frequently asked questions: cornea · what is the success rate of a corneal transplant? a: the...

Frequently Asked Questions: Cornea

DONOR CORNEAS HARVESTED BY EYE BANKS

TO PERFORM CORNEAL TRANSPLANTS BY CORNEA SURGEONS

The cornea is the clear dome at the front of your eye. It focuses light rays on your retina

allowing you to see. The cornea has five layers which can become swollen,cloudy, or

become out of shape. Once these symptoms progress to the point where vision is affected,

the diseased cornea may be removed and replaced with donor tissue. This procedure is

called a corneal transplant.

Types of Corneal Transplants

1. Penetrating Keratoplasty (PK) - PK

is a full thickness corneal transplant. The

central portion of the cornea is removed

and replaced with donated tissue. PK

corrects problems with the cornea’s

shape, opacities, orscars.

2. Descemet’s Stripping Endothelial

Keratoplasty (DSEK) - DSEK is a new

type of corneal transplant where only the back layer of the cornea (endothelium) is removed

and replaced with donated tissue. This is done to correct conditions like Fuch’s Endothelial

Dystrophy, where the back layer has suffered loss of cells and does not function properly.


3. Deep Anterior Lamellar Keratoplasty (DALK) - This surgery is a partial thickness

transplant in which most of the cornea is removed but the back layer is left in place. DALK

corrects problems with the cornea’s shape and/or opacity of the front layer. DALK is often

done for keratoconus.

Figure : Slit-lamp observations of the two representative patients before and after successful deep

anterior lamellar keratoplasty (DALK) with amniotic membrane transplantation (AMT)


Can I eat the day of surgery?

You may eat a light breakfast the morning of your surgery. Medications may be taken with

a small sip of water.

Will I be asleep for the surgery?

Your eye will be numbed and you will be awake under local anesthesia. However, you will

receive an IV medication to keep you sleepy and relaxed. How long does the surgery take?

The transplant surgery takes about 30 minutes to an hour.

When can I go back to work and resume normal activity?

Patients usually return to full activity one week after DSEK surgery and six weeks after PK

or DALK.

Where does the donor tissue come from?

The corneal tissue comes from eye banks. The tissue has been donated by someone who

is deceased

Risks & Benefits: The benefit of course is improved vision. However there are always risks

with any type of surgery. Your individual risks will be discussed at the time of your evaluation.


More FAQs and more information: What is Dsaek eye surgery? Descemet's stripping automated endothelial keratoplasty (DSAEK) and Descemet's

membrane endothelial keratoplasty (DMEK) are partial thickness corneal transplants which

replace primarily the endothelium (innermost portion of the cornea) rather than the full

thickness of the cornea (as in standard corneal transplants).

What is the difference between Dsaek and DMEK?

DMEK is very similar to DSAEK, except that the donor tissue implanted does not include

any stromal tissue. It is a pure replacement of endothelium. This tends to give better visual

results and a quicker recovery; however, donor disc dislocations and failures are more

common.

How long do you have to wait for a corneal transplant? A: The average waiting time for a cornea from the Eye Bank is approximately 6 weeks.

Your time on the waiting list may be shorter or longer depending on many factors, such as

your age and medical diagnosis.

Is a cornea transplant dangerous? A: Cornea transplant is a relatively safe procedure. Still, it does carry a small risk of serious

complications, such as: Eye infection. Increased risk of clouding of the eye's lens (cataract)

What is the success rate of a corneal transplant?

A: The overall success rate of a corneal transplant is very high using modern eye banking

and surgical techniques. However, there are many factors that influence the outcome. For

instance, keratoconus has one of the best prognoses for good vision with a greater

than 90% chance of a clear graft.


Can you see after a corneal transplant? A: Your eyesight should gradually improve a few weeks after a corneal graft, but it

could take anywhere from a couple of months up to a year to have stable vision in the eye

that receives the donor tissue. After your cornea transplant has fully healed, it's possible

to undergo LASIK eye surgery to improve your vision.

What causes keratoconus? A: Tiny fibers of protein in the eye called collagen help hold the cornea in place and keep it

from bulging. When these fibers become weak, they cannot hold the shape and the cornea

becomes progressively more cone shaped. Keratoconus is caused by a decrease in

protective antioxidants in the cornea.

Can corneal transplant change your eye color? A: Will my eye color change? No, your eye color stays exactly the same. The

transplant involves only the transparent clear cornea and not the colored part of

the eye (iris).

Why would someone need a corneal transplant? A: Your eye doctor might recommend a corneal transplant if you have vision problems

due to keratoconus or another condition that causes your cornea to become thinner.

Corneal transplants might also be recommended if you have vision loss due to

cloudy corneas caused by Fuchs' dystrophy or a similar condition.

When can I go back to work after a corneal transplant? A: After surgery, the stitches usually stay in place for about 2 to 3 months, and then are

slowly removed over many months as your cornea heals. You will probably be ableto

return to work or your normal routine in about 1 to 2 weeks after surgery. But your

vision will still be blurry.


Other General Information about Cornea.

1. Normal Cornea

This is a clear watch crystal (outer glass cover of the watch) like tissue over the colored part

of the eye called the iris. Unlike the watch glass, which is flat, the cornea is dome shaped.

Light passes through the transparent cornea, just like it would through a window so as to

focus on the retina which is the inner lining of the back of the eye, like the film of the camera.

The cornea is kept moist and nourished by a thin layer of tears. It is kept smooth by the

blinking of the eyelids. If the cornea becomes distorted in shape, scarred, or hazy (opaque)

from disease or injury, the light rays passing through it are distorted and the vision is

reduced. In some cases, a corneal transplant may be necessary to replace the diseased or

injured cornea with a healthy, clear cornea to restore good vision.

2. Foreign bodies, Corneal Abrasion and Injuries

FOREIGN BODY: A foreign object in the eye is something that enters the eye from outside

of the body. It can be anything from a dust particle to a metal shard.The foreign object will

most likely affect the cornea or the conjunctiva. Consult an ophthalmologist immediately if a

foreign object is embedded in your eye. Do not attempt to remove it yourself.

CORNEAL ABRASIONS: A corneal abrasion is a scratch or cut (abrasion) of the clear outer

layer (cornea) of the eye. Injury (trauma) is the most common cause for corneal abrasions.

It can happen in an instant. You poke your eye or something gets trapped under your eyelid,

like dirt or sand. Your eye hurts (pain, watering, sensitivity to light and blurred vision) and it

doesn’t get better when you close it. Retained foreign body also can cause abrasion.Left

untreated it can progress to ulcer.

INJURIES: Physical or chemical injuries of the eye can be a serious threat to vision if not

treated appropriately and in a timely fashion. Physical injuries can be blunt, penetrating or

perforating injuries. The most obvious presentation of ocular (eye) injuries is redness and

pain of the affected eyes.


3. Chemical burns

Chemical Eye Injury: Chemical eye injury or chemical burns to the eye are due to either an

acidic or alkali substance getting in the eye. Alkalis are typically worse than acidic burns.

Mild burns will produce conjunctivitis while more severe burns mayerode and opacify the

cornea, and may continue to do harm for some time after contact. Specialist review is

essential but the mainstay of treatment is dilution by irrigation as soon as possible after the

contact occurs.

Local anesthetic drops may be necessary in order to allow eye opening for irrigation. After

this, irrigation with sterile saline is ideal. If the chemical contains particles the lids should be

spread widely, irrigation continued and a cotton bud used to lift out particles. After irrigation,

acuity should be recorded and the surface of the eye stained to look for epithelial defects. It

is helpful to check the pH of the tear film with litmus paper to make sure that the milieu is no

long alkaline. You will have to use eye drops and may need surgical intervention depending

on the situation of the eye. Visual recovery depends on the amount of damage that has

occurred to the cornea.

4. Infections

Corneal ulcers are most commonly caused by an infection with bacteria, viruses, fungi, or a

parasite.

Fungal keratitis can occur after a corneal injury involving plant material. It may also

occur in people with a suppressed immune system.

Acanthamoeba keratitis occurs in contact lens users. It is more likely to happen in

people who make their own homemade cleaning solutions.

Herpes simplex keratitis is a serious viral infection. It may cause repeated attacks that

are triggered by stress, exposure to sunlight, or any condition that lowers the immune

response.


Corneal ulcers or infections may also be caused by eyelids that do not close all the way,

such as with Bell’s palsy, foreign bodies in the eye, scratches (abrasions) on the eye

surface, severely dry eyes, severe allergic eye disease and various inflammatory

disorders. Symptoms include pain, blurred vision, redness, photophobia and tearing.

Treatment for corneal ulcers and infections depends on the cause. Treatment should be

started as soon as possible to prevent scarring of the cornea. Many people recover

completely and have only a minor change in vision. Sometimes surgical intervention may

be required to treat the infection. However, a corneal ulcer or infection can cause long-

term damage by scarring the cornea and distorting vision, which requires corneal

transplantation for restoring vision.

5. Pterygium

It a fleshy mass of thickened sub-conjunctival tissue that grows over part of the cornea

usually from the inner side of the eyeball and causes a disturbance of vision. The term comes

from the Greek word pterygion meaning “wing”. A pterygium grows in response to exposure

to ultraviolet light. They are more common in light-skinned people living nearer the equator,

particularly where outdoor activities are popular. The pterygium pulls and distorts the cornea

as it enlarges.

Protecting the eyes from excessive ultraviolet light with proper sunglasses, avoiding dry,

dusty conditions and artificial tear supplements are all recommended in treating and

preventing its progression. If pterygium becomes red and irritated, eye drops can be used

to reduce inflammation. If the pterygium is large enough to threaten vision, it will need to be

surgically removed.

6. What is Dry Eye Syndrome?

To function normally, the cornea must be covered at all times by a coating of tears called

the tear film. Tears are made up of oil, water, and mucous. Dry Eye Syndrome is a condition

affecting the tear system of the eye. It is a spectrum of disorders with varied etiology ranging

from mild eye strain to very severe dry eyes with sight threatening complications. Dry eyes

happen from one of two factors. Either your tear system is not producing enough tears or


the produced tears are getting evaporated. Testing for dry eyes can be

performed in a number of different ways. Treatment is usually with tear

supplements and lubricants. In advanced cases microscopic plugs (temporary or

permanent) can be inserted to conserve tears and prevent them from draining away. In very

severe cases, surgical intervention may be essential.

7. Keratoconus

Keratoconus is a degenerative disorder of the cornea in which structural changes within the

cornea cause it to thin and change to a more conical shape than its normal gradual curve.

It can cause substantial distortion of vision, with multiple images, streaking and sensitivity to

light all often reported by the patient. The “cone” or steepened section of the cornea typically

occurs in the inferior region of the cornea, so frequent eye rubbing appears to cause more

and more progression of the condition. The exact cause is uncertain, but has been

associated with detrimental enzyme activity within the cornea. The most definitive way,

however, to diagnose keratoconus is to use a corneal topographer. This machine basically

maps the curvature of the eye, revealing a tell-tale red “cone” of steepening in keratoconus.

Treatment is based on the severity of the condition. In early cases, glasses and contact

lenses can be enough to correct vision. Surgical procedures are becoming increasingly more

common for treatment: Intacs and corneal cross-linking seem to be the future for long term

cone stability. In very advanced cases a full corneal transplant is required.

8. What is corneal transplantation?

In corneal transplant surgery the scarred or damaged cornea is removed and replaced by a

human donor cornea called a graft. Your eye is the recipient eye because it receives the

graft. The other person’s cornea is the donor cornea or donor tissue because the cornea is

being donated or given to you. An eye bank provides the donor tissue for corneal transplant

surgery. The corneas are obtained from deceased individuals who arranged for donation

prior to their death or whose families gave permission.


There are 3 types of corneal graft surgery.

Penetrating corneal graft – if the whole thickness of the cornea is unhealthy, the patients

whole cornea is removed and replaced with a graft.

Deep anterior lamellar corneal graft – if only the surface layers of the cornea are

unhealthy these layers are removed and replaced by a graft.

Corneal endothelial graft – if it is the inside layer of the cornea that is unhealthy, only this

is removed and replaced by a graft.

9. Are you a cornea transplant candidate?

Sometimes through injury, infection, or some inherited condition (such as keratoconus) your

cornea may lose its natural transparency or normal shape, leading to blurred vision. In many

cases glasses or contact lenses may help you to see more clearly, but there are times when

these do not work and the cornea needs to be replaced (graft/transplant).

A cornea transplant is performed to improve the function of the cornea and improve vision.

With these factors in mind, you also should consider several important questions before

you decide to undergo a corneal transplant:

Does your functional vision impede your job performance or your ability to carry out daily

activities?

Can your vision be corrected with special contact lenses or other less invasive

measures?

Are you able to take enough time off from work (up to six months to a year in some

cases) to recover properly?


10. How is cornea transplanted and is the whole eye replaced during

transplantation?

Corneal transplants are performed under local anesthesia or general anesthesia. A cookie

cutter-like knife called a trephine is used to cut and remove a circular piece from the

recipient’s scarred cornea. A similar knife is used to cut and remove a piece from the donor

cornea. The donor cornea then is placed where the recipient’s cornea was removed. It is

sewn into place with very fine sutures which are smaller in diameter than a human hair. In

some situations, your surgeon may be transplanting only part of the corneal thickness.

When only the front part is transplanted, it is called anterior lamellar keratoplasty. When

only the back part is transplanted, it is called endothelial keratoplasty. Some variations of

endothelial keratoplasty include DLEK (deep lamellar endothelial keratoplasty) and DSEK

(Descemet’s stripping endothelial keratoplasty). These procedures may not require

sutures.

11. Vision after corneal transplantation?

Vision usually is blurred after surgery. It gradually improves as healing takes place. As the

eye heals and the sutures are removed, the shape of the cornea changes. Therefore, your

surgeon usually will wait between 3 and 12 months before prescribing a new lens for your

glasses. If needed, a contact lens may be prescribed.

12. Post -operative care

Your eye will be covered with a patch and eye shield the day of surgery. Your surgeon

most likely will remove the patch and shield at your follow-up appointment the next day.

You may experience increased tearing and a slight discharge for few days following

surgery. You must wear the patch and shield over your eye while sleeping or showering.

You will need to use eye drops and ointment to quiet inflammation and prevent graft

rejection and visit for follow ups as advised by your doctor.You should avoid any activities

that could involve a direct blow to the eye, such as contact sports and lifting heavy weights.

Avoid water entry into operated eye and wear protective goggles to protect from dust.


13. How successful is corneal transplantation?

The corneal transplant or corneal graft as it is also called, is devoid of blood vessels.

Hence out of all transplants done in the body such as heart, liver, kidney etc, it has the

least chance of rejection. Even if rejection does occur, it can be successfully treated by

eye drops in most cases without having to take recourse of systemic immunosuppressive

medication, as is the case with rejected transplants elsewhere in the body.

Grafts done in eyes where the cornea is already vascularisednaturally, have a poorer long-

term prognosis (expected outcome, in layman’s terms). However, in case a graft does fail

or get rejected for some reason and the rejection is not reversed by timely treatment, all

is not lost. If the rest of the eye has no other complications, it is possible to do a re-graft

i.e. one more graft (naturally after removing the previous opaque graft!) and restore vision

once more.

14. Endothelial keratoplasty

This is transplantation of only the inner lining of the cornea – the endothelium, after

stripping off the patient’s own inner lining. For corneal endothelial grafts recovery of vision

is usually faster (approximately three months). Treatment with drops is also needed as

above and continues for several months, again this is dependent on your vision and

recovery.

For corneal endothelial grafts suture related problems and astigmatism are less of a

problem. The main complication is failure of the graft to stick to the patients own cornea

as the graft is not stitched into place but held by an air bubble that dissolves of its own

accord. This would require a further bubble of air to be put into the eye with the patient

again lying flat for a few hours. Because these endothelial grafts are very delicate if there

are problems in getting the graft into the eye at the time of surgery, primary graft failure is

a bigger risk than with penetrating grafts.


15. Corneal graft rejection

There always is a possibility that the body will reject the graft. This is like an “allergic”

reaction of the body against the donor cornea. It can occur any time after the surgery.

There is a good chance this can be treated successfully if you act immediately. There are

four danger signs you must know. If any of these occur and last for more than 12 hours,

you should consult your ophthalmologist. To remember the signs of graft rejection,

remember the letters: R S V P

■ Redness

■ Sensitivity to light

■ Vision changes

■ Pain Make a habit of checking your eye every day. Check your vision at

about the same time and in the same lighting each day, perhaps at the

same time you do another routine activity, such as brushing your teeth.

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