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Keratoconus is an abnormal condition of the cornea, the clear dome over the pupil, in
which the center bulges forward in the shape of a cone, compared to the normal
spherical shape.
The condition has been said to be hereditary, but there are few families in which there
is more than one person with it. It usually begins in the late teens or early twenties and
progresses, but usually stabilizes and rarely becomes worse after the forties or fifties.
Keratoconus disturbs the vision because the front surface of the cornea is not a
smooth, regular refracting surface. The cornea must be smooth, spherical and regular
to provide sharp, clear vision.
Early keratoconus manifests itself as mild and, later, severe astigmatism. Astigmatism
is a condition in which the cornea is curved slightly like the side of a football with two
different curves. The normal cornea is spherical like the shape of the side of a
basketball. A spherical or slightly astigmatic cornea is necessary for sharp, clear
vision. Early keratoconus can usually be treated with spectacles to provide good
vision.
As keratoconus progresses, the center of the cornea bulges forward, roughly in the
shape of a cone, or more like the end of a football. The corneal surface is no longer
spherical and vision cannot be corrected with glasses. Rigid contact lenses can be
fitted to correct the vision and provide normal eyesight. The backside of a rigid contact
lens covers up the irregular surface of the keratoconus cornea, while the front surface
provides a smooth, spherical refractive surface to allow for sharp, clear vision.
As the condition advances, fitting of the contact lens to the irregular cone-shaped
cornea can become a challenge. There are several special designs of back curved
lenses to accommodate the different shapes of keratoconus corneas.
Fitting of keratoconus contact lenses is a challenge and may require the design and
ordering of several different contact lenses to reach the final well-fitting lens that can
provide good vision. Thus, a new lens may not fit perfectly or provide good vision, but
may be necessary to learn how to design the next lens. It is discouraging for the
patient and the doctor for a new contact lens to have poor fitting characteristics and fail
to provide good vision. Keratoconus contact lens fitting can be expensive because of
the many lenses needed to finally reach the desired lens shape and power to provide
comfort and good vision.
If the corneal cone advances sufficiently so that good vision and lens comfort are not
possible, corneal transplant surgery may be necessary. A circular center corneal
section is removed and a donor cornea is sutured into the same location. Healing
takes about a year. Good vision may then be possible with glasses or a special
contact lens may be necessary to provide good vision.
Why not do corneal transplant surgeries early in the condition? Some aggressive
surgeons do just that. Other surgeons feel that only five to ten percent ever really need
surgery.
What is the downside of corneal transplant surgery? In the first place, it is surgery. It is
usually very successful surgery, yet it carries with it the risks of surgery. After surgery,
the cornea never really heals solidly. The cornea has no blood vessels. Scar tissue
that occurs in skin and other parts of the body to heal solidly cannot occur in the
cornea. The cornea is never as strong after cornea transplant surgery. Contact sports
should not be in the future of people who have had corneal transplants, because the
cornea is not as strong.
What about the future of people with keratoconus? It can be discouraging for a young
person to learn he or she has keratoconus. Experience indicates that the future should
be quite bright. It is a bother to have to comply with contact lens fittings and to take
care of the contacts. Experience with keratoconus patients indicates that they do very
well.
What is the cause of keratoconus? The cause has never been definitely determined.
The problem seems to be in the center part of the cornea, called the stroma. The
stroma is made up of interlacing, clear fibers. Why does the stroma become weak and
allow the cornea to bulge forward?
Dr Fredrick Ridley presented a lecture in Houston, Texas in 1966 and reported on
1800 cases of keratoconus from all over the British Empire that he had treated with
contact lenses. He had noticed that most of the patients were “eye rubbers” because
of allergies, and attributed this as the cause. He noted that some are “eye gougers”
and really rub their eyes vigorously with their knuckles.
The allergy theory as a cause of keratoconus has been discussed in many medical
articles. The theory considers that the rubbing causes increased pressure in the eye
and forces the cornea to bulge and become distorted due to some unknown weakness
in the center part of the cornea, called the stroma. Why is the stroma weakened?
Could it be related to some as yet unknown effect of allergy?
Other questions are unanswered. Is there an inherent weakness of the cornea due to
heredity? Could the cornea be weakened from some nutritional deficiency? The
cornea has no blood vessels to receive nutrition, as do most other organs. It receives
most of its nutrition and some of its oxygen from a clear fluid that bathes the backside
of the cornea, called aqueous humor. Among the many nutrients are vitamin C
concentrations, ten to thirty times greater than in the blood. Vitamin C enters the
aqueous humor in its oxidized form. After giving up its oxygen to the cornea, lens, and
other surrounding structures, it re-enters the blood stream in its reduced or unoxidized
form and is rapidly excreted by the kidneys in four to six hours. Thus, vitamin C
requires nutritional replacement several times daily. Vitamin C is necessary for the
production of collagen, a fibrous protein that is the “glue” that holds tissues together
and contributes to tissue stability. The cornea contains collagen. Could failure to eat
enough fruits and vegetables, which contain vitamin C, result in weakness of the
cornea and result in keratoconus? Of course, many youth do not eat enough fruits and
vegetables and only a few develop keratoconus. Could a hereditary tendency or
inherited tendency to have allergies contribute to susceptibility of the cornea to
weakness and result in keratoconus? Could some people fail to absorb an adequate
amount of vitamin C from their diets?
There are many questions as to the cause of keratoconus. The good news is that it
can be treated successfully and those with it can have normal lives.
which the center bulges forward in the shape of a cone, compared to the normal
spherical shape.
The condition has been said to be hereditary, but there are few families in which there
is more than one person with it. It usually begins in the late teens or early twenties and
progresses, but usually stabilizes and rarely becomes worse after the forties or fifties.
Keratoconus disturbs the vision because the front surface of the cornea is not a
smooth, regular refracting surface. The cornea must be smooth, spherical and regular
to provide sharp, clear vision.
Early keratoconus manifests itself as mild and, later, severe astigmatism. Astigmatism
is a condition in which the cornea is curved slightly like the side of a football with two
different curves. The normal cornea is spherical like the shape of the side of a
basketball. A spherical or slightly astigmatic cornea is necessary for sharp, clear
vision. Early keratoconus can usually be treated with spectacles to provide good
vision.
As keratoconus progresses, the center of the cornea bulges forward, roughly in the
shape of a cone, or more like the end of a football. The corneal surface is no longer
spherical and vision cannot be corrected with glasses. Rigid contact lenses can be
fitted to correct the vision and provide normal eyesight. The backside of a rigid contact
lens covers up the irregular surface of the keratoconus cornea, while the front surface
provides a smooth, spherical refractive surface to allow for sharp, clear vision.
As the condition advances, fitting of the contact lens to the irregular cone-shaped
cornea can become a challenge. There are several special designs of back curved
lenses to accommodate the different shapes of keratoconus corneas.
Fitting of keratoconus contact lenses is a challenge and may require the design and
ordering of several different contact lenses to reach the final well-fitting lens that can
provide good vision. Thus, a new lens may not fit perfectly or provide good vision, but
may be necessary to learn how to design the next lens. It is discouraging for the
patient and the doctor for a new contact lens to have poor fitting characteristics and fail
to provide good vision. Keratoconus contact lens fitting can be expensive because of
the many lenses needed to finally reach the desired lens shape and power to provide
comfort and good vision.
If the corneal cone advances sufficiently so that good vision and lens comfort are not
possible, corneal transplant surgery may be necessary. A circular center corneal
section is removed and a donor cornea is sutured into the same location. Healing
takes about a year. Good vision may then be possible with glasses or a special
contact lens may be necessary to provide good vision.
Why not do corneal transplant surgeries early in the condition? Some aggressive
surgeons do just that. Other surgeons feel that only five to ten percent ever really need
surgery.
What is the downside of corneal transplant surgery? In the first place, it is surgery. It is
usually very successful surgery, yet it carries with it the risks of surgery. After surgery,
the cornea never really heals solidly. The cornea has no blood vessels. Scar tissue
that occurs in skin and other parts of the body to heal solidly cannot occur in the
cornea. The cornea is never as strong after cornea transplant surgery. Contact sports
should not be in the future of people who have had corneal transplants, because the
cornea is not as strong.
What about the future of people with keratoconus? It can be discouraging for a young
person to learn he or she has keratoconus. Experience indicates that the future should
be quite bright. It is a bother to have to comply with contact lens fittings and to take
care of the contacts. Experience with keratoconus patients indicates that they do very
well.
What is the cause of keratoconus? The cause has never been definitely determined.
The problem seems to be in the center part of the cornea, called the stroma. The
stroma is made up of interlacing, clear fibers. Why does the stroma become weak and
allow the cornea to bulge forward?
Dr Fredrick Ridley presented a lecture in Houston, Texas in 1966 and reported on
1800 cases of keratoconus from all over the British Empire that he had treated with
contact lenses. He had noticed that most of the patients were “eye rubbers” because
of allergies, and attributed this as the cause. He noted that some are “eye gougers”
and really rub their eyes vigorously with their knuckles.
The allergy theory as a cause of keratoconus has been discussed in many medical
articles. The theory considers that the rubbing causes increased pressure in the eye
and forces the cornea to bulge and become distorted due to some unknown weakness
in the center part of the cornea, called the stroma. Why is the stroma weakened?
Could it be related to some as yet unknown effect of allergy?
Other questions are unanswered. Is there an inherent weakness of the cornea due to
heredity? Could the cornea be weakened from some nutritional deficiency? The
cornea has no blood vessels to receive nutrition, as do most other organs. It receives
most of its nutrition and some of its oxygen from a clear fluid that bathes the backside
of the cornea, called aqueous humor. Among the many nutrients are vitamin C
concentrations, ten to thirty times greater than in the blood. Vitamin C enters the
aqueous humor in its oxidized form. After giving up its oxygen to the cornea, lens, and
other surrounding structures, it re-enters the blood stream in its reduced or unoxidized
form and is rapidly excreted by the kidneys in four to six hours. Thus, vitamin C
requires nutritional replacement several times daily. Vitamin C is necessary for the
production of collagen, a fibrous protein that is the “glue” that holds tissues together
and contributes to tissue stability. The cornea contains collagen. Could failure to eat
enough fruits and vegetables, which contain vitamin C, result in weakness of the
cornea and result in keratoconus? Of course, many youth do not eat enough fruits and
vegetables and only a few develop keratoconus. Could a hereditary tendency or
inherited tendency to have allergies contribute to susceptibility of the cornea to
weakness and result in keratoconus? Could some people fail to absorb an adequate
amount of vitamin C from their diets?
There are many questions as to the cause of keratoconus. The good news is that it
can be treated successfully and those with it can have normal lives.
Keratoconus