Keratoprosthesis Explained: Procedure, Recovery, and Risks

What keratoprosthesis is meant to do

A keratoprosthesis is an artificial cornea intended to restore vision when a standard corneal transplant is not an option. The cornea is the clear front surface of your eye, so severe damage or clouding can block light before it reaches the retina. This treatment replaces the damaged corneal tissue with an artificial device.

This is generally a treatment for complex, high-risk cases after other available options have failed or are unlikely to work. Your specialist must look at the cause of the damage, the condition of the rest of the eye, and your ability to follow a long-term care plan.

The Boston keratoprosthesis received FDA approval in January 1992 for use in patients with severe corneal opacity in the United States. A systematic review examined 26 studies comparing repeat corneal transplantation with the Boston device after a failed transplant. In a meta-analysis of Boston device implantation after a failed transplant, the probability of maintaining vision of 20/200 or better at 2 years was 80%, with a reported 95% confidence interval of 68% to 88%. These results describe groups of patients, not a personal forecast.

In one multicenter study of 300 eyes from 300 patients, 93% of devices were retained at a mean follow-up of 17.1 months. Retention was 94% at 1 year and 89% at 2 years. Retention means the device remained in place; it does not by itself describe how clearly each person saw or whether later treatment was needed.

Why a specialist may consider it

A specialist may consider an artificial cornea when the natural cornea is severely damaged and a donor graft has failed or is unlikely to survive. Possible situations include:

• Multiple failed corneal transplants.
• Severe corneal opacity or blood-vessel growth into the cornea.
• Damage to limbal stem cells, which help maintain the corneal surface.
• Chemical injury or severe keratitis, meaning inflammation or infection of the cornea.
• Serious ocular-surface disease, including certain inflammatory or herpetic conditions.
• An anesthetic cornea after herpes simplex or zoster infection, meaning the cornea has lost normal sensation.

A cited medical policy lists severe opacity and vascularization, significant limbal stem-cell compromise, and an anesthetic cornea after herpes simplex or zoster infection as indications for treating corneal blindness with a Boston device.

Traditional donor grafts may have low viability in recurrent or chronic inflammation, herpetic infections, and corneas with blood-vessel growth. For repeated corneal transplantation, reported long-term graft survival was estimated at 28% to 55% over 5 years and 11% at 10 years after graft implantation in one cited study. Those figures help explain why a specialist may discuss another approach, but they do not decide which option fits your eye.

In one retrospective study of 126 treated eyes, 112 had a history of multiple failed corneal grafts. Another 14 received the artificial cornea as a primary procedure because of limbal stem-cell deficiency or significant ocular-surface disease. These numbers show the severe problems represented in that study, not a checklist you can use to determine candidacy on your own.

The device and donor tissue can be secured to the remaining corneal tissue with interrupted or running 9-0 nylon sutures, with the knots buried. The exact device and surgical plan depend on the condition of your eyelids, tears, corneal surface, and the rest of your eye.

What symptoms can and cannot tell you

Corneal problems can cause blurred or variable vision, light sensitivity, redness, tearing, a foreign-body sensation, and intense or disabling pain. Vision affected by corneal swelling or clouding may be worse upon waking and clearer later in the day. These symptoms can occur with several corneal conditions, so symptoms alone cannot show that an artificial cornea is needed.

An eye specialist considers how much vision has changed, how the problem affects daily activities, and whether discomfort is limiting your work or routine tasks. A recent history of eye surgery or complications is also part of the evaluation. Treatment may be considered when corneal swelling or clouding causes functional vision loss or discomfort.

One retrospective study involved 122 patients and 126 eyes receiving a Boston type 1 device. Most treated eyes had vision below 20/400, and the other eye did not have better vision. That description gives context for the study population; it does not mean that every person with blurred vision has the same level of disease.

What to ask during the evaluation

Your evaluation should begin with the cause of the corneal problem and the treatments you have already tried. Ask the specialist to explain how these details affect the options:

• What is the underlying diagnosis?
• What is the current condition of the cornea and the rest of the eye?
• How do prior eye surgeries, steroid use, or immunosuppression affect the plan?
• Is a donor transplant still reasonable, or would another approach be considered?
• What care would you need to provide after surgery?

A thorough eye examination assesses visual potential before placement. Your evaluation may include the ocular surface, tear production, eyelids, blinking, visual acuity, eye pressure, retina, and optic nerve. The specialist may also review surface inflammation, scarring, the space beneath the eyelids, and how completely you blink.

A moist, blinking eye may suit a Boston type 1 device, while a dry eye with impaired blinking may require a different approach. Factors that may help optimize outcomes include adequate eyelid anatomy, good blinking, controlled surface inflammation, and a sufficiently moist surface. These are clinical findings, not conditions you should try to judge without an examination.

Retina and optic-nerve findings can help determine whether surgery should proceed or be deferred. In one report, endoscopic examination found 3 of 10 patients, or 30%, to be adequate candidates, while 7 of 10, or 70%, were not because of retinal disease or optic-nerve pathology. The report involved patients with opaque corneas, and its percentages should not be applied to every clinic or patient.

Ask what visual change would count as a meaningful result for your daily activities. In one retrospective study of 122 patients and 126 eyes, 96 eyes, or 76%, had improved vision after implantation; 22 eyes, or 17.4%, did not improve; and 8 eyes, or 6.3%, lost vision. Those results came from that study population and do not predict your outcome.

What happens during the procedure

The damaged cornea is removed and replaced with an artificial cornea. For a Boston type 1 device, the structure includes a clear plastic optic and back plate around a corneal graft, secured with a titanium locking ring. The surgeon prepares the host cornea, removes the damaged tissue, positions the assembled device, and secures it to the remaining tissue.

The outpatient procedure described in a patient brochure takes approximately 60 to 90 minutes. You may remain in the operating-room area for at least 3 hours before discharge because preparation and recovery occur around the operation. A reevaluation is described for the morning after surgery.

The natural lens is removed during the procedure, and focusing power is established with a prosthetic or an intraocular lens. If glaucoma is threatening or uncontrolled, a specialist may implant a shunt valve before or during the operation. Ask which parts of this plan apply to you and whether another procedure is planned at the same time.

What recovery and follow-up require

Recovery requires planned examinations and daily care. The cited patient brochure describes a check the morning after surgery, then visits usually at 1 week, 1 month, and every 3 months throughout the first year. Your specialist may change the schedule when the eye needs closer monitoring.

The brochure says infection-prevention drops must be used indefinitely because the plastic device does not become totally incorporated into the body. Anti-inflammatory drops are described for the early months after surgery. You should use the prescribed drops exactly as directed and ask what to do if you miss a dose or develop irritation.

A special soft contact lens may remain over the artificial cornea indefinitely. It must still be removed, cleaned, and replaced regularly. This maintenance is part of long-term care, so ask who will handle lens changes, how often they are expected, and which symptoms should prompt an earlier visit.

The cited brochure also describes wearing a protective shield while sleeping at night. Ask when nighttime protection can stop, whether you need activity restrictions, and how to protect the eye from accidental rubbing or injury during recovery.

Results can change over time. In one study, 54% of eyes had vision of 20/200 or better at 3-month follow-up, 18% had 20/40 or better, and approximately 45% remained below 20/400. In a separate multicenter cohort, visual acuity improved for 85% of eyes, reaching a final mean of 20/150 during a mean follow-up of 17 months. Longer follow-up has found that vision loss can occur at or before 9 months or later at 1½ years and beyond; declines in retained vision became evident at 3 years and continued through 4 years in one study.

Which risks need ongoing monitoring

Glaucoma after surgery is common, and the hard optic can make usual eye-pressure measurement impossible. Ask how glaucoma will be prevented and monitored during your evaluation and at each postoperative visit. Joint care with a glaucoma specialist may be appropriate.

A membrane may form behind the device and interfere with vision. In some cases, a laser can open the membrane without additional surgery. Rarely, tissue around the device stem can dissolve and let fluid leak from the eye, which can lead to infection or vision loss and may require repeat surgery.

These figures come from separate studies. In a 57-procedure series with an average follow-up of 17 months, retroprosthetic membranes occurred in 44% of eyes, elevated eye pressure in 18% of eyes, and corneal stromal necrosis in 16% of patients. In a separate prospective series of 265 eyes followed for a mean of 17.8 months, membranes formed in 31.7% of eyes; the mean time to formation was 216.7 days, with a range from 7 days to 4 years.

In one study of 300 eyes, 93% of devices were retained at a mean follow-up of 17.1 months. Mean device durability in that study was 3.8 years, and autoimmune disease, ocular-surface exposure, and multiple prior failed penetrating corneal transplants were risk factors for device loss.

How to interpret results and complication numbers

Published results are not interchangeable. In one 57-procedure series, membranes occurred in 44% of eyes and overall device retention was 84%. In a different multicenter series, retention was 95% at an average follow-up of 8.5 months and 92% at a longer average follow-up of 13 months; membranes occurred in 25% of eyes and elevated eye pressure in 15%.

Follow-up time changes what a study can show. In one 57-procedure series with an average follow-up of 17 months, vision better than 20/100 was reported in 67% of eyes at 6 months, 75% at 1 year, and 100% at 3 years; the overall retention rate was 84%. Another study found that some patients lost vision after an initial gain, with declines in retained vision becoming evident at 3 years and continuing through 4 years after implantation.

The available findings come largely from case series and systematic reviews rather than randomized comparisons. A cited review found no relevant randomized trials directly comparing artificial and donor corneas for repeat transplantation. After a failed conventional transplant, the best treatment is not known, and both repeat grafts and Boston devices can cause infection, glaucoma, and failure.

When you hear a percentage, ask four questions:

• How many eyes or patients were included?
• What condition did those eyes have before surgery?
• How long were they followed?
• Does the number describe vision, device retention, or a complication?

Then ask how your own corneal surface, retina, optic nerve, and prior surgeries compare with the group being discussed.

When to book an exam or seek immediate help

Arrange an eye examination if blurred or variable vision, light sensitivity, redness, tearing, foreign-body sensation, or pain persists or interferes with daily activities. You should also arrange an evaluation if you have a history of failed corneal surgery and want to discuss whether another transplant or an artificial cornea could be considered. Bring records of prior eye operations, treatments, and medications if they are available.

Seek immediate qualified eye care for sudden worsening or loss of vision, eye pain with increased tearing, or a suspected corneal perforation. A corneal perforation can cause sudden vision loss or worsening, pain, and increased tearing. A shallow or flat front chamber, tissue protrusion, low eye pressure, or a positive Seidel’s test can signal perforation and requires immediate intervention.

Do not wait for a routine appointment when these warning signs appear. Treatment depends on the perforation’s size and location. Cyanoacrylate glue may help small perforations, while larger defects may need surgery; microbiological testing is needed to rule out a secondary infection.

That historical figure describes the global burden, not your diagnosis or your need for surgery.

Bring these questions to your appointment

Bring these questions to your appointment:

• What caused my corneal damage, and how severe is it?
• Is a donor transplant still an option for me?
• What do my retina, optic nerve, eyelids, blinking, tears, and ocular surface show?
• What visual result is realistic for my daily activities?
• Which device and additional procedures would you recommend, and why?
• What drops, protective measures, and contact-lens care would I need?
• How will you monitor eye pressure and glaucoma?
• How often would I need follow-up, and which symptoms require immediate care?

A qualified eye specialist must decide whether this treatment is suitable for your eye, medical history, and ability to complete long-term follow-up. If you want to discuss your corneal vision problem, arrange an eye exam at Northwest Eye in Minnetonka.

What should I ask an eye specialist about keratoprosthesis?

Who may be considered for a keratoprosthesis?

A specialist may consider it for severe corneal disease when a donor transplant has failed or is unlikely to work. Examples include multiple failed grafts, major corneal scarring or blood-vessel growth, limbal stem-cell damage, chemical injury, and certain inflammatory or herpetic conditions. These examples do not determine candidacy without a complete eye evaluation.

What does an eye specialist check before recommending one?

The evaluation reviews your diagnosis, previous surgeries and treatments, medications, and the condition of the eye surface. The specialist also checks tears, eyelids, blinking, vision, eye pressure, the retina, and the optic nerve. These findings help estimate visual potential and determine whether surgery should proceed, be modified, or be deferred.

What long-term care does an artificial cornea require?

Long-term care can include infection-prevention drops, early anti-inflammatory drops, nighttime eye protection, and regular cleaning or replacement of a special contact lens. Follow-up often includes an examination the next morning, visits at one week and one month, and ongoing checks. Your specialist may adjust this plan based on your eye’s condition.

How common is keratoprosthesis surgery?

How common keratoprosthesis surgery is in the general population is not known. Published reports mainly describe selected patients with severe corneal disease, failed grafts, or high-risk ocular-surface problems. A global estimate of corneal blindness describes the broader condition, not the number of people who need or receive an artificial cornea.