Light Adjustable Lens: Postoperative Refractive Tuning

The light adjustable lens is an intraocular lens whose power the surgeon can change after implantation.

A few weeks after surgery, when healing has settled, the clinician shines patterned ultraviolet light onto the lens, and the refractive power shifts to match the patient’s needs.

It tackles the weakest point of cataract surgery, which is that nobody knows the final refraction until the eye has healed (see refractive surprise after cataract surgery).

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The Problem the Light Adjustable Lens Solves

Even with good biometry, a share of eyes miss the target, and healing, capsule changes, and corneal shifts affect the result.

Surgeons cannot change traditional lenses without another operation, so patients rely on glasses, laser, or lens exchange.

Light Adjustable Lens: How the Lens Works

• Manufacturers make the lens from photosensitive silicone with light-reactive macromers
• When the surgeon applies a specific pattern of UV light, the macromers in the exposed zone link up, and the others migrate toward it, changing the shape and power of the lens
• Once the desired result is reached, a final exposure locks the lens, so that no more change occurs (see the references)

Staff program the device delivering the light with the patient’s refraction.

The Treatment Schedule

• Cataract surgery with the light adjustable lens, using standard small-incision technique
• Healing for about two to three weeks
• One to three light adjustment sessions, a few days apart, each guided by a new refraction
• Lock-in sessions, after which the power stays fixed

Patients must wear UV-protective glasses at all times until lock-in, since sunlight could change the lens in an uncontrolled way.

Light Adjustable Lens: What Can Be Adjusted?

• Spherical error, to correct myopia or hyperopia
• Astigmatism, which makes the lens useful as a toric option
• Targets for monovision, with different powers in the two eyes, adjusted after the patient tries them (see monovision cataract surgery)

The ability to try a result before locking it in gives patients a role in the decision.

Accuracy and Evidence

Clinical studies showed that a large proportion of eyes reached the target refraction within half a diopter after adjustment, and that results were stable over time (see the references).

Studies in patients after refractive surgery, in whom calculation is harder, also showed good outcomes.

Light Adjustable Lens: Who Benefits Most?

• Patients with high expectations for spectacle independence
• Eyes after laser refractive surgery, with unreliable calculation
• Eyes with significant astigmatism
• Patients who want to test monovision before committing

Limits

• Extra visits and time, with multiple sessions
• Strict use of UV-blocking glasses, which some patients find a burden
• Cost, since the lens and the light delivery are additional
• Availability limited to centers with the equipment
• The lens is a monofocal design, and does not correct near vision on its own

Light Adjustable Lens: Counselling

Explain the schedule, the glasses requirement, and the benefit of fine-tuning.

Discuss alternatives, such as toric lenses and extended depth of focus lenses (see extended depth of focus IOL).

An Example Case

A 60-year-old man had myopic LASIK years ago and now needs cataract surgery, with a lens power that is difficult to predict.

He receives a light adjustable lens, and at three weeks his refraction shows a small hyperopic error, which is corrected with a first adjustment, followed by a second to fine-tune the result and a lock-in session.

He ends with 20/20 uncorrected distance vision, and the process allowed him to try a slight monovision setting before locking it in (see phacoemulsification).

Practical Points for Clinics

• Schedule the sessions in advance, and give patients their UV glasses before surgery
• Check that patients can wear the glasses indoors and outdoors until lock-in
• Document the refraction before each session
• Offer an alternative if the patient cannot comply

Looking Ahead

Light-adjustable technology may extend to other lens designs, such as toric and multifocal, and shows a trend toward customizing outcome after healing.

Questions Patients Ask

Patients ask whether sunlight can change the lens after lock-in, and the answer is that once locked, the lens is stable and does not respond to light.

They also ask whether the procedure hurts, and the adjustment is painless and takes a few minutes per session.

Key Messages for Colleagues

Offer the lens to patients who value precision and are willing to follow the schedule, including the glasses requirement.

Prepare the staff to explain the process, and check that the adjustment device is available on the planned dates.

Record the refraction before and after each session, to audit results.

For the latest studies, see the PubMed results for light adjustable lens.

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References

1. Chayet A, Sandstedt CA, Chang SH, Rhee P, Tsuchiyama B, Grubbs R. Correction of myopia after cataract surgery with a light-adjustable lens. Ophthalmology. 2009;116:1432-1435.
2. Hengerer FH, Dick HB, Conrad-Hengerer I. Clinical evaluation of an ultraviolet light-adjustable intraocular lens implanted after cataract removal: eighteen-month follow-up. Ophthalmology. 2011;118:2382-2388.
3. Kohnen T, Koch DD, eds. Cataract and Refractive Surgery. Springer; 2005.
4. American Academy of Ophthalmology. Basic and Clinical Science Course, Section 11: Lens and Cataract. AAO; current edition.