A poster presented by Dr Eddie Chow suggests that increased myopia control can be achieved by the use of an aspheric orthokeratology lens design with a reduced Back Optic Zone Diameter (BOZD) with the addition of eccentricity over the optic zone. He believes it is related to the increased peripheral plus power across the pupil, which creates a larger blur circle in the peripheral retina¹.
This article will demonstrate the steps needed to modify the lens parameters of the Forge Myopia lens to maximise the design for myopia control based on the research poster by Dr Chow. More work is required in this area of orthokeratology design.
Select your patient. For this example choose the '_Spherica_l' patient from the Reference Maps category.
Click the Right lens design button to start the lens design process for the right eye.
Select the topography map you want to use.
To design a new lens using the selected topography, map, click the New button.
To design a Forge Myopia orthokeratology lens, click the Forge Ortho-K button.
EyeSpace will display the Forge Myopia 2 lens design by default in the drop-down list. Leave the default value and click the Next button.
Select the Use Spectacle Rx option.
Type in the spectacle prescription. In this example, we will use -3.00D.
Click the Finish button, to design the lens.
Click on the Lens Parameters button to optimize the Forge lens design for myopia control.
On the Lens Editor page, click the Show Advanced Parameters check box.
Change the Back Optic Zone Diameter to your desired size. We will change the BOZD to 5.40 mm for this example.
Change the Back Optic Zone Eccentricity to your desired value. We will use an e value of 1.20 for this example.
Click the Optimize AC and Z-Zone button. EyeSpace will redesign the lens with the updated lens parameters.
Once EyeSpace has redesigned the lens, click the Close button to close the Lens Editor page
Before ordering, make sure that:
The bearing of the lens on the cornea is evenly balanced over the horizontal alignment zone. The central tear film thickness (cTFT) provides adequate central clearance.
Once the design is complete, click the Order button.
Select the 'Add to cart' button to place the lens order in the shopping cart.
You can now go ahead and design the left lens.