Juan Carlos Abad, MD Jaime Arango, MD; Camilo Tobón, MD Poster ID: 190 Dr. Abad has received travel honoraria from Addition Technology. None of the other authors has any financial interest in the products mentioned. Asymmetrically Shortened Intrastromal Corneal Ring Segments to Manage Decentered Keratoconus: Nine-Month Results

-Decentered keratoconus accounts for the majority of keratoconus cases (88.2%) Presented by Coskunseven at the Winter ESCRS meeting in Athens, Greece in February Sharma et al. compared the use of two segments vs. one segment in the treatment of decentered keratoconus and found better results with the one segment approach ( 1) -Chan et al. compared the use of a single segment with and without corneal cross linking by UVA and riboflavin (CXL) and found better results in the latter (2 ) -Based on the work of Shanzlin ( 3) and Ruckhofer (4) who postulated that segments with a shortened arc length would correct more astigmatism but less myopia, we decided to compare two asymmetrically shortened Intacs SK -severe keratoconus- segments vs. one single standard (150°) Intacs SK segment in the correction of astigmatism in cases of decentered keratoconus with more than two diopters of cylinder. INTRODUCTION 1. Sharma M, Boxer Wachler BS. Comparison of single-segment and double-segment Intacs for keratoconus and post-LASIK ectasia. Am J Ophthalmol 2006;141: Chan CC, Sharma M, Wachler BS. Effect of inferior-segment Intacs with and without C3-R on keratoconus. J Cataract Refract Surg 2007;33: Shanzlin DJ. Studies of intrastromal corneal ring segments for the correction of low to moderate myopic refractive errors. Trans Am Ophthalmol Soc 1999;47: Ruckhofer J, Stoiber J, Twa MD, Grabner G. Correction of astigmatism with short arc-length intrastromal corneal ring segments: preliminary results. Ophthalmol 2003;110:

The INTACS SK segments were inserted using the Prolate ® system and making the incision at the steep corneal meridian. In the single segment group, the segment was placed in the most elevated corneal area. In the two shortened-segments group the longest segment (120° in arc length and 450 µm thick) was placed in the most elevated corneal area (usually inferior or inferotemporal), and the shorter segment (90° in arc length and 400 µm thick) was placed opposite to the first segment. Refractive data including LogMAR UCVA and BCVA, spherical equivalent, cylinder, keratometry, and corneal wavefront (total aberrations (RMS) and coma – Scout, Optikon, Italy) were collected preoperatively, at one month and nine months after the surgery. Patients younger than 35 years were offered corneal crosslinking with riboflavin (Ricrolin, Soof, Italy) and ultraviolet A (IROC, Peshke, Switzerland). Statistical analysis was done with StatGraph Centurion (version XV, Herndon, VA). Data were analyzed first for normality of distribution using the Kolmogorov-Smirnov test. Descriptive statistics were applied to the preoperative variables. Results are expressed as means ± standard deviation (Range). A two-tailed student T test and ANOVA were used to compare all the variables in the two groups preoperatively and at the one-month and nine-month visits.

Preoperative Values Preoperative Values Single 150° SK Segment Two Shortened SK Segments TTest Eyes (Patients) 16 (16) 16 (12) Males/Females 6/10 Age 27 ± 10,5 (13 to 53) 25,8 ± 9,1 (Range: 11 to 46) 0,63 LogMAR UCVA 1,06 ± 0,40 (0,48 to 1,90) 0,9 ± 0,41 (0,4 to 1,61) 0,27 LogMAR BCVA 0,33 ± 0,19 (0 to 0,6) 0,37 ± 0,25 (0,1 to 0,88) 0,57 Sphere -2,72 ± 3,57 D (1,75 to -12,00 D) -2,42 ± 2,71 D (1,50 to -8,25 D) 0,79 Manifest Cylinder -5,66 ± 1,97 D (-2,00 to -8,75 D) -6,13 ± 2,35 D (-2,00 to -9,00 D) 0,55 Spherical Equivalent -5, 55 ± 4, 00 D (0,13 to -14,75 D) -5,48 ± 3,03 D (-1,50 to -12,63 D) 0,96 Average K 48,89 ± 2,95 D (44,75 to 54,20 D) 48,31 ± 3,9 D (43,63 to 57,75 D) 0,64 K. Cyl. 6,10 ± 3,17 D (1,07 to 11,94 D) 6,58 ± 3,16 D (2,8 to 14 D) 0,67 Steep K 51,94 ± 3,72 D (46 to 58,39 D) 51,60 ± 5,25 D (45,25 to 64,75 D) 0,84

Preop: UCVA: 20/ – 8.00 x 20 = 20/60 9 months Postop: UCVA: 20/ – 5.00 x 15 = 20/25 Topographic differerential map pre- to nine-months postoperarative showing corneal flattening induced by the segment’s body and compensatory steepening in the opposite hemicornea. There is steepening of the flat meridian (superonasal to inferotemporal) There is no effect (green color) over the steep –incision- meridian OD

Topographic differential map pre- to five months postoperatively showing not only steepening along the flat meridian (superonasal to inferotemporal) induced by the segment’s bodies but also compensatory flattening of the steep meridian (superotemporal to inferonasal) along the gap between the segments (incision site). Preop: UCVA: 20/60 Plano – 7.00 x 35 = 20/25 6 months Postop: UCVA: 20/ – 1.00 x 44 = 20/20 OD

A Single 150° SK Segment Two Shortened SK Segments TTest Δ lines UCVA 4,6 ± 3,5 (Range: 0,8 to 13) 5,2 ± 2,4 (1,8 to 10)0,58 Δ lines BCVA 1,3 ± 1,8 (-2,2 to 4) 1,9 ± 2,4 (-1,2 to 7,8)0,23 Δ Sphere 1,00 ± 2,89 D (-3,25 to 9,00 D) -0,28 ± 1,49 D (-3,00 to 3,25 D)0,22 Δ Manifest Cylinder 2,29 ± 1,57 D (0 to 5,5 D) 4,65 ± 2,21 D (-0,50 to 8,50 D)0,001 Δ Spherical Equivalent 2,14 ± 3,17 D (-2,50 to 10,25 D) 2,04 ± 1,29 D (0,5 to 4,8 D)0,79 Δ Average K -2,29 ± 2,58 (2,27 to -7,74 D) -2,51 ± 1,63 (0,42 to -5,73 D)0,81 Δ K. Cyl. -2,17 ± 2,34 D (2,05 to -6,73 D) -4,11 ± 3,07 D (-0,63 to -12,4 D)0,1 Δ Steep K -3,37 ± 2,61 D (0,63 to -9,14 D) -4,23 ± 1,77 D (-0,75 to -8,00 D)0,36

A single 150° SK segment Two shortened SK segments TTest # Eyes (% follow up) 12 (75%) 16 (100%) CXL at 1 to 3 Months PO 8/12 (66%) 11/16 (69%) Δ lines UCVA 4,6 ± 3,3 (Range: 0 to 9) 5,13 ± 3,3 (0 to 11)0,67 Δ lines BCVA 2,2 ± 1,6 (0 to 4,8) 2,45 ± 1,43 (0 to 6)0,37 Δ Sphere 0,92 ± 2,84 D (-3,00 to 7,50 D) 0,64 ± 1,84 D (-2,75 to 4,00 D)0,76 Δ Manifest Cylinder 2,58 ± 1,29 D (0 to 4,5) 3,43 ± 1,79 D (-1,75 to 6)0,17 Δ Spherical Equivalent 2,21 ± 2,9 D (-1,5 to 8,75) 2,23 ± 1,6 D (-0,75 to 5,38)0,98 Δ Average K -2,49 ± 1,83 D (0,50 to -5,35 D) -2,15 ± 1,58 D (1,75 to -6,00 D)0,98 Δ K. Cyl -2,54 ± 2,19 D (0,89 to -6,09 D) -3,62 ± 2,00 D (1,75 to -6,00 D)0,92 Δ Steep K -3,77 ± 2,29 D (-0,25 to -8,39) -3,82 ± 1,91 D (-0,3 to -8,0)0,94 There were no statistical differences between the changes at one and nine months (p>0.10). Since most patients were CXL’d, no meaningful statistical comparisons could be made between CXL’d and not CXL’d patients within each group.

DISCUSSION The only reports that compare different strategies for the treatment of decentered keratoconus with Intacs use 7.0 mm segments. (Table 1 –next slide) Our two shortened segment group compares favourably with them with better BCVA, spherical equivalent and astgmatism improvement. Sharma et al. Included cases of post- LASIK ectasias which could have hightened their results The only published report of the use of Intacs SK in native keratoconus ( Table 2 – next slide) does not differentiate between centered and decentered keratoconus. Confirming our hypothesis, we had less spherical equivalent but more cylindrical correcion that them.

SEGMENT TYPE UCVA (lines) BSCVA (Lines) Spherical Eq. (Diopters) ASTIGMATISM (Diopters) Sharma 2 seg2.5< / / Intacs (7 mm OZ) Sharma 1 seg / / Chan 1 seg w/o CXL / / Chan 1 seg + CxL / / Sharma M, Boxer Wachler BS. Comparison of single-segment and double-segment Intacs for keratoconus and post-LASIK ectasia. Am J Ophthalmol 2006;141: Chan CC, Sharma M, Wachler BS. Effect of inferior-segment Intacs with and without C3-R on keratoconus. J Cataract Refract Surg 2007;33: Sansanayudh W, Bahar I, Kumar NL, et al. Intrastromal corneal ring segment SK implantation for moderate and severe keratoconus. J Cataract Refract Surg 2010;36: SEGMENT TYPE UCVA (lines) BSCVA (Lines) Spherical Eq. (Diopters) ASTIGMATISM (Diopters) intacs SK (6 mm OZ) Sansanayudh 2 seg 150° 5.3 +/ Abad 1 seg 150°4,6 ± 3,32,2 ± 1,62,21 ± 2,9 D 2,58 ± 1,29 Abad 2 shorted seg 5,13 ± 3,32,45 ± 1,432,23 ± 1,6 D3,43 ± 1,79 D Table 1 Table 2

-The two-segment group had 44 % more correction of astigmatism than the one-segment group at nine months (although not statistically significant) with similar improvement in UDVA, CDVA and spherical equivalent. -Further studies with a standardized set of segments, a larger number of patients and longer follow up are needed to validate our preliminary findings. CONCLUSIONS