She first visited us for consultation about cataract surgery because things had been hard to see for a year.
From the power of her previous glasses and her long axial length of about 27.0 mm, she had clearly always been highly myopic, but she had developed dense cortical cataracts with anterior capsule fibrosis, so much so that refraction could not even be measured accurately, and corrected visual acuity had fallen to 0.2.
She believed that "multifocal lenses make things look as if through a film," and said she did not mind using reading glasses for fine print and distance glasses when she wanted to see far clearly, so, if she was a candidate, she wanted TECNIS Eyhance set for intermediate distance. Specifically, she wanted to see piano scores and distances for housework and cooking, so first, for the right eye, we decided to operate targeting about 75–50 cm (aiming at −1.36 D) to reliably secure those distances. Because of scheduling, left eye surgery was planned for one month after the right, so we also suggested that, once she was used to the right eye after surgery, if she felt intermediate to near was quite good enough, the left eye could be set slightly toward distance.
Her husband, who accompanied her, is a department head physician at a general hospital, though not an ophthalmologist. He knew about technically difficult points that usually only surgeons know, and asked some quite sharp questions about details of the test images, which made me nervous (sweat), but he was satisfied with our explanation, including the advantages, disadvantages and surgical risks specific to his wife, and agreed to the lens and target she wanted.
Corneal topography showed with-the-rule astigmatism exceeding 2.0 D in both eyes, so toric lenses were needed. At the time, however, there was information that shipments of the toric TECNIS Eyhance Toric would soon be suspended, so to respond flexibly after right eye surgery, we ordered and secured several lenses for the left eye in advance, more toward distance, the same, and more toward near (shipments remain suspended as of September 2022).
First, right eye surgery. We used Verion for setting the astigmatic axis and the ORA system, an intraoperative wavefront aberrometer, for lens power and checking residual astigmatism. She originally had with-the-rule corneal astigmatism, and since TECNIS Eyhance has monofocal characteristics, to avoid the risk of overcorrection turning it into against-the-rule astigmatism, we deliberately chose a lens power leaving about 0.5 D of with-the-rule astigmatism. The figure below is the ORA system screen after inserting the toric lens: NRR: No Rotation Recommended, meaning the axis is exactly aligned and no further rotation is needed; at this point 0.54 D of with-the-rule astigmatism remains (a real-time value that usually changes during postoperative wound healing). The anterior capsule fibrosis called for care during the anterior capsulotomy, but the nucleus itself was mild in hardness, so the surgery was completed safely without much ultrasound.
One month after right eye surgery, uncorrected vision had improved greatly to 0.7p distance / 1.2 near; distance vision was better than expected, the important score and housework/cooking distances were clearly visible, and she could see her smartphone without glasses, and she was very satisfied.
So, for the left eye, after discussion she wished for "toward distance, but not too far." To find out specifically what target would satisfy her, we placed lenses shifting toward distance in front of the right eye and checked distance and near vision, set an appropriate shift for her, and set the distance focal point at about 1.5 m (aiming at −0.66 D), targeting uncorrected distance vision of 1.0.
For left eye surgery, likewise, we used Verion and the ORA system and chose a lens power leaving a little with-the-rule corneal astigmatism; after surgery she was satisfied that, as targeted, she could see well at distance, with uncorrected vision of 1.2p distance / 0.7p near. Because of optimization issues, even the ORA system cannot bring postoperative refractive error completely to zero, but it is a very reassuring tool when creating an appropriate difference between the eyes.
As a result, the theoretical ranges of clear vision were 1.6 m to 89 cm (−0.625 D) for the right eye and 73 cm to 53 cm (−1.375 D) for the left eye, with a 0.75 D difference in refraction between the eyes, so-called micro-monovision; binocular uncorrected vision was 1.2 at both distance and near, and she was delighted to be able to live without glasses.
When a patient wishes for an intermediate setting, there are many uncertain factors (individual differences), such as pseudo-accommodation from corneal astigmatism (aberrations) and pupil size, so it is difficult to predict how good uncorrected distance and near vision will be after surgery, and in practice it is hard for surgeons to promise patients how well they will see. However, by first reliably securing the focal distance they most want in daily life, as with her, and then using staged implants, determining an appropriate shift for the fellow eye from that result and setting its target, we can make the most of binocular visual function and ultimately raise postoperative satisfaction. We hope this case will be helpful to those considering an intermediate setting.
2022.09.13