Overview of Therapeutic Keratoplasty

Therapeutic keratoplasty (TPK) is a type of eye surgery that replaces a section of a patient’s cornea, the transparent front part of the eye, that is diseased, with a healthy one from a donor. This procedure is typically used when infections in the cornea do not get better with regular medication. So, if a corneal ulcer – which is a sore on the cornea – continues to get worse even after two weeks of intensive treatment, or if the overall structure of the eyeball is threatened, therapeutic keratoplasty might be needed.

Another form of this surgery, known as tectonic keratoplasty, is done when the cornea is severely damaged to the point of perforation or melting, causing the front part of the eye to collapse and the internal fluid of the eye, called aqueous humor, to ooze out. By performing TPK, the infection, as well as any associated inflammation and pain, can be significantly reduced, preserving the overall health of the eye and even saving it from the risk of multiple complications. These complications can, otherwise, lead to conditions such as scleritis (inflammation of the white part of the eye), scleral abscess (a painful infection in the white part of the eye), inflammation inside the eye, secondary glaucoma (a condition that damages the eye’s optic nerve), etc.

In countries with less access to healthcare, therapeutic keratoplasty is commonly used to treat stubborn infections in the cornea and perforated corneal ulcers. In some studies, between 13% to 18% of corneal transplants were therapeutic or tectonic, mainly to treat corneal ulcerations and perforations.

The process of TPK involves careful removal of infected and inflamed tissue from the front part of the eye, creation of a new opening in the iris (the coloured part of your eye) if needed, washing with a special saline solution, and perhaps even removing the natural lens of the eye, depending on the specific situation. Following this, the healthy donor’s corneal tissue is stitched on to the patient’s eye. Patients are then given antibiotic treatment and carefully monitored to prevent any complications.

There are different types of therapeutic keratoplasty procedures, including full-thickness therapeutic keratoplasty, tectonic keratoplasty, patch graft, and therapeutic deep anterior lamellar keratoplasty. What procedure is used depends on the nature and extent of the corneal disease. For example, in therapeutic DALK, a partial thickness graft is used to replace just the diseased part of the cornea, instead of replacing the entire thickness of the cornea, as done in full-thickness therapeutic keratoplasty.

Anatomy and Physiology of Therapeutic Keratoplasty

The cornea, which is the clear front surface of the eye, is composed of cells and other non-living parts. It has three types of cells: epithelial cells, keratocytes, and endothelial cells. Along with the cells, it also contains proteins and long sugar molecules. The outer layer of the cornea, known as the epithelium, originates from the external layer of an embryo, while the other two cell types trace back to the part of the embryo that later forms the nervous system.

The cornea has five main layers: the epithelium, the Bowman’s layer, the stroma, the Descemet layer, and the endothelium. Recently, a sixth layer called Dua’s layer has also been identified, which sits just before the Descemet layer.

Different procedures focus on different parts of the cornea. In anterior lamellar keratoplasty, a procedure that treats the front part of the cornea, the main area of concern is the anterior stroma. For posterior lamellar keratoplasty, which treats the back part of the cornea, the Descemet and endothelium layers are the main focus. In penetrating keratoplasty, the whole thickness of the cornea is removed and replaced with a donor cornea, transplanting all the layers of the cornea. In certain other procedures, only the outer layers up to the anterior stroma are operated on, and a partial thickness donor patch is stitched to the remaining part of the patient’s cornea.

The eye has a special type of immune system protection, called ocular immune privilege. In the active part of this system, the eye releases inhibitors that slow down the immune response and produce several substances that suppress the immune response, such as transforming growth beta (TGF-B), Alpha melanocytic stimulating hormone (a- MSH), Vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), migration inhibitory factor (MIF) and free cortisol.

The passive part of ocular immunity contributes to the barrier between the blood and the eye tissue, lack of outgoing lymphatic vessels, and reduced expression of MHC complex I and II, which are proteins that are usually present on the surface of cells during an immune response.

Why do People Need Therapeutic Keratoplasty

Infectious keratitis is an inflammation of the cornea, that’s the clear, rounded window at the front of your eye, caused by an infection with bacteria, viruses, fungi, or parasites. It can cause severe discomfort and potentially, vision loss. Here are the different types of keratitis and the reasons why treatment may not work (refractory), often requiring a surgery known as keratoplasty.

Fungal Keratitis: The typical treatment window is about two weeks, but if the inflammation and infection does not improve, or if the condition worsens rapidly leading to corneal perforation or a rapid corneal melt, a keratoplasty might be conducted earlier. Also, if the patient can’t consistently use the prescription medications, a surgical approach might be necessary. A descemetocele, a severe ulcer that thins the cornea and can create a clear bubble, is another reason for surgery.

Bacterial Keratitis: Again, if the condition doesn’t improve after about two weeks of intensive medical treatment, surgery can be considered. There are also certain cases, such as with an infection named pseudomonas keratitis, where surgery might be performed sooner. Other reasons for surgery can include severe ulcers (descemetocele), a perforation in the cornea, infection extending across the entire cornea, a severe combined cornea and sclera (the white part of the eye) infection, or an infection resistant to conventional treatments. Mycobacterial keratitis and infectious crystalline keratopathy, certain types of corneal infections, can also lead to surgery.

Pythium Keratitis: For this type of infection, surgery might be necessary within one week to ten days if medical treatment isn’t effective. Other reasons for surgery include severe ulcers, perforation, spread to the edge of the cornea, or melting of the cornea. Secondary complications such as a second infection in the transplanted graft or persistent inflammation inside the eye are also indications for surgery.

Acanthamoeba Keratitis: Similar to the others, if eye drops and medications are not effective, if there is a severe infection even in the white part of the eye, or if the cornea gets perforated, surgery might be necessary.

Viral Keratitis: For viral infections like those caused by the herpes simplex or herpes zoster virus, surgery might be necessary if the infection worsens and the cornea gets perforated, or if a secondary bacterial infection causes rapid melting of the cornea.

Other conditions: Finally, Keratitis might be caused by other factors, such as nerve damage to the cornea (neurotrophic keratitis), thermal injury, dryness of the eye leading to perforation (keratoconjunctivitis sicca), nerve paralysis (neuroparalytic keratitis), inability to close the eyelids (exposure keratopathy) and persistent healing defect of the cornea (persistent epithelial defect), all of which might necessitate surgery.

Equipment used for Therapeutic Keratoplasty

Surgeons use a variety of tools for eye surgeries:

– A 15-degree side port or MVR blade, which are types of small, sharp instruments.

– A screw speculum is used to keep the eye open during surgery.

– A device known as a Corneoscleral fixation- Flieringa ring, which is used to hold the eye in place.

– An ophthalmic viscosurgical device, a tool used to protect the eye’s tissue and help manage space during the procedure.

– Normal saline or balanced salt solution for cleaning.

– Different types of forceps and scissors like conjunctival forceps, Vannas scissors, and Lim’s forceps, are used to handle delicate eye tissues.

– A trephine, a circular cutting tool, and a graft punch are used for create precise holes in tissues.

– A 26 G needle cystitome is a needle-like tool used for making small punctures.

– The bimanual irrigation and aspiration Simcoe cannula device is used to simultaneously introduce fluids into the eye and remove unwanted material.

– Different types of solutions like Cornisol solution, topical betadine, and injection moxifloxacin and injection voriconazole, which are medications to prevent infection and inflammation.

– The automated anterior vitrectomy is a device that’s used to carefully remove the vitreous, a gel-like substance that fills the eye.

– Many types of forceps like suture holding, McPherson and suture-tying plane forceps, used to hold sutures (stitches) during the procedure.

– 10-0 and 9-0 nylon monofilament suture, which are the types of threads used for stitches in the eye.

– Cotton bud and swabs for cleaning.

– Fluorescein dye, a special dye that’s used to help the surgeon see the structures of the eye more clearly.

Who is needed to perform Therapeutic Keratoplasty?

An eye doctor, known as an ophthalmic surgeon, is in charge of preparing you for surgery, planning the surgery, performing a procedure known as keratoplasty, and looking after you once the surgery is finished. The word ‘keratoplasty’ may sound daunting, but it’s simply a type of eye surgery to repair the cornea. The cornea is the clear front surface of the eye. To ensure your well-being and successful recovery, the doctor works alongside other health professionals.

There are nurses in outpatient departments, meaning those not based in the hospital, who also look after you once you have gone home after the procedure. Furthermore, you can find nursing staff in the operation theatre. They help the surgeon during your eye operation ensuring everything runs smoothly.

Apart from that, counselors are available to make the entire process easy for you. They provide emotional support and help solve any issues or concerns you may be having about your surgery. Lastly, there’s your pharmacist. They ensure you get the right medication both before and after the operation. Remember, each one plays a crucial part in your treatment journey. All these health professionals aim to make sure you get the best care possible from start to end.

Preparing for Therapeutic Keratoplasty

Proper preparation before undergoing keratoplasty, or cornea transplant surgery, is of utmost importance.

A thorough eye examination is needed before this procedure. In simple terms, this includes a detailed examination of the eye using a handheld flashlight and a specialized microscope. This helps doctors to see how your eye is moving, check for any misalignment of the eyes, and recognize any issues related to the structures that surround the eye.

In the next part, the doctors examine the front region of the eye. This is crucial to find out the depth of any swelling or infection, how much the cornea (the outer clear section of the eyes) is affected, and any issues with the colored part of the eyes (iris), the pupil, and if the lens inside the eye can be seen clearly. To have a better look at any problems, doctors will take pictures of any abnormalities on the cornea. A special test, known as Seidel’s test, may be done if there is doubt about any tiny holes in the cornea. Furthermore, other evaluations are made for any inflammation or side effects inside the eye.

The back portion of the eye also needs to be examined. This can be tough as the issues of the cornea might not allow the doctors to get a clear view. In such a scenario, an ultrasound of the eye (also known as a B scan) might be done. However, some doctors suggest delaying the B scan until after the surgery to avoid any risk of spread of infection.

Patients undergoing keratoplasty must be given medicines that kill bacteria and other germs before the operation. These are used to reduce the effect of disease-causing agents in the eye. Broad ‘catch-all’ treatments are used when the exact cause of the infection is uncertain. According to one study, a type of eye drop (ofloxacin 0.3%) should be used hourly before the surgery to refrain from any other bacterial infection. The medicines should also be taken by mouth or given through a vein in the hospital. However, it’s important to avoid certain medicines (steroids) that may make infections worse.

Sometimes, a sample of the cornea is gently scraped off when the patient first comes to the clinic. This can help doctors understand the cause of the infection and use the most effective medication against it. The sample is then cultured, or multiplied in a lab dish for two to three days, and the results of the culture can guide the treatment after surgery.

Just before the operation, patients are given an intravenous solution called mannitol. This helps to relieve pressure in the eye during the surgery. Caution must be taken as mannitol cannot be used in patients with certain medical problems like kidney disease, lung congestion, severe dehydration, active brain bleeding, worsening heart failure, or those who are allergic to mannitol. For such patients, a solution that can be taken by mouth, glycerol, might be suggested.

How is Therapeutic Keratoplasty performed

TPK, or a type of eye surgery, is seen as one of the more challenging procedures in the field of ophthalmology. It’s typically carried out on an inflamed or injured eye. It’s a good idea for an expert surgeon who’s done a lot of keratoplasties to carry out this operation. The operation is usually done using local anesthesia to numb the area, but sometimes it’s necessary to use general anesthesia, which puts you to sleep. This is decided based on the individual patient’s situation. If the anesthesia isn’t strong enough, it can lead to complications during the operation. There are also certain drugs, called depolarizing agents, which should not be used because they can increase pressure inside the eye.

Eye donors provide the tissue that’s used in the surgery. The tissue is obtained from an eye bank, and it should be checked for quantity and the conditions in which it has been stored. The tissue is preserved using specific compounds. Not all the tissue used in this procedure needs to be ‘top-tier’, but if you have the option, high-quality tissue can be beneficial for visual recovery. You’ll also see less chance of infection with quality tissue.

Certain tools are used during the surgery to make it more manageable: a ‘lid speculum’ or sutures (a kind of special stitch) to stop pressure on the eyeball; and a ‘scleral fixation ring’ to provide structural support. However, use of the scleral fixation ring differs from surgeon to surgeon and clinic to clinic. Sometimes, the conjunctiva (which is the clear tissue covering the white of the eye) is purposely cut in the surgery for various reasons. Another step in the process involves a small technique known as ‘paracentesis’ which reduces the pressure in your eye, and helps in other crucial parts of the surgery.

One key step of the procedure is the ‘host trephination’, where the size of the damaged area is measured, and then partially removed. Care is taken to prevent excessive pressure which might damage other parts of the eye. The size of the replacement graft is decided based on the size of the tissue removed from your eye, and it’s usually kept slightly larger than the removed tissue, to allow for better healing.

After the replacement has been put into place, extra care is taken to make sure that everything inside your eye is clean and properly positioned. They also perform a small procedure called an ‘iridectomy’ to ensure normal fluid movement inside your eye. In some situations, there can be significant bleeding after the iridectomy, but this can be controlled with gentler fluid application. They will usually leave your lens as is because it serves as a barrier, stopping the bacteria from moving into the more sensitive parts of the eye.

In summary, TPK is a complex eye operation undergone in cases of severe eye inflammation or injury. It involves several techniques and it’s essential to be performed by a skilled surgeon. This procedure, as described above, is designed to control and rectify the damage to the eye, and restore, as much as possible, normal visual function.

Possible Complications of Therapeutic Keratoplasty

Therapeutic teratoplasty is a kind of eye surgery that can sometimes have complications. Here are some things that could go wrong:

During the surgery:

* Not enough pain relief
* Insufficient movement control
* Off-center drilling in the host’s cornea
* Uneven host rim
* Irregular ledge at the host’s rim
* Damage to the iris
* Lens dislocation
* Break in the back of the lens capsule
* Jelly-like substance in the eye oozing out
* Sudden bleeding inside the eye
* Blood in the anterior chamber of the eye (hyphema)

After the surgery:

Early complications:

* Gaps in the surgical wound
* Loose stitches
* Infiltration around the stitches
* Shallow or flattened front of the eye
* Fluid leaking from the front part of the eye
* Iris coming out through the junction of the graft and the host
* Infiltration into the graft
* Damage to the outermost layer of the eye
* Inflammation in the front part of the eye
* Adhesions at the edge of the anterior chamber
* Increased pressure in the eye (secondary glaucoma)

Late complications:

* Fluid accumulation in the choroidal layer of the eye
* Adhesions at the edge of the anterior chamber
* Low pressure in the eye
* Choroidal tissue coming off
* Retina coming off
* Clouding of the lens (cataract)
* Failure of the graft
* Bulging of the graft
* Increased pressure in the eye (secondary glaucoma)

Secondary Glaucoma reasons:

There are many reasons why a person could get glaucoma after surgery. They include:

* Leftover viscoelastic substance
* Glaucoma due to blocked pupil
* Closure of the angle due to adhesions
* Large graft blocking the angle
* Smaller graft with a crowded angle of the anterior chamber
* Glaucoma caused by steroids as a late effect
* Serious type of glaucoma (malignant glaucoma)

What Else Should I Know About Therapeutic Keratoplasty?

Therapeutic penetrating keratoplasty (TPK) is an important procedure that helps treat serious eye infections and improve patients’ sight and quality of life. It’s especially impactful in improving eye health in developing countries.

TPK becomes especially crucial when the eye is structurally compromised due to disease. Before and after the operation, patients need to take special anti-infection medications to help ensure the success of the surgery.

In cases where the infection has spread to a large area of the eye, a large piece of donor tissue may be needed to replace the infected area. The upside is that TPK can not only potentially restore your vision, but in some cases, it may also eliminate the need for another procedure known as optical keratoplasty.

Frequently asked questions

1. What is the specific procedure that will be used for my therapeutic keratoplasty? 2. What are the potential risks and complications associated with this surgery? 3. How long is the recovery period after therapeutic keratoplasty? 4. Will I need to take any medications after the surgery? If so, what are they for and how long will I need to take them? 5. What are the expected outcomes and success rates for therapeutic keratoplasty in cases like mine?

Therapeutic Keratoplasty is a procedure that treats different parts of the cornea depending on the specific issue. It can involve removing and replacing the whole thickness of the cornea or only operating on the outer layers. The eye has a special immune system protection called ocular immune privilege, which helps to suppress the immune response during the procedure.

Therapeutic keratoplasty may be necessary for individuals who have certain conditions or injuries affecting their cornea. Some reasons why someone may need therapeutic keratoplasty include: 1. Corneal infections: Severe infections of the cornea, such as fungal or bacterial keratitis, can cause significant damage to the corneal tissue. Therapeutic keratoplasty may be performed to remove the infected tissue and replace it with a healthy donor cornea. 2. Corneal dystrophies: Certain inherited corneal dystrophies, such as Fuchs' dystrophy or lattice dystrophy, can lead to progressive corneal thinning and clouding. Therapeutic keratoplasty may be recommended to replace the diseased cornea with a healthy one. 3. Corneal scars: Trauma, infections, or previous surgeries can cause scarring on the cornea, leading to vision impairment. Therapeutic keratoplasty can help remove the scarred tissue and restore clear vision. 4. Corneal ulcers: Non-healing or deep corneal ulcers that do not respond to other treatments may require therapeutic keratoplasty to promote healing and prevent further damage. 5. Corneal melting: Conditions such as autoimmune diseases or severe dry eye syndrome can cause corneal melting, where the cornea thins and becomes prone to perforation. Therapeutic keratoplasty may be necessary to reinforce the weakened cornea and prevent complications. 6. Corneal ectasia: Conditions like keratoconus or post-LASIK ectasia can cause progressive thinning and bulging of the cornea, leading to distorted vision. In some cases, therapeutic keratoplasty may be recommended to improve visual acuity. It is important to note that therapeutic keratoplasty is typically considered when other treatments have failed or are not suitable for the specific condition. The decision to undergo therapeutic keratoplasty is made by an ophthalmologist based on a thorough evaluation of the individual's eye health and visual needs.

Therapeutic Keratoplasty should not be pursued if the patient's cornea can be effectively treated with alternative methods, such as medication or non-surgical interventions. Additionally, individuals with certain medical conditions or eye disorders may not be suitable candidates for this procedure.

The recovery time for Therapeutic Keratoplasty can vary depending on the specific procedure and the individual patient. However, it generally takes several weeks to several months for the eye to fully heal after the surgery. During this time, patients will need to follow post-operative care instructions, including taking prescribed medications and attending follow-up appointments with their ophthalmic surgeon.

To prepare for Therapeutic Keratoplasty, the patient should undergo a thorough eye examination to assess the condition of the eye and determine the extent of the corneal disease. Medications that kill bacteria and other germs may be prescribed before the surgery to reduce the effect of disease-causing agents in the eye. Additionally, patients may be given an intravenous solution called mannitol to relieve pressure in the eye during the surgery.

The complications of Therapeutic Keratoplasty include not enough pain relief, insufficient movement control, off-center drilling in the host's cornea, uneven host rim, irregular ledge at the host's rim, damage to the iris, lens dislocation, break in the back of the lens capsule, jelly-like substance in the eye oozing out, sudden bleeding inside the eye, blood in the anterior chamber of the eye (hyphema), gaps in the surgical wound, loose stitches, infiltration around the stitches, shallow or flattened front of the eye, fluid leaking from the front part of the eye, iris coming out through the junction of the graft and the host, infiltration into the graft, damage to the outermost layer of the eye, inflammation in the front part of the eye, adhesions at the edge of the anterior chamber, increased pressure in the eye (secondary glaucoma), fluid accumulation in the choroidal layer of the eye, low pressure in the eye, choroidal tissue coming off, retina coming off, clouding of the lens (cataract), failure of the graft, bulging of the graft, and increased pressure in the eye (secondary glaucoma). Secondary glaucoma can occur due to leftover viscoelastic substance, glaucoma due to blocked pupil, closure of the angle due to adhesions, large graft blocking the angle, smaller graft with a crowded angle of the anterior chamber, glaucoma caused by steroids as a late effect, and a serious type of glaucoma (malignant glaucoma).

Symptoms that require Therapeutic Keratoplasty include severe discomfort, vision loss, corneal perforation, rapid corneal melt, severe ulcers, infection resistant to conventional treatments, spread of infection to the edge of the cornea, melting of the cornea, and persistent inflammation inside the eye.

There is no specific information provided in the given text about the safety of Therapeutic Keratoplasty (TPK) in pregnancy. It is recommended to consult with a healthcare professional, such as an ophthalmologist or obstetrician, to discuss the potential risks and benefits of the procedure during pregnancy. They will be able to provide personalized advice based on the individual's specific situation.

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