Measurement of Combined Corneal, Internal, and Total Ocular Optical Quality Analysis in Anterior Segment Pathology with the OPD-Scan and OPD-Station

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 intraocular 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 preoperatively to select the best IOL shape that would compensate for the corneal spherical aberration. This would require precise measurements of the preoperative corneal spherical aberration. Wavefront aberrometry could also be used postoperatively 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 aberrometer, 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]

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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

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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-

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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 incision. 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; 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).

A ifest refraction of plano Ϫ0.50 ϫ 150°. Postoperatively, origins is likely due to implantation of a spherical IOL. the OPD-Scan map showed an uneven distribution of The increase in coma seen postoperatively is likely due refractive power caused by a slight increase in some to less than optimal centration of the implanted IOL. of the higher order aberrations such as coma-like and spherical aberrations (Fig 2B). The higher order aberra- PHAKIC IOL SURGERY tions increased from 0.658 µm preoperatively to 0.737 Case 3. A 35-year-old man who had undergone µm postoperatively. Coma increased from 0.194 µm (Ϫ15.00 D) Artisan lens implantation 3 months pre- preoperatively to 0.566 µm postoperatively. Spherical viously was satisﬁ ed with his vision during the day; aberrations increased from 0.230 µm preoperatively to however, he complained about halos and monocular 0.397 µm after insertion of the spherical IOL. OPD-Sta- vertical diplopia at night. OPD-Scan analysis showed tion analysis revealed that corneal higher order aberra- that higher order aberrations were Ͼ3 µm, which is tions decreased from 1.100 µm preoperatively to 0.909 considered very high (Fig 3A). A coma pattern domi- µm postoperatively. The lower corneal aberrations nates the higher order map, and third order coma has postoperatively are likely due to the beneﬁ cial effects the highest magnitude in the Zernike graphs (Figs 3A of the 3.2-mm incision on the corneal shape, improv- and 3B). Slit-lamp examination revealed a slight infe- ing its regularity while reducing both the second order rior decentration of the Artisan lens, exposing a cres- corneal-induced astigmatism and some of the corneal cent of pupil superiorly. The OPD-Scan and internal higher order aberrations (see Figs 2A and 2B). Hence, OPD-Scan maps in Figure 3A show a superior “myo- the increase in higher order aberrations seen postop- pic rim” of persistent myopic power within the pupil eratively is likely due to the internal optics of the eye. corresponding to the crescent of pupil not covered by The increase in spherical aberrations due to internal the phakic IOL. The coma aberrations are highest from

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Figure 4. Case 4. A) OPD-Scan analysis of the right eye of a patient with pterygium invading the nasal quadrant of the cornea. B) OPD-Scan analysis after pterygium excision and a limbal autograft.

the internal optics of the eye (see Fig 3B). Hence, the Postoperatively, the magnitude of trefoil and coma aberrations were arising from the internal optics of the were signifi cantly reduced. This reduction was like- eye due to the decentered IOL. Centration of the IOL ly due to a combination of mechanisms, including relieved the patient’s symptoms. the reduction of tear fi lm pooling beneath the pterygium head and the release of corneal traction by PTERYGIUM SURGERY the pterygium. Case 4. A 38-year-old man was referred for pterygium evaluation in the right eye. Preoperative UCVA CONTACT LENS FITTING AFTER COMPLICATED REFRACTIVE was 20/40 and BSCVA was 20/25, with a manifest SURGERY refraction of ϩ2.00 Ϫ4.00 ϫ 180°. The patient com- When further surgical intervention is not possible plained of glare and permanent horizontal monocular after excimer laser refractive surgery, rigid contact diplopia that increased with spectacle correction. The lenses may be a useful alternative. The OPD-Scan can preoperative OPD-Scan map shows multiple myopic be used as an aid to contact lens fi tting and selection. and hyperopic areas within the pupil likely causing For example, during the trial lens-fi tting procedure, the diplopia and degradation of visual quality (Fig the eye can be measured with the contact lens in place 4A). High magnitudes of coma and trefoil were pres- to determine which contact lens provides optimum vi- ent preoperatively. The preoperative simulations of sual acuity and visual quality. The magnitude of high- the optotype images with and without best spectacle er order aberrations, the area under the MTF, and the correction for a photopic pupil show signifi cant deg- point spread function (PSF) are objective metrics that radation of visual quality. The patient underwent can be used during contact lens fi tting. pterygium excision and limbal autograft under local Case 5. A 28-year-old woman was referred for the anesthesia, which resulted in immediate improve- management of a decentered ablation after LASIK ment of the UCVA and BSCVA with concurrent reso- in her left eye. Uncorrected visual acuity was 20/30 lution of the glare and monocular diplopia (Fig 4B). and BSCVA was 20/25 with a manifest refraction of

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Figure 5. Case 5. OPD-Station analysis of an eye with a post-LASIK decentered ablation fitted with A) a Menicon Ex RGP contact lens and B) a Menicon Ex RGP contact lens with a smaller central radius. plano Ϫ1.50 ϫ 150°. The patient complained about quality. Therefore, we recommend using a variety glare, vertical diplopia, and reduced contrast. The of metrics of optical visual quality in combination decentered ablation was not easily seen on axial cor- rather than relying on a single metric to determine neal topography, but it was clear on the OPD-Scan the effect of higher order aberrations on vision. map. The estimated residual posterior bed thickness was Ͻ250 µm and therefore further excimer laser CHARACTERIZATION OF MULTIFOCALITY treatment was not performed. Rather, a rigid gas per- The compensation of presbyopia can be achieved by meable (RGP) contact lens fi t was chosen as the ap- increasing the multifocality of the eye. Multifocality propriate treatment for this patient. Different types of can be achieved by fi tting multifocal contact lenses, RGP contact lenses were fi tted to restore satisfactory performing multifocal corneal ablations, or implanting UCVA and visual quality. Our selection criteria for an accommodating IOL. The effect of induced multifo- the contact lens were based on the standard contact cality on the optical quality of the eye is an important lens fi tting parameters and assessing which contact factor in patient satisfaction. lens yielded a greater reduction in the higher order Case 6. A 52-year-old woman underwent hyperopic aberrations, the largest area under the MTF curve, LASIK for a preoperative refractive error of ϩ3.50 the sharper PSF, and sharper visual acuity simula- ϩ1.00 ϫ 180°. Postoperatively, UCVA was 20/25, and tion. Comparison of Figures 5A and 5B show that a the patient could read J2 at near uncorrected vision. Menicon (Nagoya, Japan) RGP contact lens with re- The patient was satisfi ed with the outcome of the verse geometry and smaller central radius provided a surgery, because it provided her with excellent func- sharper PSF and clearer visual acuity simulation due tional results for both near and far vision. The corneal to reduced levels of high order aberrations. Based on topography map showed marked steepening and an these parameters, we elected to provide the patient inferior decentration. However, the OPD-Scan map with a Menicon RGP contact lens. Upon subjective showed emmetropia centrally and increasing myo- comparison, the patient preferred the Menicon RGP pia up to Ϫ1.50 D inferiorly (Fig 6). The multifocality lens with a smaller central radius curve. An MTF shown on the OPD-Scan map explains the excellent graph showed a larger area under the curve after near and far uncorrected vision. Treatment for this contact lens insertion, indicating better visual per- patient demonstrates the importance of measuring formance. Although contrary to conventional think- the full optical properties of the eye rather than one ing, greater levels of higher order aberrations do not aspect, such as corneal topography. In this particular necessarily portend reduced visual quality, because patient, corneal topography evaluation alone would different combinations of higher order aberrations lead to the conclusion that this had been an unsuc- may interact in a manner that is benefi cial to visual cessful procedure.

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Figure 6. Case 6. Postoperative axial corneal topography map and OPD-Scan map of a patient who underwent hyperopic LASIK.

front Customized Visual Corrections: the Quest for Super Vi- DISCUSSION sion II. Thorofare, NJ: SLACK Inc; 2004:19-38. The precise qualitative and quantitative assessment 2. Applegate RA, Hilmantel G, Thibos LN. Assessment of visual of the main components of the eye’s optical system performance. In: Krueger RR, Applegate RA, MacRae SM, eds. (cornea and crystalline lens) facilitates a better under- Wavefront Customized Visual Corrections: the Quest for Super Vision II. Thorofare, NJ: SLACK Inc; 2004:65-75. standing of the patient’s symptoms in various clini- 3. Artal P, Guirao A, Berrio E, Williams DR. Compensation of cor- cal conditions other than customized laser refractive neal aberrations by the internal optics in the human eye. J Vis. surgery. Modern cataract surgery and complex contact 2001;1:1-8. lens ﬁ tting represent a wide range of applications for 4. Artal P, Guirao A. Contributions of the cornea and lens to the the use of devices such as the OPD-Scan, which can aberrations of the human eye. Opt Lett. 1998;23:1713-1715. measure corneal and internal optical quality. We be- 5. Yeung IY, Mantry S, Cunliffe IA, Benson MT, Shah S. Corre- lieve that the use of the OPD-Scan will become an in- lation of Nidek OPD-Scan objective refraction with subjective refraction. J Refract Surg. 2004;20:S734-S736. dispensable tool in daily ophthalmology practice. 6. Pieger S. Pearls, tips, and tricks for use of the Nidek OPD-Scan and FinalFit software. J Refract Surg, 2004;20:S741-S746. REFERENCES 7. Applegate RA, Marsack JD, Ramos R, Sarver EJ. Interaction 1. Williams DR, Porter J, Yoon G, Guirao A, Hofer H, Chen L, Cox between aberrations to improve or reduce visual performance. I, MacRae SM. How far can we extend the limits of human vi- J Cataract Refract Surg. 2003;29:1487-1495. sion? In: Krueger RR, Applegate RA, MacRae SM, eds. Wave-

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