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Clinical StudyOne-Year Results of SimultaneousTopography-Guided Photorefractive Keratectomy andCorneal Collagen Cross-Linking in Keratoconus Utilizinga Modern Ablation Software

A. M. Sherif, M. A. Ammar, Y. S. Mostafa, S. A. Gamal Eldin, and A. A. Osman

Department of Ophthalmology, Faculty of Medicine, Cairo University, Cairo , Egypt

Correspondence should be addressed to A. M. Sheri; [email protected]

Received May ; Accepted August

Academic Editor: David P. Pinero

Copyright A. M. Sheri et al. Tis is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Purpose.o evaluate effectiveness o simultaneous topography-guided photoreractive keratectomy and corneal collagen cross-linking in mild and moderate keratoconus. Methods. Prospective nonrandomized interventional study including eyes o patients with grade - keratoconus that underwent topography-guided PRK using a Custom Ablation ransition Zone (CAz)prole with .% MMC application immediately ollowed by standard mw/cm2 UVA collagen cross-linking. Maximum ablation

depth did not exceed m. Follow-up period: months. Results. Progressive statistically signicant improvement o UCVA rom0.830.37 logMAR preoperative, reaching 0.250.26 logMAR at months ( < 0.001). Preoperative BCVA (0.270.31 logMAR)showed a progressive improvement reaching0.08 0.12logMAR at months ( = 0.02). Meanmax reduced rom48.9 2.8to45.4 3.1 D at months ( < 0.001), meanmin reduced rom45.9 2.8 D to 44.1 3.2 D at months ( < 0.003), meankeratometric asymmetry reduced rom3.012.03 D to 1.251.2 D at months( < 0.001). Tesaety index was .at monthsand efficacy index . at months.Conclusion. Combined topography-guided PRK and corneal collagen cross-linking are a saeand effective option in the management o mild and moderate keratoconus.Precis. o our knowledge, this is the rst publishedstudy on the use o the CAz ablation system on the Nidek Quest excimer laser platorm combinedwith conventional cross-linkingin the management o mild keratoconus.

1. Introduction

Keratoconus is a chronic bilateral noninammatory cornealdegeneration, characterized by localized corneal thinningand corneal steepening, leading to irregular astigmatism andimpaired visual acuity [].

Cornealcollagen cross-linking has ounda broad interna-tional application or keratoconus in recent years [,]. Tecombination o ultraviolet A (UVA) light with riboavin asa photosensitizing agent produces interbrillar cross-linkingbetween corneal stromal collagen bers, thus increasingcorneal rigidity and halting the ectatic process. Te sphero-cylindrical change that it causes is limited [].

Several adjuvant therapies in combination with CXL havebeen proposed in an effort to develop a technique thatcan offer patients keratectasia corneal stability together withimproved unctional vision, including intracorneal rings []and phakic intraocular lenses [].

opography-guided PRK to correct ametropia and irreg-ular astigmatism in orm ruste and rank keratoconus wasintroduced over a decade ago [] with good results.However, concerns were raised about the long-term compli-cations, being a tissue subtraction technique.

Te mechanism o topography-guided ablation is thetting o an ideal corneal shape (usually a sphere) under

Hindawi Publishing CorporationJournal of OphthalmologyVolume 2015, Article ID 321953, 7 pageshttp://dx.doi.org/10.1155/2015/321953


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the present topography map with the ablation o tissue inbetween.

opography-guided PRK attens not only some o thecone peaks but also an arcuate broader area o the corneaaway rom the cone, usually in the superior nasal periphery;this ablation pattern will resemble part o a hyperopic

treatment and thus will cause some amount o steepening,or elevation adjacent to the cone, effectively normalizing thecornea [].

Kanellopoulos and Binder were the rst to combineCXL with topography-guided PRK in the management okeratoconus. Tey introduced a two-step procedure withCXL perormed rst and topography-guided PRK afer a -year interval [].

However, the act that cross-linked corneas may have adifferent ablation rate rom normal corneaswhich couldlead to unpredictable PRK resultsand the hypothesis thatthe removal o the cross-linked corneal tissue by the PRKprocedure could decrease the stiffening effects o the CXLtreatment in addition to the increased possibility o hazeormation afer PRK were serious limitations [].

Since then, several studies have evaluated the simultane-ous use o topography-guided PRK ollowed immediately byCXL in progressive keratoconus [,].

Te aim o this study is to evaluate the effectiveness ocombined corneal collagen cross-linking and topography-guided PRK in cases o mild and moderate keratoconus usingan advanced ablation sofware with the Quest laser platorm(Nidek, Gamagori, Japan).

2. Materials and Methods

Tis nonrandomized prospective clinical study was con-ducted on eyes o Caucasian patients in between Febru-ary and December . Te study was conducted withinthe tenets o the Declaration o Helsinki afer the approval othe institutional review board. A written inormed consentwas obtained rom all patients.

All cases were perormed at Eye Care Centeror reractivesurgery, Cairo, Egypt.

Inclusion criteria included grade or stable keratoconus(Amsler-Krumeich classication) [] documented by topog-raphy with a corneal thickness not less than m andabove years o age. Exclusion criteria included patientsbelow years o age, advanced (stage or Amsler-

Krumeich classication), BSCVA worse than logMAR, cen-tral corneal scars, cases that underwent previous reractivesurgery, and patients with history o herpetic eye disease orwho were pregnant or lactating.

Preoperative examination included complete ocularexamination included the ollowing: assessment o uncor-rected visual acuity (UCVA) and best spectacle corrected

visual acuity (BSCVA), slit-lamp examination, intraocularpressure (IOP) measurement using Goldmans applanationtonometry, assessment o maniest and cycloplegic reraction,and undus examination using indirect ophthalmoscopy.

Corneal topography was perormed using Optical PathDifference (OPD scanII) scanning System (Nidek, Gamagori,

Japan). Te device collects corneal topography, ocular wave-ront, autoreraction, and pupillometric data. Te topographyis Placido-based, collecting data rom more than points.Axial map data were collected. Measurements were repeatedat least times, and the best image was chosen or the nalanalysis (the best one was being dened as the image with

the best quality peaks or individual points). Sof contactlenses were stopped one week beore topography while rigidgas permeable and hard contact lenses were stopped weeksbeore topography.

Corneal pachymetry was done using PacScan P ultra-sound pachymeter (Sonomed Escalon, NY, USA) with mapmode to measure points at the cornea (centre, superior,inerior, temporal, and nasal area). Measurement accuracyand repeatability are assured by each scan actually consistingo individual measurements and an automatic measure-ment algorithm to ensure that only scans with proper probealignment are accepted.

Surgeries were perormed by surgeons (Y. S. Mostaaand A. M. Sheri).

.. Operative Steps

Step (topography-guided PRK). Afer topical anaesthesia,the epithelium was mechanically removed within an . mmdiameter using hockey knie. opography-guided PRK wasperormed with the aim to normalize the cornea, by reducingirregular astigmatism and also treating part o the reractiveerror. Custom Ablation ransition Zone (CAz) ablationprole (Quest, Nidek, Japan) was used. Te CAz algorithmdelivers aspheric treatment zones combined with the treat-ment o corneal elevation irregularities or corneal waverontat the surgeons choice. Te treatment was planned using theFinal Fit sofware version ., (Nidek, Co., Ltd.) basedon the curvature and elevation maps rom the Placido discsystem o the linked topography device OPD scan II.

o ensure minimal tissue removal, the effective opticalzone diameter was decreased to . mm. Te transitionzone was . mm. Correction o up to % o cylinder inaddition to up to % o the spherical componentwithoutexceeding a maximal ablation depth limit o mwasattempted. Corneal target asphericity was set to. and notilt correction was attempted. An example o the ablationpattern is shown inFigure .

Afer completion o ablation, .% mitomycin C wasapplied or seconds, ollowed by copious irrigation with

balanced salt solution.

Step (corneal collagen cross-linking). For the next minutes, .% riboavin -phosphate plus % Dextran ophthalmic solution (Ribolink Isotonic, Optos, Australia)was applied topically every minutes. Te solution appearedto soak into the corneal stroma rapidly, as it was centrallydevoid o Bowmans layer. Following the initial riboavinadministration, collagen cross-linking was perormed byprojecting Ultraviolet (UV) light at nm wavelength (

to nm) and mW/cm2 radiance at . cm onto the suraceo the cornea or -minute X link cross-linking system(Opto Global, Australia). Te device has an accurate internal


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power meter andeedback loop control deliver consistent UVirradiation during the entire procedure and eliminates theneed or periodic calibration.

A bandage contact lens was placed on the cornea at thecompletion o the procedure and was removed at daysollowing complete reepithelialization.

Postoperative treatment included the topical antibioticmoxioxacin (Vigamox, Alcon) our times a day or therst week and topical nonsteroidal anti-inammatory dropsNepaenac .% (Nevanac, Alcon Research Ltd., Fort Worth,X) or to days until complete epithelial healing. Tiswas ollowed by an antibiotic/steroid combination (obradex,Alcon) to be tapered over days. mg Vitamin C wasgiven orally or days.

Postoperative examinations were perormed by inde-pendent observes (M. A. Ammar and A. A. Osman).

Patients were assessed month, months, months,and months afer surgery. On each visit, the patientswere examined or uncorrected visual acuity (UCVA), bestcorrected visual acuity (BCVA), epithelial healing, and hazeormation according to Fantes haze grading system using slitlamp [] and corneal topography was perormed using OPDscan II. otal eye aberrometry was not recorded in all casesand thus was not included in the results. Examples o pre-and postoperative topography maps are shown inFigure .

.. Statistical Methods. Data management and analysiswere perormed using Statistical Package or Social Sciences(SPSS) version .

Data were summarized using means and standarddeviations. o examine the changes between the differenttime periods or normally distributed variables, a one-way repeated measures analysis o variance was conducted.For nonnormally distributed variables, the analyses wereperormed by the Friedman test, a nonparametric repeatedmeasures one-way analysis o variance. Pairwise comparisonswere done using the Wilcoxon Signed test afer adjusting the values using the Bonerroni corrections. values .were considered signicant.

Te main outcome measureso the study were UCVA andBCVA.

Secondary outcome measures were max, min, andkeratometric asymmetry. Te data were obtained rom theaxial maps o the OPD scan.

In addition, the saety andefficacy indices were calculated[].

Te predictability index was not included because wewere not sure about the ne accuracy o the subjectivespherical equivalent and because the aim was more o suraceregularization rather than spherocylindrical correction.

3. Results

Te study included eyes o patients: eyes belonged tomales (%) and eyes belonged to emales (%). Te age opatients ranged rom to years with a mean o23.6 3.2.

Te results are summarized inable .Te mean ablation depth was 48.099.6m (range .

. m).

0.0

0.2

0.4

0.6

0.8

1.0

Preoperative

12thmonth

6thmonth

3rdmonth

1stmonth

0.83

0.47

0.35 0.310.26

MeanUDVA

F : Preoperative and postoperative uncorrected distance vis-ual acuity.

0.27 0.27

0.18

0.12

0.08

0.0

0.2

0.4

Preoperative 1st month 3rd month 6th month 12th month

MeanCDVA

F : Preoperative and postoperative best corrected distancevisual acuity.

Te mean target cylindrical correction was 1.25 0.85 D(range . D).

Te preoperative and -, -, -, and -month postoper-ative sphere, cylindrical, and spherical equivalent data areshown inable .

Tere was a statistically signicant difference between themean preoperative logMAR UCVA (0.83 0.37) (0.21 0.19decimals) and -month postoperative logMAR UCVA (0.470.23) (0.41 0.27decimals) ( < 0.001). UCVA continued toimprove progressively until the end o the -month ollow-up period (0.25 0.26 logMAR) (0.63 0.25decimals) (

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