ORTHOKERATOLOGY (ortho-k) uses rigid GP materials with various curves to temporarily correct refractive error and may also provide myopia management. Discussed here is one of the most customized options for ortho-k—topography-guided software-based designs. 

To get started, eyecare practitioners (ECPs) must acquire software that allows for the design of ortho-k retainers. They should download the software onto a workstation, where they will be able to make the initial design and any subsequent modifications.

Next, and perhaps most impotant, is acquiring a great topographer. Depending on the software platform chosen, ECPs may need to get a specific topographer, as some integrate with only a few companies. When using topography-guided software-based ortho-k designs, the accuracy of the topographical data is vital.

When choosing the topographer, choose one that is not only conducive to easy clinic flow, but provides the most accurate corneal data with the least amount of extrapolation. Since the initial design is guided by the topographical maps that are imported into the software, this data is crucial for initial fit success. As the saying goes, “garbage in, garbage out,” so do not make this decision lightly.

Lastly, a good understanding of fluorescein patterns is necessary. While the initial designs may be calculated by integrating the software with the topographer, troubleshooting and fluorescein evaluation are still necessary. Consider investing in an anterior segment imaging system as well, to monitor the progress of different designs.

The three main ways to design an ortho-k retainer are:

1) In-Office Fitting Set  An in-office trial set with varying parameters of ortho-k retainers are used. The ECP then selects different retainers to visualize the on-eye fluorescein pattern. Based on the fluorescein patterns observed, he or she can order a retainer that will provide the best overall fit and achieve the target correction.

2) Empirical Ordering  No fitting set is used and no retainers are applied to the eye in the empirical ordering process. Instead, the ECP provides the lab with relevant data for the manufacture of the initial ortho-k retainer based on the company’s independent algorithm. The data that is often needed for these cases includes manifest refraction, keratometry readings, and horizontal visible iris diameter (HVID). In some cases, the practitioner can send images of corneal topography as well.

3) Topography-Guided Software-Based Designs  In this case, the design of the ortho-k retainer is 100% up to the ECP who selects the best baseline topography maps to upload into the software program of his or her choice. Refraction and HVID are needed as well. At that point, the software generates an initial ortho-k design that is visualized in a tear layer profile. This is different from the other two design philosophies, as typically the ortho-k architecture is described in terms of millimeters of radius of curvature or diopters of power. In a software-based platform, the design is displayed as microns of tear film, specifically between the posterior surface of the ortho-k retainer and the anterior surface of the cornea.

Figure 1 is an example of a software platform showing the tear film layer in an ortho-k design.

While there is a learning curve to implement software-based designs into the ortho-k practice, the benefits will truly impact the fitting results. With complete control of the design process, more customized treatments can be done and more challenging cases can be taken on as well.