Eyeworld

EW REFRACTIVE 56 November 2018 Presentation spotlight by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer Special cases The challenge is knowing which more complex corneas stand to benefit from phakic IOL placement. According to Dr. Alio, the special cases would include corneas with a combination of regular and irregular astigmatism. He considers phakic IOLs in special cases with post-kera- toplasty surgery after stitch removal, stable keratoconus eyes, stable pel- lucid marginal degeneration (PMD), and in eyes with corneal scars due to traumatic events or infectious keratitis. "Regular astigmatism is a naturally and symmetric occur- ring cylinder due to the difference between the steepest and flattest meridian power. It can be totally corrected with a toric lens. Irregular astigmatism occurs secondary to a corneal disease or injury, and it is not symmetric. A corneal procedure to modify the corneal shape needs to be performed in order to correct it or an RGP to compensate it," Dr. Alio said. In an irregular cornea, refraction is a key factor to decide on whether to implant or not implant a phakic IOL. If the patient has good visual acuity with spectacles, usually over 0.5 D, this can be a good indicator of success with a toric phakic IOL. Dr. Alio pointed out that in contrast, refraction is not helpful in cataract patients with irregular corneas when a pseudophakic toric IOL is consid- ered. Higher order aberrations, like coma, are also good indicators of the outcomes with phakic IOLs. High ametropia associated with the cor- rection of high astigmatism usually leads to the best visual outcomes, he said. To treat the regular component in an irregular astigmatism, Dr. Alio thinks that higher order aberrations can be telling. Dr. Alio, the coin- vestigator of a study, explained that keratoconus patients treated in the study had coma-like aberrations that correlated well with the degree of corneal irregularity, usually coma- like, non-radial aberrations lower than 2 µm (RETICS classification for Toric phakic IOLs offer visual improvement in astigmatic eyes, even in more complex case scenarios P hakic IOLs offer a viable method of adjusting the eye's refraction without removing the natural lens and are a highly effective alternative to LASIK and PRK surgery for the correction of moderate to severe myopia. These lenses are designed to correct high myopia between –5 D and –20 D in patients with a residual anterior chamber depth of at least 3 mm. Irregular cor- neas can also strongly benefit from phakic IOL placement, according to Jorge L. Alio, MD, PhD, professor and chairman of ophthalmology, Miguel Hernandez University, and scientific director, Vissum-Instituto Oftalmologico de Alicante, Spain. "Phakic IOLs are designed to correct regular astigmatism. In our hands, toric phakic IOLs are a remarkable tool, even in eyes with irregular astigmatism. We have spe- cific indications for their use in eyes with irregular corneas and categorize and treat these eyes as either stan- dard or special cases," Dr. Alio said in a presentation at the 2018 World Ophthalmology Congress. Phakic devices are either sup- ported by the iris or placed in the posterior chamber. Posterior cham- ber phakic IOLs are easier to implant and have a shorter learning curve and shorter surgical time, but they have rotated in some cases. Iris-fixat- ed phakic IOLs have no rotation or vaulting issues, but they are associat- ed with a longer, more cumbersome surgery and a longer learning curve. Standard cases According to Dr. Alio, standard cases for phakic IOLs include corneas with regular astigmatism. "Our general indications for phakic toric IOLs include first and foremost a sta- ble refraction for at least 1 year in patients who are poor candidates for corneal refractive surgery," Dr. Alio explained. "One of the major ad- vantages of astigmatism correction with phakic IOLs is the opportunity to correct both myopia and astigma- tism, or hyperopia and astigmatism, in one surgery. A second surgery to correct the astigmatism (bioptics) is avoided in most of the cases. Toric IOLs can correct higher levels of astigmatism than lasers, and the IOL calculation is relatively easy as it is based on refraction, which is far easier than in pseudophakic toric IOLs," he said. To be considered for a toric pha- kic IOL, the endothelium/crystalline lens distance must be greater than or equal to 2.85 mm, the anterior chamber angle greater than or equal to 35 degrees, and the crystalline lens rise should be below 20 µm. In addition, Dr. Alio stipulated a flat iris configuration, a refractive cylinder greater than or equal to 1.25–1.5 D, and an endothelial cell count (ECC) in excess of 3,000 cells in patients under 25 years, an ECC of more than 2,500 cells in patients between 25 and 30 years, and an ECC of more than 2,200 cells in those older than 30 years of age. Indications for toric phakic IOLs Patient suffering a sport-fishing trauma to the left eye that has caused a corneal scar Nine months following PTK treatment. The improvement allowed toric IOL implantation Source (all): Jorge Alio, MD

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