JCRS Highlights Chosen By Professor Thomas Kohnen, European Editor, JCRS

Fifty years after Fyodorov published the first paper on theoretical IOL calculation, achieving an ideal outcome remains a challenge

Thomas Kohnen

Posted: Friday, September 1, 2017

IOL Calculations – progress needed
Fifty years after Fyodorov published the first paper on theoretical IOL calculation, achieving an ideal outcome remains a challenge. While biometric tools, a variety of calculation formulas and improvements in surgical techniques have increased the percentage of patients within 0.5 dioptre of predicted outcome postoperatively, the number of patients not achieving this result ranges from 10 to 20%, and worse for difficult eyes. With the goal of stimulating progress, the JCRS commissioned four editorials by experts from around the world. The first of the series covers reclassifying IOL calculation formulas. Douglas D Koch MD suggests doing away with the generational classification system in favour of classifying formulas by their method of calculating IOL power and the data used for these calculations. Future editorials will discuss measurement foibles; analysing astigmatic change; and criteria for analysing outcomes. D Koch et al., “Pursuing perfection in intraocular lens calculations: I. Logical approach for classifying IOL calculation formulas,” Volume 43, Issue 6, 717–718.

Changing reasons for IOL exchange
The original indications for IOL exchange were IOL decentration or displacement for posterior chamber lenses, and corneal decompensation and inflammation for anterior chamber lenses. However, in recent years the indications for IOL exchange have expanded to include refractive concerns driven by increased patient and physician expectations for refractive targets and the desire for spectacle independence, a population-based retrospective data analysis indicates. The study showed that while the absolute number of secondary IOL procedures increased from 2000 to 2013, the five-year risk for surgery decreased. Repositionings and exchanges were performed most commonly by retinal surgeons (39.3%), followed by glaucoma surgeons (25.5%), general ophthalmologists (22.4%) and corneal surgeons (12.9%). Szigiato et al., “Population-based analysis of intraocular lens exchange and repositioning,” Volume 43, Issue 6, 754–760.

MIOL exchange outcomes
Although most complications following multifocal IOL (MIOL) implantation can be managed conservatively with the use of spectacle correction, keratorefractive surgery or neodymium:YAG (Nd:YAG) laser capsulotomy, up to 7% of these patients ultimately require multifocal IOL explantation. How well do patients do after MIOL exchange? Researchers reviewed the 29 cases (35 eyes) that underwent exchange surgery for indications including blurred vision photic phenomena, photophobia and diminished contrast sensitivity. The types of IOLs implanted after multifocal IOL explantation included in-the-bag IOLs (74%), iris-sutured IOLs (6%), sulcus-fixated IOLs with optic capture (9%), sulcus-fixated IOLs without optic capture (9%) and anterior chamber IOLs (3%). The CDVA was 20/40 or better in 94% of eyes before the exchange and 100% of eyes after the exchange. EJ Kim et al., “Refractive outcomes after multifocal intraocular lens exchange,” Volume 43, Issue 6, 761–766.