Doktor Vedat Kaya, Canan Aslı Utine, Sezen Harmancı Karakuş, Işılay Kavadarlı ve Ömer Faruk Yılmaz tarafından hazırlanmış olan bu makaleyi ilginize sunarız.
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Dr. Vedat Kaya (MAKALE)
1. ORIGINAL ARTICLE
Refractive and Visual Outcomes After
Intacs vs Ferrara Intrastromal Corneal Ring
Segment Implantation for Keratoconus:
A Comparative Study
Vedat Kaya, MD; Canan Asli Utine, MD, MSc; Sezen Harmanci Karakus, MD; Isilay Kavadarli, MD;
Ömer Faruk Yilmaz, MD
ABSTRACT
PURPOSE: To evaluate the refractive, topographic,
optical, visual acuity, and quality outcomes of two types
I ntrastromal corneal ring segments (ICRS) have been
implanted to delay or prevent the need for penetrating
keratoplasty and to achieve refractive correction with
improvement in visual acuity and quality in corneal ectatic
diseases.1-14 Intacs (Addition Technology Inc, Sunnyvale,
of intrastromal corneal ring segment (ICRS) implanta-
tions in keratoconus. California) and Ferrara ICRS (Ferrara Ophthalmics Ltda, Belo
Horizonte, Brazil) aim to improve geometry of the corneal sur-
METHODS: In this retrospective study, 16 eyes that had face and modulation of refractive effect with their unique de-
been implanted with Intacs ICRS (Addition Technology
Inc) (Intacs group) and 17 eyes implanted with Ferrara
signs, internal and external diameters, thicknesses, and arc
ICRS (Ferrara Ophthalmics Ltda) (Ferrara group) were lengths.2,12
evaluated. Pre- and postoperative examinations includ- Topographic and refractive results of ICRS implantation with
ed uncorrected and corrected distance visual acuities different designs have been compared previously.15,16 Because
(UDVA and CDVA, respectively), manifest refraction, the aim of ICRS implantation is visual rehabilitation, postop-
slit-lamp examination, topography, and ocular wavefront
analysis. Contrast sensitivity measurements under phot-
erative visual quality is as important as topographic, refractive,
opic, scotopic, and scotopic with glare conditions were and visual acuity outcomes. Improved lower and higher order
performed 1 year postoperatively. aberrations and uncorrected and corrected distance visual acu-
ities (UDVA and CDVA, respectively) after Intacs implantation
RESULTS: One year postoperatively, a significant de- have been reported.13 In our study, a comparative evaluation of
crease was noted in spherical equivalent refractive error Intacs and Ferrara ICRS implantations was performed in terms
of 3.76Ϯ0.39 diopters (D) and 3.42Ϯ0.88 D and
keratometry of 3.43Ϯ0.24 D and 3.28Ϯ0.78 D in the
of visual acuity, refraction, topography, objective ocular opti-
Intacs and Ferrara groups, respectively; and increase cal quality (ie, wavefront aberrations), and subjective visual
in mean UDVA and CDVA in Snellen lines of 0.18Ϯ0.04 quality (ie, contrast sensitivity function).
and 0.21Ϯ0.05, respectively, in the Intacs group and
0.21Ϯ0.09 and 0.26Ϯ0.08, respectively, in the Ferrara PATIENTS AND METHODS
group (PϽ.01 for all). The postoperative increase in
UDVA and CDVA and decrease in keratometry readings
In this retrospective, comparative study, eyes implanted
were not significantly different between groups (PϾ.05 with Intacs ICRS (Intacs group) between January 2008 and
for all). Mean higher order aberrations decreased in the January 2009 and Ferrara ICRS (Ferrara group) between May
Intacs group and increased in the Ferrara group (PϾ.05
for both). Postoperatively, a significant decrease was
noted in scotopic contrast sensitivity when glare was in- From Beyoglu Eye Research and Training Hospital (Kaya, Karakus, Kavadarli,
troduced in the Ferrara group, which was positively cor- Yilmaz); and Yeditepe University, Department of Ophthalmology (Utine),
related with pupil diameter (r(15)=0.50, P=.04). Istanbul, Turkey.
The authors have no financial or proprietary interest in the materials pre-
CONCLUSIONS: Both ICRS types provided comparable sented herein.
refractive, topographic, and optical quality outcomes.
Eyes with Ferrara ICRS experienced greater decrease in This study was presented at the 44th Turkish Ophthalmology Society national
scotopic contrast sensitivity under glare, which was sig- meeting, September 29 - October 3, 2010, Antalya, Turkey.
nificantly correlated with pupil diameter. [J Refract Surg. Correspondence: Canan Asli Utine, MD, MSc, Yeditepe University, Dept of
2011;xx(x):xxx-xxx.] doi:10.3928/1081597X-2011 Ophthalmology, Gazi Umur Pasa sok. No: 28, Besiktas Balmumcu 34345 Istanbul
Turkey. Tel: 90 533 5587635; Fax: 90 212 2112500; E-mail: cananutine@gmail.
com
Received: February 8, 2011; Accepted: July 18, 2011
Posted online:
Journal of Refractive Surgery • Vol. xx, No. x, 2011 1
3. Intacs vs Ferrara Intrastromal Corneal Ring Segments/Kaya et al
TABLE 1 TABLE 2
Preoperative Characteristics of Postoperative Characteristics of
22 Patients Implanted With Intacs 22 Patients Implanted With Intacs
or Ferrara Intrastromal Corneal Ring or Ferrara Intrastromal Corneal Ring
Segments Segments
MeanϮStandard Deviation MeanϮStandard Deviation
Intacs ICRS Ferrara ICRS P Value Intacs ICRS Ferrara ICRS P Value
Spherical refractive Ϫ4.16Ϯ0.89 Ϫ3.95Ϯ1.41 .63 Spherical Ϫ2.18Ϯ1.11 Ϫ1.81Ϯ2.11 .53
error (D) refractive error
(D)
Cylindrical refractive Ϫ3.98Ϯ1.32 Ϫ3.54Ϯ1.26 .34
error (D) Cylindrical Ϫ2.61Ϯ0.93 Ϫ2.13Ϯ1.03 .17
refractive error (D)
SEQ (D) Ϫ6.15Ϯ1.16 Ϫ5.39 Ϯ2.11 .21
SEQ (D) Ϫ2.39Ϯ0.77 Ϫ1.97Ϯ1.23 .24
Maximum K (D) 52.54Ϯ3.48 51.95Ϯ3.78 .64
Maximum K (D) 49.11Ϯ3.24 48.67Ϯ3.00 .70
UDVA (Snellen) 0.18Ϯ0.11 0.20Ϯ0.14 .72
UDVA (Snellen) 0.37Ϯ0.15 0.41Ϯ0.23 .53
CDVA (Snellen) 0.34Ϯ0.14 0.34Ϯ0.21 .97
CDVA (Snellen 0.55Ϯ0.19 0.60Ϯ0.29 .58
Total aberrations 6.11Ϯ1.40 5.99Ϯ1.80 .84
(µm) Total aberrations 4.33Ϯ1.42 4.46Ϯ2.04 .86
(µm)
HOA (µm) 1.88Ϯ0.45 1.77Ϯ0.51 .49
HOA (µm) 1.55Ϯ0.55 2.06Ϯ1.29 .25
ICRS = intrastromal corneal ring segments, SEQ = spherical equivalent
refraction, K = keratometry, UDVA = uncorrected distance visual acuity, Photopic CS 126.75Ϯ120.05 121.65Ϯ102.25 .90
CDVA = corrected distance visual acuity, HOA = higher order aberrations
Scotopic CS 103.44Ϯ92.94 72.94Ϯ53.46 .25
Scotopic CS with 90.25Ϯ74.39 40.06Ϯ49.28 .03*
glare
Intracorneal channel depth was determined by ICRS = intrastromal corneal ring segments, SEQ = spherical equivalent
the pachymetric map on Orbscan topography in both refraction, K = keratometry, UDVA = uncorrected distance visual acuity, CDVA
= corrected distance visual acuity, HOA = higher order aberrations, CS =
groups as 70% of the thinnest pachymetric reading in contrast sensitivity
the 3.4-mm diameter zone in the Intacs group and the *Statistically significant.
Note. Luminance level was 85 cd/m2 and 3.0 cd/m2 for photopic and scotopic
2.4-mm diameter zone in the Ferrara group, with the lighting, respectively.
origin as the fixation point. Inner and outer diameters
of the intracorneal channels were 6.8 and 7.8 mm, re-
spectively, in the Intacs group and 4.8 and 5.6 mm,
respectively, in the Ferrara group. divided by mean preoperative CDVA. Correlations be-
tween preoperative maximum keratometry and post-
STATISTICAL ANALYSIS operative gain in UDVA and CDVA, and between pupil
Statistical analysis was performed using the Statis- diameter and postoperative gain in contrast sensitivity
tical Package for Social Sciences (SPSS Inc, Chicago, function at photopic and scotopic conditions with or
Illinois), version 15.0. The Kolmogorov-Smirnov without glare were studied using Pearson’s correlation
test was used for normality of distribution of each coefficient (r) if variables were normally distributed. A
parameter. A Mann-Whitney U test was conducted to P value Ͻ.05 was considered statistically significant.
compare stages of keratoconus in both groups. If data
were normally distributed, paired-samples t test was RESULTS
performed to compare pre- and postoperative find- In the Intacs group, 16 eyes of 11 patients (4 men and
ings in each group. An independent-samples t test was 7 women) were implanted and 17 eyes of 11 patients
performed to compare pre- and postoperative UDVA, (7 men and 4 women) were implanted in the Ferrara
CDVA, keratometry, spherical, cylindrical and spheri- group. Mean patient age was 23.0Ϯ2.7 and 24.2±3.9
cal equivalent manifest refractive errors, pupil diam- years in the Intacs and Ferrara groups, respectively.
eters, total and higher order wavefront aberrations, Mean preoperative pupil diameter was 5.99Ϯ0.39 and
and postoperative contrast sensitivity scores in both 6.16Ϯ0.50 mm in the Intacs and Ferrara groups, respec-
groups. Efficacy index was defined as mean postop- tively (P=.30). No significant difference in stages of kera-
erative UDVA divided by mean preoperative CDVA. toconus was detected between groups (U=78.50, P=.23).
Safety index was defined as mean postoperative CDVA All eyes in the Intacs group and all but three eyes
Journal of Refractive Surgery • Vol. xx, No. x, 2011 3
5. Intacs vs Ferrara Intrastromal Corneal Ring Segments/Kaya et al
corneal cross-linking surgery has been increasingly signs. Additionally, the small sample size may be the
performed in eyes with keratoconus, the need for pen- cause of the statistical insignificance. In both groups,
etrating keratoplasty may decrease and subsequently, refractive error was generally undercorrected. Postop-
the importance of visual rehabilitation in these eyes erative spherical equivalent refraction of Ϯ1.00 D was
has increased. Refractive predictability is particularly achieved in only 6.3% and 17.6% of eyes in the Intacs
important when surgery is performed monocularly, to and Ferrara groups, respectively. All other eyes had
target a tolerable amount of anisometropia. To achieve myopic spherical equivalent refraction ϾϪ1.00 D. The
high-quality vision postoperatively, preoperative low relationship between uncorrected and corrected visual
UDVA and CDVA should be improved, combined with gain and preoperative maximum keratometry readings
a decrease in or minimal induction of wavefront ab- yielded a mild negative correlation in the Intacs group
errations and avoidance of postoperative visual com- and moderate positive correlation in the Ferrara group,
plaints (eg, halo and glare). which was not statistically significant.
Significant improvement in UDVA and CDVA after To the best of our knowledge, Intacs and Ferrara
ICRS implantation has been reported, accompanied ICRS have not been compared in terms of wavefront
by decrease in spherical refraction in all studies1,2,7,8,19 aberrations and contrast sensitivity in photopic and
and decrease in cylindrical refraction in some stud- scotopic environments and under glare effect. Wave-
ies,1,7,8,10,19 but not in others after Intacs implanta- front aberrations affect ocular optical quality that
tion.2,4,16 This has been explained by a greater segment may not be accurately evaluated by visual acuity and
diameter of Intacs ICRS, which induces only mini- conventional refractive error measurements alone.20
mal central corneal flattening.16 However, the closer Contrast sensitivity is a measure of threshold contrast
the locations of segments from the pupil margins, the for seeing the target, impairment of which is closely
greater the likelihood of light scattering by ICRS, in- linked to visual–task performance problems, including
ducing blur and glare sensation and reduction in con- difficulties in mobility, driving, reading, face recogni-
trast sensitivity.16 tion, and an assortment of everyday tasks such as using
To date, few comparative studies exist between the tools and finding objects.21 In our study, visual qual-
two types of ICRS.15,16 Although good outcomes have ity of patients implanted with these two types of ICRS
been reported for Intacs, Ferrara, and KeraRing (Medi- was evaluated in terms of wavefront aberrations and
phacos Ltda, Minas Gerais, Brazil) ICRS,1-14 in compar- contrast sensitivity function. Implanted ICRS were not
ative studies, implantation of KeraRings, with virtu- selected according to patients’ preoperative character-
ally the same characteristics as Ferrara ICRS, has been istics or demands; but patients implanted with two dif-
found to be superior to Intacs implantation in terms of ferent types of ICRS at different times were examined 1
refractive correction and visual outcome.15,16 year postoperatively in this respect.
In a comparative study, Kubaloglu et al15 found In the current study, total ocular aberrations were
that patients implanted with KeraRing had greater im- measured and compared, unlike previous studies,16,20
provement in CDVA and greater decrease in maximum to outline the effect of ICRS implantation on ocular
keratometry compared with Intacs at 6 months and 1 aberration profiles. Significant improvement in total
year postoperative. In that study, the nomogram used wavefront aberrations was noted in both groups post-
for Intacs implantation was not clearly indicated; but operatively, which accompanied significant improve-
in the current study, nomograms recommended by ments in spherical and cylindrical refractive errors.
manufacturers for each ICRS type were used. Piñero Mean higher order aberrations decreased in the Intacs
et al16 also compared the short-term refractive and ab- group and increased in the Ferrara group postop-
errometric performance of Intacs and Ferrara ICRS in eratively, although not statistically significantly. The
ectatic corneas. In that study, although spherical error smaller inner diameter of the Ferrara ring may cause
and spherical equivalent refraction were significantly greater effect on higher order aberrations, should any
reduced in both groups, cylindrical error decreased small amount of tilt or decentraton with respect to
significantly in the Ferrara group but not in the Intacs pupil occur in ICRS implantation.
group, indicating that Intacs have limited effect in cor- In both groups, postoperative scotopic contrast sen-
recting astigmatism. sitivity decreased significantly when glare effect was
In the current study, refractive and visual outcomes introduced. Interestingly, this decrease in contrast
were better in the Ferrara group, but the difference sensitivity in eyes implanted with the Ferrara ICRS was
between groups did not reach statistical significance. greater compared with Intacs-implanted eyes and was
Both types of ICRS rely on a similar mechanism of ac- significantly negatively correlated with pupil diameter.
tion, although with different optical diameters and de- These results suggest that smaller inner diameter, as
Journal of Refractive Surgery • Vol. xx, No. x, 2011 5
![ORIGINAL ARTICLE
Refractive and Visual Outcomes After
Intacs vs Ferrara Intrastromal Corneal Ring
Segment Implantation for Keratoconus:
A Comparative Study
Vedat Kaya, MD; Canan Asli Utine, MD, MSc; Sezen Harmanci Karakus, MD; Isilay Kavadarli, MD;
Ömer Faruk Yilmaz, MD
ABSTRACT
PURPOSE: To evaluate the refractive, topographic,
optical, visual acuity, and quality outcomes of two types
I ntrastromal corneal ring segments (ICRS) have been
implanted to delay or prevent the need for penetrating
keratoplasty and to achieve refractive correction with
improvement in visual acuity and quality in corneal ectatic
diseases.1-14 Intacs (Addition Technology Inc, Sunnyvale,
of intrastromal corneal ring segment (ICRS) implanta-
tions in keratoconus. California) and Ferrara ICRS (Ferrara Ophthalmics Ltda, Belo
Horizonte, Brazil) aim to improve geometry of the corneal sur-
METHODS: In this retrospective study, 16 eyes that had face and modulation of refractive effect with their unique de-
been implanted with Intacs ICRS (Addition Technology
Inc) (Intacs group) and 17 eyes implanted with Ferrara
signs, internal and external diameters, thicknesses, and arc
ICRS (Ferrara Ophthalmics Ltda) (Ferrara group) were lengths.2,12
evaluated. Pre- and postoperative examinations includ- Topographic and refractive results of ICRS implantation with
ed uncorrected and corrected distance visual acuities different designs have been compared previously.15,16 Because
(UDVA and CDVA, respectively), manifest refraction, the aim of ICRS implantation is visual rehabilitation, postop-
slit-lamp examination, topography, and ocular wavefront
analysis. Contrast sensitivity measurements under phot-
erative visual quality is as important as topographic, refractive,
opic, scotopic, and scotopic with glare conditions were and visual acuity outcomes. Improved lower and higher order
performed 1 year postoperatively. aberrations and uncorrected and corrected distance visual acu-
ities (UDVA and CDVA, respectively) after Intacs implantation
RESULTS: One year postoperatively, a significant de- have been reported.13 In our study, a comparative evaluation of
crease was noted in spherical equivalent refractive error Intacs and Ferrara ICRS implantations was performed in terms
of 3.76Ϯ0.39 diopters (D) and 3.42Ϯ0.88 D and
keratometry of 3.43Ϯ0.24 D and 3.28Ϯ0.78 D in the
of visual acuity, refraction, topography, objective ocular opti-
Intacs and Ferrara groups, respectively; and increase cal quality (ie, wavefront aberrations), and subjective visual
in mean UDVA and CDVA in Snellen lines of 0.18Ϯ0.04 quality (ie, contrast sensitivity function).
and 0.21Ϯ0.05, respectively, in the Intacs group and
0.21Ϯ0.09 and 0.26Ϯ0.08, respectively, in the Ferrara PATIENTS AND METHODS
group (PϽ.01 for all). The postoperative increase in
UDVA and CDVA and decrease in keratometry readings
In this retrospective, comparative study, eyes implanted
were not significantly different between groups (PϾ.05 with Intacs ICRS (Intacs group) between January 2008 and
for all). Mean higher order aberrations decreased in the January 2009 and Ferrara ICRS (Ferrara group) between May
Intacs group and increased in the Ferrara group (PϾ.05
for both). Postoperatively, a significant decrease was
noted in scotopic contrast sensitivity when glare was in- From Beyoglu Eye Research and Training Hospital (Kaya, Karakus, Kavadarli,
troduced in the Ferrara group, which was positively cor- Yilmaz); and Yeditepe University, Department of Ophthalmology (Utine),
related with pupil diameter (r(15)=0.50, P=.04). Istanbul, Turkey.
The authors have no financial or proprietary interest in the materials pre-
CONCLUSIONS: Both ICRS types provided comparable sented herein.
refractive, topographic, and optical quality outcomes.
Eyes with Ferrara ICRS experienced greater decrease in This study was presented at the 44th Turkish Ophthalmology Society national
scotopic contrast sensitivity under glare, which was sig- meeting, September 29 - October 3, 2010, Antalya, Turkey.
nificantly correlated with pupil diameter. [J Refract Surg. Correspondence: Canan Asli Utine, MD, MSc, Yeditepe University, Dept of
2011;xx(x):xxx-xxx.] doi:10.3928/1081597X-2011 Ophthalmology, Gazi Umur Pasa sok. No: 28, Besiktas Balmumcu 34345 Istanbul
Turkey. Tel: 90 533 5587635; Fax: 90 212 2112500; E-mail: cananutine@gmail.
com
Received: February 8, 2011; Accepted: July 18, 2011
Posted online:
Journal of Refractive Surgery • Vol. xx, No. x, 2011 1](https://image.slidesharecdn.com/jrsonlinekaya-120306065414-phpapp01/85/Dr-Vedat-Kaya-MAKALE-1-320.jpg)
