Extended Depth of Focus IOL: Pros, Cons and Selection

An extended depth of focus IOL stretches a single focal point into an elongated range, so the patient sees well from far to intermediate distances.

It was developed to offer spectacle independence with fewer of the halos and glare that multifocal lenses cause.

Also, the cost is usually weaker near vision, and the lens needs careful patient selection.

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How an Extended Depth of Focus IOL Works

Multifocal lenses split light into separate foci, each with its own image, and the brain picks the one it needs.

An extended depth of focus lens extends one focus by using a diffractive echelette design, small corneal-like aberrations, or a controlled spherical aberration, so that the image stays acceptable over a longer range (see the references).

Some lenses use wavefront shaping to extend the range slightly, and they are also classed as enhanced monofocals.

Because there is no sharp second focus, the halos are fewer and the contrast is better preserved.

Extended Depth of Focus IOL: What Patients Gain

• Sharp distance vision, and good intermediate vision for computers and cooking
• Fewer photic phenomena than with most multifocal lenses
• Reduced dependence on glasses for most daily tasks
• Good tolerance of small residual refractive errors in some designs

Clinical studies show that distance and intermediate acuity are comparable to or better than those of multifocals, with less visual disturbance, and a lower rate of dissatisfaction (see the references).

Limitations of Extended Depth of Focus IOL

• Near vision: often limited, and many patients need reading glasses for fine print
• Dysphotopsia: still present in a minority, such as halos at night
• Contrast sensitivity: slightly reduced compared with monofocal lenses in some studies
• Sensitivity to errors: residual astigmatism, decentration, and ocular surface disease affect the results (see toric IOL misalignment)
• Cost, which patients usually bear

Neuroadaptation is needed, and results improve over weeks.

Patient Selection

Good candidates are patients who want less dependence on glasses for distance and computer use, who accept that reading glasses may be needed, and who have healthy eyes (see multifocal IOL selection).

• Healthy macula and optic nerve
• Regular corneal astigmatism of low degree, or treatable with a toric lens or incision
• A normal ocular surface
• Realistic expectations and a calm personality about small visual changes

Patients with macular disease, glaucoma, severe dry eye, or irregular cornea should also be steered to a monofocal lens.

Planning and Targets

• Accurate biometry with modern formulas is essential, and a target near emmetropia is advised
• Correct astigmatism over about 0.75 diopters, since it blurs the image
• Some surgeons aim a dominant eye at distance and the other eye at slight myopia, in a mini-monovision approach, to improve near vision
• Combine with a good surface treatment before measurements (see dry eye disease)

Counselling

Explain that the lens gives a range of vision and not a full range, and that reading glasses may be needed for small print.

Also, describe the likelihood of halos at night, and that most patients adapt.

Also, give time for questions, and record that the discussion took place.

Extended Depth of Focus IOL: Follow-Up and Problems

Check the refraction, the position of the lens, and the capsule at each visit.

In addition, posterior capsule opacification can reduce the benefit, and laser capsulotomy can restore the image (see YAG laser capsulotomy).

Patients who remain unhappy despite correction of the refractive error may need an IOL exchange, which is rare.

Comparing EDOF and Multifocal Lenses

A multifocal lens gives better near vision.

A patient who wants to read without glasses may prefer it, at the cost of more halos and glare.

An extended depth of focus lens gives smoother intermediate vision and less night disturbance.

A patient who drives often at night or works at a computer may also prefer it.

Some surgeons combine different lenses in the two eyes, to broaden the range, with careful counselling and a test of tolerance with contact lenses.

Trial Frames and Simulation

A test with contact lenses or a simulator can help patients to judge the effect of a blended vision before surgery, though it does not copy the optics of the implanted lens exactly.

When Results Disappoint

The first step is to check for residual refractive error, dry eye, and capsule opacity, and to correct them with drops, laser, or a small adjustment.

If symptoms persist after several months, the options include a lens exchange or a piggyback lens, although most patients adapt without surgery.

Document the discussion of expectations, including the need for reading glasses, and recheck satisfaction at the three-month visit, when most adaptation has taken place.

For the latest studies, see the PubMed results for extended depth of focus IOL.

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References

1. Kohnen T, Suryakumar R. Extended depth-of-focus technology in intraocular lenses. J Cataract Refract Surg. 2020;46:298-304.
2. Cochener B, Boutillier G, Lamard M, Auberger-Zagnoli C. A comparative evaluation of a new generation of diffractive trifocal and extended depth of focus intraocular lenses. J Refract Surg. 2018;34:507-514.
3. Rocha KM. Extended depth of focus IOLs: the next chapter in refractive technology? J Refract Surg. 2017;33:146-149.
4. American Academy of Ophthalmology. Basic and Clinical Science Course, Section 11: Lens and Cataract. AAO; current edition.