Ravera Vittoria, Bovone Cristina, Scorcia Vincenzo, DʼAngelo Sergio, Busin Massimo
Department of Ophthalmology, Ospedali Privati Forlì, Forlì, Italy.
Istituto Internazionale per la Ricerca e Formazione in Oftalmologia (IRFO), Forli, Italy.
Cornea. 2019 May;38(5):642-644. doi: 10.1097/ICO.0000000000001906.
To evaluate the possibility of using the intrastromal corneal ring segments (ICRSs) previously implanted as a depth reference for performing pneumatic dissection in deep anterior lamellar keratoplasty (DALK).
The depth of placement of 2 symmetrical ICRSs placed in the superior and inferior midperipheral cornea of 4 eyes of 4 patients with keratoconus was measured by means of anterior segment optical coherence tomography. Because of irregular and/or high astigmatism, DALK using pneumatic dissection was performed in all eyes. The standardized procedure included the following: 1) Deep trephination of the recipient cornea outside the ICRSs (9 mm in diameter), aimed at facilitating the insertion and advancement of a dedicated cannula under the ICRS implant, just within its peripheral margin; 2) air injection for pneumatic dissection; 3) removal of about 80% of the anterior stroma; 4) perforation of the "big bubble" ceiling under viscoelastic protection and removal of its central 6 mm; and 5) suturing of a donor lamella of the anterior stroma obtained by microkeratome dissection using a 450-μm head and punched to a diameter of 9 mm.
In all cases, the site for air injection was selected where the thickness of the stroma underlying the superior ICRS did not exceed 150 μm. Pneumatic dissection succeeded uneventfully in all eyes; postoperative best spectacle-corrected visual acuity was 20/20 in 3 of 4 eyes, whereas refractive astigmatism was less than 3 diopters in all cases.
The presence of ICRSs facilitates gauging the depth of cannula insertion at the time of DALK, to succeed with pneumatic dissection.
评估将先前植入的基质内角膜环片（ICRS）用作深度参考，以在深板层角膜移植术（DALK）中进行气体分离的可能性。
通过眼前节光学相干断层扫描测量4例圆锥角膜患者4只眼中置于上方和下方周边角膜中部的2个对称ICRS的植入深度。由于存在不规则散光和/或高度散光，所有眼均采用气体分离法进行DALK。标准化操作步骤如下：1）在ICRS外侧对受体角膜进行深板层环切（直径9mm），目的是便于将专用套管插入ICRS植入物下方并在其周边边缘内推进；2）注入空气进行气体分离；3）切除约80%的前基质；4）在粘弹剂保护下穿刺“大气泡”顶部并切除其中心6mm；5）缝合使用450μm刀头的微型角膜刀剖切并冲压成直径9mm的供体前基质板层。
在所有病例中，气体注入部位选择在上方ICRS下方基质厚度不超过150μm处。所有眼的气体分离均顺利成功；4只眼中3只眼术后最佳矫正视力为20/20，而所有病例的屈光性散光均小于3屈光度。
ICRS的存在有助于在DALK时测量套管插入深度，从而使气体分离成功。
