OPD-SCAN DIAGNOSIS Measurement of Combined Corneal, Internal, and Total Ocular Optical Quality Analysis in Anterior Segment Pathology With the OPD-Scan and OPD-Station Damien Gatinel, MD; Thanh Hoang-Xuan, MD avefront aberrometers are increasingly used in ABSTRACT mainstream ophthalmology. Wavefront aberrom- PURPOSE: To show the clinical use of the NIDEK OPD- W eters provide the critical fi rst step in the measure- Scan wavefront aberrometer and OPD-Station software ment and correction of the spherical and cylindrical compo- in anterior segment surgery and pathology. nents of the refractive error in addition to the higher order aberrations of the visual system that affect visual perfor- METHODS: Case examples are presented along with mance. The ability to acquire a more detailed measurement discussion about the relevant clinical data obtained of the optics of the eye may allow for achieving optical visual from the OPD-Scan and OPD-Station software. outcomes beyond those currently seen using conventional 1,2 RESULTS: Six case examples including cataract surgery, subtractive or additive refractive surgical procedures. secondary IOL implantation, phakic intraocular lens sur- Wavefront aberrometers are tools to diagnose visual com- gery, pterygium surgery, contact lens fi tting, and multifo- plaints of optical origin. Hence, the use of wavefront sensors cal ablations are discussed. should not be restricted to the fi eld of wavefront-guided laser correction but should be used in any clinical situation that CONCLUSIONS: A complete understanding of the optics requires precise assessment of the optical quality of the eye. of the eye facilitates a better clinical comprehension of a variety of conditions in anterior segment surgery and The crystalline lens and the cornea contribute to the optical pathology. [J Refract Surg. 2006;22:S1014-S1020.] quality of the eye by balancing their respective aberrations in normal eyes.3,4 The recent introduction of aspheric intraocu- lar lenses (IOLs) to reduce the total spherical aberration and improve the optical quality of the pseudophakic eye is one potential application of aberrometry. Ideally, one may want to quantify the aberrations of the cataractous eye preopera- tively to select the best IOL shape that would compensate for the corneal spherical aberration. This would require precise measurements of the preoperative corneal spherical aberra- tion. Wavefront aberrometry could also be used postopera- tively to determine the induced aberrations and their effect on visual quality. However, only a few aberrometers exist that can separately quantify the aberrations of the anterior corneal surface and internal optics of the eye. In this article, we describe the use of one such aberrome- ter, the NIDEK OPD-Scan with OPD-Station software (NIDEK Co Ltd, Gamagori, Japan), in anterior segment surgery and pathology, separate from its use in customized ablations, and show its application as an “everyday practice tool.” From the Rothschild Foundation, YAP-HP Bichat Claude Bernard Hospital, Paris VII University, Paris, France. The authors have no financial interest in the materials presented herein. Correspondence: Damien Gatinel, MD, 25 rue Manin, 75019 Paris, France. E-mail: [email protected] S1014 journalofrefractivesurgery.com Anterior Segment Assessment With the NIDEK OPD-Scan/Gatinel & Hoang-Xuan A B Figure 1. Case 1. Zernike analysis of the aberrations of the A) right and B) left eye out to the sixth order. Root-mean-square values in microns are shown for a 5-mm pupil. Aberrations for the entire eye are tabulated for the total aberrations (Total); tilt; higher-order aberration (High); total coma aberration (T. Coma); total trefoil (T. Trefoil); total quadrafoil (T. 4Foil); total spherical aberration (T. Sph); and higher order astigmatism (HiAstig). PATIENTS AND METHODS age contrast with spatial frequency for an object with Six patients undergoing anterior segment surgery 100% contrast. The MTF is a quantitative measure of are used to illustrate the use of the NIDEK OPD-Scan image quality that is far superior to classic resolution with OPD-Station software as an aid in clinical as- criteria, because it describes the ability of the eye to sessment, diagnosis, and treatment planning. The transfer object contrast to the image. The MTF corre- OPD-Scan is a multifunction instrument that com- sponds to the ratio of image contrast to object contrast bines Placido-based corneal topography with wave- as a function of the spatial frequency of a sinusoidal front aberrometry of the entire eye. This wavefront grating. The MTF describes the contrast at each spa- measuring apparatus is based on retinoscopic prin- tial frequency, usually normalized to range from ciples that use a slit of infrared light to scan along all zero to one, zero being gray (no contrast) and one be- 360° meridians over a 6-mm pupil. The timing and ing perfect black/white contrast. If an object grating scan rate of the refl ected light are analyzed with an of a given spatial frequency is imaged by the eye, the array of photodetectors to determine the wavefront intensity contrast of adjacent bars in the image at the aberrations along each meridian. same spatial frequency will be given by the transfer In addition to the determination of an accurate re- function. Perfect imagery of black/white motifs cor- fraction,5 the OPD-Scan provides a complete set of responds to a transfer function of one. Conversely, maps, including four different corneal topography when the transfer function is zero, the bars in the maps, local refractive power of the entire eye due to image will undergo complete washout and appear aberrations at various locations within the pupil, a as continuous shades of gray. The OPD-Station soft- variety of wavefront aberration maps, and photopic ware allows the determination of the MTF of the en- and mesopic pupillometry.6 By computing the corneal tire eye as well as for each of its main optical com- wavefront aberration and comparing it with the total ponents (cornea and lens). In addition, the effect of wavefront map, it is possible to estimate optical quality total higher order aberrations, specifi c aberrations due to the internal aberrations of the eye. The internal (eg, spherical aberration), and combinations of aber- aberrations represent all aberrations behind the ante- rations7 on the MTF and visual acuity charts can be rior corneal surface. The data provided by the OPD- determined. Scan can be further processed using the OPD-Station software to compute useful metrics of optical quality CASE EXAMPLES such as the modulation transfer function (MTF) or to simulate maximum contrast visual acuity charts cor- PRIMARY CATARACT SURGERY responding to the entire eye, cornea, or internal aber- Case 1. A 55-year-old man presented with unilateral rations. The MTF corresponds to the variation of im- reduced vision. The patient wore spectacles with the Journal of Refractive Surgery Volume 22 November (Suppl) 2006 Commercially Sponsored Section S1015 Anterior Segment Assessment With the NIDEK OPD-Scan/Gatinel & Hoang-Xuan A B Figure 2. Case 2. A) Preoperative OPD-Scan analysis of the right eye in a patient with aphakia. B) Postoperative OPD-Scan analysis of the right eye after insertion of a spherical IOL. following prescription: Ϫ6.00 ϩ1.25 ϫ 10° (20/20) in SECONDARY IOL IMPLANTATION the right eye and Ϫ9.00 ϩ1.00 ϫ 90° (20/20) in the left Case 2. A 25-year-old man was referred for second- eye. Upon further discussion, the patient described re- ary IOL implantation in the right eye. During his fi rst duced vision at night in the right eye, along with the decade of life, the patient had undergone intracapsular perception of halos at night. crystalline lens extraction. Spectacle correction was OPD-Scan/OPD-Station analysis of the aberrations of ϩ6.50, yielding 20/20 best spectacle-corrected visual the entire eye showed increased levels of higher order acuity (BSCVA). Preoperative slit-lamp examination aberrations in the right eye (root-mean-square [RMS] revealed a persistent peripheral zonular and capsular 0.730 µm) compared with the left eye (RMS 0.302 µm) rim. The preoperative OPD-Scan map showed an even (Figs 1A and 1B). Spherical aberration in the right eye distribution of hyperopic refractive power across the (RMS 0.496 µm) was considerably higher than in the open pupil (Fig 2A). Comparison of the axial map and left eye (RMS 0.191 µm) (see Figs 1A and 1B). Corneal higher order map indicate that the aberrations are like- spherical aberration was similar in both eyes, measur- ly corneal (see Fig 2A). ing 0.119 µm for the right eye and 0.172 µm for the left An AcrySof MA50BM 21.00 diopter (D) spherical eye. The difference in spherical aberration must have IOL (Alcon Laboratories Inc, Ft Worth, Tex) was im- been due to changes in lens shape and refractive index planted in the ciliary sulcus through a 3.2-mm incision resulting from the greater nuclear sclerosis in the right placed superotemporally, centered on the 150° merid- eye. A well-developed cataract was seen in the right ian. The postoperative course was uneventful. Two eye and mild nuclear opalescence in the left eye with months postoperatively, uncorrected visual acuity slit-lamp microscopy. (UCVA) was 20/25, and BSCVA was 20/20 with a man- S1016 journalofrefractivesurgery.com Anterior Segment Assessment With the NIDEK OPD-Scan/Gatinel & Hoang-Xuan B Figure 3. Case 3. A) OPD-Scan analysis of an eye 3 months after Ϫ15.00 D phakic IOL implantation through a 6-mm superior limbal inci- sion. B) Zernike analysis of the total, corneal aberrations, and internal aberrations of an eye that underwent phakic IOL implantation out to the sixth order. Root-mean-square values in microns are shown for a 6-mm pupil. Aberrations are tabulated for the total aberrations (Total); tilt; high- er order aberration (High); total coma aberration (T.