The front part of the eye contains a glass like structure called the cornea that allows light to enter the eye and get focussed on the light sensitive layer of the eye-retina. Any factor that affects the health of the cornea leads to degradation of its clarity and thereby directly affects the quality of vision. The health of the ocular surface is maintained by the tear film, normal functioning eyelids, and healthy population of corneal stem cells. The tear glands continuously produce a watery secretion that moistens and lubricates the ocular surface, allowing smooth movement of the eyelids and the eyeball. The tear film also washes away any debris that accumulates on the surface of the eye, and provides a smooth refracting surface of the cornea. Any deficiency of a stable tear film, directly affects the quality of vision, besides producing a variety of symptoms. These range from dryness, burning sensation, irritation, foreign body sensation, itching, and redness etc. I amsure as you read this section, you will recall experiencing some of these symptoms in the past. Well with the advent of 24 hours television channels, and usage of computers in day to day work, dry eye syndrome has become quite common, and is often referred to as "Computer Vision Syndrome" While watching television or working long hours on computer, people tend to blink less frequently. This leads to drying of the ocular surface in between blinks, making the surface rough, with resultant symptoms of irritation and burning etc. Moreover sitting in an air conditioned environment leads to faster evaporation and drying of the eyes. Hence it is important to realize this and consciously blink more frequently, or take a break after an hour, and keep the eyes closed to allow the surface to recover. But it is extremely important to remember that all dry eyes may not be a result of infrequent blinking.... There may be an actual reduction in tear production, leading to all the symptoms described earlier. A proper assessment of the ocular surface status is essential to diagnose the exact etiology. Proper counselling of the patient is done, following which appropriate dry eye therapy is started. Follow up visits are essential to assess the extent of recovery of the health of the ocular surface. Patients often tend to skip these visits as they get symptomatically better with the medications. Due to this, often it leads to inadequate treatment, and recurrence of symptoms after some time..
A clinical condition characterised by thinning and forward protrusion of the cornea resulting in conical shape. This disorder is usually bilateral, with onset at the age of 10 -14 years Although it has been reported in families, the risk of inheritance is reasonably low.
It is possible that this condition could be secondary to increased breakdown of the stromal collagen lamellae by the lysosomal enzymes released by the basal epithelium in these eyes.
Glasses can be prescribed to correct the induced astigmatism in early keratoconus. Once the cylindrical power increases beyond 4.0 diopters, patients find it difficult to tolerate such high power in glasses.
Semisoft or RGP or Rose K contact lens, can help in cases with mild to moderate keratoconus. The front surface of the contact lens now acts like the front surface of the cornea with a regular shape. This provides reasonably clear vision for normal daily activities. However, fitting of contact lens in eyes with keratoconus requires expertise in CL fitting and a special set of trial lenses. With increasing progression of keratoconus, patients may find it difficult to wear the contact lens, and at times the lens keeps falling out of the eye. In such situations, piggy back lens ie RGP lens mounted on a soft contact lens can be tried.
This is a new modality of treatment for keratoconus, where in Riboflavin eye drops are applied followed by exposure of the cornea to ultraviolet radiation for a duration of 30 minutes. This results in cross linking of the collagen fibres of the cornea, thereby increasing its physical strength by upto 300%. Thus further progression of keratoconus can be arrested, and in 15 -20% cases regression has also been noted. Longest followup duration following this treatment is for 10 years. A variety of options for collagen crosslinking treatment are now available at Cornea Clinic, Apollo Hospitals, Hyderabad.
This is a newer surgical treatment for mild to moderate keratoconus. In this surgery, fine plastic implants are placed in the peripheral cornea, which helps flatten the central cornea, thereby improving the unaided vision. Patients are able to return back to normal glass wear or comfortable contact lens wear post treatment. This procedure is painless and simple to perform. The surgery is performed under topical anesthesia using the Ziemer Z6 femtosecond laser, and takes only 5 -10 minutes per eye.
Surgical intervention is often necessary in advanced Keratoconus to restore corneal anatomy and thereby improve quality of vision. Traditionally full thickness corneal transplantation procedures have been commonly performed for advanced keratoconus. Although this procedure has successful outcome in a large number of cases, it sacrifices the healthy endothelium of the host cornea. The transplanted donor cornea is at risk for rejection,and requires steroid therapy for a long duration to prevent rejection. This predisposes the eye to steroid induced complications such as cataract and glaucoma.
With advancement in corneal surgical techniques, it is now possible to selectively remove the anterior layers from the cornea and replace it with donor tissue to restore its anatomy and function. Deep anterior lamellar keratoplasty (DALK) is one such procedure wherein the host corneal endothelium is retained, and anterior corneal tissue is replaced with normal thickness donor tissue. As the host endothelium is retained there is no risk of rejection, and steroids have to be given only for a short duration of time. However DALK surgery requires more surgical expertise compared to the traditional full thickness keratoplasty, and hence performed by only well trained corneal surgeons all over the world.
In advanced stages of Keratoconus, due to extreme thinning, the inner layer of the cornea can rupture, leading to increased leakage of fluid into the cornea. This results in whitening of the cornea, with sudden decrease in vision. This condition is called acute hydrops. In this situation, topical medications have to be applied for symptomatic relief. It takes 3 - 4 months for the corneal oedema to resolve, following which a standard full thickness keratoplasty is required to restore corneal clarity and visual improvement. Specialised penetrating keratoplasty using Ziemer Z6 femtosecond laser allows customized grafts to be prepared and transplanted. It this situation lamellar surgery is not recommended, and hence one should not wait for this complication to occur, and take advantage of lamellar procedures at an early stage.
Stanard full thickness corneal transplantation procedure, is very successful in restoring corneal structure and function. However one needs to use topical steroids for a longer duration than lamellar procedures. Full thickness corneal grafts in keratoconus have the best clinical outcome, when compared with other indication of corneal transplantation surgery.
A variety of corneal conditions can affect the clarity or shape of the cornea. Traditionally full thickness corneal transplantation procedures are being commonly performed to restore corneal shape and clarity and thereby improving vision. In most of these corneal conditions, the innermost layer of the cornea - the endothelium is usually healthy. (This is the functional layer of the cornea, that contains cells that pump fluid out of the cornea and maintain its clarity.) However in full thickness corneal transplantation procedures (conventional corneal grafting surgery) this layer is also sacrificed and replaced with donor tissue. The body senses this layer as being non self ie foreign and attempts to reject this tissue. Hence post operative steroid medications are necessary for a long term duration to prevent rejection of the corneal graft. Long term use of steroids can predispose to complications such as cataract and glaucoma, besides the increased risk of secondary infections.
Deep anterior lamellar keratoplasty (DALK), is a newer method of corneal surgical procedure that selectively removed the diseased anterior layers of the cornea and retains the healthy innermost layer (endothelium). As the inner layer is retained the body does not recognize the donor tissue, hence there is no risk of rejection, and steroid medications need not be continued for a long duration.