PRK with Schwind ESIRIS Excimer Laser and C3R Treatment in ...

556 AIOC 2010 PROCEEDINGS
PRK with Schwind ESIRIS Excimer Laser and C3R Treatment in
Keratoconus Patients in the Same Sitting
Collagen cross-linking (C3R), though
established primarily as a tectonic procedure
for eyes with keratoconus, has also been found to
have a relatively predictable refractive outcome,
albeit of a small magnitude.1 Photorefractive
keratectomy (PRK), as against laser in situ
keratomileusis, is a relatively safe refractive
procedure for eyes with keratoconus with thin
corneas, more so if corneal ablation is performed
Dr. Kumar J. Doctor
(Presenting Author: Dr. Kumar J. Doctor)
to undercorrect the refractive error. The residual
refractive error could then be eliminated by the
C3R process, when applied upon the bed of
ablated corneal tissue. The purpose of our study
was thus to determine whether a small optic zone
(5.5 mm) photorefractive keratectomy along with
collagen cross linking could be combined in a
single procedure in terms of predictability of
refractive outcome and safety in eyes with

REFRACTIVE SURGERY SESSION
557
keratoconus.
Materials and Methods
The prospective, non-comparative, interventional
study employed 3 eyes of 3 patients with
established keratoconus as per Orbscan II
(Bausch and Lomb) criteria. Their preoperative
refractive error, keratometry and pachymetry
details were noted. For analysis reasons, all
cylindrical errors were converted into their
spherical equivalents. The 3 eyes underwent PRK
by the routine procedure, except that the
diameter of corneal ablation selected was 5.5 mm
(optic zone) and the ablation was aimed at
leaving a residual spherical error of -2 D Sph.
This meant that all cylindrical error was
attempted to be eliminated by PRK. The ablation
depth thus achieved and the residual stromal bed
thickness was noted in all cases. C3R by the
routine procedure was then applied upon the
residual stromal bed. Postoperatively, residual
refractive error, keratometry and pachymetry
details were noted on the first postoperative day
and then every month for 5 months. A note of
any adverse events inclusive of regression and
ectasia were noted at the end of 5 months followup
period. Since the sample size was small and
the parameters non-Gaussian in nature, analysis
was performed using both parametric as well as
non-parametric statistical methods.
Results
Three eyes of 3 patients completed the entire 5
months follow-up. The preoperative pachymetry
noted was 469.3 + 7.02 (mean + SD) microns
(median = 470 microns, range 462 to 476 microns)
with a preoperative refractive error of -4.7 + 0.8 D
Sph (median = -4.5 D Sph, range -4 to -5 D Sph).
Two out of 3 eyes had cylindrical error which
was reduced to its spherical equivalent. The
ablation depth achieved with the small optic
zone PRK was found to be 36.7 + 11.7 microns
(median = 32 microns, range 28 to 50 microns).
At 5 months follow-up, the residual refractive
error was found to be 0.17 + 0.14 D Sph (median
= 0.25 D Sph, range 0 to 0.25 D Sph). No
regression or ectasia was noted in any case at the
end of 5 months follow-up. No persistent corneal
1. Vinciguerra P, Albè E, Trazza S, Seiler T, Epstein D.
Intraoperative and postoperative effects of corneal
collagen cross-linking on progressive keratoconus.
References
haze was seen in any eye at the end of 5 months
follow-up. Pachymetry performed at 5 months
was 426.7 + 15.3 microns (median = 430 microns,
range 410 to 440 microns). This was found to be
statistically insignificant (p = 0.53, paired t test)
compared to the pachymetry obtained on the first
post operative day 428 + 16 microns (median =
428 microns, range 412 to 444 microns).
Discussion
As an individual procedure, C3R has been
known to give good refractive outcomes in eyes
with keratoconus/ corneal ectasia post LASIK,
ranging from 1 D Sph at 6 months2 up to 2 D Sph
at 1 year.3 When C3R was applied with
conductive keratoplasty, there was no significant
change in the refractive outcome.4 The above,
coupled with the clinical experience of over a 100
eyes with C3R performed in our practice, in our
study, it was assumed that a residual refractive
error of 2 D Sph be kept after PRK for C3R to
work upon.
On attempting to perform a literature review of
combined PRK with C3R, there was presently
just one report by Kymionis et al5 of 14 eyes
showing excellent results. Our study showed
comparable results in terms of refractive
outcome. Also, in our study, it was noted that
C3R applied post PRK on the residual stromal
bed did not significantly alter corneal
pachymetry at 5 months. This is comparable to a
study by Kymionis et al6 where corneal
pachymetry did not alter intra and post
operatively after performing C3R for
keratoconus. No eyes were noted to have
persistent haze at 5 months follow-up. We could
thus establish not only the efficacy, but also the
safety of a combined PRK with C3R. However,
the inherent limitations of our study remain its
small sample size, absence of a control arm and a
relatively short follow-up.
As a combined procedure, in our pilot series,
PRK with C3R gives predictable refractive
outcomes with no significant adverse events.
However, the same needs to be established by a
comparative trial with a larger sample and a
longer follow-up.
Arch Ophthalmol 2009;127(10):1258-65.
2. Wittig-Silva C, Whiting M, Lamoureux E, et al. A
randomized controlled trial of corneal collagen

558 AIOC 2010 PROCEEDINGS
cross-linking in progressive keratoconus:
preliminary results. J Refract Surg 2008;24(7):S720-
5.
3. Vinciguerra P, Camesasca FI, Albè E, Trazza S.
Corneal Collagen Cross-Linking for Ectasia After
Excimer Laser Refractive Surgery: 1-Year Results. J
Refract Surg 2009;22:1-12.
4. Kymionis GD, Kontadakis GA, Naoumidi TL,
Kazakos DC, Giapitzakis I, Pallikaris IG.
Conductive Keratoplasty Followed by Collagen
Cross-Linking With Riboflavin-UV-A in Patients
With Keratoconus. Cornea 2009 Dec 16. [Epub
ahead of print]
5. Kymionis GD, Kontadakis GA, Kounis GA, et al.
Simultaneous topography-guided PRK followed by
corneal collagen cross-linking for keratoconus. J
Refract Sur 2009;25(9):S807-11.
6. Kymionis GD, Kounis GA, Portaliou DM, et al.
Intraoperative pachymetric measurements during
corneal collagen cross-linking with riboflavin and
ultraviolet A irradiation. Ophthalmology
2009;116(12):2336-9.