New IOLs for keratoconus and other aberrated corneas

Infrared light used to see the retina. (Images courtesy of Claudio Trindade, MD, PhD)

There are positives and negatives to using the XtraFocus pinhole implant, according to Claudio Trindade MD, PhD, an anterior segment surgeon based in Brazil, who has assisted in the development of the implant. “It is a powerful tool for complicated corneas,” Trindade said during an interview with Ophthalmology Times®, following his presentation at the 53rd Sally Letson Symposium in Canada.

The XtraFocus is a supplementary pinhole implant designed to be used in piggyback with a regular IOL. It can be implanted both in the sulcus or in the bag with the IOL. XtraFocus is intended for the treatment of irregular astigmatism, such as in keratoconus and postradial keratotomy, but Trindade suggests a wider view of the uses of the implant.

The XtraFocus pinhole implant.

This black, hydrophobic acrylic implant has an overall diameter of 14 mm, an occlusive zone of 6 mm, a pinhole aperture of 1.3 mm, and a required incision of 2.2 mm. “This implant is not a tool for only cataract surgery,” Trindade said. “We should also consider it in cases of irregular corneas and a clear lens. If the cornea is stable and still has a reasonable optical quality, it might be wiser to bypass the topographic imperfection than try to fix it. Refractive lens exchange is a reliable method to tackle lower order aberrations, and the pinhole effect takes care of the higher order aberrations.”

For many patients who don’t do well with scleral lenses, it’s either this or deep anterior lamellar keratoplasty, Trindade said. “Even for those who do well with scleral lenses, we must weigh the risks and burdens of long-term contact lens dependency.”

The greatest advantage of this approach is the reduced level of uncertainty, which is quite the contrary of what we see in anterior corneal transplantation. To use the XtraFocus pinhole implant, the cornea must have a minimum level of optical quality, Trindade explained. “Our experience suggests a cutoff of approximately 20/100 in BCVA [best-corrected visual acuity]. If BCVA is below 20/100 or the cornea has central opacities, this approach is usually not recommended,” he said.

A preoperative pinhole acuity test, along with BCVA, provides a fair estimation of the final surgical outcome in most patients, but it’s important to take this test with a grain of salt. “Patients with mild central corneal opacities might do well during a pinhole acuity test but are not good candidates for intraocular pinhole devices,” Trindade said.

In terms of adverse events associated with the use of the implant, patients can report a darkening of their vision. “It might be a problem in a very dark environment, but overall, it is usually well tolerated if they are getting something out of it,” Trindade said. “[Because] there is remarkable improvement in visual acuity, the balance is very much favorable.”

A key point to remember, according to Trindade, is that these patients already have terrible night vision before surgery, with incapacitating glare and reduced acuity. Despite a reduction in the overall brightness, these patients often report greater visual comfort at night, even though they might have some trouble under conditions of very low light. Another common inconvenience is the perception of halos around focal light sources, but the benefit of improved vision outweighs this adverse event, according to Trindade.

One key disadvantage of the XtraFocus is that it limits the view of the retina. “The infrared transparency of the black material helps, but it is still a challenge, especially for the far periphery,” Trindade said. “You will need to rely on retinal cameras…. The fact that more and more infrared, wide-field retinal cameras are becoming available is great [because] they are very useful in this scenario.”

Moreover, Trindade noted that both the iCare Eidon and the Heidelberg Spectralist offer infrared fundus imaging, with extra benefit of an add-on ultra-widefield lens. Patients diagnosed with active retinal pathologies or patients who might need retinal interventions in the future should not receive the XtraFocus pinhole implant. “You need the green light from the retinal specialist before you do this,” Trindade said.

Although there are concerns about retinal detachment, retinal complications, and how to manage those if they occur, compromises are inevitable in the management of highly debilitated patients, according to Trindade. “We are talking about very impaired eyes, and the options are just not very attractive,” he said. “We must carefully weigh the risks and benefits for both short and long term.”

Claudio Trindade MD, PhD

E: claudio.trindade@ioct.org

Trindade is a consultant for Morcher GmbH, the manufacturer of the XtraFocus pinhole implant.