BEYOND THE BASICS: ORTHO-K TROUBLESHOOTING

This article was originally published in a sponsored newsletter.

Most eyecare practitioners (ECPs) fitting orthokeratology (ortho-k) are familiar with troubleshooting tools to improve lens centration. Ortho-k designs’ basic troubleshooting guides cover resolving issues such as superior, inferior, and lateral lens decentration. But what if those basic tools don’t fix the problem? Let’s delve into some of the less common ortho-k fit issues practitioners might encounter and explore strategies to improve ortho-k fitting success.

It’s important to note that many of the topographical presentations discussed can occur without causing problems and may not necessitate any lens modifications. In general, avoid making fit changes if there is no compromise to corneal health or vision.

Glare and Haloes

Glare and haloes are a common side effect of ortho-k lens wear, typically present in dim light conditions due to the dilation of the pupil outside of the effective corneal treatment zone (Figure 1). The symptoms are generally present at the beginning of ortho-k wear as patients’ corneas adjust to the reshaping effect and may resolve with continued lens wear. If persistent after a month of lens wear, though, consider changing the lens to improve this condition.

Figure 1. Corneal topography of an ortho-k lens where the reverse curve ring is located inside the pupil, potentially resulting in haloes and glare.

Glare and haloes are not typically reported by younger patients (< 16 years old), though older patients (16+ years) may notice issues when they begin driving or spend a great deal of time in low-light conditions. While research indicates that smaller optic zones may provide better myopia management,¹ the risk of myopic progression typically slows after age 16.²

If myopia management is not the primary goal of treatment, consider increasing the optic zone size to reduce haloes and glare for most patients. But if myopia management is the primary goal of treatment, consider the potential trade-offs of choosing a larger versus a smaller treatment zone.

Incomplete Reverse Curve Ring

Incomplete reverse curve rings form when a lens fails to align to the peripheral cornea in one meridian. This results in an uneven ring of mid-peripheral steepening, preventing the central fluid pressure from achieving the desired corneal compression. On topography, incomplete reverse curve rings will present as an uneven “bull’s-eye” ring. The reverse curve may be incomplete in only one quadrant (Figure 2) or across an entire meridian (Figure 3).

Figure 2. Corneal topography showing an incomplete reverse curve supratemporally.

Figure 3. Corneal topography showing an incomplete reverse curve across the horizontal meridian.

Such topography patterns can commonly occur without issue and may not require any lens modifications. If the patient’s vision is significantly reduced, consider adjusting the peripheral toricity of the ortho-k design to resolve this issue.

Air Bubbles

Bubbles arise when air becomes trapped between the lens and cornea, typically upon lens application. Small-sized bubbles are common and do not usually cause corneal or visual complications (Figure 4).

Moderate to large-sized bubbles can cause double-ring patterns on topography and vision complaints (Figures 4, 5, and 6). If there is no compromise to corneal health or vision, application bubbles can be monitored without lens adjustments. If corneal health or vision complaints are observed, advise the patient to use a more viscous application drop, apply the lens face down, and immediately go to sleep. If the air bubbles persist, the sagittal height of the lens may be too high and require flattening of the reverse curve to resolve the issue.

Figure 4. Tiny air bubbles in the reverse curve of an ortho-k lens.

Figure 5. Large air bubble in the reverse curve of an ortho-k lens.

Lens Binding

Lens binding occurs when a lens has excessive sagittal height, resulting in a fit that is too tight in the mid-periphery/periphery and accompanied by < 1mm of lens movement with the blink. Lens binding can cause corneal staining, and patients may display a ring-like imprint on the cornea immediately after lens removal. If lens binding is observed, changes should be made to avoid further complications.

Topographies may show a focal area of steepening corresponding to the epithelial indentation site (Figure 7).

Figure 7. Corneal topography of a patient experiencing lens binding. Note the sharp ring of localized steepening superiorly.

Fluorescein may not appear under the lens or only appear when manual pressure is applied. The lens may move 1mm or less with the blink.

Binding can occur mid-peripherally or peripherally and can be identified by the location of corneal indentation (Figure 8). If the indentation appears focused mid-peripherally, consider flattening the reverse curve to loosen the fit. If staining occurs peripherally, flatten the alignment and peripheral curves to loosen the fit.

Become adept at managing these four common situations and you’ll see your ortho-k patients have better outcomes.

References

1. Guo B, Cheung SW, Kojima R, Cho P. One‐year results of the Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study: a prospective randomised clinical trial. Ophthalmic Physiol Opt. 2021 Jul;41:702-714.

2. COMET Group. Myopia stabilization and associated factors among participants in the Correction of Myopia Evaluation Trial (COMET). Invest Ophthalmol Vis Sci. 2013 Dec 3;54:7871-7884.

NICHOLAS GIDOSH, OD is an assistant professor at the Pennsylvania College of Optometry and a Fellow of the American Academy of Optometry. He has a research grant or contract with Euclid Vision Group, has received travel reimbursement from CooperVision, and has received non-COPE CE lecture or authorship honoraria from Aculens and Bausch + Lomb SVP.

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