Enhanced Monofocal IOL: Intermediate Vision, Few Halos

An enhanced monofocal IOL is a lens that behaves mostly like a standard monofocal lens, with a small gain in vision at intermediate distance.

Designers changed the optic surface to give a little more depth of focus, without splitting light into separate foci as multifocal lenses do.

The goal is also better computer and dashboard vision with little cost in halos and glare.

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Why the Enhanced Monofocal IOL Was Developed

A standard monofocal lens gives excellent distance vision but needs glasses for near and intermediate tasks.

Multifocal and extended depth of focus lenses improve the range, but some patients complain of halos, glare, and loss of contrast (see multifocal IOL selection).

In addition, enhanced monofocal lenses try to fill the gap between these choices.

Enhanced Monofocal IOL: How the Designs Work

• Modified aspheric optics: a continuous change in power from the periphery to the center of the lens raises power slightly in the middle, which extends the focus a little (see the references)
• Wavefront-shaping optics: a smooth, non-diffractive element in the center stretches and shapes the wavefront to extend the range

Neither design splits the light, so image quality at distance stays close to that of a monofocal lens.

What Studies Show

Comparisons with standard monofocal lenses showed better intermediate vision with enhanced designs, by about one or two lines on defocus curves, with similar distance acuity (see the references).

Photic phenomena, however, were similar to those of monofocal lenses and lower than those of multifocal lenses.

Near vision is usually not improved enough to read small print, so reading glasses are still needed.

Enhanced Monofocal IOL: Compared With Other Lens Types

• Standard monofocal: best contrast, least halos, but limited range
• Enhanced monofocal: slight gain at intermediate distance, similar quality to a monofocal
• Extended depth of focus lens: a longer range and more disturbance (see extended depth of focus IOL)
• Multifocal lens: the widest range, with the most halos

Who Is a Good Candidate?

• Patients who want better computer distance without more halos
• Those with a high demand for night driving
• Patients with mild macular or corneal disease, who may not tolerate multifocal lenses
• People who accept reading glasses

Enhanced Monofocal IOL: Who Should Be Careful?

• Patients who expect full spectacle independence
• Those with an unstable surface, high astigmatism, or irregular cornea, in whom any premium lens may also disappoint
• Patients with advanced macular disease, in whom a standard monofocal is safe

Planning Pointers

• Accurate biometry and a target close to emmetropia are therefore essential
• Treat dry eye before measuring, and correct astigmatism with a toric version or an incision (see limbal relaxing incisions)
• Some surgeons aim a small myopic target in the second eye to add near function, with careful counselling
• Discuss expectations in plain words, and then record the discussion

Counselling

Explain that the lens gives a little extra range, that glasses may still be needed for reading, and that visual quality is similar to that of a standard lens.

An Example Case

A 66-year-old accountant has bilateral cataracts, works at a computer all day, drives at night, and dislikes halos.

He chooses an enhanced monofocal lens in both eyes, with a target near emmetropia, and sees well at distance and at the computer screen, with reading glasses for books and menus (see phacoemulsification).

He reports no bothersome halos, which matches his expectation.

What to Tell Patients Before Surgery

• The lens is designed to give slightly more range than a standard lens, not a full range
• Reading glasses will probably be needed
• Night vision quality is also expected to be close to that of a standard lens
• A small residual refractive error can also reduce the extra benefit

Cost and Choice

Enhanced monofocal lenses cost less than most multifocal lenses, while in some systems they are offered at little or no extra cost.

The decision should also come from lifestyle and expectations, and not from a sales pitch.

Follow-Up for Enhanced Monofocal IOL

Check the refraction at one month, treat dry eye if blur persists, and review the capsule for opacification, since any haze reduces the benefit of the lens.

Key Messages for Colleagues

Describe these lenses as monofocal lenses with a small bonus, and avoid language that suggests a multifocal result.

Also, patients who are told clearly what to expect are more satisfied, whatever the lens, and a documented discussion protects both sides.

Also, audit your own patient-reported outcomes, and compare them with standard lenses in your practice.

For the latest studies, see the PubMed results for enhanced monofocal IOL.

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References

1. Mencucci R, Cennamo M, Venturi D, Vignapiano R, Favuzza E. Visual outcome, optical quality, and patient satisfaction with a new monofocal IOL, enhanced for intermediate vision: preliminary results. J Cataract Refract Surg. 2020;46:378-387.
2. Nanavaty MA, Ashena Z, Gallagher S, Borkum S, Frattaroli P, Barbon E. Visual acuity, wavefront aberrations, and defocus curves with an enhanced monofocal and a standard monofocal intraocular lens: a prospective randomized study. J Refract Surg. 2022;38:10-20.
3. Kohnen T, Suryakumar R. Extended depth-of-focus technology in intraocular lenses. J Cataract Refract Surg. 2020;46:298-304.
4. American Academy of Ophthalmology. Basic and Clinical Science Course, Section 11: Lens and Cataract. AAO; current edition.