15 EyeWorld Asia Pacific | June 2024 CATARACT Dr. Cummings incorporates several tests to determine whether a patient will tolerate monovision, minimonovision, or blended vision and to determine which eye tolerates which tasks. He shows the patient their eyes fully corrected, followed by 0/–1.50 (fully correcting the right eye and correcting the left eye to a myopic target). He asks the patient to rate this out of 100 compared to their prior fully corrected vision. “If this is rated at 80% or higher, the odds of blended vision working are well above 95%,” he said. Then he’ll move to –1.50 in the right eye and fully correct the left. “Score this against the 100% score. If this is scored at 85% or 90%, you have the answer. Correcting the left eye to emmetropia and the right eye for reading is destined to work.” If the score is less than 80%, he puts the patient in a trial frame with the right eye targeted to –1.50 and left eye targeted for emmetropia, giving the patient up to 30 minutes to test this range of vision. “Some will come back saying they love it. Others will say they dislike it, and that rules out blended vision. Others will say that they need more time or that they want to test this in their own home and work environment, and they continue with [a contact lens trial],” Dr. Cummings said. Dr. Cummings tests suppression with the Worth four dot test. Furthermore, he said once the decision is made on the dominant eye, a stereo target is put up on the chart and stereopsis is assessed. Correct both eyes to emmetropia and assess stereopsis. “In my experience, 95% of patients will have good distance stereopsis,” Dr. Cummings said. “Now start defocusing the eye assigned to reading. Ask the patient to continually assess the stereo target and to note when distance stereo is lost. Defocus to –0.25, –0.50, and –0.75. Almost everyone still enjoys stereopsis for distance vision at this level. Once the defocus is –1.00 in the reading eye, some will start losing their stereo vision. For these, their reading target should not exceed –0.75 D. Some can maintain stereo vision up to –1.50 and lose it at –1.75 D. Their reading eye target should not exceed –1.50. A small part of the population can maintain stereo vision at –1.75 and even –2.00 D and have the freedom to select their target.” Dr. Cummings added that with mono/ blended vision being set with laser vision correction or ICL surgery, there is likely still some residual accommodation, and these patients might receive a slightly less myopic reading target. With a monofocal IOL, he said some may target –1.0 but still require readers, or target –2.0 and then need assistance at intermediate vision. With advanced technology IOLs like EDOF, target emmetropia in the distance eye and –0.75 to –1 in the reading eye for a complete to near complete range of vision, he said. If a patient is seeking a full range of vision but needs to drive at night, Dr. Cummings said dominance again plays a key role in creating a “custom match.” This approach starts with a diffractive trifocal IOL in the non-dominant eye. Prior to the second eye surgery, glare and halo tolerance is assessed. If it’s not bothersome, the patient can choose a trifocal for their dominant eye as well; however, if the patient is bothered with the glare and halo in the nondominant eye, they receive a non-diffractive EDOF IOL in the dominant eye. “With this combination, they have an excellent range of vision and can still drive at night thanks to there being no glare and halos in the dominant eye [with a non-diffractive EDOF],” Dr. Cummings said. Distance and near preferred vision and the LAL Dr. Kopstein, whose sole private practice is performing refractive lens exchange (RLE), said assessing distance and near preferred eyes is important with the Light Adjustable Lens (LAL, RxSight). “It’s an important technology. It’s powerful because it can be adjusted, and it’s equally powerful because of the quality of the optics and the EDOF that you get from the LAL,” Dr. Kopstein said, noting that the original LAL has allowed his practice to get 92% of people completely out of glasses; he thinks this number will rise to 95% with the LAL+. When it comes to distance and near preferred eyes, Dr. Kopstein said his practice has learned that in about 20% of patients, the dominant eye is not their distance preferred eye. “I am one of those people. If you put me in contact lenses that fully correct me for distance and you hold a +1 lens over my right eye and a +1 lens over my left eye, I will
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