He had come to us two years earlier for the ward's glaucoma screening, and returned after six months because his left eye had become hard to see with.
Both eyes had extreme myopia of about −15.0 D; the nuclear cataract was not very advanced, but, matching his symptoms, there was cortical opacity predominantly in the left eye. Corrected vision in the left eye had fallen to about 0.8, but the right eye still saw 1.0, so we did not strongly recommend surgery and monitored him. However, he complained strongly of subjective difficulty seeing, and wished to have cataract surgery, starting with the left eye, with multifocal lenses if he was a candidate.
The power range in which intraocular lenses are manufactured differs by lens; ordinary lenses, including PanOptix, start from 6.0 D, so none suited him: despite a long axial length of 28.77 mm, his corneal power was relatively high at about 45.0 D. We therefore chose TECNIS Synergy, which is made from 5.0 D (LENTIS Comfort and Intensity, by the way, start from 10.0 D).
From the Barrett Universal II (BU II) results at upper right in the figure below, the first choice would be the 4.5 D lens, whose target refraction of 0.09 D is closest to zero as recommended by the manufacturer, but 4.5 D is outside the manufactured range, so we had to choose 5.0 D, leaving −0.21 D of myopia. A point needing care here, however, is that the formula below calculates lenses of 5.0 D or less as plano-convex rather than biconvex, so the difference in target refraction between the 5.5 D and 5.0 D lenses is as much as 1.07 − 0.21 = 0.86 D (normally it is about 0.30 D; for details see https://morohoshi-ganka.com/opeex/1118).
So, to be safe, we also calculated with the Kane formula, a new formula using AI; the results are shown below. Here the problem with the lens shape described above is resolved, and you can see that the target refractions from 5.5 D to 5.0 D follow an almost arithmetic progression.
In any case, for eyes with poor proportions like this (long axial length and high corneal power), the risk of postoperative refractive error (power deviation) is greater, as can be seen from the disagreement among the BU II, SRK/T and Haigis results in the figure above. So this time too we used the ORA System and decided the lens power from intraoperative wavefront aberrometry; since no 4.5 D lens exists, we told him that distance vision might not come out as expected, and he wished for surgery with TECNIS Synergy, saying that if he could see near and intermediate, using glasses for distance would be fine.
The figure below shows the intraoperative wavefront aberrometry results. According to the ORA System, the predicted postoperative refraction with the 5.0 D lens was −0.68. However, in our clinic's optimization process with TECNIS Synergy, we had statistically confirmed an error of 0.39 D (hyperopic shift) between the ORA System's prediction and the actual postoperative subjective refraction, so the predicted subjective refraction was −0.68 + 0.39 = −0.29 D, and we could use the 5.0 D lens with confidence.
As a result, after surgery both eyes had uncorrected vision of almost 2.0 at distance and 1.2 or better at near, better than expected, and he was very satisfied; what struck me, and made me very happy too, was that, as he wrote in the postoperative survey, he said, "My worries are gone."
TECNIS Synergy is a lens with relatively strong photic phenomena such as halos, glare and starbursts, but if the power is matched exactly, it can give a very wide range of clear vision (focal range). However, compared with PanOptix, its refractive sweet spot is narrower, and vision seems less likely to come out when there is a power deviation, which makes it feel like a demanding lens to handle from the surgeon's side.
To bring out the full performance of these premium lenses, I believe accurate preoperative testing and surgery are essential, so we will continue to strive for high-precision surgery without compromise. If patients, too, tell us their wishes without compromise, we will do our utmost to achieve a result as close as possible to them, so please feel free to consult us.
2022.08.28