Keratoconus
What is Keratoconus?
Keratoconus is a disorder of the anterior surface of the eye (the cornea). In simple terms this means that the cornea becomes thinner causing the cornea to bulge from its normal round shape to a cone shape. This bulging interferes with a person's vision and can severely affect the way they see the world making simple tasks like reading, watching TV or driving very difficult. The distortion caused by keratoconus has been compared to viewing a street sign through your car windscreen during a driving rainstorm.
The progression of keratoconus is unpredictable but generally the condition progresses slowly and can cease at any stage. While keratoconus interferes with the clarity of a person's sight it rarely causes blindness and in its early stages, keratoconus causes slight blurring and distortion of vision and increased sensitivity to glare and light. As the disorder progresses the degree of vision obtained through glasses becomes less acceptable and contact lenses often become the best method of correcting vision problems.
Most people can successfully manage their condition using special keratoconus contact lenses; however in a small number of cases where the cornea can no longer successfully be fitted with contact lenses, a corneal transplant may be needed.
Treatment for Keratoconus
In early stage keratoconus, distortion of vision can be treated using glasses to correct minor myopia (nearsightedness) and astigmatism caused by the condition. As keratoconus advances, gas permeable (GP) contact lenses are the first choice to correct vision. Most of the time, this is a permanent remedy.
The Rose K lens has a number of features that make it ideal for keratoconus and is internationally recognized as the leading lens for the treatment of keratoconus.
- The lenses are designed using complex computer models and manufactured on special computerized lathes.
- The complex geometry of Rose K lenses take into account the conical shape of the cornea in all stages of the condition.
- Lenses can be customized to suit each eye and can correct the myopia and astigmatism associated with the condition.
- Rose K lenses allow the cornea to 'breathe' oxygen directly through the lens material providing excellent health to the eye.
- The lenses are easy to insert, remove and clean.
As a result the entire lens fits better over the eye leading to better comfort and optimum visual acuity (sharpness) for patients. However due to the progressive nature of the condition, it is important that lenses are fitted with great care and reassessed at least annually by your eye care professional.
The Boston Scleral Lens Prosthetic Device (BSLPD) avoids all contact with the sensitive cornea. Instead, it rests entirely on the sclera (the tough, relatively insensitive white tissue of the eye) and creates a pool of artificial tears over the cornea that functions as a unique liquid eye bandage. This is why the BSLPD can be worn comfortably when other types of contact lenses have failed and why it never decenters, becomes dislodged or traps foreign bodies. Moreover, even severe dry eye is not an impediment to their wearing tolerance. In fact, their liquid eye bandage has been a very successful treatment for this condition.
Frequently Asked Questions
I have Keratoconus, will I go blind?
No, Keratoconus is not a blinding condition, although vision is likely to progressively worsen. Keratoconus causes thinning and distortion of the cornea, which is the clear dome at the front of the eye. The cornea normally has a rounded dome-like shape, but in Keratoconus the thinned area bulges forward to produce a cone like protrusion. This results in distortion and reduced vision, blurred distance vision, glare, light sensitivity and disturbed night vision. However with the use of contact lenses, most Keratoconus patients can maintain good functional vision and a normal lifestyle.
I'm 15 and have just found out that I have Keratoconus. Is the cone very noticeable to other people?
The corneal changes in Keratoconus are so subtle that special instruments and training are required to see them. Except in the most advanced cases, it is virtually impossible for someone other than a doctor to tell that you have Keratoconus.
Is it possible for Keratoconus to simply get better and heal on its own or is it a permanent condition that can only
degenerate?
Keratoconus either progresses or remains stable: it does not get better.
Is my Keratoconus going to get worse and how quickly will it change?
Keratoconus invariably does get worse in the majority of cases, however progression is difficult to predict. In some cases it changes very little from the time it is first diagnosed. In other cases progression occurs rapidly over a relatively short period of time. The younger the patient is when keratoconus first appears, however, the more chance there is that it will progress significantly, particularly during the teenage years. It is very important to control any allergies which affect the eye during this time, so that any eye rubbing can be avoided.
Keratoconus has been confirmed in my right eye. Will my left eye be affected also?
Keratoconus is bilateral (i.e. affects both eyes) in about 97% of all cases. Only about 3% of cases are truly unilateral. A topography or mapping of the cornea by your practitioner will nearly always show some steepening in the unaffected eye at the time of the first diagnosis of keratoconus, even though the vision at this stage in this eye may be unaffected. Frequently one eye will show symptoms before the other, and the degree of severity is normally worse in one eye and often remains this way.
Will certain activities, such as sports or long hours in front of the computer, hasten the progression of Keratoconus?
There is no evidence that any physical or visual activity has any affect on the progression of Keratoconus. The exception is eye rubbing where the trauma caused by eye rubbing can damage the cornea which may cause the condition to advance more rapidly.
Why is my vision sometimes more than "double"? I only have 2 eyes so where do the other images come from?
Multiple images can be caused by a disparity between the two eyes or from multiple refractive zones within the optical zone of just one eye. If you see double and it disappears when you close either eye, it is most likely a binocular problem caused by the two eyes not working together. The causes of this are many and some are potentially serious. Multiple images in one eye occur more frequently in ocular surface diseases like Keratoconus or in diseases affecting the lens or iris of the eye. In Keratoconus, surface thinning can create multiple optical zones that individually focus the same image to different areas of the retina, thus creating the additional perceived multiple images. Contact lenses usually eliminate most of these problems.
What is the difference between Keratoconus and "Common Astigmatism"?
Astigmatism is a common condition where the curvature of one or more of the optical surfaces of the eye (the cornea and lens surfaces) is more "curved" in one direction than the other. In "regular" astigmatism the maximum and minimum powers of the cornea are aligned at 90 degrees to each other, while in "irregular astigmatism" they do not align. An egg is a good example of a surface with regular astigmatism, whereas an orange (sphere) is a good example of a surface which has no astigmatism. Keratoconus is a degenerative condition where the cornea thins in affected areas. This can lead to astigmatism – often regular at first but becoming increasingly irregular as the condition progresses. It is possible to correct regular astigmatism with glasses or soft contact lenses, however for irregular astigmatism, where the cornea can often have multiple curves (giving multiple focuses), it is impossible to correct these multiple focuses with spectacles or soft contact lenses.
What is the meaning of the numbers used to describe the degree of Astigmatism?
Astigmatism is measured in diopters (D), a standard optical measure. In simple terms, the diopter represents the reciprocal of the focal distance in metres. For example, a patient with 2 D of nearsightedness would have a far focal point of 1/2 metre. A patient with 4 D would have a focal length of 1/4 metres or 25cm. A patient with 1/2 D would have a focal point 2 metres in the distance. Many patients have between 0.25 and 2.00 D of astigmatism. Between 2.25 and 3.75 is less common but still seen. Much above that in a "normal" patient is unusual. Keratoconus and post-transplant patients can have up to 10 D of astigmatism or even more.
What is the best contact lens for Keratoconus?
There is no single lens type or brand that works for every Keratoconus patient. In the early stages, conventional soft lenses can work remarkably well. As Keratoconus progresses, gas permeable (GP) lenses work best for the majority of patients. In other cases where tolerance of a GP lens is a problem, piggybacking a rigid lens over the top of a soft disposable lens, can in many cases improve the tolerance dramatically and provide successful contact lens wear. Unfortunately, contact lenses alone may not completely correct your vision. For some patients, spectacles worn over contact lenses or special lens designs may help. In some cases, corneal scarring or other problems may limit vision, and no amount of correction will be completely effective. Surgery may be the best choice when the vision obtained with a contact lens correction is inadequate.
Can I still wear soft lenses if I have Keratoconus?
Soft contact lenses may work well in early Keratoconus. In more advanced cases they will do no harm but they rarely provide adequate visual correction. GP contact lenses usually offer better vision correction for Keratoconus.
My friend wears soft contact lenses for her short sightedness. Why can't I wear soft lenses for my Keratoconus?
Unfortunately soft contact lenses very rarely provide the same standard of vision that GP lenses provide. By nature, soft lenses wrap around the cornea giving rise to that same optical issues (distorted vision) that the keratoconus cornea causes. A GP (rigid lens) provides a new optical surface for light entering the eye, so light can be focused back to a single point. However in some early cases of keratoconus where the corneal distortion is minimal, soft lenses can provide an acceptable standard of vision.
I am going on 58 and have just been diagnosed with Keratoconus. My doctor has recommended contact lenses but I've never worn them before and I'm worried that I may not be able to handle them at my age.
Give contact lenses a try. Handling lenses is far less difficult than you would imagine and the improvement in your vision is likely to be substantial. Make sure that you find a contact lens specialist who is patient, and is willing to take the time needed to properly train you on how to remove and insert your contact lenses and how to care for them. With sufficient training it would be most unusual that lens handling would prevent you from being able to use contact lenses.
Can I take advantage of different brands of contact lens solutions and eye drops, depending on what's on sale?
Recently published research has shown significant incompatibilities between newer contact lens materials and some contact lens care products. The result is irritation and increased risk of more serious problems. Clearly, not all care products are the same. You should avoid problems by first checking with your contact lens specialist before switching lens care products.
Recently I have noticed a 'general fog' which affects my vision like my lens is not clean. This usually comes on after a few hours of contact lens wear. What would cause this?
Fogging can be caused by a build up of deposits on the surface of the contact lens, or by some physiological change to the cornea. If fogging occurs, always remove the lens, clean it with a GP cleaner such asBoston Intensive Cleaner, rewet the lens and reinsert it. If the fogging problem is resolved then this was obviously due to some build up on the lens surface. However if the fogging persists, then it is likely to be due to some change in the cornea such as oedema, where the cornea swells and becomes less transparent. In this case you should consult your contact lens fitter as soon as possible, to determine the cause of your symptoms.
Some GP Keratoconus lenses have aberration control incorporated into their design. Is this necessary and what an advantage does this have over lenses that do not have aberration control?
The most common type of lens aberration is spherical aberration and it is caused by two lens surfaces not being parallel; the front surface of the lens being significantly flatter than the back surface. This causes light passing through different points on the lens to have different focal points onto the retina (back of the eye) and produces a 'ghost' image around the original image like a tv set that is not tuned properly. By subtly changing the curves on the surface of the lens a significant amount of the spherical aberration can be eliminated. The amount of spherical aberration produced is proportional to the lens power, so as keratoconus gets worse, the lens power also needs to increase and so does the spherical aberration. Keratoconus patients commonly require very high powers on their lenses to see well and therefore obtain significant benefit from having aberration control incorporated into their lenses. RoseK2 is an example of a lens which has aberration control. In a study in the USA, where a group of over 50 patients wore Rose K lenses both with and without aberration control, 100% reported their vision with Rose K2 to be the same or better than the original Rose K design which did not incorporate aberration control, and 75% of patients reported their vision with Rose K2 to be better or much better. Many patients gained at least one line of vision which is very significant.
I've had transplant surgery and I've been told to expect changes in my vision for many months. How long should it take for my eye to stabilize, and is the astigmatism likely to get better or worse as my eye continues to heal? Also, will I need contact lenses after surgery?
Healing and refractive results after transplant surgery vary tremendously from patient to patient making it difficult to predict results. There is also no way to know if a contact lens will be necessary until your eye is stable. In addition to contact lenses and glasses, several adjunctive surgical procedures can be performed to reduce post transplant astigmatism if needed. The majority of patients can obtain reasonable vision with spectacles; however for both eyes to work together to give good binocular vision, a contact lens is still often required.
Can I have LASIK?
No, Keratoconus is a corneal thinning condition and LASIK is a corneal thinning procedure. Surgically making a thin cornea thinner will weaken an already weak cornea and speed the progression of Keratoconus thereby worsening the condition.
My lenses become uncomfortable in airplane cabins. What can I do?
Ideally one would never wear any contact lenses in an airplane cabin because of the reduced oxygen available and the very low humidity. This is certainly not an ideal environment for contact lens wear. Both of these factors invariably lead to dryness, irritation, discomfort and subsequent reduced wearing time. However for the keratoconic patient, leaving the lenses out when flying is often not an option as their uncorrected vision is insufficient for them to manage. Therefore while flying, we recommend frequent (at least hourly) use of contact lens rewetting drops, removal of lenses if sleeping, and removal of the lenses even for short periods to clean and rewet the lens if this is a possible option. Also keep your body hydration levels to a maximum by drinking plenty of water and avoid alcohol and coffee, both of which cause dehydration.