This case highlights how high myopia with astigmatism can be effectively treated with orthokeratology lenses designed through Eyespace to offer great vision throughout the day.
Our patient is a 15 year old male myope that has worn monthly Biofinity (comfilcon A) soft contacts lenses for several years but has had three bouts of giant papillary conjunctivitis over the last year. His most recent spectacle Rx is R: -6.00/-1.25 x 66 (6/6), L: -5.75/-3.00 x 160 (6/7.5). He was wearing a spherical lens in the RE and a toric in the LE with AOSept as his cleaning solution. Pred Forte had been prescribed to treat the palpebral conjunctiva on several occasions but as the patient was reliant on his contact lenses due to a dislike for spectacles the GPC continued to flare up.
CAPTION:Superior tarsal plate with contact lens induced giant papillary conjunctivitis
A discussion was had with the patient and his family about future options with less chance of lens deposit formation like daily soft contact lenses, rigid gas permeable lenses and orthokeratology. Our patient comes from a family of young myopes and had two other brothers already using orthokeratology. Being familiar with orthokeratology, we decided to try this option for the patient.
CAPTION:Medmont composite topography maps showing the oblique central astigmatism present on both corneas
The Medmont topography information shows that the patient has apical or central corneal astigmatism (i.e. not limbus to limbus) corresponding to his spectacle cylinder. His eccentricities are on the high side in the flat meridian (RE 0.61 and LE 0.72) and average in the steep meridian (OD 0.49 and LE 0.48). The corneal horisontal visible iris diameter or HVID was 12.00 mm for both eyes.
The Medmont topography information was exported into Eyespace contact lens design software. Due to his moderately high myopia a Forge High Myopia Toric OrthoK design was used to design a custom toric orthokeratology lens for each eye.
Eyespace lens designs
The initial design used in each eye was: R: Forge HMT / Flat 9.4 / 385/ 7.9, Steep 9.3 / 400 / 7.7, Diameter 11.6 mm L: Forge HMT / Flat 9.6 / 375/ 8.0, Steep 9.6 / 430/ 7.6, Diameter 11.6 mm
After one nights wear this patient was seeing 6/18 in each eye unaided!
CAPTION:Medmont topography of the astigmatic orthokeratology mold after the first night of sleeping with the lenses. The small treatment zone and incomplete para central steepening is normal for the first night of molding.
Topographical maps showed -3.80D of axial power change in the right eye and -5.00D in the left. Importantly the initial centration looked excellent, tangential maps show a ring of paracentral steepening in both eyes and a more peripheral ring of flattening outside this. Treatment zones were very small at this early stage. It is important for a lens to compress peripherally (the landing zone) to encourage the corneal tissue to build into the paracentral clearance area. This is the only way that higher levels of myopia can be corrected successfully with wide treatment zones. Purely compressing at the center can only theoretically yield ~4.00 diopters of change.
After a further weeks wear vision was R 6/12-, L 6/24.
CAPTION:Medmont topography of the astigmatic orthokeratology mold after 7 nights of wear.
Topography showed widening of the central treatment zones and an axial power change of -4.20D in the RE and -5.20D in the LE. As these high myopia lenses can continue to improve over 2-3 weeks we decided to review the case in 2 weeks.
Vision today was R 6/10, L 6/12 (despite the fact that the patient had neglected to wear the lenses the previous night!).
CAPTION:Medmont axial power map of the astigmatic orthokeratology mold showing a small central island in the treatment zone
Axial power change was still -4.10D in the R but only -4.60D in the L. A small central island seemed to be developing in the left eye too (shown above). It was decided that while the lenses centered beautifully they were not correcting enough power at the cornea.
CAPTION:EyeSpace optical analysis graph
If we look at the above optical analysis of the lenses in Eyespace we see that the tear lens power in the flat meridian is only -1.00D flatter than the vertex spectacle Rx in the right but -1.75 flatter in the left eye.
To improve the correction of these lenses we flattened the base curve of the right eye by -1.50D while keeping the alignment curves the same. In the left eye we flattened the base curve of the steep meridian by -1.50D, but kept the flat meridian’s base curve the same. Due to the left eye’s astigmatism we need to correct -7.90D in the steep meridian in the left eye. Having a purely spherical base-curve typically allows approximately 50-60% of the corneal astigmatism to be corrected, this would leave this patient with ~1.25D of astigmatism. By creating a toric back optic we can tailor the amount of correction in each meridian more precisely, provided there is enough corneal toricity in the periphery for the toric alignment curves to stabilise any lens rotation.
CAPTION:EyeSpace design page showing the simulated toric high minus forge lenses fitted on the eye. The pressure zones in the alignment and central treatment zones are shown in blue.
The final parameters of this patient’s lenses were: R Flat 9.7/395/7.9, Steep 9.6/410/7.7, Diameter 11.6mm L Flat 9.6/375/8.0, Steep 9.9/450/7.6, Diameter 11.6mm
Day 14 with the new lenses
CAPTION:Photos of the two Forge lenses on the eye. The three letter engravings are unique to each lens and can be used to look up the lens parameters online. The line engravings represent the flat meridian of the lens.
The patient reported at 5pm for his review. Vision even late in the afternoon was R 6/6+ and L 6/7.5. He noticed no reduction in vision towards the end of the day and was very happy with the quality of his vision. Maximum axial power change was -6.00D in the R and -6.80D in the L. Importantly the LE shows full correction of the astigmatism: if we click 1 mm from the pupil center we are getting -5.40D of change along 160, but -8.0D along 70, -2.60D of difference nicely correcting the corneal cylinder. It is worth noting that SimK readings give no indication of the correction of astigmatism in OrthoK as the change in corneal cylinder is occurring in the central 1-2mm, not at ~3mm from pupil where the SimK measurement is calculated.
CAPTION:EyeSpace difference map of the RE
CAPTION:EyeSpace difference map of the LE
Treatment zone sizes calculated in EyeSpace are 5.20 mm in the right and left eye. We are getting around +3.00D of mid peripheral steepening on the axial power map 3 mm from pupil center, providing approximately 10.00D of hyperopic defocus when light enters off-axis. Given this patient is still at an age where his myopia is likely to progress this potential myopia control effect should be beneficial to avoid further eye elongation.
The patient has also been happy with the comfort of his new lenses and is noticing none of the itchiness and redness that he did with his soft lenses. Photo’s after 6 weeks in his OrthoK lenses show a marked decrease in palpebral inflammation, with a decrease in size of his papillae. Hopefully these should disappear with time.
CAPTION:The superior tarsal plate with reduced giant papiliary conjunctivits