Contents
Overview / Preoperative findings and background / Choosing the lens / Why IOL power calculation was difficult / Left eye surgery and course / Right eye: deciding whether RLE was indicated / Right eye surgery and final results / Cautions regarding RLE / Cautions regarding multifocal IOL candidacy and refractive error
Overview
As this is the 100th case in our collection, I considered presenting a special case. Instead, partly as a caution against undergoing cataract surgery with a multifocal lens too casually, I present the case of a woman in her 40s living in Switzerland who received the toric (astigmatism-correcting) MiniWELL Toric.
She was a contact lens wearer with high myopia, and her main problem was reduced vision from atopic posterior subcapsular cataract. The degree of opacity (and corrected visual acuity) differed between the eyes, and the corneal shape of the two eyes was completely different, so this case required particular care in IOL power calculation. In addition, the cataract in the right eye was not advanced enough for us to actively recommend surgery, so we also had to judge whether Clear Lens Exchange (CLE, also called Refractive Lens Exchange/RLE) was appropriate.
Until the very end she considered the Well Fusion system, a mix-and-match combination with MiniWELL PROXA, which provides vision at closer distances. In the end she chose micro-monovision with the toric MiniWELL Toric in both eyes. After surgery, her uncorrected visual acuity was excellent: 1.2–1.5 in both eyes at both distance and near.
Preoperative findings and background
How she came to our clinic
About two years earlier she had been diagnosed with cataracts at a hospital in Switzerland, and the hospital there recommended surgery in Japan and gave her a referral letter. During a temporary stay in Japan she had already seen another clinic and scheduled surgery, but that surgery was later cancelled. She then came to our clinic for the first time without a referral letter, and from the start she wished to have surgery with multifocal lenses.
Atopic posterior subcapsular cataract
In people with atopic dermatitis, rubbing the eyes because of itching and inflammatory changes are known to cause a characteristic opacity that begins in the posterior subcapsular region (the center of the back surface of the lens). Because a posterior subcapsular cataract affects the center of the visual axis, it tends to reduce vision even when the opacity is relatively mild. In this patient, posterior subcapsular opacity had progressed in the left eye and corrected visual acuity had fallen to 0.9p, whereas the right eye had only very slight opacity and maintained a corrected visual acuity of 1.2.
Because vision was preserved in the right eye, we could not actively recommend surgery from the standpoint of medical necessity, and we ourselves hesitated to operate. How we ultimately came to operate is described below.
Preoperative corrected and near visual acuity
Her visual acuity at the first visit was as follows (see figure below).
Because of her high myopia she naturally could see almost nothing in the distance without correction, but even fully corrected, the left eye reached only 0.8–0.9. The right eye, on the other hand, saw up to 1.2. Near visual acuity with her own glasses was reduced to 0.7 in the left eye but good at 1.0 in the right eye. We therefore told her that we would not actively recommend surgery on the right eye, and asked her to return if she wished to proceed with surgery. We also explained that, because she had not stopped wearing contact lenses for long enough, at this point we could not accurately judge whether she was a candidate for multifocal lenses.
Eight days later she returned, still wishing to have surgery, having stopped wearing her contact lenses.
Choosing the lens
The dominant eye and the eye with the worse cataract were reversed
In the preoperative questionnaire, her priority of distances was near > intermediate > far. As noted above, we did not recommend surgery on the right eye, but she strongly wished to have both eyes operated on, and wanted the Well Fusion system, a mix-and-match of the standard MiniWELL and the more near-oriented MiniWELL PROXA.
With Well Fusion, it is usually recommended to operate first on the dominant eye with the MiniWELL. In this patient, however, the dominant eye was the right eye, with a mild cataract and good corrected vision, while the cataract had progressed in the non-dominant left eye.
In such cases, which eye to operate on first and what lens combination to use for the two eyes must be considered carefully.
Even though she wanted Well Fusion, we explained that in our experience we should not start with the right eye, which had good corrected vision. After discussion, while keeping open the option of not operating on the right eye depending on the result in the left eye, we proposed the following two plans.
Plan 1: MiniWELL Toric in both eyes
This choice follows the patient's wishes. Among EDOF (extended depth of focus) lenses, MiniWELL is classified as a progressive design with added power in the center. Unlike diffractive lenses, it causes little unwanted light scattering such as halos and glare, and provides continuous vision from about 40 cm to distance. A slight difference between the two eyes, as in micro-monovision, can also widen the range of clear vision.
Plan 2: MiniWELL Toric in the right eye + MiniWELL PROXA Toric in the left eye
Well Fusion as recommended by the manufacturer: MiniWELL in the dominant right eye, combined with the more near-oriented MiniWELL PROXA in the non-dominant left eye.
After we also explained the anatomical differences between her eyes, such as axial length and corneal power described below, and the risk of refractive error, she chose Plan 2 and, contrary to the usual order, wished to have the PROXA in the non-dominant left eye first. We asked her to discuss it once more with her family in Switzerland. After considering her lifestyle as a whole (living in Switzerland, with occasions to drive at night), she agreed by email that we would first operate on the left eye, which had reduced vision and the more advanced cataract, using a MiniWELL Toric, and decide the plan for the right eye after checking her vision after surgery.
Why intraocular lens (IOL) power calculation was difficult
Once the lens type is decided, the next step is to determine the power to order. In this case, IOL power calculation required particular care for the following two reasons.
Left eye: long axial length, flat cornea, against-the-rule astigmatism
Biometry of the left eye with ARGOS showed a flat corneal power of 41.74 D with against-the-rule astigmatism (see the blue frame for the ARGOS left eye in the figure below). In eyes with a flat cornea and non-standard ocular proportions, postoperative refractive error is more likely, and against-the-rule astigmatism also calls for care in setting the power and axis of a toric lens.
Right eye: with-the-rule astigmatism, so the error in one eye could not guide the other
The right eye, on the other hand, had a corneal power of 43.41 D, steeper than the left eye, with with-the-rule astigmatism (see the red frame for the ARGOS right eye in the figure below). In other words, she had an unusual corneal shape in which the type of astigmatism was exactly opposite between the two eyes. This meant we could not use a strategy often used in bilateral surgery: using the actual refractive error in the first (left) eye to adjust the lens power for the second (right) eye.
Discrepancy between Barrett Universal II and Kane formula results
Another problem was that the powers recommended by the IOL formulas we referred to (Barrett True AL and the Kane formula) differed by about 1 D in both eyes (see the Barrett True AL results in the figure above and the Kane results in the figure below).
- Left eye: Barrett True AL → 13.0 D (predicted −0.32 D) / Kane → 12.0 D (predicted −0.17 D)
- Right eye: Barrett True AL → 11.5 D (predicted −0.29 D) / Kane → 10.5 D (predicted −0.12 D)
Discrepancies between formulas are often seen in highly myopic, long eyes, but a difference this large makes the final lens choice difficult. Here we show the Barrett True AL result from ARGOS, which uses segmental refractive indices to measure axial length more accurately, as the representative value. At our clinic, however, we choose the lens power by comparing results from four instruments in total: multiple axial length measuring devices, values from Verion, and intraoperative measurements optimized with the ORA system. In the end, using AI-based results together with a regression formula derived from our own MiniWELL cases over the past 9 years, we narrowed the lens power down to two candidates before surgery.
Left eye surgery and postoperative course
In the left eye, zonular weakness typical of atopic cataract was not marked, and removal of the lens went smoothly. We performed intraoperative wavefront aberrometry with the ORA system to determine the power. As a result, we chose a 12.5 D lens, calculated from a regression formula using intraoperative total aberration values as the explanatory variable; this differed from both the ARGOS recommendation and the Kane result. We also inserted a capsular tension ring (CTR) to improve long-term lens stability, and the surgery was completed without any notable events.
Visual acuity after surgery (the next day)
On the day after left eye surgery, her uncorrected visual acuity was already excellent at 1.5p distance / 1.2p near, and neither the refractive error nor the astigmatic axis shift we had feared occurred, which was a relief (see the change in visual acuity in the figure below).
Right eye: deciding whether RLE was indicated
Her wish for right eye surgery
After the good result in the left eye, she again told us that she strongly wished to have the right eye operated on as well. However, the cataract in the right eye was very mild, and given her age she should still have had some accommodation. Surgery in this situation is considered Clear Lens Exchange (CLE), also called Refractive Lens Exchange (RLE), performed to correct refraction.
I am basically skeptical of RLE. In an eye with minimal lens opacity and remaining accommodation, surgery carries the risk of making some aspects worse than before if the lens type and target refraction are not chosen appropriately. With RLE using multifocal lenses, quite a few people come to our clinic with the complaint that "I could see well up close without glasses before surgery, but now it is harder to see." If your own accommodation exceeds the near performance of the lens, near vision will actually decrease after surgery.
Objective evaluation by preoperative near visual acuity
Because she strongly wished to have the right eye operated on, we measured her near visual acuity while wearing her usual contact lens as an objective indicator.
- Right eye (corrected with soft contact lens), visual acuity at 40 cm: 1.0
- Right eye (corrected with soft contact lens), visual acuity at 30 cm: 0.7p
The left eye (3 days after MiniWELL surgery), on the other hand, had an uncorrected visual acuity of 1.2 at 40 cm and 0.8 at 30 cm (see figure below).
These results were very important for deciding whether surgery was indicated. Although the right eye still had its natural lens (with accommodation) plus contact lens correction, the left eye with the MiniWELL had better visual acuity at 40 cm and 30 cm. In other words, we were able to confirm before surgery that "the near performance of the MiniWELL already exceeded the current accommodation of the right eye." We explained that "surgery would very likely improve both distance and near vision compared with before," and at her request we proceeded with surgery on the right eye.
Next came setting the target refraction for the right eye. Although the right eye was the dominant eye, it originally had a longer axial length and steeper cornea than the left eye, meaning it was more myopic than the left eye. Perhaps for this reason, she asked that the right eye be set "slightly" more toward near than the left eye. As with bilateral surgery using EDOF lenses such as TECNIS PureSee, the meaning of "slightly" differs from patient to patient. Whether it is specifically 0.25 D, 0.5 D, or 0.75 D only becomes clear with a postoperative simulation (the FEST method) and cannot be known beforehand. This is why I recommend, when possible, not operating on both eyes on the same day and operating first on the eye intended for distance (the dominant eye?). However, eye dominance can switch relatively easily after surgery (dominant switch), so I think it need not be a concern to the extent it is with mix-and-match.
Right eye surgery and final results
For the right eye as well, we checked the results of intraoperative wavefront aberrometry with the ORA system and chose a 12.0 D MiniWELL Toric T2.0 so that the eye would be set slightly more toward near than the left eye. The surgery was completed without problems.
After surgery there was no significant refractive error or astigmatic axis shift, and the refraction was, as targeted, slightly more toward near than the left eye. The final result was distance 1.2–1.5 and near 1.2 at 40 cm in both eyes, and she was very satisfied (see figures below).
Cautions regarding RLE
Prompted by this case, there is something I would like to say again.
Unfortunately, as in the case of residual astigmatism problems in Case #92 (Japanese), we continue to see multiple people who had surgery at clinics that actively promote the MiniWELL and come to us saying, "I can no longer see up close after surgery." To identify the cause of dissatisfaction after surgery, the first step is comparison with the preoperative condition. Some of these patients brought their complete medical records from the previous clinic, and in some cases the basis for deciding on a multifocal lens was questionable: near visual function had never been evaluated before surgery, or no detailed corneal topography had been performed even though the eye had undergone LASIK.
Many people with myopia can see well up close without glasses. If the cataract is mild, its effect on visual function is often small too, and multifocal lenses should not be implanted casually in such people. In particular, people who can see at 30–40 cm without glasses need to understand before surgery that, depending on the lens type, distance vision may improve but the near vision they have had until now may decrease.
Even a single aspect that is worse than before surgery can lead to dissatisfaction and regret. Rather than deciding on surgery quickly based on information from social media, it is important to think carefully yourself about the choice of lens and whether surgery is necessary. In particular, with self-pay treatment such as the MiniWELL, follow-up visits for any problems are also, as a rule, entirely self-pay, so I recommend choosing a surgical facility after checking carefully how postoperative issues are handled.
Cautions regarding multifocal IOL candidacy and refractive error
There is no uniform standard for deciding whether a patient is a candidate for a multifocal lens, but accurate preoperative testing can identify in advance eyes in which, structurally, the multifocal function of the lens is unlikely to work well. One basis for this judgment is detailed corneal topography. If multifocal lenses are used simply at the patient's request without corneal topography using instruments such as anterior segment OCT or wavefront analysis, perhaps 90% of patients will still be satisfied. However, I recommend that patients undergo surgery only after receiving a clear explanation of why they are a candidate for a multifocal lens, that is, the evidence that the lens's functions can work properly in their eyes.
It is also important whether measures are taken to bring refractive error as close to zero as possible. Whether a clinic truly prioritizes refractive error can be judged to some extent from the instruments it uses, including the corneal topography devices mentioned above. The basic way to reduce refractive error is to optimize lens constants for the same measuring instrument. That alone may keep refractive error within 0.5 D in more than 80% of patients, but if a clinic truly prioritizes refractive error, it is recommended to determine lens power with multiple different instruments and processes. It is also important to ask to see, in advance, the specific measures and test results that support a claim of "prioritizing refractive error."
Many of the people who come to us with problems after surgery seem to have chosen their clinic because they trusted announcements on social media such as YouTube saying "we properly assess candidacy for multifocal lenses" or "we prioritize refractive error." Unfortunately, as in the residual astigmatism case and the post-LASIK cases mentioned above, in reality even the necessary tests were sometimes not performed; in other words, these were problems that could have been avoided.
Recent multifocal lenses have become far more capable than before, and the range of suitable patients has widened. Not every facility, including ours, can perform ideal preoperative testing. But if surgery is performed at a facility that at least understands your preoperative visual function, confirms that nothing will be worse after surgery, and properly carries out the two points above (corneal topography and measures against refractive error), you can usually expect a satisfactory result. Conversely, many postoperative problems arise because these tests and measures were not carried out, so I recommend that patients who are unsure about surgery check these points once more. At our clinic, as shown in the figure below, we list preoperative measurements, intraoperative wavefront values, refractive errors and other data for each lens we have used and perform regression analysis, in an effort to keep postoperative refractive error as small as possible.
Closing
This case is the 100th in our case collection.
We are honored and grateful to have received many inquiries about lens and power selection, not only from patients but also from fellow ophthalmologists. We hope that publishing our accumulated work, case by case, on preoperative evaluation, lens selection and measures against refractive error has been of some help to people considering surgery with multifocal lenses and to doctors considering introducing multifocal lenses.
We will continue to present not only cases with good results but also difficult cases and cases in which the decision was hard.
2026.7.26