iDesign-guided PRK with cross-linking addresses keratoconus
The combined procedure allows surgeons to stabilize the disorder and restore good vision at the same time.
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My colleagues and I published a prospective, interventional case series of 47 eyes of 28 adults with mild to moderate progressive keratoconus who underwent high-resolution wavefront-guided PRK with simultaneous accelerated cross-linking.
The impact of cross-linking on corneal biomechanics and its ability to halt progression of keratoconus in most eyes has been well documented. However, cross-linking is not intended to fully rehabilitate the patient’s vision, especially in cases with significant corneal warpage. For this reason, many patients still have poor vision after successful cross-linking.
Topography-guided PRK has been used successfully in eyes with keratoconus, but it may not fully restore good vision, as it only takes into account the anterior corneal anatomy and does not consider internal aberrations or refraction. Ideally, we would like to regularize the cornea and address lower- and higher-order aberrations to improve the retinal image quality. For this study, we used a newer high-resolution wavefront system (iDesign, Johnson & Johnson Vision) that has the ability to measure more highly aberrated corneas.
Subjects in the study ranged from 18 to 51 years old. Cross-linking and PRK were performed on the same surgical day. First, the epithelium was removed, and iDesign-guided PRK was performed with the Star S4 IR excimer laser (Johnson & Johnson Vision). Treatment was targeted to achieve a residual bed thickness of at least 350 µm. Immediately after PRK, cross-linking was performed with the KXL system and VibeX Rapid (Avedro/Glaukos). At the end of the procedure, mitomycin C 0.02% was applied for 1 minute. After rinsing the MMC, a bandage contact lens was placed. Patients were followed at day 3, week 1, and months 1, 3, 6 and 12.
Source: Gustavo E. Tamayo, MD
We were able to improve the mean manifest refraction spherical equivalent from –2.39 D preop to –0.13 D at 12 months postop, with good stability of the refraction over time. There was a corresponding improvement in uncorrected distance visual acuity (UDVA) from 0.77 logMAR to 0.08 logMAR. Ninety-three percent of eyes were within 1 D of the intended correction; 63% were within 0.5 D. Ninety-three percent of eyes had UDVA of 20/32 or better and 56% were 20/20 or better (Figure 1). Mean flat and steep K were significantly reduced from 42.49 D and 45.94 D, respectively, to 41.36 D and 42.65 D postop. There was no clinically significant haze or loss of corrected distance visual acuity.
The advancement of wavefront technology to the point that we can capture these more highly aberrated eyes provides new options for our patients with keratoconus. Where feasible, I believe a wavefront-guided procedure that addresses all ocular aberrations, including those from the anterior and posterior cornea, in conjunction with cross-linking, is the best option for the management of keratoconus. Performing both procedures on the same day (with MMC at the conclusion of the case) can speed visual recovery and avoid haze. In eyes that have already undergone cross-linking, a later wavefront-guided PRK procedure is also an option.
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- Gustavo E. Tamayo, MD, director of Gustavo Tamayo Fernández Centro Oftalmológico and Bogota Laser Refractive Institute in Bogota, Colombia, can be reached at email: centrogustavotamayo@gmail.com.
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