London Vision Clinic, London, UK.
J Refract Surg. 2013 Aug;29(8):526-33. doi: 10.3928/1081597X-20130719-02.
To demonstrate improved effectiveness of transepithelial phototherapeutic keratectomy (PTK) where topography-guided ablation is degraded by epithelial compensation for localized irregularities.
Artemis very high-frequency digital ultrasound (ArcScan Inc., Morrison, CO) scanning was performed on five eyes (four patients) after LASIK in which a truncated nasal flap was created but the ablation was still performed, resulting in irregular astigmatism and double vision. The stromal ablation pattern of a transepithelial PTK ablation was modeled and compared to topography-guided ablation simulations. Artemis-assisted transepithelial PTK procedures were performed in three eyes (two patients).
In all cases, Artemis very high-frequency digital ultrasound demonstrated a crevice on the stromal surface caused by ablation on the underside of the flap nasally, which had been compensated for by epithelial thickening, thus masking a significant proportion of the stromal surface irregularity from corneal surface topography. The transepithelial PTK ablation pattern appeared logically to reduce the ridge nasal to the crevice, whereas topography-guided ablation patterns demonstrated poor targeting of the stromal ridge. Artemis-assisted transepithelial PTK greatly reduced the stromal irregularity, resulting in smoother epithelium and topography. In one eye, the epithelium had compensated fully for the irregularity and the patient reported 95% subjective improvement. One patient (two eyes) reported little change in visual symptoms despite significant anatomical regularization due to the partial nature of epithelial compensation, demonstrating that multiple procedures may often be required.
Compensatory epithelial remodeling masks stromal irregularities from the corneal surface, meaning that topography-guided (or wavefront-guided) ablations may not provide an adequate treatment option and may potentially worsen the irregularity. The effectiveness of transepithelial PTK will depend on the proportion of epithelial masking due to remodeling, related to the rate of change of curvature of the stromal surface.
证明经上皮光性角膜切削术（PTK）在因上皮对局部不规则性的补偿而使地形引导消融效果降低的情况下更为有效。
对 LASIK 术后五眼（四例）进行 Artemis 甚高频数字超声（ArcScan Inc.，Morrison，CO）扫描，其中创建了一个截断的鼻瓣，但仍进行了消融，导致不规则散光和复视。模拟经上皮 PTK 消融的基质消融模式，并与地形引导消融模拟进行比较。在三例（两例患者）中进行了 Artemis 辅助经上皮 PTK 手术。
在所有情况下，Artemis 甚高频数字超声均显示在瓣下鼻侧消融引起的基质表面裂隙，上皮增厚对此进行了补偿，从而掩盖了角膜表面地形图中相当一部分基质表面不规则性。经上皮 PTK 消融模式似乎可以合理地减少裂隙处的鼻侧脊，而地形引导消融模式显示出对基质脊的靶向不佳。Artemis 辅助经上皮 PTK 极大地减少了基质不规则性，使上皮和地形更平滑。在一只眼中，上皮已完全补偿了不规则性，患者报告主观改善 95%。尽管由于上皮补偿的部分性质导致解剖学上的显著规律性，但一位患者（两只眼）报告视觉症状变化不大，表明可能需要多次手术。
补偿性上皮重塑掩盖了角膜表面的基质不规则性，这意味着地形引导（或波前引导）消融可能不是一个足够的治疗选择，并且可能潜在地使不规则性恶化。经上皮 PTK 的有效性将取决于由于重塑引起的上皮覆盖的比例，这与基质表面曲率变化的速度有关。
