of lens design modifications. The latest generation of the ICL (version 4) has the largest vault and lowest rate of cataract formation, Dr. Marino said.

Interestingly, however, different investigators using that same model have reported varying rates of cataract.

For example, in a study by Carlo F. Lovisolo, MD, no cataracts were seen among 331 eyes, while in the FDA phase III study, there was a 3.4% incidence of cataract, and others have reported even higher rates.

"I believe the explanation has to do with ICL sizing. Absence of cataracts in the Lovisolo series can be explained by very accurate sizing," Dr. Marinho said.

Anterior subcapsular cataract development has been much less common with the Phakic Refractive Lens (PRL, IOLtech) because that silicone posterior chamber IOL "floats" in the aqueous humor rather than being sulcus-based.

"Therefore, it is independent of the inner dimensions of the eye. However, zonular damage with IOL migration to the vitreous has been rarely, but uniquely, reported with the PRL," Dr. Marinho said.

Anterior chamber phakic IOLs are usually not associated with cataracts, although there does appear to be a risk for earlier development of nuclear cataracts in recipients of these implants.

"These changes have been seen in patients aged 40 to 50 years, have no relationship with time since implantation, but do occur earlier than in control myopic eyes. The mechanism is not known, but various hypotheses suggest opening of the anterior chamber, changes in aqueous humor circulation caused by iridectomy/ iridotomy, or subclinical chronic inflammation as playing a role," Dr. Marinho said.

Elevated IOP

Both acute glaucoma and chronic glaucoma may develop in eyes with phakic IOLs. Acute glaucoma arises due to incomplete viscoelastic removal or pupillary block by the IOL.