AFTER A RUN of popularity as a refractive surgical procedure in the 1970s and ’80s, radial keratotomy (RK) stopped being performed due to long-term complications such as incision dehiscence (Figure 1) and vascularization, inclusion cysts and edema; irregular astigmatism; ectasia; hyperopic drift; and corneal, tear film, and refractive/visual instability (Ensley and Miller, 2017; Arnold and Vincent, 2021; Weber et al, 2022). Even with the switch to safer and more effective surgical options, specialty contact lens fitting practitioners are still often tasked with helping former RK patients regain stable vision years after surgery.

If vision is unacceptable in spectacles or soft contact lenses, GP lenses should be considered. Post-RK corneas are usually oblate and irregular, with sometimes significant central flattening and mid-peripheral steepening. This shape is difficult to fit with corneal GP lenses, even when utilizing reverse geometry designs or hybrids. It can be easier to bypass fitting the cornea altogether and fit a scleral lens instead for best centration and comfort, though this lens modality can have its own complications. Research continues to point out corneal hypoxia associated with scleral lenses due to the thickening of the fluid chamber reservoir and the lens (Dhallu et al, 2020; Compañ et al, 2014; Giasson et al, 2017).

Unfortunately, post-RK corneas are likely to be even more susceptible to potential hypoxia (Arnold and Vincent, 2021) The vascularization that is commonly found along the RK incisions suggests this, but the inherent refractive and fitting properties of the scleral lenses also contribute (Arnold and Vincent, 2021). These patients usually need hyperopic correction (plus lenses with increased central thickness) and the oblate shape of their corneas results in deeper central sagittal lens depth and fluid reservoirs that lower oxygen transmission to the cornea.

Additionally, if there is too much suction created upon scleral lens removal, there may be undesirable force upon any already vulnerable incisions, with a worst-case scenario ending in corneal perforation (Weber et al, 2022).

Surgical corrective options include more refractive surgery (e.g., LASIK and photorefractive keratectomy), however these options do nothing to increase corneal stability and can result in even more complications such as flap tears and incision ruptures, epithelial ingrowth, haze, and further ectasia (Elbaz et al, 2014). It is postulated that corneal cross-linking (CXL) may be a useful tool in stabilizing post-RK corneas prior to any further refractive surgery and has been shown to have modest success to date (Elbaz et al, 2014; Lee, 2014; Mazzotta et al, 2011; Fuentes-Páez et al, 2012).

Further study is needed, as there are issues with this approach; CXL is a procedure known to flatten the treated cornea, which would worsen any already present RK-induced hyperopic drift (Lee, 2014). Also, CXL does not reach a treatment depth in the cornea sufficient to affect the full depth of the RK incisions and, therefore, may not be entirely effective (Mazzotta et al, 2011). Additionally, any risks inherent in CXL would be present post-RK, and it is unclear whether these risks are even higher in a post-RK cornea.

Management of post-RK patients can be challenging, and potential complications and risks should be discussed with each patient before proceeding with any treatment. CLS

References

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