Intraocular implants

01 · Overview

Overview

A lens placed inside the eye

When myopia, hyperopia or astigmatism is too severe to be corrected with a laser, or when the cornea is too thin, vision can be corrected in another way: by placing a corrective lens inside the eye.

This lens is inserted through a very small incision and positioned behind the iris, in front of the natural crystalline lens, which is left intact. It works like a permanent contact lens, but is placed inside the eye.

Two major differences from laser treatment:

• the cornea is not altered — no tissue is removed, which makes the technique accessible to eyes that are not eligible for laser treatment;
• the implant can be removed or exchanged — the technique is reversible in principle, whereas laser treatment is not.

The trade-off: lifelong monitoring

A foreign body is introduced into the eye, in a narrow space containing delicate structures: the inner surface of the cornea, the iris, the crystalline lens and the drainage pathways for intraocular fluid.

This requires regular, lifelong ophthalmological monitoring: measurement of eye pressure, counting of corneal endothelial cells and examination of the crystalline lens. This monitoring is not optional — it allows silent complications to be detected in time. Choosing this technique means accepting this follow-up for the decades ahead.

02 · Indications

Indications

Who might this technique be suitable for?

• myopia, hyperopia or astigmatism too severe for laser treatment;
• a cornea that is too thin or whose topography does not permit laser treatment;
• significant dry eye that contraindicates laser treatment;
• a correction that has been stable for at least one year;
• adulthood, with ocular growth complete;
• compatible eye anatomy: sufficient anterior chamber depth and satisfactory corneal endothelial cell density;
• no eye disease contraindicating the procedure;
• acceptance of long-term follow-up.

A different option must not be confused with this one. In older people, particularly after the age of forty-five or fifty, the ophthalmologist may suggest replacing the natural crystalline lens with an intraocular lens rather than adding an implant — the same procedure used for cataracts, performed before one develops. This option permanently removes the risk of future cataract and can correct presbyopia, but it eliminates any remaining natural accommodation and carries the risks of crystalline-lens surgery, particularly retinal detachment in people with high myopia. These are two different strategies that must be clearly distinguished during consultation.

03 · Preparation

Preparation

A particularly demanding assessment

The assessment is more extensive here than for most eye procedures because anatomy determines feasibility:

• precise measurement of the correction, with and without pupil dilation;
• measurement of anterior chamber depth and the internal diameter of the eye — these measurements determine the size of implant to order;
• counting the cells on the inner surface of the cornea: these cells do not regenerate, and their initial number determines long-term safety;
• corneal topography and measurement of intraocular pressure;
• examination of the back of the eye, particularly carefully in people with high myopia, to look for peripheral retinal lesions that must be treated before the procedure;
• assessment of dry eye.

The implant is custom-ordered using these measurements. This has an important practical consequence: surgery cannot be arranged immediately after a first examination, because manufacturing and delivery time is required.

04 · Procedure

Procedure

How the procedure is performed

The procedure is brief and is most often performed under local anaesthesia with eye drops, as day surgery, with one eye treated after the other or both eyes treated a few days apart depending on the clinical team.

The surgeon makes a very small incision, inserts the folded implant using an injector, and then carefully positions it behind the iris. The position and the distance between the implant and the natural crystalline lens are checked: this is a decisive parameter, since an implant that is too close or too far away may need to be exchanged.

05 · Aftercare

Aftercare

After the procedure

Vision

Improvement is often rapid, sometimes from the next day, with a period of fluctuation during the first few days.

Discomfort

A foreign-body sensation, watering and sensitivity to light during the first few days.

Eye drops

Local treatment is prescribed for several weeks and must be followed rigorously.

Pressure check

Checked early: an increase may occur during the first hours or days.

Precautions

Do not rub the eye; avoid swimming pools, hammams, make-up, dust and significant exertion for the specified period.

Halos

Halos around lights at night are common at first and often lessen over time.

Signs requiring urgent medical attention

Reduced vision, increasing pain, significant redness, or coloured halos accompanied by headache and nausea. These signs may indicate an intraocular infection or a sudden rise in eye pressure — two emergencies in which the outcome can depend on a matter of hours. Never wait.

06 · Outcomes

Outcomes

What can reasonably be expected

The quality of vision achieved is usually excellent, often better than with glasses for high corrections, with a more natural field of view.

Three limitations must be understood:

• a residual refractive error is possible and may sometimes require an additional correction;
• the implant does not correct presbyopia: the need for reading glasses will appear or continue with age;
• night-time halos may persist in some people.

People with high myopia must also understand that the procedure does not remove the risks associated with myopia itself — retinal detachment, macular disease and glaucoma. Lifelong examination of the back of the eye remains necessary, independently of the implant.

07 · Risks

Risks

Risks and complications

• Cataract — contact with, or prolonged proximity to, the natural crystalline lens may promote clouding, sometimes years later. This is the most characteristic risk of this technique;
• Progressive and silent loss of cells from the inner surface of the cornea, which may eventually compromise corneal transparency — hence the need for regular cell counts;
• Raised intraocular pressure, early or late, with a risk of glaucoma;
• An incorrectly sized implant, too close to or too far from the crystalline lens, requiring an exchange;
• Rotation of a toric implant, requiring repositioning;
• Intraocular infection — rare but serious, an absolute emergency;
• Intraocular inflammation;
• Halos, glare and difficulty with night vision;
• Retinal detachment, particularly in people with high myopia;
• A change in pupil shape;
• Residual refractive error or change in the correction over time.

08 · Contraindications

Contraindications

Situations requiring particular assessment

• insufficient anterior chamber depth;
• corneal endothelial cell density that is too low;
• an unstable correction;
• glaucoma or raised intraocular pressure;
• early cataract;
• a history of intraocular inflammation;
• untreated peripheral retinal lesions;
• diabetes with progressive retinopathy;
• active eye infection;
• pregnancy or breastfeeding — the procedure is usually postponed;
• inability to maintain long-term monitoring;
• unrealistic expectations, particularly regarding presbyopia.

09 · Frequently asked questions

Frequently asked questions

Questions patients often ask