Do not underestimate challenges of IOL selection with combined procedures
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TREVISO, Italy — Combined surgery in eyes with coexisting cataract and macular hole or macular pucker may be beneficial, but it also makes IOL choice and power calculation a challenge, according to one surgeon.
“Cataract and macular pathologies often present together because the prevalence of both increases with age and because they share several risk factors. Therefore, quite frequently surgeons have to face the dilemma of choosing between sequential and combined procedures,” Alessandro Franchini, MD, said at the Retina 2020: New Trends meeting here.
While the techniques of combined procedures are fairly standardized, the challenges of selecting and implanting an IOL in these cases should not be underestimated. Several studies have shown that postoperative refractive error after phacovitrectomy is much greater as compared with cataract surgery alone, and it often has a significant impact on the patient’s functional vision and life quality.
“Axial length measurement is difficult in eyes with a thickened macula, and there is evidence from studies that a 0.1 mm miscalculation results in a refractive error of 0.25 D. In addition, tamponades might move the lens forward,” Franchini said.
But the main source of error is the calculation of the effective lens position, which is difficult even in standard cases and much more in eyes with weak zonules and no support from the vitreous.
“We simply don’t know where the lens will be eventually,” he said.
Currently, there are no biometry formulas with constants optimized for phacovitrectomy and taking into account the different refractive index of the aqueous as compared with the vitreous. This can determine an additional 0.25 D of refractive error.
Further problems arise if surgeons consider implanting a premium lens, Franchini said. He does not personally recommend the use of multifocal IOLs in these cases.
“First of all, because multifocal IOLs are very unforgiving with even a small amount of refractive error. In addition, vitrectomized eyes where tamponade agents have been used are more likely to develop capsule fibrosis, leading to IOL tilting and decentration,” he said. “A displaced IOL, multifocal or toric, will partially if not totally lose its specific optical properties and induce significant, complex aberrations.” – by Michela Cimberle
Reference:
Franchini A. Anterior segment and macular surgery: Therapeutic alliance? Presented at: Retina 2020: New Trends; Jan. 24-25, 2020; Treviso, Italy.
Disclosure: Franchini reports no relevant financial disclosures.