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1、Thickness variations within endothelial grafts for DSAEK surgery. A spectral domain anterior segment OCT studyAlberto Neri, Rosachiara Leaci, Patrizia Scaroni, Claudio MacalusoOphthalmology, University of Parma, ItalyThe authors have no financial interest in the subject matter of this posterDSAEKDSA
2、EK Descemet Stripping Descemet Stripping Automated Endothelial Automated Endothelial KeratoplastyKeratoplastyCurrently the standard procedure for endothelial pathology. Surgical procedure:Descemet strippingInsertion of the endothelial graftAdesion with air bubbleMicrokeratome (or femtosecond laser)
3、cut: asportation of a 300 / 350 / 400 m anterior lamellaDonor button harvesting:TrephinationThe normal cornea is thicker in the periphery and thinner in the center. Tissue harvesting with microkeratome and femtolaser, that measure lamellar thickness from epithelial surface, creates regular lamellae
4、for anterior keratoplasty techniques, but the remaining endothelial lamellae, that are the one used for DSAEK, necessarily change in thickness from center to periphery. Cross sectional profile = MeniscusPURPOSETo evaluate variations in thickness of endothelial grafts for DSAEK surgery dependent on b
5、oth eccentricity and meridian orientation using high resolution anterior segment OCT (CASIA, Tomey, Japan). MATERIALS and METHODS20 eyes of 20 patients who underwent DSAEK surgery were examined.Full anterior segment scans were captured with CASIA OCT.The optical centre of the cornea and eight meridi
6、ans (0, 45, 90, 135, 180, 225, 270 and 315) were analyzed with the FLAP TOOL, that allowed precise identification and measurement of endothelial graft thickness. Flap thickness was measured at the center and at 1,5mm and 3mm eccentricity along each meridian. ANALYSISDATA for each analyzed eye (20):
7、Central flap thickness 8 thickness values at 1.5 mm eccentricity8 thickness values at 3mm eccentricityDescriptive analysis of thickness values was performed for each eccentricity. To describe the variation in thickness at a given eccentricity, the SD of the corresponding eight measurements was calcu
8、lated in every eye.Casia Flap Tool: Measurement of Total Corneal Thickness + Flap thicknessThe optical center of the cornea and eight meridians (0, 45, 90, 135, 180, 225, 270 and 315) were analyzed with the FLAP TOOL, that allowed precise identification and measurement of endothelial graft thickness
9、. Flap thickness was measured at the center and at 1,5mm and 3mm eccentricity along each meridian. RESULTS: Thickness variability along meridiansCentral graft thickness varied significantly among cases, ranging from 53 to 259m (43.3m SD, mean 169.7m)Graft thickness tended to increase slightly from t
10、he center to 1.5 mm eccentricity, that resulted in a mean value of 174.7m. (p=0.22) The mean increase in thickness from center to 1,5mm was +5,5% (SD = 11,4%)At 3mm eccentricity the flap thickness was greater, its mean value being 202.6m (36,9m SD) (p0.0001). Mean increase in thickness from center t
11、o 3mm was +25,7 % (SD = 17%) SD of the thickness values at 1.5mm of eccentricity ranged between 5,2% and 18,9% of central thickness and mean SD was 11,4% of central thickness.At 3mm, thickness SD range was: 8,4 - 29,6 % of central thickness (mean SD = 17%)RESULTS: Thickness variability at given ecce
12、ntricityCONCLUSIONS: thickness variation ALONG MERIDIANSMean center-3mm difference = + 27,5 % (32.9 m)This gradient in thickness is inevitably linked to the procedure of microkeratome cut. It has been demonstrated that an hyperopic shift in the eyes refraction is caused by DSAEK surgery and it is co
13、rrelated with the thickness difference from the center to the periphery of the cornea. (J Cataract Refract Surg 2008; 34:578584) We found also a significant variability of graft thickness at a given eccentricity: at 1,5 mm SD of 11,4 %; at 3 mm SD of 17,0 % Flap thickness variability can be caused b
14、y Irregularity of the cut Misalignment of the thinnest point of the donor cornea with the optical center, that can be caused by:1.Not-centered microkeratome cut 2.Not-centered punching3.Not-centered adhesion of the graft moreover, optical center can be different from geometrical center CONCLUSIONS:
15、thickness variation at GIVEN ECCENTRICITIESFurther work is needed to clarify the optical effects of this variability in flap thickness. Fortunately little difference exists between the optical constants of the cornea and acqueous umor, reducing optical aberrations linked to graft irregularities. THANK YOU FOR YOUR ATTENTION!THANK YOU FOR YOUR ATTENTION!
