Eyeworld

APRIL 2022 | EYEWORLD | 61 C Contact Salz: dasalz@gmail.com Shammas: hshammas@aol.com to subject them to another procedure. Dr. Sham- mas said patients are more likely to complain if the error is in their dominant eye with an unex- pected anisometropia and/or aniseikonia. Dr. Salz said most patients with some resid- ual refractive error are corrected with glasses. However, if a patient does not want glasses, there are other options. "We'll say, 'The effective lens position ended up –0.5 in the other eye; I need to take that into account for the selection of the IOL power for the second eye,'" he explained. Dr. Salz said he's making this second eye adjustment in 5–10% of cases, though it's not necessarily because the patient is unhappy. It's because "I think I can get their other eye even better." Dr. Shammas said his practice follows a protocol based on a comprehensive study that found patients who had refractive error exceed- ing 0.5 D in their first eye could benefit from modifying the IOL power in the second eye. 1 Dr. Shammas said this protocol can correct up to 50% of the error in the first eye. A study pub- lished earlier found that "accounting for 50% of the observed error of predicted refraction in the first eye reduced the error of predicted refrac- tion in the second eye." 2 If a patient doesn't want to move on to their second eye until they are happy with the vision in their first, Dr. Salz said options include IOL exchange (his preference in the immediate postop period unless there are issues precluding it), laser vision correction, or a piggyback lens (the latter is the least used of all the options, he said). How to avoid misses in the first place Dr. Salz said he always performs measurements on a different day than when the patient comes in for an exam or evaluation. "It's important for the cornea to be as pristine as possible. … If you put drops in the eye, you're going to distort the surface," he said, adding that if the patient is found to have dry- ness or blepharitis, that should be well treated before performing measurements. He said if a patient has posterior subcap- sular cataracts, it can be difficult to obtain accurate axial length measurements with optical biometry. Dr. Salz said if the patient wants to defer surgery for later, he'll get axial length measurements earlier so he doesn't need to do immersion A-scan later. Dr. Shammas also noted that most misses are due to errors in axial length measurements, often due to advanced cataracts that cannot be measured with optical biometry. "Newer biometers based on swept-source OCT, such as Argos [Alcon] or IOLMaster 700 [Carl Zeiss Meditec], have a much higher rate of acquisition, thus decreasing the need for ultrasound biometry. Also, these new biometers will display a two-dimensional B-scan image that can be used to ensure an accurate measure- ment has been performed," he said. Dr. Shammas said surgeons should review their measurements preoperatively and ensure the correct IOL power is used during surgery. This "cannot be underestimated," he said.

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