Corneal inlays are tiny lenses or optical devices that are implanted into the cornea to change its shape and correct vision disorders. They are inserted in the stroma, which is the thicker middle layer of the cornea. The eye surgeon can use laser energy to sculpt the artificial material instead of the eye tissue. It preserves the corneal thickness.
The implants are stable and provide long-lasting and predictable results. They don’t need ongoing care or removal and are becoming the preferred choice for patients and eye doctors.
Corneal inlay surgery may also have fewer risks and is less invasive than other refractive surgery options. The procedure doesn’t need the removal of tissue from the cornea. It reduces the risk of bulging eye, dry eye and other complications that may go with more invasive vision correction surgery.
Also Known As
- Corneal implants
Types of surgery
There are three main types of corneal implants:
- Refractive corneal inlays
These are disc-shaped corneal implants that are similar in design to an intraocular lens or multifocal contact lens. They correct near vision by changing the corneal refractive index. The middle area of the inlay is neutral, without refractive power, which preserves distant vision. It allows light from distant objects to focus on the retina. Surrounding the middle zone is a circular area with more positive power; it improves near vision by focusing light from near sources on the retina.
- Corneal reshaping inlays
This type of corneal implant works by changing the curvature of the anterior surface of the cornea. The inlays are placed in the anterior of the cornea to create a hyper prolate corneal surface. To improve near vision, reshaping inlays increase the curvature of the middle zone of the anterior surface of the cornea. They allow paracentral light to pass through the thinner area of the implant which enables the person to see distant objects. The curved central part of the cornea enables the individual to view near objects.
- Small aperture inlays
These are ring-shaped, opaque corneal implants with a central aperture. They improve near vision by using the principle of pinhole optics which increases the depth of focus. The ring allows only the central light to pass unhindered and blocks the peripheral light.
Corneal inlays work by increasing the refractive power of the paracentral or central area of the cornea. Their primary purpose is to improve near vision. They reduce the need for reading glasses for people with presbyopia. It is an age-related eye disorder in which the ability to focus on near objects decreases.
The implants can also be used in combination with other procedures, like LASIK, to correct refractive disorders such as myopia, hyperopia and astigmatism.
Preparation & expectation before Surgery
Corneal inlays are ideal for early and mid presbyopic individuals between the ages of 40 and 60. Patients should undergo topography to screen for corneal disorders. The eye care professional may also perform pachymetry to ensure the patient has adequate corneal thickness.
Corneal inlay surgery is not recommended for patients with:
- Corneal diseases such as keratoconus
- Ocular surface diseases like blepharitis or dry eye
The surgery is reversible; the patient can remove the device if the results are not satisfactory.
Corneal inlays are inserted into the non-dominant eye only. The eye surgeon uses a laser to cut a small flap or pocket at the center of the cornea. He/she then inserts the inlay under the flap or into the pocket, depending on the type of device, and closes the cut.
The surgery can be performed in the surgeon’s office and takes about 15 minutes. It is done under a local anesthesia and the patient is awake during the procedure.
After care, recovery, results
The patient will use antibiotic drops for a week and steroid eye drops for a period of one month. They help to cut haze formation, interface wound healing and opacification. The medication also prevents refractive shifts.
Risks & complications
Corneal inlay surgery is safe because it is limited to the cornea. Side effects may include:
- Corneal haze
- Halos and glare
- Loss of contrast sensitivity
- Disturbances in night vision
- Difficulty in reading in low light
Complications may include:
- Dry eyes
- Keratolysis, vascularization and opacification, especially with older inlay designs
- Epithelial ingrowth which may cause blurred vision, starbursts and light sensitivity
- Lens decentration which decreases the quality of vision and particularly impacts distance vision