EyeWorld China September 2019 Issue

Streamlight TM One-step Trans-Epi PRK Dr. Arthur Cummings Table 6: Conventional PRK vs. StreamLight TM Conventional PRK StreamLight TM • PTK induces -0.75 more myopia • PTK is neutral • PTK followed by any treatment profile • PTK followed by WFO optimized profile • 2-Step Procedure • 1-Step Procedure 10 Figure 5: Post-operative HOA after FS-AK Medium and Long-term Follow-up Observation of the Efficacy of FS-AK Prof Bai Ji FS-AK guided by corneal topography combined with T-CAT is safe and effective for myopic astigmatism correction and is especially suitable for patients with thin cornea and inadequate anterior chamber conditions for IOL. StreamLight TM (EX500 transPRK) is the newest, no-touch, one-step technology used to perform Trans-Epi photorefractive keratectomy (Trans- Epi PRK) in patients who cannot have a LASIK flap. Unlike conventional PRK (Table 6), which is a 2-step procedure and involves removal of corneal epithelium followed by laser ablation, SteamLight TM is a one-step PRK followed by wavefront optimization (WFO). StreamLight TM is usually applied to the thickest section of the epithelium resulting in the reduction of thickness and refractory change in the surrounding epithelium. Before using StreamLight TM , epithelial mapping is a powerful diagnostic, therapeutic and planning tool to detect corneal abnormalities. “If you do not have epithelial mapping, my advice would be to do StreamLight TM only on virgin eyes, where we expect the epithelium to be regular”, added Dr. Cummings. While sharing his experience using StreamLight TM , Dr. Cummings explained that the entire procedure is done below the body temperature. The cornea is chilled with balanced salt solution and PTK as deep as thickest epithelium in treatment zone to nearest 5µ is performed. The recommendation is to pause for 10 seconds, which allows the cornea to cool down by about 2 degrees and then perform the last part of the treatment, which is the PRK element with wavefront optimized profile without any adjustment. Another important consideration while doing Trans-epi PTK is the use of Phorcides TM , which is Astigmatic keratotomy is a useful technique for the treatment of astigmatism, amongst other options such as LASIK PRK, Toric IOL and SMILE . By virtue of its precision and versatility, femtosecond guided astigmatic keratotomy (FS-AK) makes the surgery more accurate while allowing individualization over conventional AK. Patients with thin cornea and those with shallow anterior chamber who are not suitable for intraocular lenses are ideal candidates for FS-AK. Prof. Bai Ji presented the role of FS-AK combined with T-CAT in correction of myopic astigmatism. In the study, patients with myopic astigmatism treated with FS-AK showed relatively stable post- operative astigmatism 3 months after surgery, but without significant change in UCVA while there was a significant increase in HOAs (Figure 5). Since AK was unable to correct myopia and led to increase in HOA, the need for refractive surgery enhancement was established and a follow-up T-CAT was the preferred choice. Following T-CAT, there was a significant increase in UCVA and a significant decrease in irregular astigmatism. 2-year follow-up showed that the cornea was normal, AK incision was visible, there was no abnormality under LASIK corneal flaps and there was no haze. “Though satisfactory visual outcome was achieved, further long-term studies in larger patient population are necessary to establish the role of FS-AK with T-CAT in myopic astigmatism.” cautioned Prof. Bai.