intacs with or without same-day corneal collagen cross-linking to treat corneal ectasia

ORIGINAL ARTICLE

Intacs with or without same-day corneal collagen cross-linkingto treat corneal ectasiaMarie Eve Legare, MD, FRCSC,*,† Alfonso Iovieno, MD,*,† Sonia N. Yeung, MD, PhD, FRCSC,*,†

Alejandro Lichtinger, MD,*,† Peter Kim, MBBS(Hons), FRANZCO,*,† Simon Hollands, BSc,z

Allan R. Slomovic, MD, FRCSC,*,† David S. Rootman, MD, FRCSC*,†

ABSTRACT ● RESUME

Objective: To compare combined intrastromal corneal ring segment implantation with same-day ultraviolet-A/riboflavin cornealcollagen cross-linking (ICRS-CXL) versus ICRS implantation alone in patients with corneal ectasia.

Design: Retrospective comparative study.Participants: Sixty-six eyes from 54 patients with corneal ectasia were included in the study. The groups were composed of 32

eyes from 27 patients and 34 eyes from 27 patients for the ICRS-CXL and ICRS groups, respectively.Methods: We reviewed the charts of all patients who underwent these procedures from November 2008 to February 2011 for

preoperative and for up to 1 year postoperative uncorrected (UDVA) and best corrected distance visual acuity (BDVA), refraction,topographical analysis (mean and steepest keratometry [K]), as well as root mean-square (RMS) of higher-order aberrations(HOAs).

Results: Overall, a significant improvement was seen in both groups for UDVA, BDVA, sphere, cylinder, mean refractive sphericalequivalent (MRSE), mean and steepest K, coma, spherical and total HOA at 12 months. Trefoil did not improve, and higher-orderastigmatism worsened in the ICRS group (p ¼ 0.0466). There was no statistically significant difference between the 2 groups forvisual acuity, sphere, cylinder, coma, trefoil, and spherical HOA. Outcomes were significantly more improved in the ICRS groupfor MRSE (p ¼ 0.0082), mean K (p ¼ 0.0021), steepest K (p ¼ 0.0152), and total HOAs (p ¼ 0.0208). No complications wereobserved.

Conclusions: ICRS-CXL and ICRS alone were both safe and effective in treating corneal ectasia. The ICRS alone groupdemonstrated better outcomes of MRSE, mean and steepest K, as well as total HOA.

Objet : Comparer l’implantation de segments d’anneau corneen intrastromal (SACI) avec ou sans reticulation du collag �ene corneenpar riboflavine/ultraviolet-A (CXL) pour traiter l’ectasie corneenne

Nature : Etude comparative retrospectiveParticipants : Soixante-six yeux de 54 patients avec ectasie corneenne ont ete inclus dans l’etude. Il y avaient 32 yeux de 27

patients dans le groupe SACI-CXL et 34 yeux de 27 patients dans le groupe SACI.Methodes : Etude des dossiers de tous les patients ayant subi ces interventions de novembre 2008 �a fevrier 2011 pour l’acuite

visuelle sans correction (AVSC), meilleure acuite visuelle corrigee (MAVC), refraction, topographie (keratometrie (K) moyenne,maximale et les aberrations d’ordre superieur (AOS)) en pre-operatoire et jusqu’ �a 1 an en post-operatoire.

Resultats : Amelioration significative �a 12 mois de AVSC, MAVC, sph �ere, cylindre, l’equivalent spherique (ES), K moyenne etmaximale, ainsi que les AOS totales, coma et spherique dans chaque groupe. L’astigmatisme d’ordre superieur s’est deterioredans le group SACI (p ¼ 0.0466). Il n’y avait pas de difference significative entre les 2 groupes pour l’acuite visuelle, sph �ere,cylindre, coma, trefoil et l’aberration spherique. L’ES (p ¼ 0.0082), K moyenne (p ¼ 0.0021), K maximale (p ¼ 0.0152) et les AOStotales (p ¼ 0.0208) etaient significativement plus ameliorees dans le group SACI. Aucune complication fut observee.

Conclusions : Le traitement de l’ectasie corneenne par SACI et SACI-CXL est securitaire et efficace. Le groupe SACI a obtenuune meilleure amelioration de l’ES, K moyenne et maximale, ainsi que des AOS totales.

Corneal ectasia is a progressive, noninflammatory dis-order having the potential to progress to an advancedstage characterized by reduced, fluctuating, and dis-torted vision. Until recently, these patients wouldultimately require a lamellar or penetrating keratoplastyto improve visual acuity if contact lens (CL) intolerant.Keratoplasty may be avoided because less invasive treat-ments such as corneal collagen cross-linking (CXL) andintrastromal corneal ring segment (ICRS) implantationare available.

From then

Yonge-Eglinton Laser Center; yDepartment ofOphthalmology, Toronto Western Hospital, University HealthNetwork, Toronto; and the zDepartment of Epidemiology andBiostatistics, University of Western Ontario, London, Ont.

Presented orally at the Canadian Ophthalmology Society meeting inToronto, Ont., June 26–29, 2012.

Originally received Oct. 15, 2012. Final revision Jan. 25, 2013.Accepted Feb. 1, 2013

These procedures have different goals. CXL aims tostabilize the progressive deformation of the ectatic corneaand maintain vision by creating covalent bonds betweencollagen fibres.1–4 ICRS surgery modifies the cornealshape toward a more prolate configuration in hopes ofrestoring vision or improving its quality.5–8 Every patientwith a progressive mild-to-moderate ectasia shouldundergo CXL, whereas ICRS is suggested when CLintolerance or poor quality of corrected vision is present.Sometimes both procedures are required to reshape and

Correspondence to Marie Eve Legare, MD, FRCSC, Department ofOphthalmology, Toronto Western Hospital, East Wing 6-401, 399Bathurst Street, Toronto ON M5T 2S8; [email protected]

Can J Ophthalmol 2013;48:173–1780008-4182/13/$-see front matter & 2013 Canadian OphthalmologicalSociety. Published by Elsevier Inc. All rights reserved.http://dx.doi.org/10.1016/j.jcjo.2013.02.001

CAN J OPHTHALMOL—VOL. 48, NO. 3, JUNE 2013 173

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Intrastromal corneal ring segments for corneal ectasia—Legare et al.

stabilize the cornea to treat progression and unsatisfyingvision. The beneficial additive effect of CXL is to halt thedisease and could potentiate the flattening effect ofICRS.9,10 Each of these interventions has been shown tobe safe and effective when performed alone. However,superiority of combined ICRS and CXL (ICRS-CXL)versus ICRS alone is not well established yet.

The aim of our study was to compare the efficacy ofimplanting ICRS with same-day CXL compared withICRS alone in ectatic corneas over the first year.

METHODS

Study design

This study conformed to the provisions of the Decla-ration of Helsinki and was approved by the InstitutionalResearch Ethics Board of the University Health Network,University of Toronto. This study included all consec-utive patients undergoing either combined ICRS-CXL orICRS insertion alone performed between November 2008and March 2011 at the Yonge-Eglinton Laser Center.Intacs (Addition Technology, Des Plaines, Ill.), bothregular and Intacs Severe Keratoconus, were used forthese patients. Inclusion criteria were a Snellen bestcorrected distance visual acuity (BDVA) of 20/80 orbetter and mild-to-moderate corneal ectasia defined asGrades I to III of the modified Amsler–Krumeichclassification.11

Progression of ectasia was defined as a decrease in visualacuity of at least 1 line (excluding noncorneal causes ofdeterioration), a steepening of at least 1 D in steepestkeratometry (K) over the last 6 months, or more than1 change in prescription of glasses or CL over the last2 years. Exclusion criteria were a centrally located cornealscar, an ultrasound central corneal thickness measurementthinner than 400 mm, or inadequate thickness for ICRSinsertion.

Our younger patients were expected to have a greaterpotential for progression and were therefore offered toundergo ICRS-CXL. Older patients were suggested toundergo ICRS first as progression was less probable.Same-day ICRS-CXL was performed based on previousstudies demonstrating the safety and efficacy of a 1-daycombined surgery,12–15 and also based on the patient’sdesire to go through the healing process and risk forcomplications only once. Every patient received detailedinformation about the different procedures and providedinformed written consent.

Examinations

The chart review covered all available preoperative andpostoperative data at 1, 3, 6, and 12 months. Thecomplete eye evaluation done at the initial visit includeduncorrected distance visual acuity (UDVA), BDVA,manifest and cycloplegic refraction, topography (Nidek

174 CAN J OPHTHALMOL—VOL. 48, NO. 3, JUNE 2013

OPD-Scan ARK 10000, Gamagori, Japan), slit-lampexamination, and dilated fundus examination. Cornealtomography (Pentacam, Oculus, Wetzlar, Germany) andcentral ultrasonic pachymetry (Sonogage Corneo-GagePlus; Sonogage Inc, Cleveland, Ohio) were also done fordiagnostic purposes and to ensure adequate cornealthickness for ICRS insertion and CXL. The mean andsteepest K readings were recorded from the topography, aswere the higher-order aberrations (HOA) including theroot mean-square (RMS) of total, coma, trefoil, spherical,and higher-order (HO) astigmatism. For statistical anal-ysis, Snellen values were converted into logMAR equiv-alent. Mean refractive spherical equivalent (MRSE) wascalculated from the manifest refraction.

Surgical technique

Topical proparacaine hydrochloride 0.5% was used forthe procedure. The ICRS selection was based on thepresurgical planning guide provided by the manufacturer(Addition Technology, Des Plaines, Ill.). In both groups,the incision was placed at the steepest topographical axis,and the stromal channels were created at a depth of 400mm using an IntraLase FS-60 kHz femtosecond laser(IntraLase Corp; Abbott Medical Optics, Santa Ana,Calif.). The segments were then manually inserted andthe incision was sutured. For the combined procedure, theepithelium was removed immediately after channel creationusing 50% alcohol for 5 seconds. The Dresden protocol1

was then applied, and hypo-osmotic drops were used forvalues of central corneal thickness inferior to 400 mm.16

In both groups, moxifloxacin hydrochloride 0.5%(Vigamoxs; Alcon, Fort Worth, Tex.) and dexametha-sone 0.1% (Maxidex&; Alcon) eye drops were adminis-tered at the end of the procedure and a soft bandage CLwas applied. Moxifloxacin was used 4 times a day for1 week, whereas the dexamethasone was applied hourlyfor 2 days, then 4 times a day for 2 weeks. Preservative-free artificial tears were also frequently used for the firstfew months. The patient was seen for early follow-up atday 1; 4 for CL removal and 10 after surgery.

Statistical analysis

Mean values of visual acuity (UDVA and BDVA),refraction (sphere, cylinder, MRSE), K (mean and steepest),and RMS of HOA were examined to determine changesfrom preoperative values over 1, 3, 6, and 12 months,comparing ICRS with ICRS-CXL. Mixed-models, repeated-measures analysis of variance (Proc Mixed in SAS version9.2; SAS Inc, Cary, N.C.) were used to model these changes.The covariance matrix was unstructured (compound sym-metry was not assumed), and the correlation betweenfollow-up times was treated as nonlinear. A p valueo0.05was considered significant. Plots were done in MicrosoftOffice, Excel (Microsoft Corp, Redmond, Wash.).

To quantify the effect of astigmatism correction, weused vector analysis to determine the changes in astigmatic

Table 2—Type 3 tests of fixed effects for visual acuity andrefraction


refraction. This was conducted using Naeser polar valueanalysis.17

p

Effect (df ¼ 64) UDVA BDVA Sphere Cylinder MRSE

Time o0.0001 o0.001 0.0002 o0.0001 0.0004

Group-time 0.6324 0.36 0.1062 0.3956 0.0082

df, degrees of freedom; UDVA, uncorrected distance visual acuity; BDVA, best corrected

distance visual acuity; MRSE, manifest refraction spherical equivalent.

RESULTS

Demographics

Table 1 shows patient demographics. Sixty-six eyes from54 patients with corneal ectasia were included in the study.The majority of the cohort was diagnosed with keratoco-nus, each group containing only 3 eyes with post-LASIKectasia. In general, the patients of the ICRS-CXL groupwere younger and had a milder ectasia, whereas they wereolder with a more advanced ectasia in the ICRS group.UDVA (p ¼ 0.0415), cylinder (p ¼ 0.004), steepest K(p ¼ 0.0036), and spherical aberrations (p ¼ 0.0285) weresignificantly more advanced in the ICRS group comparedwith the ICRS-CXL group. Although not significantly so,mean K and total HOA were also more advanced in theICRS group (p ¼ 0.0791 and p ¼ 0.0637, respectively).

Visual outcomes

Table 2 displays the results of the type 3 tests of fixedeffects for visual acuity and refraction. Overall values ofUDVA and BDVA significantly improved over time(po0.001). Mean UDVA improved from 0.79 to 0.48logMAR (20/125 to 20/60 on the Snellen chart) in theICRS-CXL group and from 0.97 to 0.53 logMAR (20/200 to 20/70) in the ICRS group. Mean BDVA improvedfrom 0.198 to 0.119 logMAR (20/30 to 20/25) and from0.309 to 0.107 logMAR (20/40 to 20/25) in the ICRS-CXLand ICRS groups, respectively. There was no significant

Table 1—Baseline demographics and outcomemeasurements

Baseline ICRS-CXL group (means) ICRS group (means)

Patients (n) 27 27

No. of eyes 32 34

Diagnosis 29 Keratoconus 31 Keratoconus

3 Post-LASIK ectasia 3 Post-LASIK ectasia

Sex, F/M (n) 8/19 7/20

Age (yr) 28.96�8.08 37.04�13.22

Follow-up (mo) 9.8�3.6 6.5�3.7

6 mo (n) 26 (81.3%) 24 (70.6%)

12 mo (n) 22 (68.8%) 9 (26.5%)

Number of Intacs 1 Intacs: 5 eyes 1 Intacs: 5 eyes

2 Intacs: 27 eyes 2 Intacs: 29 eyes

UDVA (logMAR) 0.79�0.43 0.97�0.36

BDVA (logMAR) 0.20�0.16 0.31�0.25

Sphere (D) –1.59�4.05 –3.85�5.09

Cylinder (D) –3.55�1.43 –4.29�2.29

MRSE (D) –3.37�4.09 –6.03�5.41

Mean K 47.52�5.08 49.92�4.96

Steepest K 49.81�5.97 52.80�5.44

RMS

Total (mm) 9.48�4.44 12.68�6.95

Coma (mm) 1.97�0.93 2.50�2.06

Trefoil (mm) 1.32�0.54 1.74�1.57

Spherical (mm) 0.56�0.41 0.65�0.85

HO astig. (mm) 0.41�0.26 0.59�0.72

ICRS, intrastromal corneal ring segment; CXL, corneal collagen cross-linking; UDVA,

uncorrected distance visual acuity; BDVA, best corrected distance visual acuity; MRSE,

manifest refractive spherical equivalent; K, keratometry; RMS, root mean-square; HO

astig., higher-order astigmatism.

difference in the treatment effect between the groups forUDVA (p ¼ 0.6324) and BDVA (p ¼ 0.36).

Refractive outcomes

In both groups, the refractive outcomes significantlyimproved over time (sphere: p ¼ 0.0002; cylinder:po0.0001; and MRSE: p ¼ 0.0004). In the ICRS group,the improvement of MRSE over time was significantlybetter than the ICRS-CXL group (p ¼ 0.0082), decreasing5.45 D compared with 1.28 D in the ICRS-CXL group(Fig. 1, Table 2). There was no significant difference in theeffect of treatment over time between the 2 groups, forsphere and cylinder, over the 12 months of follow-up.

Vector analysis of astigmatism

Vector analysis demonstrated a significant flattening ofthe surgical meridian of 3.46�2.64 D with a non-significant induced clockwise cylinder of 0.10�2.75 Dfor the ICRS-CXL group. The flattening of the surgicalmeridian was also significant in the ICRS group with adecrease of 4.06�3.38 D and a nonsignificant inducedanticlockwise cylinder of 0.85�2.80 D.

Keratometric measurements

Overall values for mean K and steepest K flattened inboth treatment groups (po0.001; Figs. 2 and 3). Table 3shows the progressive flattening observed in K over time.It was significantly higher in the ICRS group (mean K:p ¼ 0.0021; steepest K: p ¼ 0.0152).

Higher-order aberrations

For total HOA, the values significantly decreased withtime in both groups (po0.001; Table 4). The improvementwas significantly greater in the ICRS group, decreasing 5.23mm versus 2.82 mm (p ¼ 0.0208). Overall, coma was signi-ficantly improved over time in both groups (p ¼ 0.0017),whereas trefoil did not change. There was a significantchange of HO astigmatism over time (p ¼ 0.0013), and theICRS-CXL group improved by 0.11 mm, whereas the ICRSgroup worsened by 0.75 mm (p ¼ 0.0466).

Clinical outcomes

All the interventions were well tolerated, and nocomplications occurred during or after the procedures.The reepithelialization was complete in all eyes within aweek, and no infectious keratitis, corneal melt, segment


Dio

pter

s

-7.00

-6.00

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

Baseline 1 3 6 12

Follow-up Time (Months)

MRSE ICRS-CXL MRSE ICRS

p = 0.0082

Fig. 1 — Change from baseline in mean keratometry (K) inpatients with mild-to-moderate corneal ectasia at 1, 3, 6, and12 months after intrastromal corneal ring segments implanta-tion with (ICRS-CXL) or without (ICRS) same-day cornealcollagen cross-linking.

Dio

pter

s

p = 0.0152

47

48

49

50

51

52

53

54

Baseline 1 3 6 12


Steepest K ICRS-CXL Steepest K ICRS

Fig. 3 — Change from baseline in mean refractive sphericalequivalent (MRSE) in patients with mild-to-moderate cornealectasia at 1, 3, 6, and 12 months after intrastromal cornealring segments implantation with (ICRS-CXL) or without (ICRS)same-day corneal collagen cross-linking.


extrusion, or perforation was observed. The expected hazeseen after CXL during the first few months did not resultin scarring in any patient.

DISCUSSION

ICRS implantation and CXL are important treatmentsfor patients with mild-to-moderate corneal ectasia,including keratoconus, post-LASIK ectasia, and pellucidmarginal degeneration. Previous studies reported thatcombining these 2 complementary interventions has beenshown to be safe and effective.9,10,12–15,18–22 Varioussequences of treatments have been described: performingCXL before ICRS implantation,18,21,22 after,9,10,14,18–20

or on the same day,12–15 with controversial results.

Collagen cross-linking before intrastromal corneal

ring segment insertion

Coskunseven et al.18 demonstrated in 2009 that theorder of intervention yields different results. CXL done7 months after ICRS insertion resulted in greater

p = 0.0021

44

45

46

47

48

49

50

51

Baseline 1 3 6 12

Dio

pter

s


Mean K ICRS-CXL Mean K ICRS

Fig. 2 — Change from baseline in steepest keratometry (K) inpatients with mild-to-moderate corneal ectasia at 1, 3, 6, and12 months after intrastromal corneal ring segments implanta-tion with (ICRS-CXL) or without (ICRS) same-day cornealcollagen cross-linking.


improvement of BDVA, MRSE, and mean K comparedwith CXL done 7 months before. Since then, thegenerally accepted theory suggests that we should let theICRS settle in before applying CXL, rather than implant-ing ICRS in a relatively more structurally rigid cornea.

However, Henriquez et al.21 recently demonstrated asignificant improvement of UDVA, BDVA, and kerato-metric values in eyes operated for CXL 6 months beforeICRS implantation. Renesto et al.22 showed no differencebetween ICRS implantation alone versus 3 months afterCXL surgery.

Collagen cross-linking after intrastromal corneal

ring segment implantation

CXL was reported to be safe 1 day and 1 month afterICRS implantation in post-LASIK ectasia, with no differ-ence in visual acuity, refraction, and keratometric valuesbetween the 2 eyes.19 This group then demonstrated thatCXL done 4 months after ICRS insertion significantlyenhanced UDVA, BDVA, sphere, and steepest K.9

El Awady et al.10 described that CXL has an additivebut insignificant effect when done, on average, 4.5 monthsafter ICRS implantation, and Pinero et al.20 found nosignificant change of refractive and keratometric valueswhen done at least 3 months after ICRS. El-Raggal14

also demonstrated that mean K was significantly moreflattened by same-day ICRS-CXL compared with CXL

Table 3—Evolution of keratometry over 12 months bytreatment

Steepest K (means) Mean K (means)

ICRS-CXL ICRS ICRS-CXL ICRS

Baseline 49.81 52.98 47.52 49.92

1 mo 48.43 51.44 46.20 48.49

3 mo 48.08 51.87 45.65 48.88

6 mo 48.17 50.90 45.85 47.95

12 mo 47.43 47.97 45.14 45.59

K, keratometry; ICRS, intrastromal corneal ring segment; CXL, corneal collagen cross-

linking.

Table 4—Type 3 tests of fixed effects for higher-orderaberrations

p

Effect (df ¼ 172) Total Coma Trefoil Spherical HO Astig.

Time o0.001 0.0017 0.1145 0.0285 0.1337

Group-time 0.0208 0.0802 0.1000 0.0012 0.0013

df, degrees of freedom; HO astig., higher-order astigmatism.


done 6 months later, whereas all other parameters weresimilar.

Same-day collagen cross-linking and intrastromal

corneal ring segment implantation

Same-day ICRS-CXL was shown to be safe andefficient, because it significantly improved UDVA,BDVA, sphere, cylinder, and mean K.15 Also, Chanet al.12 retrospectively compared ICRS with or withoutCXL. They reported an improvement of cylinder, mean,and steepest K significantly greater in the ICRS-CXLgroup, whereas our results demonstrated significantfavourable keratometric outcomes in the ICRS group.In addition, they reported that a greater improvement inBDVA after same-day ICRS-CXL was associated withpoorer baseline BDVA and MRSE.13

In our study, the overall values of UDVA, BDVA,sphere, cylinder, MRSE, mean and steepest K, totalHOA, coma, spherical, and HO astigmatism were sig-nificantly improved for both groups over the 12-monthfollow-up period. Also, we found a significant differencebetween treatments, suggesting a favourable outcome inthe ICRS alone group for MRSE, mean and steepest K,and total HOA. HO astigmatism improved in thecombined group, whereas it worsened in the ICRS group.No complications were seen during the entire follow-upperiod for either group.

The strengthening effect of CXL happens on the day ofsurgery and seems to restrict the progressive effect ofICRS usually seen during the first 6 months. Therefore,performing CXL either before or simultaneously to ICRSinsertion seems to lessen the effect of ICRS on the ectaticcornea.

Limitations of this study were its retrospective nature,the relatively high loss to follow-up rate, and the differ-ence between the groups at baseline. Only 26.5% of eyeswere analyzed at 12 months in the ICRS group because agood proportion of these patients were living in a distantlocation and follow-up could not be obtained. In addi-tion, patients in the ICRS-CXL group were younger, andtherefore had a greater risk for progression and oftenchose the combined surgery to stabilize the disease. Incontrast, the older group responded well to ICRS alone,showing no sign of progression and demonstrating betteroutcomes overall than the ICRS-CXL group.

Also, in the ICRS group, UDVA, cylinder, steepest K,as well as spherical HOA were significantly worse at

baseline. Among these, only steepest K showed a signifi-cantly greater improvement in the ICRS group. More-over, the difference in mean K and total HOA at baselinewere nearly significant. These parameters were signifi-cantly more improved in the ICRS group. This could be abias because the ICRS group had a greater theoreticalpotential for improvement in K and HOA.

In contrast, there was no difference between the groupsfor UDVA and spherical HOA, and the cylinder showedbetter improvement in the ICRS-CXL group, althoughthis was not significant. Although similar at baseline,MRSE was still significantly better and the sphere nearlyso in the ICRS group. Therefore, having a more severeectasia at baseline did not necessarily favour the ICRSgroup overall, but we did observe a greater improvementof the K and total HOA.

Visual acuity was not more improved in the ICRSgroup despite that K and total HOA were significantlymore improved. Maybe visual acuity in ectatic eyes ismore influenced by coma.

CONCLUSION

To the best of our knowledge, this is the largest studycomparing the efficacy of combining ICRS with orwithout same-day CXL for the treatment of mild-to-moderate corneal ectasia. We have demonstrated thatboth treatments significantly improve the visual acuity,refraction, K, as well as some HOA with better out-comes for the ICRS group. The CXL could limit theprogressive effect of ICRS, therefore explaining thebetter outcomes in the ICRS group. In light of theseresults, it may be reasonable to wait a few months afterICRS implantation to consider CXL, especially forolder patients who are at less risk for progression. Aprospective study comparing same-day ICRS-CXL withsequential ICRS and then CXL done 6 and 12 monthslater would have a stronger statistical significance andcould help confirm if and when CXL should be doneafter ICRS insertion.

Disclosure: The authors have no proprietary or commercialinterest in any materials discussed in this article.

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intacs with or without same-day corneal collagen cross-linking to treat corneal ectasia

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