Two years earlier his previous doctor had performed cataract surgery with the toric FineVision Toric, a diffractive trifocal lens, but his eyes had become hyperopic and he had difficulty seeing both far and near, so he came to us.
Indeed, uncorrected near vision was about 0.2 in both eyes, and he could not see near without adding +2.25 D in the right eye and +2.75 D in the left, so FineVision's multifocality was being wasted.
When we asked in detail, he said he had seen well at both distances right after surgery, but from about three to four weeks after surgery both distance and near became hard to see; his previous doctor apparently explained that "the lens has moved backward within the capsular bag and the anterior chamber has deepened, making you hyperopic."
In fact he brought a diagram he had made of the change in lens position and a graph of the change in postoperative anterior chamber depth, which we present here with his permission.
On examination, the capsular bag in both eyes, especially the anterior capsule, had indeed contracted, and the lens optic seemed to have been pushed backward (toward the vitreous), pivoting on the haptics. In this situation removing and exchanging the lens carries risks, and the expensive toric trifocal FineVision had been inserted beautifully, without decentration and with the astigmatic axis exactly aligned, so we proposed treatment that preserves the lens and adds an add-on lens to correct the power. He had researched various options in advance and agreed on the spot to treatment with an add-on lens.
However, the anterior capsule contraction had also weakened the multifocal effect, and releasing the contraction might somewhat lessen the hyperopic shift, so we made a two-stage treatment plan: first (1) anterior capsulotomy with a YAG laser, and after the power change settled, (2) insertion of the add-on lens.
The figure below shows photos before and after the anterior capsulotomy: after the YAG laser the optic is widely exposed, and he said things subjectively looked clearer too. Also, since the force pushing the optic backward from anterior capsule contraction was partly released, the hyperopia lessened by 0.5 D and vision improved slightly.
Before capsulotomy ⇒ After capsulotomy
Next, deciding the add-on lens power: we had him experience it in simulation with glasses and contact lenses, and set the power where FineVision's multifocality worked fully. Deciding the power of an add-on lens is similar to prescribing glasses or contact lenses, so unlike lens power selection in cataract surgery, power deviations hardly ever occur. Unfortunately, however, powers come in 0.5 D steps, not 0.25 D steps like contact lenses. Add-on lenses can be inserted in both eyes on the same day, but to be safe we operated one eye at a time, starting with the right, and decided the left eye's power based on his satisfaction with the right.
Since he wanted the right eye to reliably secure uncorrected near vision, we set the power slightly favoring near. The surgery only involves trimming the laser-opened anterior capsule and inserting the add-on lens, and it was completed without problems.
One week after surgery, the right eye had uncorrected vision of 1.2p at distance and 1.0 at 30 cm, a very good result just as he wished, and he was satisfied. For the left eye we had prepared two lenses, one slightly more toward distance than the right and one more toward near; after discussion he chose the one slightly toward distance.
Left eye surgery was also completed without problems, and vision improved to 1.5p uncorrected at distance and 0.9p at 30 cm, good vision with FineVision's original multifocal effect working properly. He works with electronic circuits and the like, and he was delighted to see well at both distances without glasses for the first time in a full two years.
The figure below is a postoperative photo of the right eye; on a quick examination, even we ophthalmologists usually cannot tell whether an add-on lens is in place.
<Postoperative slit-lamp photo>
When, as for him, an expensive premium multifocal lens is already in place and the cause of poor vision is not poor adaptation to the multifocal mechanism but simply a power deviation, an add-on lens is safer and more accurate than an exchange, and also economically advantageous: a very useful tool.
Types of add-on lenses are increasing, including monofocal, toric, bifocal and trifocal, but multifocal add-ons are, on specifications, inferior to current regular multifocal lenses. Even so, inserting a multifocal add-on lens as a second stage after surgery with a monofocal lens lets patients experience the pros and cons of each lens, and the multifocal add-on can, if necessary, be removed safely, so this seems a method we can recommend to patients who want to try multifocal lenses safely.
Next time we will present a case in which a patient (originally myopic) who received a monofocal lens set for reading distance at our clinic wished, a year after surgery, to "see far without glasses too after all," and had a multifocal add-on lens inserted.
2021.12.31