Based on the captured corneal data, measured HVID, and entered spectacle prescription, EyeSpace will either design a Forge Myopia rotationally symmetric (spherical) or Forge Toric orthokeratology lens and automatically calculate the optimal treatment zone, sagittal height, alignment curve and diameter of the Forge Ortho-K lens.
For the experienced Orthokeratology fitter, EyeSpace offers override options to customise the Forge Myopia Ortho-K lens further. To access the advanced parameters, click the 'Lens Parameters' button on the lens design overview page.
The 'Lens Editor' page will open. To access the advanced parameters activate the 'Show Advanced Parameters' checkbox.
The following advanced parameter options will become available to modify:
The BOZD can be increased or decreased depending on the clinical requirement. Decreasing the BOZD introduces more plus into the pupil zone periphery which can be useful for Myopia Control or Presbyopic Orthokeratology moulding. Please note by decreasing the BOZD smaller than the pupil diameter will also introduce more glare and flare into the optical system. Always review the pupil size and warn the patient of the possible visual side effects by reducing the BOZD.
The BOZ eccentricity value can be modified between the values of 0 and 1.5, with the default value set at 0. The higher the e-value, the more aspheric the BOZR becomes. The higher BOZ asphericity could possibly be more beneficial for Myopia Control moulding
Changing the edge width value will increase or decrease the outer edge width of the Forge Ortho-K lens, affecting the edge clearance. It usually is not necessary to change this value.
Adjusting the edge radius will affect the edge clearance of the lens (visualised by the edge tear profile) and is helpful to regulate the tear flow under the lens and to control lid attachment . Flattening the edge radius value will increase the edge clearance, and conversely steepening the edge radius will decrease the edge clearance.
For Forge Orthokeratology lenses, aim to have the horizontal edge tear profile between 50 - 75 microns and the vertical edge tear profile between 75 - 100 microns.
The AC eccentricity controls the asphericity of the alignment curve. The default value is 1.1. The high e-value allows the lens to centre better on corneas with uneven elevation contours.
If any of the Advanced Parameters are adjusted, the lens-to-cornea fit relationship may become incorrect. Click the 'Optimize AC and Z-Zone' button, and EyeSpace will optimise the Forge Ortho-K lens parameters to restore the ideal lens-to-cornea fit relationship.
If you are unsure remember to order the lens with the ‘Review' option and your troubleshooting consultant will be happy to provide you with design feedback.