By Dr. John Rinehart
AG a 12 year old female began orthokeratology as part of an FDA study to get approval of various lens designs and the Polymer Technology materials. In 2001 her unaided DVA was 20/70 OD, OS. Subjective refraction was :
OD -1.25 sphere 20/20
OS -1.25 -0.50 x 090 20/20
K’readings OU 44.00/44.00 @ 090
My site was chosen to work with the BE lens developed by John Mountford of Brisbane Australia. This was the first design (to my knowledge) to use cone angles rather than curves to control the positioning.
The lens is fit through the aid of topography and overnight diagnostic fitting. Sagittal depth over a given chord is used to select the first diagnostic lens. The patient is instructed in the care and handling of the lens and told to wear the lens overnight then return to the clinic early the next morning with the lenses on the eye. After it is determined that the lenses are in place and moving they are removed. Acuities, keratometic readings, subjective refraction and topography are performed.
The critical part of this evaluation is analysis of the topography difference maps. If they show a well centered bull’s eye pattern the lenses can be ordered if not the diagnostic fitting is repeated until the lens fit results in a well centered treatment zone with no central islands.
The lab is supplied with the information on the diagnostic fitting and refractive information from which they design the patient’s lenses.
Done properly this method assures success. Prior to the patient’s lenses being ordered it has been determined that a well centered treatment zone is created. Yes more time is invested ahead of time but all of the problems solving takes place before lenses are ordered.
Below are difference maps from day one, 2 months and 7 years.
Day one shows a treatment zone decentered slightly superior. This was such a small amount of decentration that rather than repeat the diagnostic fitting the sagittal depth was increased when the patient’s lens was ordered.
Topography from 2 months and 7 years both show a well centered treatment zone.
Currently the patient is 20/20 unaided OD, OS in the mid afternoon. She wears her lenses every night.
Subjective refraction OU -0.25 sphere 20/20
OD 42.00/41.50 @ 090
OS 41.50/41.50 @ 090
By Dr. John Rinehart
I first examined JN, an active 8 year old, in April 2006.
Unaided DVA OD, OS 20/70
OD -1.75 sphere 20/20
OS -2.00 sphere 20/20
K reading OU 44.25/45.75 @ 090
Various correction options were discussed including spectacles, soft lenses GP lenses and OrthoK. The patient and parents liked the option of OrthoK because she is a very athletically active child and to be without any vision correcting appliance seemed to offer the most advantages.
I did explain to the patient and parents that I did have one reservation about the potential success of this therapy. From the Ks and subjective refraction it appears that there could be as much as 1.50 D of residual astigmatism. The final commitment to this treatment was reserved until we had performed an overnight diagnostic fitting.
The initial diagnostic lens has a base curve of 8.13, 10.6 diameter with a 7.63 mm alignment curve radius. This is my own design and the sagittal depth of the lens is determined by the radius of the alignment curve, the reverse curve is used to control the sagittal depth when it is necessary to change either the base curve or the alignment curve. The topographic results of one night of wear are shown below.
The treatment zone is reasonable well centered. Unaided distance acuity at one day OD 20/20, OS 20/20 -2. K readings OU 42.00/42.50 @ 090 zero distortion.
After 7 months of overnight orthok lens wear she wears the lenses 5 nights per week and is very satisfied with her vision.
Unaided DVA OD, OS 20/20
Subjective refraction OD, OS +0.50 sphere
K-readings OD, OS 43.00/43.00 @ 090
Topography (below) continues to show a well centered treatment zone.
After nearly 3 years of overnight orthok lens wear JN’s unaided distance acuity is OD, OS 20/20, K readings OU 43.00/43.25 @ 090 zero distortion. Topography continues to show a well centered treatment zone.
Orthokeratology can be a very viable long term solution to vision correction. With properly fit lenses that are well maintained patients can expect to have their vision corrected for many years. Careful monitoring allows for lens changes to be made in order to maintain clear vision and a healthy cornea. I typically see all of my orthok patients every 6 months.
I also believe it is wise for an orthok practitioner to be well versed in the fitting process of more than one design. I do expect to be able to fit at least 80% of the patients with my first choice lens but occasionally it is necessary to utilize another design in order to get optimum results for some patients.
By Dr. Jeff Walline
Discussion Topic 1: Myopia Control
Discussion Topic 2: Myopia Progression
Discussion Topic 3: How Does Corneal Reshaping Work?
Discussion Topic 4: Topographical Maps