Orthokeratology
Encyclopedia
Orthokeratology marketed under brand names like "EyeDream", "MiracLens", "DreamLens", "i-GO OVC", "GOV", "Wake and See", "CRT" and "Emerald", is the use of rigid gas-permeable contact lens
es, normally worn only at night, to improve vision through the reshaping of the cornea
. This method can be used as an alternative to eyeglasses, refractive surgery
, or for those who prefer not to wear contact lenses during the day. The latter may be due to discomfort from working in air-conditioned or dusty environments, from extended computer usage which reduces blink rates and tear film production or from displacement or loss during sports activities.
George Jessen
created what was probably the first orthokeratology design in the 1960s made from PMMA material, which he marketed as "Orthofocus". These early designs had generally unpredictable results, leading to the belief that applied orthokeratology was more art or luck than science. Many groups and individuals claim to have been the first to develop modern orthokeratology solutions. However, Dr. Richard Wlodyga, in particular, is generally credited with developing the first reverse zone lens design in the 1980s.
However, it was not until computerized corneal topography
became available during the 1990s that it became possible to apply the theory to create designs with repeatable results through being able to accurately map the surface curvature of the cornea
using a non-invasive, painless imaging procedure. Additionally, the development of new base materials for rigid gas permeable
lenses which provided much higher levels of oxygen permeability
opened up the possibility of orthokeratology becoming an overnight procedure rather than being used for daytime wear alone. Finally, the introduction of computer-controlled precision lathes meant that lens designs could be manufactured to sub-micron levels of accuracy thereby offering the prospect of high volume production becoming commercially viable.
In the summer of 2000, at an educational meeting of optometrists in Toronto, the Orthokeratology Academy of America (OAA) was formed to support, promote and advance orthokeratology. By providing quality education and scientific information on the subject of ortho-k to all interested practitioners, the OAA provides an unbiased forum for the free exchange of ideas and concepts relating to all aspects of orthokeratology. Its membership has the opportunity to advance their role in the field by applying for and passing comprehensive exams in order to achieve Fellowship status in the Academy. In parallel, the British Orthokeratology Society (BOKS) was established in the UK with similar objectives to promote orthokeratology as a new procedure to correct myopia.
A significant milestone for the US market occurred in June 2002 when the FDA granted approval for overnight wear of a type of corneal reshaping called "Corneal Refractive Therapy" (CRT). This forms the basis of the "Paragon CRT" product backed by Paragon Vision Sciences
Inc. Subsequently in 2004, the U.S. Food and Drug Administration (FDA) approved a design from Euclid Systems Corporation ("Emerald"). Each FDA approval has a Premarket approval
(PMA) number. The PMA number of the FDA approval for Paragon CRT is P870024; the PMA number of the FDA approval for Emerald is P010062.
However, nightwear ortho-k solutions were available to consumers in many countries outside the US much earlier as a result of different regulatory controls and bodies.
In 2005, Bausch & Lomb
acquired the PMA for the Emerald lens design from Euclid (which is marketed in Europe as 'i-GO OVC') and created the "Vision Shaping Treatment" (VST) program to collectively market a number of ortho-k lens designs which were manufactured using Bausch & Lomb base material. This program currently comprises five lens designs in addition to Emerald.
In 2006 and 2007, papers presented at the British Contact Lens Association and the Global Orthokeratology Symposium indicated the possibility of orthokeratology slowing or stopping myopic progression. This was found to be effective in children in Hong Kong and is the subject of wider study to verify this data. More recently, the first year results from the SMART Study (Stabilizing Myopia by Accelerated Reshaping Technique) – a five-year longitudinal study currently underway in the Greater Chicago area – show a statistically significant difference for children in the treatment group wearing orthokeratology lenses who exhibited no overall prescription change against children in the control group wearing conventional soft contact lenses for whom there was a mean increase in myopia of 0.40 diopters.
and up to −1.75 diopters of astigmatism
whilst the approvals for Euclid (and thus for the other five lens designs offered under the Bausch & Lomb 'Vision Shaping Treatment' portfolio) cover procedures up to −5.00 diopters of myopia and up to −1.50 diopters of astigmatism.
In the United Kingdom, the procedure is offered primarily for myopic correction up to −5.00 diopters and up to −1.50 diopters of astigmatism. Fitting evidence for the leading lens designs indicates that procedures undertaken within these parameters have the highest probability of success. Some patients with higher degrees of myopia are successfully treated by specialist practitioners with "off-label
" uses of these same lenses.
In countries like South Africa, Australia and Taiwan, practitioners using the GOV orthokeratology system have achieved successful fits as high as −10.00D of myopia
and +5.00D of hyperopia
. Not every patient within these parameters will be suitable for the procedure and, for example, conditions such as flat or steep cornea
s may result in the procedure being less successful.
measured by its 'Dk' rating (the higher the value, the greater the degree of oxygen permeability) – is important for maintaining eye-health during the treatment.
Paragon Vision Sciences
manufactures a lens trademarked "Paragon CRT" (Paragon Corneal Refractive Therapy) and marketed as "Accelerated Orthokeratology" (AOK) using base material manufactured in-house. Euclid Systems and the other five overnight orthokeratology lens designs offered under the Bausch & Lomb
"Vision Shaping Treatment" (VST) portfolio are manufactured by various contact lens laboratories in the US and internationally using Bausch & Lomb base materials and in North America may only be fitted by VST certified practitioners.
The seven designs in the VST portfolio comprise (alphabetically):
No other design of ortho-k lenses has been approved by the FDA for overnight wear and currently there are no other studies underway for any new lens designs.
Non FDA approved designs are available, such as Menicon Z Night which uses fenestrations in the reverse curve to maximize fluid flow while maintaining centration with a high Dk material. Menicon Z material is FDA approved for up to 30 day wear in regular GP form.
Some practitioners have also designed their own orthokeratology lenses typically by using various software packages which combine corneal topographical data with the practitioners' own knowledge and experience to determine the appropriate lens parameters for individual patient prescriptions. Wave/Z-Wave is one such software package which allows for a CNC lathe manufacturing method of lenses customized by the practitioner with a wide variety of material choices.
Overnight Ortho-K is generally very well accepted though since the main feeling is due the eyelids moving over the lens edges. When the eyes remain closed for sleep, there is generally no residual feeling of the lens after the adaptation period.
Orthokeratology has rarely had severe side-effects, although this is confined to a March 2004 report of a very small sample of cases in China where supply of lenses at that time was not subject to any regulatory regime covering safety and efficacy. More typically, complications can occur due to the patient's failure to follow appropriate hygiene recommendations when handling or cleaning the lenses including the use of tap water to rinse (although some systems allow for or suggest the use of "clean" tap water) or store. Complications may also be due to relative corneal hypoxia
(lack of oxygen) with prolonged or overnight contact lens wear in lenses made from the wrong material. However, the use of high or hyper oxygen-permeable materials as approved by the US Food and Drug Administration and manufactured by leading contact lens companies such as Bausch and Lomb and Paragon Vision Sciences
significantly reduces hypoxia, and these are the materials that are normally used in orthokeratology.
An article in the January 2005 issue of "Eye & Contact Lens: Science & Clinical Practice" discusses two case reports of children who developed corneal ulcers when fit with Paragon CRT contact lenses, which were worn nightly. Each patient presented with a bacterial corneal ulcer after wearing CRT contact lenses for less than 6 months. In the first patient, Pseudomonas aeruginosa was identified as the causative organism. In the second patient, Haemophilus influenza was cultured from the ulcer. Both patients were treated with antibiotics, resulting in a rapid resolution of the corneal ulcers and preservation of vision. The writers conclude that "Paragon CRT lenses have been approved for use in patients of all ages. When used in children, these lenses may present unique problems. The absolute incidence of bacterial corneal ulcers in patients with CRT lenses are unknown. Severe caution should be used before prescribing CRT lenses for children and informed consent should include potential sight-threatening corneal ulcers."
Contact lens
A contact lens, or simply contact, is a lens placed on the eye. They are considered medical devices and can be worn to correct vision, for cosmetic or therapeutic reasons. In 2004, it was estimated that 125 million people use contact lenses worldwide, including 28 to 38 million in the United...
es, normally worn only at night, to improve vision through the reshaping of the cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
. This method can be used as an alternative to eyeglasses, refractive surgery
Refractive surgery
Refractive eye surgery is any eye surgery used to improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This can include various methods of surgical remodeling of the cornea or cataract surgery. The most common methods today use excimer lasers to...
, or for those who prefer not to wear contact lenses during the day. The latter may be due to discomfort from working in air-conditioned or dusty environments, from extended computer usage which reduces blink rates and tear film production or from displacement or loss during sports activities.
History
Doctors discovered the reshaping phenomena of glass lenses as early as the 1940s. This history of orthokeratology includes contributions made by Jessen, Ziff, Nolan, Paige, Gates, May, Grant, Fontana, Tabb, Freeman, Shed, Kerns, and Binder to the use of contact lenses for myopia reduction.George Jessen
George Jessen
George Jessen was an optometrist who was an early pioneer of the contact lens. He is credited with being on of the first to employ the concept of orthokeratology, a direct attempt to reduce refractive error with the use of a contact lens, under the term orthofocus.Jessen received his training at...
created what was probably the first orthokeratology design in the 1960s made from PMMA material, which he marketed as "Orthofocus". These early designs had generally unpredictable results, leading to the belief that applied orthokeratology was more art or luck than science. Many groups and individuals claim to have been the first to develop modern orthokeratology solutions. However, Dr. Richard Wlodyga, in particular, is generally credited with developing the first reverse zone lens design in the 1980s.
However, it was not until computerized corneal topography
Corneal topography
Corneal topography, also known as photokeratoscopy or videokeratography, is a non-invasive medical imaging technique for mapping the surface curvature of the cornea, the outer structure of the eye...
became available during the 1990s that it became possible to apply the theory to create designs with repeatable results through being able to accurately map the surface curvature of the cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
using a non-invasive, painless imaging procedure. Additionally, the development of new base materials for rigid gas permeable
Rigid gas permeable
Rigid gas permeable lenses are rigid contact lenses made of oxygen-permeable polymers. Initially developed in the late 1970s, and through the 1980s and 1990s, they were an improvement over prior 'hard' lenses that restricted oxygen transmission to the eye....
lenses which provided much higher levels of oxygen permeability
Oxygen permeability
Oxygen permeability is a parameter of a contact lens. OP expresses the ability of the lens to let oxygen reach the eye by diffusion. Another parameter is the transmissibility level , the Dk per thickness of the lens, and is generally more used. Typical values are from 25 to 50...
opened up the possibility of orthokeratology becoming an overnight procedure rather than being used for daytime wear alone. Finally, the introduction of computer-controlled precision lathes meant that lens designs could be manufactured to sub-micron levels of accuracy thereby offering the prospect of high volume production becoming commercially viable.
In the summer of 2000, at an educational meeting of optometrists in Toronto, the Orthokeratology Academy of America (OAA) was formed to support, promote and advance orthokeratology. By providing quality education and scientific information on the subject of ortho-k to all interested practitioners, the OAA provides an unbiased forum for the free exchange of ideas and concepts relating to all aspects of orthokeratology. Its membership has the opportunity to advance their role in the field by applying for and passing comprehensive exams in order to achieve Fellowship status in the Academy. In parallel, the British Orthokeratology Society (BOKS) was established in the UK with similar objectives to promote orthokeratology as a new procedure to correct myopia.
A significant milestone for the US market occurred in June 2002 when the FDA granted approval for overnight wear of a type of corneal reshaping called "Corneal Refractive Therapy" (CRT). This forms the basis of the "Paragon CRT" product backed by Paragon Vision Sciences
Paragon Vision Sciences
Paragon Vision Sciences manufactures the Paragon CRT orthokeratology contact lenses.-History:Founded in 1976, Paragon was the first company to introduce oxygen permeable contact lens materials to independent laboratories in the United States....
Inc. Subsequently in 2004, the U.S. Food and Drug Administration (FDA) approved a design from Euclid Systems Corporation ("Emerald"). Each FDA approval has a Premarket approval
Premarket approval
Premarket approval is the U.S. Food and Drug Administration process of scientific and regulatory review to evaluate the safety and effectiveness of Class III medical devices and is significantly different from the Premarket Notification process known as 510...
(PMA) number. The PMA number of the FDA approval for Paragon CRT is P870024; the PMA number of the FDA approval for Emerald is P010062.
However, nightwear ortho-k solutions were available to consumers in many countries outside the US much earlier as a result of different regulatory controls and bodies.
In 2005, Bausch & Lomb
Bausch & Lomb
Bausch & Lomb, an American company based in Rochester, New York, is one of the world's leading suppliers of eye health products, such as contact lenses and lens care products today. In addition to this main activity, in recent years the area of medical technology has been developed...
acquired the PMA for the Emerald lens design from Euclid (which is marketed in Europe as 'i-GO OVC') and created the "Vision Shaping Treatment" (VST) program to collectively market a number of ortho-k lens designs which were manufactured using Bausch & Lomb base material. This program currently comprises five lens designs in addition to Emerald.
In 2006 and 2007, papers presented at the British Contact Lens Association and the Global Orthokeratology Symposium indicated the possibility of orthokeratology slowing or stopping myopic progression. This was found to be effective in children in Hong Kong and is the subject of wider study to verify this data. More recently, the first year results from the SMART Study (Stabilizing Myopia by Accelerated Reshaping Technique) – a five-year longitudinal study currently underway in the Greater Chicago area – show a statistically significant difference for children in the treatment group wearing orthokeratology lenses who exhibited no overall prescription change against children in the control group wearing conventional soft contact lenses for whom there was a mean increase in myopia of 0.40 diopters.
Mechanism
Tissue growth and propagation studies indicate that epithelial cells adjust growth in response to presence of a foreign material. CRT lens proximity to the cells therefore is thought to stimulate cell growth where less proximity coincides with added growth and more proximity coincides with growth repression thereby creating a 'proximal pressure' on the epithelial cells.Indications
The US FDA overnight orthokeratology approval for Paragon CRT is for procedures up to −6.00 diopters of myopiaMyopia
Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...
and up to −1.75 diopters of astigmatism
Astigmatism
An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances...
whilst the approvals for Euclid (and thus for the other five lens designs offered under the Bausch & Lomb 'Vision Shaping Treatment' portfolio) cover procedures up to −5.00 diopters of myopia and up to −1.50 diopters of astigmatism.
In the United Kingdom, the procedure is offered primarily for myopic correction up to −5.00 diopters and up to −1.50 diopters of astigmatism. Fitting evidence for the leading lens designs indicates that procedures undertaken within these parameters have the highest probability of success. Some patients with higher degrees of myopia are successfully treated by specialist practitioners with "off-label
Off-label use
Off-label use is the practice of prescribing pharmaceuticals for an unapproved indication or in an unapproved age group, unapproved dose or unapproved form of administration...
" uses of these same lenses.
In countries like South Africa, Australia and Taiwan, practitioners using the GOV orthokeratology system have achieved successful fits as high as −10.00D of myopia
Myopia
Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...
and +5.00D of hyperopia
Hyperopia
Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance...
. Not every patient within these parameters will be suitable for the procedure and, for example, conditions such as flat or steep cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
s may result in the procedure being less successful.
Types of lenses
Orthokeratology lenses are made by a number of companies globally, primarily using one of the two FDA approved technologies. All use special gas permeable lenses to reshape the cornea. The lens material – and especially its oxygen permeabilityOxygen permeability
Oxygen permeability is a parameter of a contact lens. OP expresses the ability of the lens to let oxygen reach the eye by diffusion. Another parameter is the transmissibility level , the Dk per thickness of the lens, and is generally more used. Typical values are from 25 to 50...
measured by its 'Dk' rating (the higher the value, the greater the degree of oxygen permeability) – is important for maintaining eye-health during the treatment.
Paragon Vision Sciences
Paragon Vision Sciences
Paragon Vision Sciences manufactures the Paragon CRT orthokeratology contact lenses.-History:Founded in 1976, Paragon was the first company to introduce oxygen permeable contact lens materials to independent laboratories in the United States....
manufactures a lens trademarked "Paragon CRT" (Paragon Corneal Refractive Therapy) and marketed as "Accelerated Orthokeratology" (AOK) using base material manufactured in-house. Euclid Systems and the other five overnight orthokeratology lens designs offered under the Bausch & Lomb
Bausch & Lomb
Bausch & Lomb, an American company based in Rochester, New York, is one of the world's leading suppliers of eye health products, such as contact lenses and lens care products today. In addition to this main activity, in recent years the area of medical technology has been developed...
"Vision Shaping Treatment" (VST) portfolio are manufactured by various contact lens laboratories in the US and internationally using Bausch & Lomb base materials and in North America may only be fitted by VST certified practitioners.
The seven designs in the VST portfolio comprise (alphabetically):
- "BE Retainer" backed by BE Enterprises Inc
- "CKR" backed by Eye Care Associates
- "Contex OK-E System" backed by Contex Inc.
- "DreamLens" backed by Dreimlens Inc
- "Emerald" designed and manufactured by Euclid Systems Corporation
- "MiracLens" designed and manufactured by MiracLens,LLC
- "NightMove" backed by Advanced Corneal Engineering Inc
No other design of ortho-k lenses has been approved by the FDA for overnight wear and currently there are no other studies underway for any new lens designs.
Non FDA approved designs are available, such as Menicon Z Night which uses fenestrations in the reverse curve to maximize fluid flow while maintaining centration with a high Dk material. Menicon Z material is FDA approved for up to 30 day wear in regular GP form.
Some practitioners have also designed their own orthokeratology lenses typically by using various software packages which combine corneal topographical data with the practitioners' own knowledge and experience to determine the appropriate lens parameters for individual patient prescriptions. Wave/Z-Wave is one such software package which allows for a CNC lathe manufacturing method of lenses customized by the practitioner with a wide variety of material choices.
Comfort
Lenses are generally considered to be not as comfortable as Soft contacts and can feel similar to an eyelash trapped in the wearer's eye, especially during initial wear periods and while the eye is open/blinking. This is due to the shape requirements of the lens and edge design which has to serve more purposes than a traditional lens. Generally the feeling is reduced as the body becomes used to the lens, though it may never become as comfortable as traditional soft or rgp contact lens designs which are designed to be used for active vision correction.Overnight Ortho-K is generally very well accepted though since the main feeling is due the eyelids moving over the lens edges. When the eyes remain closed for sleep, there is generally no residual feeling of the lens after the adaptation period.
Cautions
During the first month of lens wear when the treatment zone on the surface of the cornea is in the process of becoming fully formed, some users may experience vision issues such as ghosting, double vision, contrast problems and/or starbursting, especially at night. These issues are generally resolved by the end of the first month of lens wear. If these issues persist beyond this initial period, the cause may be due to lack of centration of the lens on the eye and/or overly large pupil size (in light or dark). Resolution may be possible through redesign, material changes, better eye moisture retention (night eye masks, duct blocking, Restatis etc.) or other techniques. All issues should be immediately discussed with the Practitioner.Orthokeratology has rarely had severe side-effects, although this is confined to a March 2004 report of a very small sample of cases in China where supply of lenses at that time was not subject to any regulatory regime covering safety and efficacy. More typically, complications can occur due to the patient's failure to follow appropriate hygiene recommendations when handling or cleaning the lenses including the use of tap water to rinse (although some systems allow for or suggest the use of "clean" tap water) or store. Complications may also be due to relative corneal hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
(lack of oxygen) with prolonged or overnight contact lens wear in lenses made from the wrong material. However, the use of high or hyper oxygen-permeable materials as approved by the US Food and Drug Administration and manufactured by leading contact lens companies such as Bausch and Lomb and Paragon Vision Sciences
Paragon Vision Sciences
Paragon Vision Sciences manufactures the Paragon CRT orthokeratology contact lenses.-History:Founded in 1976, Paragon was the first company to introduce oxygen permeable contact lens materials to independent laboratories in the United States....
significantly reduces hypoxia, and these are the materials that are normally used in orthokeratology.
An article in the January 2005 issue of "Eye & Contact Lens: Science & Clinical Practice" discusses two case reports of children who developed corneal ulcers when fit with Paragon CRT contact lenses, which were worn nightly. Each patient presented with a bacterial corneal ulcer after wearing CRT contact lenses for less than 6 months. In the first patient, Pseudomonas aeruginosa was identified as the causative organism. In the second patient, Haemophilus influenza was cultured from the ulcer. Both patients were treated with antibiotics, resulting in a rapid resolution of the corneal ulcers and preservation of vision. The writers conclude that "Paragon CRT lenses have been approved for use in patients of all ages. When used in children, these lenses may present unique problems. The absolute incidence of bacterial corneal ulcers in patients with CRT lenses are unknown. Severe caution should be used before prescribing CRT lenses for children and informed consent should include potential sight-threatening corneal ulcers."