Diapositiva 1

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Asymmetrically Shortened Intrastromal Corneal
Ring Segments to Manage Decentered Keratoconus
Nine-Month Results
Poster ID 190
Juan Carlos Abad, MD Jaime Arango, MD Camilo
Tobón, MD
Dr. Abad has received travel honoraria from
Addition Technology. None of the other authors
has any financial interest in the products
mentioned.
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INTRODUCTION
-Decentered keratoconus accounts for the majority
of keratoconus cases (88.2) Presented by
Coskunseven at the Winter ESCRS meeting in
Athens, Greece in February 2007 -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.
1. Sharma M, Boxer Wachler BS. Comparison of
single-segment and double-segment Intacs for
keratoconus and post-LASIK ectasia. Am J
Ophthalmol 2006141891-5. 2. Chan CC, Sharma M,
Wachler BS. Effect of inferior-segment Intacs
with and without C3-R on keratoconus. J Cataract
Refract Surg 20073375-80. 3. Shanzlin DJ.
Studies of intrastromal corneal ring segments for
the correction of low to moderate myopic
refractive errors. Trans Am Ophthalmol Soc
199947815-90. 4. Ruckhofer J, Stoiber J, Twa
MD, Grabner G. Correction of astigmatism with
short arc-length intrastromal corneal ring
segments preliminary results. Ophthalmol
2003110516-24.
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METHODS

• 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.

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Preoperative Values
Single 150 SK Segment Two Shortened SK Segments TTest
Eyes (Patients) 16 (16) 16 (12)
Males/Females 6/10 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
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Case in point A Single Segment
Preop UCVA 20/60 -0.25 8.00 x
20 20/60 9 months Postop UCVA 20/50
-1.50 5.00 x 15 20/25
OD
Topographic differerential map pre- to
nine-months postoperarative showing corneal
flattening induced by the segments 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
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Case in point Two shortened segs
Preop UCVA 20/60 Plano
7.00 x 35 20/25 6 months Postop UCVA 20/30
0.25 1.00 x 44 20/20
OD
Topographic differential map pre- to five months
postoperatively showing not only steepening along
the flat meridian (superonasal to inferotemporal)
induced by the segments bodies but also
compensatory flattening of the steep meridian
(superotemporal to inferonasal) along the gap
between the segments (incision site).
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One-month Results
A Single 150 SK Segment Two Shortened SK Segments TTest
? lines UCVA 4,6 3,5 (Range 0,8 to 13) 5,2 2,4 (1,8 to 10) 0,58
? lines BCVA 1,3 1,8 (-2,2 to 4) 1,9 2,4 (-1,2 to 7,8) 0,23
? 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
? 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
? 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
? Average K -2,29 2,58 (2,27 to -7,74 D) -2,51 1,63 (0,42 to -5,73 D) 0,81
? 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
? 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
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Nine-month Results
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)
? lines UCVA 4,6 3,3 (Range 0 to 9) 5,13 3,3 (0 to 11) 0,67
? lines BCVA 2,2 1,6 (0 to 4,8) 2,45 1,43 (0 to 6) 0,37
? 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
? Manifest Cylinder 2,58 1,29 D (0 to 4,5) 3,43 1,79 D (-1,75 to 6) 0,17
? Spherical Equivalent 2,21 2,9 D (-1,5 to 8,75) 2,23 1,6 D (-0,75 to 5,38) 0,98
? 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
? 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
? 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 (pgt0.10). Since
most patients were CXLd, no meaningful
statistical comparisons could be made between
CXLd and not CXLd patients within each group.
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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.

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Comparison Between Published Studies
Table 1
SEGMENT TYPE UCVA (lines) BSCVA (Lines) Spherical Eq. (Diopters) ASTIGMATISM (Diopters)
Sharma 2 seg 2.5 lt1 2.01 /- 3.10 1.58 /- 3.09
Intacs (7 mm OZ) Sharma 1 seg 9 2.5 0.65 /- 1.77 5.69 /- 3.10
Intacs (7 mm OZ) Chan 1 seg w/o CXL 9.5 1 0.25 /- 2.12 1.48 /- 1.17
Intacs (7 mm OZ) Chan 1 seg CxL 6.5 1 0.12 /- 1.72 2.73 /-1.87
Table 2
SEGMENT TYPE UCVA (lines) BSCVA (Lines) Spherical Eq. (Diopters) ASTIGMATISM (Diopters)
intacs SK (6 mm OZ) Sansanayudh 2 seg 150 5.3 /- 3.9 2.5 3.05 1.15
intacs SK (6 mm OZ) Abad 1 seg 150 4,6 3,3 2,2 1,6 2,21 2,9 D 2,58 1,29
intacs SK (6 mm OZ) Abad 2 shorted seg 5,13 3,3 2,45 1,43 2,23 1,6 D 3,43 1,79 D
1. Sharma M, Boxer Wachler BS. Comparison of
single-segment and double-segment Intacs for
keratoconus and post-LASIK ectasia. Am J
Ophthalmol 2006141891-5. 2. Chan CC, Sharma M,
Wachler BS. Effect of inferior-segment Intacs
with and without C3-R on keratoconus. J Cataract
Refract Surg 20073375-80. 3. Sansanayudh W,
Bahar I, Kumar NL, et al. Intrastromal corneal
ring segment SK implantation for moderate and
severe keratoconus. J Cataract Refract Surg
201036110-3.
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CONCLUSIONS
-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 .