Lesson 22 - Orthokeratology and Keratoconus Flashcards
Orthokeratology (ortho-kera-tah’-ogy)
The process of reshaping the cornea with gas permeable lenses to flatten the cornea to try to slow myopia.
Keratoconus (ker-uh-toe-koh’-nus)
Keratoconus is a corneal condition where the cornea gradually steepens over time. The cause is thought to be a genetic mutation, injury to the eye, or related to certain diseases. As an optician, you will most likely see patients who have various stages of keratoconus and need to be fit with gas permeable lenses because they won’t see as well out of traditional glasses as they would with specialty contact lenses.
Another possible cause is frequent ocular allergies causing the person to constantly rub their eyes, thinning the cornea.
Ortho-k
Short abbreviation for orthokeratology
Reverse geometry design
The central optic zone is flatter than the intermediate lens
Ortho-K is approved by the FDA for children, sometimes as young as __ years old, through ___. It can correct nearsightedness up to about __ diopters and less amounts of ____ and _____. Besides slowing down myopia, ortho-k has been popular with people who cannot successfully wear contacts for ___, who cannot have or don’t want to have ____, or who work in ____ environments.
Ortho-K is approved by the FDA for children, sometimes as young as 8 years old, through adulthood. It can correct nearsightedness up to about 6 diopters and less amounts of astigmatism and hyperopia. Besides slowing down myopia, ortho-k has been popular with people who cannot successfully wear contacts for sports, who cannot have or don’t want to have LASIK, or who work in dusty environments.
Prior to fitting ortho-k, the health of the eyes should be checked and corneal measurements must be taken just as you would before fitting any gas permeable contact lens. The ____ is used to assess eye health. The ___ is used to take corneal curvature measurements, and the ____ and/or ____ is used to look for any corneal irregularities and to monitor the changing shape of the cornea over time.
Prior to fitting, the health of the eyes should be checked and corneal measurements must be taken just as you would before fitting any gas permeable contact lens. The slit lamp is used to assess the eye health. The keratometer is used to take corneal curvature measurements, and the topographer and/or OCT is used to look for any corneal irregularities and to monitor the changing shape of the cornea over time.
You can ask your gas permeable lab for help fitting your patient with their initial lenses, or you can use an ortho-k gas permeable lens fitting set. The ortho-k lenses are made with what design?
You can ask your gas permeable lab for help fitting your patient with their initial lenses, or you can use an ortho-k gas permeable lens fitting set. The ortho-k lenses are made with a reverse geometry design.
The ortho-k fitting set is designed how? The lenses are worn when for how long? Sometimes the lenses can be left off when for how long?
The ortho-k fitting set is designed so the lenses are gradually fit flatter and flatter, so over time the final cornea is flat enough that the power of the eye is changed. The lenses are worn each night while the patient is sleeping about 6-8 hours. Sometimes the lenses can be left off during waking hours for 1-2 days.
The time it takes ortho-k to flatten the cornea enough to correct nearsightedness depends what?
The time it takes ortho-k to flatten the cornea enough to correct nearsightedness depends on the original amount of nearsightedness, astigmatism, and cornea shape the patient has.
How are ortho-k lenses inserted, removed, and cleaned?
These lenses are inserted, removed, cleaned, and maintained just like any gas permeable lens.
Many people who experience vision benefits from ortho-k appreciate the fact that it is temporary and potentially reversible. Although many have no eye health or vision problems from it, some may experience what problems?
Lenses are so tight and flat that the cornea swelling causes vision blur and light sensitivity during waking hours.
Dry eye due to the lens being stuck onto the cornea overnight
Cornea cell deposits caused by inflammation from constant irritation over time
Cornea thinning
Eye infections or scarring from abrasions
Keratoconus is characterized by what?
Keratoconus is characterized by highly irregular corneal astigmatism, poor vision even when corrected with glasses, and irregular mires seen on the keratometer. Distortions are also seen on the topographer, and corneal thinning can be seen on the OCT.
The rate of keratoconus caused thinning will vary from person to person. If left untreated, what will happen? Early treatment for the keratoconic cornea includes what? Late-term complications may require what?
The rate of thinning will vary from person to person. If left untreated, the thinning will cause corneal scarring and loss of vision. Early treatment for the keratoconic cornea includes fitting with a gas permeable lens design to try to flatten and reshape the cornea, using either a spherical, hybrid, or scleral design. Other surgical and laser treatments exist for keratoconus. Late-term complications may require a cornea transplant.
The best way to fit a keratoconic patient is with what?
The best way to fit a keratoconic patient is with a fitting set from the contact lens manufacturer. This set contains several specially designed gas permeable lenses with different curves that could fit a cone-shaped cornea.
The most popular gas permeable designs for fitting keratoconus are what? The doctor would select a diagnostic lens based on what?
The most popular gas permeable designs for fitting keratoconus are scleral lens designs, but hybrid lenses and traditional smaller-diameter lenses are used for early keratoconus. The doctor would select a diagnostic lens based on where the cone is and the curvature of the cone.
