MYOPIA MANAGEMENT: Toric Orthokeratology Case
Emily Gottschalk OD, FAAO
Toric ortho-K lenses offer improved stabilization for limbus-to-limbus astigmatism with corneal sagittal height greater than 25um between primary meridians at the 8mm chord. In accordance with United States Food and Drug Administration (FDA) approval, laboratory manufacturers of ortho-K lenses define ideal candidates as myopes between 1.00D to 5.00D with astigmatism up to 1.50D. Patients with refractive astigmatism greater than one-half of the sphere or against-the-rule (ATR) astigmatism greater than 0.75D are considered poor candidates. This case demonstrates the use of toric ortho-K lenses to correct high astigmatism beyond the recommended parameters.
History
- HPI: 24y/o WF
- CC: Seeking spectacle free correction for running
- MHx: atopy including asthma, eczema, and cold urticaria.
- OHx: intolerant to soft toric contact lenses due to untreated GPC at age 19. At age 21, treatment was initiated with courses of topical prednisolone acetate, loteprednol etabonate, and fluorometholone, which minimally improved the chronic GPC. Both corneal GP and scleral lenses were unsuccessful due to discomfort.
Examination
- Refraction:
- OD -2.25 -2.00 x 180 20/20
- OS -1.50 -2.75 x 168 20/20
- Corneal Topography (Figure 1):
Figure 1. Baseline axial topography showing high limbus-to-limbus with-the-rule (WTR) corneal toricity (OD left photo; OS left photo).
| OD | OS | |
| Keratometry | 43.54D/45.85D | 43.30D/46.29D |
| Corneal cyl | ΔK=2.32D @ 11° | ΔK=2.99D @ 172° |
| Sag differential @ 8mm | 49um | 65um |
| HVID | 11.3mm | 11.3mm |
Treatment/Plan
Ortho-K fit was initiated, and lenses were ordered empirically. Toric ortho-K lenses were ordered due to high corneal cylinder with sag differential greater than 25um in each eye.
- Lens parameters:
| OD | OS | |
| BCR | 8.40 mm | 8.23 mm |
| OAD | 10.6 mm | 10.6 mm |
| OZD | 6.2 mm | 6.2 mm |
| Toric reverse and peripheral curves | Toric reverse and peripheral curves |
- Patient was followed at 1-day, 1-week, and 1-month. Ortho-K lenses resulted in an ideal bullseye fluorescein pattern on the eye with central bearing, a consistent band of mid-peripheral pooling, minimal edge lift 360 OU, and minimal movement. Over-refraction was +0.75 OD/OS.
- Corneal topography with lens treatment (Figure 2):
Figure 2. Tangential difference map for treatment outcome compared to baseline OD (above) and OS (below)
| OD | Outcome Data | OS |
| 20/20 | Unaided VA | 20/20 |
| -2.91D | Max correction on axial difference map | -2.61D |
| -0.25 -0.50 x 170 20/20 | Subjective Refraction | -0.50 -0.75 x 170 20/20 |
Plan: Patient achieved spectacle-free correction with orthokeratology lenses and reported increased comfort compared to soft and gas permeable lens designs attempted previously.
Clinical Pearls
- Toric reverse geometry lenses have a spherical base curve. The asymmetric reverse and alignment curves allow for stabilization on highly toric corneas, especially with limbus-to-limbus astigmatism as in both cases.
- Centration of the treatment zone is essential for optimal correction and to minimize subjective glare for patients.
- Astigmatic correction results from corneal elevation changes during treatment. A higher sag differential between flat and steep meridians can result in better correction.
- Use of off-label, toric reverse geometry designs can correct high astigmatism for carefully selected patients interested in temporary refractive correction.