On target: Accurate alignment of toric IOLs
A digital markerless system can be considered more accurate than manual methods when attempting to align toric IOLs, said Daniel Black, MBBS, FRANZCO.
San Diego-A digital markerless system can be considered more accurate than manual methods when attempting to align toric IOLs, said Daniel Black, MBBS, FRANZCO.
In his non-randomized, single-surgeon study with the digital markerless system (Callisto, Carl Zeiss Meditec), Dr. Black used a single toric IOL.
Patients who presented before August 2014 had traditional ink marks used to align their toric lenses, and those who presented after August 2014 had the digital system used for lens alignment. He used the ASICO Nuijts-Lane and the Mastel Gimbel Mendez analogue ink markers (for the manual marking group).
Careful marking of the eye to ensure accurate axis alignment of the IOL is essential for toric lens success, he said, noting that for every 1° a toric lens is off-axis, its effect for reducing astigmatism is decreased by 3.3%-so if the lens is off by even 10°, its efficacy is deceased by a third. Some studies have found if a lens is 30° off target the entire effect of the lens is lost.
“The hypothesis is that the digital system is potentially more accurate because it can eliminate a lot of sources of error,” Dr. Black said, adding he personally uses the Holladay toric formula to determine IOL power.
“When patients first present in our office, we get biometry on virgin tear film, and our data is imported electronically,” said Dr. Black, who practices in Queensland, Australia. “This helps to avoid transcription error.”
All surgeries had temporal bimanual phaco-chop, with the IOL implanted through a 2.2-mm incision; the IOL was aligned with the marked steep axis.
“Ideally, you want the astigmatic correction in the IOL plane,” he said.
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