Cornea - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group - Corneabulbar redness. Being an objective measure, it reduces the inherentvariability of subjective assessments. Subjective assessment mayoverestimate redness due to normally present large blood vessels onthe conjunctiva that are not indicative of inflammation. Thekeratograph takes into account proportion of bulbar area occupied byvessels, number of vessels and the proportion of area occupied bythin vessels and thus reduces overestimation of hyperemia. Thus thisnovel instrument may prove to be a non-invasive, objectivebiomarker of ocular surface inflammation and thus serve as animportant endpoint in clinical trials of ocular surface disease.Table 1Commercial Relationships: Neha Gadaria-Rathod, None; Kyu-InLee, None; Benyamin Y. Ebrahim, None; Penny A. Asbell, RPS(F)Support: This study was supported in part by Research to PreventBlindness (RPB) Foundation and the Martin and Toni SosnoffFoundation.Program Number: 528 Poster Board Number: B0165Presentation Time: 10:30 AM - 12:15 PMClinical Validation of the Cassini Color LED CornealTopography (CLCT) in post penetrating keratoplasty (PKP)Ronald Ensing 1 , Fleur de Lange 2 , Harry de Vries 1 , Michel Zaal 2 ,Victor A. Sicam 1 . 1 i-Optics B.V., The Hague, Netherlands; 2 OMCZaandam, Zaandam, Netherlands.Purpose: To report results of a clinical investigation involvingcomparison of corneal aberration measurements of CLCT withconventional Placido based and Scheimpflug based topographers.Methods: 23 PKP eyes from 16 subjects (age: 58 years ± 14 years,ranging from 35 to 81 years, 9 OD and 14 OS) were measured bythree instruments: Cassini (i-Optics BV, The Hague, TheNetherlands), OPD Scan (Nidek, Gamagori, Japan) and Pentacam(Oculus, Wetzlar, Germany). Corneal aberrations (ZernikeConvention at 6 mm corneal zone) were compared. An artificial toricsurface with gold standard measurement of 2.22 Diopter was alsomeasured to assess the accuracy of the instruments. The standarddeviation of three trials for every eye measurement was used tocharacterize precision of the instrument. The measurement withmedian defocus was used for inter-instrument comparison. Thepaired student’s t-test was used on the median data to findstatistically significant differences.Results: Nidek OPD measures astigmatism of the toric surface with2.7% error while CLCT measures the toric surface with with 0.5%error. The Pentacam has a precision reaching a mean of 0.25 μm forastigmatism measurements. Both the OPD and CLCT do not exceed amean of 0.096 μm of precision in the measurement of cornealaberrations. Statistically significant differences have been foundbetween the Cassini and the OPD for astigmatism (p = 0.0292) andquadrafoil (p = 0.0281) aberrations. The spherical aberrationmeasured with Pentacam was significantly different from bothCassini and OPD (p = 0.0114 and p = 0.0194 respectively).Conclusions: The lower accuracy of the OPD in measuringrotationally non-symmetric aberrations such as astigmatism andquadrafoil, can be explained by the fact that rings are used in themeasurement. The use of rings does not measure the irregularfeatures of the cornea accurately. The poorer repeatability of thePentacam is a result of motion artifacts during acquisition. TheCassini and the OPD have comparable repeatability because it takesinstantaneous measurements and is therefore not affected by motionartifacts. Among the three instruments, the Cassini measures cornealaberrations both accurately and precisely.Commercial Relationships: Ronald Ensing, i-Optics B.V. (E);Fleur de Lange, None; Harry de Vries, i-Optics (E); Michel Zaal,i-Optics (F); Victor A. Sicam, i-Optics BV, The Hague, TheNetherlands (E), Patent/i-Optics BV, The Hague, The Netherlands(P), Patent/VU University Medical Center, Amsterdam, TheNetherlands (P)Support: The research is supported by i-Optics BV, The Hague, TheNetherlands.Program Number: 529 Poster Board Number: B0166Presentation Time: 10:30 AM - 12:15 PMTopographically Guided Corneal Cross-LinkingDavid B. Usher, Radha Pertaub, Marc D. Friedman, Ronald F.Scharf, David Muller. Avedro Inc, Waltham, MA.Purpose: To determine the feasibility of a topographically guidedcorneal cross-linking device.Methods: A proprietary corneal cross-linking device was developed.A UVA LED source illuminates a digital micromirror device (DMD).Light reflected from the DMD is projected on to a subject’s eye. Thesystem controls the configuration of the DMD’s mirrors such that anarbitrary UVA pattern can be projected on to the eye and modulatedat video rates. A digital camera is used to record views of thesubject’s eye. A Graphical User Interface allows an operator toimport topographies from a third party corneal topographer anddefine UVA irradiation patterns based on the imported topographydata set. A common reference frame between the cross-linking deviceand the topographer is established via a registration algorithm.Images of the subject’s iris exported by the topographer are comparedto images recorded by the cross-linking device’s digital camera. Iristextures and limbus boundaries visible within each dataset are used tocalculate a geometrical relationship between the two camera views.Eye motion during the application of the UVA light is accounted forby tracking the location of the eye in the cross-linking device’sdigital camera. This detected eye motion forms feedback formodulating the DMD mirrors such that the incident UVAillumination tracks relative to the eye. Eye motion, in terms of pupildisplacements, was calculated for 20 eyes from 10 subjects each over30 second periods.Results: An average frame-to-frame (60 Hz) eye motion of 23.9 um(Range: 16.6 - 38.0) was recorded across subjects. Rotations of 2.1°and 2.8° were measured for two subjects where images were recordedby both the cross-linking device and the corneal topographer.Conclusions: The proposed UVA treatment system demonstratesunique features that will be able to advance the science of cornealcross-linking. Each individual mirror of the DMD can be controlledto correct beam uniformity through irradiance calibrations. Itsflexibility allows a surgeon complete freedom when configuring theUVA dose across different areas of the cornea to a high degree ofaccuracy. The eye tracking preserves this accuracy by accounting foreye motion. The integration of the topography data allow a surgeon touse variables such as corneal elevations, power maps, k readings,corneal thickness maps, and epithelial thickness maps when creatingpatent specific cross-linking pretreatment plans and procedures.©2013, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permissionto reproduce any abstract, contact the ARVO Office at arvo@arvo.org.