Corneal crosslinking is a procedure used to treat patients suffering from keratoconus, a disorder of the eye in which the cornea thins, weakens, and becomes distorted and cone-shaped. The distortion of the cornea due to keratoconus causes astigmatism, leading to decreased visual acuity in sufferers.
What is Corneal Crosslinking?
The cornea is composed of collagen, which maintains the cornea’s shape and strength. Collagen fibers have crosslinks, which work like support beams, holding the collagen fibers together. In keratoconus, too few of these crosslinks exist, leading to the weakening of the cornea.
Corneal crosslinking is a procedure which increases the amount of crosslinking or binding fibers within the cornea’s collagen, strengthening the cornea and helping it to better retain its shape.
Two types of corneal crosslinking exist: traditional corneal crosslinking and transepithelial CXL technique. In a traditional procedure, the epithelial, a thin piece protective tissue covering the cornea, is removed prior to the procedure. In a transepithelial CXL, the epithelial is left intact. An eye care professional can help you determine which procedure is right for you.
During the procedure, the patient lies on his or her back, and is administered anesthetic eye drops and an oral sedative. In a traditional CXL procedure, the epithelial is then removed. Eye drops containing the vitamin riboflavin are then administered while the patient looks into a blue ultraviolet light. The procedure lasts from 60 to 90 minutes.
How does corneal crosslinking improve vision?
By increasing the amount of crosslinks within the cornea’s collagen fibers, corneal crosslinking strengthens the cornea and allows it to maintain its shape, correcting astigmatism and improving visual acuity.
When is corneal crosslinking required?
Corneal crosslinking is never required, but is an effective treatment alternative to corneal transplant surgery, uncomfortable contact lenses, and LASIK surgery for patients suffering from keratoconus. The procedure, however, is not right for everyone. To qualify for the procedure, the patient’s cornea cannot be too thin or scarred. An eye care professional can measure the thickness of the cornea, and help a patient decide whether corneal crosslinking is the right treatment option.
While medical science offers several conservative methods of correcting poor vision caused by corneal issues, some patients may opt for a cornea transplant when these other options can’t help them. Corneal transplants, which usually involve replacing the damaged cornea with one from a human donor, are not always accepted by the body and may require lengthy recovery times, but in most cases they can restore vision to the affected eye.
Reasons for a Corneal Transplant
A variety of problems might cause your cornea, the spherical transparent surface at the front of the eye, to stop refracting incoming light properly. These problems include keratoconus (a cone-like malformation in the cornea’s shape), thinning of the corneal tissue, scarring from infections or injuries, ulceration or the clouding of the corneal surface, and a disorder known as Fuchs’ dystrophy. Rarely, complications from laser vision surgery or cataract surgery might also leave you with a malfunctioning cornea.
Without the ability to correctly receive refracted light from the outside world, your retina cannot send coherent images to the brain, leading to blurred or cloudy vision. Fortunately, many corneal issues can be compensated for with corrective lenses and other technologies. But those who cannot benefit from these treatments may need to consider the possibility of having a corneal transplant.
Types of Transplants
There are two primary types of corneal transplants. The traditional kind, known as penetrating keratoplasty or PK, involves removing and replacing the full thickness of the corneal tissue. Usually a human cornea from a donor is used, but patients with a history of organ rejection may receive a synthetic cornea instead. The more recent type of transplant, known as endothelial keratoplasty or EK, removes and replaces only inner tissue at the rear of the cornea. EK makes sense when only this part of the cornea is diseased or damaged.
Recovery from a corneal transplant takes patience. You will be asked not to overexert yourself for a few weeks, and your vision in the treated eye may remain as least as bad as before for several months as the tissues heal and the eye becomes accustomed to its new cornea. Since the new cornea may not precisely duplicate the curvature of the old one, you may require corrective lenses to fully restore your vision. But as an alternative to total or permanent vision loss, cornea transplants can often repay the effort and expense involved.
INTACS FOR KERATOCONUS
If you have been losing your battle against keratoconus, a progressive bulging of the cornea that causes rapidly worsening vision, then you should know about a state-of-the-art surgical option that might provide lasting relief. Tiny inserts called Intacs can effectively reshape the cornea, reducing the bulge that interferes with normal refraction of incoming light.
Why Might You Need Intacs?
People with keratoconus, a weakening or thinning or the cornea that allows this tissue to bulge outward, often find that they have to keep changing their lens prescription to keep up with the progress of the disorder. For these patients, a brief surgical procedure to install Intacs may make good long-term sense. Intacs are thin, crescent shaped inserts made of a clear biocompatible material. Once they have been implanted, they work by exerting just enough pressure against the sides of the cornea to flatten out the exaggerated curvature caused by keratoconus. The thicker the implanted ring, the more flattening will occur. Your eye care provider may use one or two rings to achieve the best possible curvature adjustment.
About the Surgery
The surgery itself takes only a few minutes as an outpatient procedure. The doctor makes a tiny cut along the surface of the cornea, in many cases using a precision laser device, so that the layers of tissues within the cornea may be separated. A centering guide placed on the eye allows the surgeon to line up the Intacs as precisely as possible along the peripheral zone of the cornea (outside your normal visual field). Once the Intacs have been implanted into the incision, the incision is sutured closed. You may be advised to give the eye a rest for a couple of days following surgery, but many patients enjoy sharper, clearer vision the very next day.
Intacs have several features that make them a safe, convenient choice for patients with keratoconus. The fact that they are made of the same biocompatible material as the lenses used for cataract surgery means that they are unlikely to cause irritation or other problems. If you are unhappy with the degree of vision correction provided by Intacs, you can opt to reverse the process and have the Intacs removed — after which your cornea will eventually return to its previous curvature. Ask your eye care provider whether Intacs could prove helpful in taming your keratoconus symptoms.
Vitreoretinal surgery refers to a group of surgeries which take place inside the eye’s interior where the vitreous (gel-like material) and retina (photosensitive membrane) are located. Vitreoretinal procedures are either performed with traditional surgical tools or lasers, and address a range of ophthalmic issues including diabetic retinopathy, macular degeneration, detached retina, macular hole, CMV retinitis, epiretinal membrane, and diabetic vitreous hemorrhage.
What is Vitrectomy?
A specific type of vitreoretinal eye surgery, a vitrectomy procedure removes the vitreous, a gel-like substance located in the middle of the eye. A vitrectomy is usually performed under general anesthesia, but depending on the patient’s health, is sometimes performed with local anesthesia.
During a vitrectomy, an eye surgeon inserts small instruments into the eye. The surgeon cuts the fibers which attach the vitreous gel to the retina, and suctions out the vitreous. The surgeon then repairs any holes or tears in the retina or macula (center of the retina), flattens any areas where the retina is detached, and removes any vitreous fibers or scar tissue still attached to the retina. At this point, the eye care provider fills the vitreous cavity with either a gas, saline solution, or a silicone oil to restore normal eye pressure.
The vitrectomy procedure was developed to address several eye-related problems such as retinal detachment, macular hole, epiretinal membrane, proliferative vitreoretinopathy, endophthalmitis, and intraocular foreign body removal. Commonly, vitrectomy is used to treat diabetic vitreous hemorrhage, a condition in which the retina bleeds into the vitreous.
Vitrectomy has been shown to vastly improve the visual acuity of patients suffering from vision loss, distortion, or disruption due to vitreous hemorrhage. The procedure also reduces the risk of severe bleeding in patients who have begun to experience vitreous hemorrhage and for patients with abnormal blood vessels in the iris.
When is Vitrectomy Needed?
A vitrectomy is a complicated surgical procedure with the potential for complications like elevated intraocular pressure, retinal detachment, continued bleeding into the vitreous, corneal edema (fluid buildup in the cornea), or internal eye infection. As a result, this type of eye surgery is only used as a last resort in extreme cases of vitreous hemorrhage which do not clear up without treatment.
Every patient and every eye is different, and therefore responds differently to treatment. For this reason, diagnosis from an eye care professional specializing in retinal conditions and procedures is necessary before undergoing a vitrectomy.