One Orchestra, Two Coordinated Sections

Monocular trifocal in exacting emmetropes

One eye holds the melody as the other adds the harmony. For motivated emmetropic presbyopes, one-eye trifocal implantation widens range without dulling distance when selection, targeting and coaching are precise.

The clinical puzzle is all too familiar: emmetropic, relatively young presbyopes who cherish their crisp distance vision but struggle with the creeping burden of near tasks. Rather than asking both eyes to share diffractive duties, Medellín refractive surgeon and founder of Black Mammoth Surgical, Dr. Kepa Balparda (Colombia), prefers to keep the dominant eye for distance and upgrades the fellow eye for near and intermediate vision.

In his retrospective pilot study (n=13) using the pentafocal Intensity SL (Hanita Lenses; Shlomi, Israel) in the non-dominant eye, uncorrected near and intermediate vision improved in the operated eye, binocular distance was maintained, no exchanges were required, and 100% reported spectacle independence for daily tasks at three months.¹ With careful dominance testing, precise biometry and conservative targeting, binocular vision behaves like an ensemble: distance carries the melody, the upgraded eye fills the harmony, and the brain conducts the blend.

Casting and score

These are exacting patients: emmetropic presbyopes who take pride in their uncorrected distance visual acuity (UDVA) yet feel the growing drag of readers. Think of them as listeners who love a clear solo line but crave a fuller arrangement for everyday tasks.

Bilateral diffractive implantation can certainly widen the score, though some notice a subtle softening in perceived contrast when the whole orchestra plays through diffractive optics.² Monovision LASIK offers another route, but comfort depends on how much anisometropia a person can live with and what their daily “set list” demands.³

A monocular trifocal aims to preserve distance clarity in the “first violin” while letting the fellow eye quietly add near and intermediate support—the phakic-pseudophakic duet that rounds out the sound.

Still, the selection process is exacting. You want a quiet surface, regular topography, a healthy macula and nerve, minimal cylinder, normal pupils and goals that match reality. Yellow flags include irregular astigmatism, forme fruste keratoconus (FFK), large mesopic pupils with a history of glare, or low tolerance for any quality shift. As Dr. Balparda puts it, “premium lenses require premium eyes.”

When planning and targeting, it’s important to confirm ocular dominance with history, sighting and real-world tasks, then reserve the dominant eye for distance. Centering and effective lens position prediction matter, so pay attention to chord mu, angle alpha and anterior corneal power so the implant sits where the music blends. Targets should stay conservative, since heavy monovision risks bending the main theme for distance-critical patients.³

In practice, Dr. Balparda observes that monocular contrast sensitivity in the implanted eye may dip slightly, which is expected with diffractive optics, while binocular contrast for distance generally holds steady because the dominant eye carries that line.

Reading the score

First, the solo. In emmetropic presbyopes, a unilateral trifocal lifts near performance without flattening binocular distance in everyday use.⁴ A second unilateral cohort showed similar outcomes in patient-reported function, with VF-14 scores above three across most tasks. The predictable trouble spots were small print and night driving, yet overall tolerance remained high.⁵

Then the section work. Larger emmetropic comparisons confirmed the expected trade. When both eyes receive diffractive optics, peak binocular near and intermediate improve. Even so, a one-eye upgrade can satisfy patients who seek range for daily life but insist on keeping distance clarity as their anchor.⁶

For long-view context, blended bilateral strategies show how a “melody eye” and a “range eye” share duties over time. Across three years, pairing an enhanced monofocal for distance with either a trifocal or a trifocal-extended depth of focus (EDOF) in the fellow eye maintained excellent binocular distance and intermediate vision, favored near in the trifocal arm, kept halos and glare modest, and showed Nd:YAG rates within expectations—more often in the enhanced-monofocal eyes than in the diffractive ones.⁷

Within that backdrop, Dr. Balparda’s pilot adds a focused clinical datapoint. A pentafocal in the non-dominant eye widened the usable range, improved near and intermediate vision in the implanted eye, preserved binocular distance, required no exchanges, and produced complete spectacle independence at three months, with roughly 92% across his broader clinical experience.¹

Contrast, night work and the rehearsal period

Contrast is the dynamic range of the visual score. Diffractive optics can shave a little off the monocular peaks at higher spatial frequencies when judged in isolation, consistent with long-term studies.² The good news is that the ensemble effect helps: binocular summation tends to restore the volume, so distance performance feels stable once both eyes are “playing” together.

In unilateral cataract models, monofocal or accommodative lenses show higher high-frequency contrast than multifocals, yet within multifocal groups the binocular result reliably exceeds the monocular read—an important point for chairside expectations.²

Coaching sets the tempo. Early on, encourage good lighting, practice at typical working distances, and avoid direct A–B eye comparisons that may make the parts sound mismatched before the brain blends them. As Dr. Balparda explains, patients should expect a period of neuroadaptation and clear preoperative conversations make those first weeks far smoother. He cuts straight to the core: “What you tell before surgery is information; what you tell afterwards is an explanation for a complication.”

A practical follow-up rhythm through three to six months lets the “rehearsal” conclude, providing space to fine-tune comfort, refraction and habits along the way.

Where it sits in the repertoire

Every clinic has more than one way to play the piece. For patients comfortable with anisometropia who spend less time on fine near work, monovision LASIK can still be a solid choice, but stereo and satisfaction depend on how much imbalance they can tolerate and what their days demand.³ The monocular trifocal approach aims to preserve stereo and binocular summation while adding useful range, which is why it resonates with distance-protective emmetropes.

Against bilateral trifocals, it’s a trade in emphasis. Two diffractive optics typically deliver stronger peak binocular near and intermediate vision, whereas the monocular route favors steadier distance dynamics in contrast-sensitive patients who value that clarity above all else.⁶ When ocular status or temperament suggests a different score, small-aperture IOLs are solid alternatives that can extend depth without diffractive artifacts.⁸

Keeping time and closing the gaps

On the practical side, the short-term monocular cohorts here reported no exchanges, and follow-up works best when it keeps time with adaptation. Tidy the surface, check refraction, and look closely at the lens and capsule during the early adjustment period, then again as the ensemble settles. These milestones help patients stay on tempo while neuroadaptation finds its rhythm.^1,4,5 For context on photic phenomena and capsulotomy needs when one diffractive eye shares duties with a distance-optimized fellow eye, the three-year blended-optic data offer a useful reference point.⁷

The score, however, is still being written. Many monocular series remain small, single-center, and short in follow-up. The field would benefit from prospective studies stratified by age, glare testing, pupil behavior and centration analysis.^2,6,9,10 Dr. Balparda’s series is early and under peer review; but the signal is encouraging and the disclosures transparent, with larger and longer cohorts needed to define durability and generalizability.¹

Coda

For the right emmetropic presbyope, one orchestra can carry two coordinated sections. Keep the dominant eye on the melody. Let the non-dominant add near and intermediate with a well-chosen diffractive profile. Select precisely, target conservatively, center meticulously and coach through rehearsal. Most patients will leave the concert hall humming, glasses-free for everyday routines and without dulling the distance line they prize.

Editor’s Note: This content is intended exclusively for healthcare professionals. It is not intended for the general public. Products or therapies discussed may not be registered or approved in all jurisdictions, including Singapore. A version of this article was first published on CAKE Issue 28.

References

Balparda K, Escobar-Giraldo M, López-Velásquez M, et al. Early results after the monocular implantation of a continuous full range of focus intraocular lens (Intensity SL) in emmetropic, young, presbyopic patients. [Unpublished study]. Medellín, Colombia: Oftalmólogos El Tesoro; 2025.
Mesci C, Erbil HH, Olgun A, et al. Differences in contrast sensitivity between monofocal, multifocal and accommodating intraocular lenses: Long-term results. Clin Exp Ophthalmol. 2010;38(8):768-777.
Schallhorn SC, Teenan D, Venter JA, et al. Monovision LASIK versus presbyopia-correcting IOLs: Comparison of clinical and patient-reported outcomes. J Refract Surg. 2017;33(11):749-758.
Levinger E, Titonelli A, Duker IS, et al. Unilateral refractive lens exchange with a multifocal intraocular lens in emmetropic presbyopic patients. Curr Eye Res. 2019;44(7):710-714.
Ozturkmen C, Kesim C, Sahin A. Evaluation of vision-related quality of life after unilateral implantation of a new trifocal intraocular lens. Beyoglu Eye J. 2022;7(3):167-172.
Fernández-García JL, Llovet-Rausell A, Ortega-Usobiaga J, et al. Comparison of patients with emmetropia and presbyopia and different accommodation who undergo unilateral or bilateral implantation of a trifocal IOL. J Refract Surg. 2023;39(12):817-824.
Danzinger V, Lisy M, Schartmüller D, et al. 3-Year Comparison Of Two Mix-And-Match Strategies: Enhanced Monofocal And Trifocal Versus Enhanced Monofocal And Trifocal EDOF IOLs. J Cataract Refract Surg. 2025 Oct 17. [Epub ahead of print]
Hayashi K, Uno K, Hayashi S, et al. Comparison of visual function between phakic and pseudophakic eyes with small-aperture intraocular lenses. Am J Ophthalmol. 2025;223:53-59.
Hayashi K, Uno K, Hayashi S, Yoshida M. Age-related difference in the presbyopia-correcting effect of trifocal and enhanced monofocal intraocular lenses. Jpn J Ophthalmol. 2025 Jul 9. [Epub ahead of print]
Cho JY, Won YK, Park J, et al. Visual outcomes and optical quality of accommodative, multifocal, extended depth-of-focus, and monofocal IOLs in presbyopia-correcting cataract surgery: A systematic review and Bayesian network meta-analysis. JAMA Ophthalmol. 2022;140(11):1045-1053.