A new method of cornea modulation with excimer laser for simultaneous correction of presbyopia and ametropia

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1 DOI /s REFRACTIVE SURGERY A new method of cornea modulation with excimer laser for simultaneous correction of presbyopia and ametropia Detlef Uthoff & Markus Pölzl & Daniel Hepper & Detlef Holland Received: 2 July 2011 /Revised: 5 December 2011 /Accepted: 30 January 2012 # Springer-Verlag 2012 Abstract Purpose To investigate the outcomes of simultaneous correction of presbyopia and ametropia by a bi-aspheric cornea modulation technique, based on the creation of a central area hyperpositive for near vision and leaving the pericentral cornea for far vision in hyperopic, emmetropic, and myopic presbyopic patients. Setting Sixty eyes of 30 patients were treated with the PresbyMAX technique by one surgeon (D.U.) at the Eye Hospital Bellevue, Kiel, Germany. Methods Twenty eyes with hyperopic presbyopia, 20 eyes with emmetropic presbyopia, and 20 eyes with myopic presbyopia underwent Femto-Lasik, and were assessed up to 6 months postoperatively. All eyes underwent cornea treatment using the PresbyMAX software, delivering a biaspheric multifocal ablation profile developed by SCHWIND eye-tech-solutions (Kleinostheim, Germany). All flaps were created by Ziemer LDV Femtolaser (Port, Switzerland). Results The mean binocular distance of uncorrected visual acuity (DUCVA) improved in the hyperopic group from 0.28±0.29 logmar to 0.04±0.07 logmar, in the emmetropic group from 0.05±0.07 logmar to 0.02±0.11 log- MAR, and in the myopic group from 0.78±0.27 logmar to 0.09±0.08 logmar. The mean binocular near uncorrected visual acuity (NUCVA) increased in the hyperopic group from 0.86±0.62 lograd to 0.24±0.23 lograd, and in the The authors have no financial interests in the presented products, and no financial relationship with the Schwind Company. The authors have full control of all primary data, and agree to allow Graefe s Archive to review the data on request. D. Uthoff (*) : M. Pölzl : D. Hepper : D. Holland Eye Hospital Bellevue, Lindenallee 21, D Kiel, Germany d.uthoff@augenklinik-bellevue.de emmetropic group from 0.48±0.14 lograd to 0.18±0.11 lograd. The myopic presbyopes showed a decrease of the mean binocular NUCVA from 0.04±0.19 lograd to 0.12± 0.18 lograd. The mean postoperative spherical equivalent for distance refraction was 0.13±0.61 D for the hyperopic presbyopia, 0.43±0.35 D for the emmetropic presbyopia, and 0.68±0.42 D for the myopic presbyopia group, whereas the software took aim at 0.50 D in all groups. Conclusions In presbyopic patients without symptomatic cataracts, but refractive errors, PresbyMAX will decrease the presbyopic symptoms and correct far distance refraction in the same treatment, offering spectacle-free vision in daily life in most of the treated patients. Further investigation is necessary to evaluate the overall benefit of this procedure. Keywords Presbyopia. Ametropia. Presbylasik. LASIK Introduction Presbyopia and its refractive correction is one of the most frequently discussed topics in refractive surgery today. The surgical techniques used to correct presbyopia can be broadly categorized as follows: bi- or multifocal techniques [1, 2], optic shift and monovision [3, 4] procedures. Since the introduction of laser technologies [5, 6] for refractive surgery [7], the change of the corneal curvature to compensate in a controlled manner for refractive errors of the eye [8, 9] is more accurate than ever [10 12]. In general, presbyla- SIK treatment uses the principles of LASIK surgery and creates a multifocal corneal surface in order to reduce near-vision spectacle dependence in presbyopic patients, and constitutes the next step in the correction of presbyopia after monovision LASIK [13, 14]. The term presbylasik indicates a corneal surgical procedure based on traditional

2 LASIK to create a multifocal surface able to correct visual defect for distance, while simultaneously reducing the near spectacle dependency in presbyopic patients [15, 16]. In central presbylasik, a central area is created for near vision and a peripheral area is created for distance vision [17], whereas in peripheral presbylasik, the central area is for distance vision and the pericentral area is for near vision [18, 19]. More specifically, central presbylasik produces an increased curvature (smaller radius) in the central cornea, thus producing an increase of refractive power in the corneal vertex, improving near vision. The purpose of this clinical trial is to investigate the objective and subjective visual results of a central multifocal presby- LASIK approach called PresbyMAX, based on the creation of a bi-aspheric multifocal corneal surface with a central hyperpositive area to achieve D to D of nearvision correction, surrounded by an area where ablation is calculated to correct the distance refractive error. In this clinical trial we report the results obtained in a series of presbyopic hyperopic, emmetropic, and myopic patients. Patients and methods Patient population This study is a prospective non-randomised clinical evaluation with 30 patients enrolled for bilateral treatment: ten hyperopic, ten emmetropic, and ten myopic presbyopes (21 women and nine men). Mean patient age was 54 years (range: years) for the hyperopic presbyopic group, 52 years (range: years) for the emmetropic presbyopic group, and 51 years (range: years) for the myopic presbyopic group. All patients were dependent on reading glasses in daily life. Mean preoperative spherical equivalent was +1.48±0.60 D (range: to D, median D) for the hyperopes, +0.34±0.53 D (range: 0.63 to D, median D) for the emmetropes, and 2.59±0.73 D (range: 3.88 to 1.50 D, median 2.44 D) for the myopes. Mean preoperative astigmatism was 0.41±0.31 D (range: 0.00 to 1.00 D, median 0.50 D) for the hyperopes, 0.35± 0.27 D (range: 0.00 to 1.00 D, median 0.25 D) for the emmetropes, and 0.69±0.43 D (range: 0.00 to 1.50 D, median 0.75 D) for the myopes, and mean spectacle near addition was +1.85±0.53 D (range: 0.75 to 2.50 D, median 2.00 D) for the hyperopes, +1.90±0.48 D (range: 0.75 to 2.50 D, median 2.00 D) for the myopes and +2.03±0.51 D (range: 1.00 to 2.50 D, median 2.13 D) for the emmetropes. All patients were informed, and signed consent in accordance with the tenets of the Declaration of Helsinki. Inclusion criteria were a sphere within 4.0 and +4.0 dioptersandanastigmatismequaltoorsmallerthan2diopters. Prior to the operation, all patients had to have a corneal curvature of between 40 and 48 D, as well as a central pachymetry thicker than 500 μm. Preoperative distance bestcorrected visual acuity (DBCVA) of 0.1 logmar or better and a near vision of 0.1 lograd or better with an addition of +1.5 D was required. Patients had to have pupil diameters within 2.5 to 3.0 mm in photopic and larger than 4.5 mm in mesopic low condition to be included. Patients with irregular patterns of corneal topography or history of ocular disease were excluded. Additional exclusion criteria were clinically-relevant lens opacity, an ectopic pupil more than 1 mm off-centre and any signs of binocular vision anomalies at distance and near. Distance visual acuities, i.e., distance uncorrected visual acuity (DUCVA) and DBCVA, were tested using the decimal scale visual charts at 5 m. Near vision, i.e., near uncorrected visual acuity (NUCVA), and near distance corrected visual acuity (NDCVA), and near best-corrected visual acuity (NBCVA), was determined using a decimal reading chart with luminance of cd/m² and 100% contrast at 40 cm. All tests were performed monocularly and binocularly. For evaluation of the results, decimal scale was translated into logmar for distance acuities and into lograd for reading acuities. Contrast sensitivity was tested with the Pelli Robson Contrast Sensitivity Chart, monocularly and binocularly, as well. A slit lamp was used to verify lens clarity, and photopic and scotopic pupil sizes were measured using the Colvard pupillometer (OASIS Medical Inc., Glendora, CA, USA). Corneal topography maps were taken with the Orbscan II (Bausch and Lomb, Rochester, NY, USA). Corneal and ocular aberrations were investigated at a standardised pupil diameter of 6 mm with the Combi Wavefront Analyzer (SCHWIND eye-techsolutions, Kleinostheim, Germany). PresbyLASIK surgical procedure In this study, all patients were treated with an excimer laser and FemtoLASIK flap technique on both eyes on the same day with equal optical zone, and by the same surgeon (D. U.). A SCHWIND AMARIS excimer laser with flying spot technology of 0.54 mm full-width-half-maximum, a repetition rate of 500 Hz, and a six-dimensional eye tracker with 1050 Hz were used. For flap creation, a LDV femtosecond laser (Ziemer, Port, Switzerland) was used in all cases. A 9.5 mm flap with a 4 mm superior hinge was performed in each case. Flap thickness was predetermined at 110 μm in all cases. The excimer laser ablation was centred to the corneal vertex whenever the pupil centre to corneal vertex distance exceeded 200 μm; otherwise, the pupil centre was used as a reference for the ablation map. All aspheric treatments were prepared using the SCHWIND PresbyMAX treatment planning module in Aberration-Free mode (SCHWIND eye-tech-solutions, Kleinostheim, Germany). The PresbyMAX module integrates bi-aspheric multifocal

3 ablation profiles combining two focus-shifted aspheric profiles with different asphericities that compensate as well for the peripheral loss of energy due to an increased angle of incidence on the cornea, and for biomechanical changes induced during LASIK. A bi-aspheric multifocal corneal profile is created over the optical zone size that is used: 6.5 mm in our study patients. The individual distance refractive correction is applied over the entire optical zone with an automatically adjusted central treatment zone ( 3 mm) to be hyperpositive. This hyperpositive shape is influenced by the amount of addition, i.e., the higher the addition the more dominant the central area. A circumferential transition zone of gradually changing power connects the region of the cornea corrected for distance with the portion corrected for near. The term bi-aspheric refers to the aspherical optimisation of the central corneal area for near vision and the pericentral cornea for far vision, for each patient eye. In this presbyopic concept, both eyes equally contribute to providing visual acuity at all distances by actively participating in the visual process for creating binocular vision impressions. No differences between the dominant eye and the non-dominant eye are applied. The profile includes the aim of 0.50D myopic defocus for distance correction, equally for both eyes (Fig. 1). The treatment of ocular or corneal wavefront aberrations was not intended in this study. The planned addition was accepted from D to D, depending on the patient s age. Postoperatively, all patients were treated with ofloxacin 5x/d, dexamethason 5x/d, and hydromellose 5x/d for the first week; then with hydromellose for the following weeks. Postoperative follow-up was performed at 1 day and 1, 3 and 6 months in all cases. Outcome measures Results for 60 eyes of 30 patients after 1 day, 1 month, 3 months and 6 months are documented. The main outcome measures were accuracy, efficacy, safety, and stability. Efficacy Binocular DUCVA, binocular NUCVA, monocular and binocular distance efficacy indices (ratio between mean postoperative DUCVA versus mean preoperative DBCVA), monocular and binocular near efficacy indices (ratio between mean postoperative NUCVA versus mean preoperative NBCVA) were assessed. Safety Loss and gain in lines of DBCVA as well as safety index (defined as mean postoperative BCVA versus mean preoperative BCVA) were monocularly and binocularly evaluated. Accuracy Scattergram for spherical equivalent refraction of all eyes at 1-month, 3-month, and 6-month follow-ups was plotted. The refractive deviation from target for distance correction was evaluated in spherical equivalent and astigmatism. Fig. 1 The SCHWIND PresbyMAX module integrates bi-aspheric multifocal ablation profiles combining two focus-shifted aspheric profiles with different asphericities. The example depicts a bi-aspheric refractive correction compared to bifocal refractive correction for +2 D of hyperopia combined with +2 D of presbyopic add Local refractive correction (D) 6,00 4,00 2,00 0,00-2,00 Bifocal Bi-aspheric multifocal -4,00-6,00-5,00-4,00-3,00-2,00-1,00 0,00 1,00 2,00 3,00 4,00 5,00 Radial distance (mm)

4 Stability Stability has been assessed by comparing manifest refraction at 1- and 6-month follow-ups. Contrast sensitivity Contrast sensitivity was measured monocularly as well as binocularly using the Pelli Robson Contrast Sensitivity Chart. Higher-order aberrations In addition to the aim of a distance myopic target of 0.50 D, the reading performance is mainly supported by a defined change of higher order aberrations, particularly the spherical aberration terms C(4,0) and C(6,0). The equation to compute radial symmetric multifocality from Zernike primary and secondary spherical aberrations (in microns) to dioptres of multifocality is displayed as follows [20]: Multifocality ¼ 16 3 pffiffiffi pffiffi 5 C C 0 6 AD 2 C4; ð 0Þ : primary spherical aberration ðμmþ C6; ð 0Þ : secondary spherical aberration ðμmþ AD : analysis diameter ðmmþ Achieved multifocality was obtained and analysed from the radial symmetric Zernike terms of the Corneal Wavefront Analyzer (OPTIKON, Rome, Italy) at 6 mm diameter. The equation to compute attempted multifocality (in dioptres) is shown as follows: Multifocality ¼ Add 2 Results Efficacy Add : additionðdþ The mean binocular DUCVA improved from pre-operation to 6 months post-operation as follows: the hyperopic group from 0.28±0.25 logmar to 0.04±0.07 logmar, the emmetropic group from 0.05±0.07 logmar to 0.03± 0.11 logmar, and the myopic group from 0.78±0.27 log- MAR to 0.09±0.08 logmar. The mean binocular NUCVA increased in the hyperopic group from 0.86±0.62 lograd pre-operation to 0.24±0.23 lograd 6 months postoperation, and in the emmetropic group from 0.48±0.14 lograd to 0.18±0.11 lograd. The myopic presbyopes showed a decrease of the mean binocular NUCVA from 0.04±0.19 lograd pre-operation to 0.12±0.18 lograd 6 months after surgery. At 6 months post-operation, the distance efficacy index (ratio between mean postoperative DUCVA versus mean preoperative DBCVA) showed for hyperopes 0.7 monocular and 0.8 binocular, for emmetropes 0.7 monocular and binocular, and for myopes 0.5 monocular and 0.6 binocular. The near efficacy index (ratio between mean postoperatively NUCVA versus mean preoperative NBCVA) counted for hyperopes 0.4 monocular and 0.5 binocular, for emmetropes 0.5 monocular and binocular, for myopes 0.5 monocular and 0.6 binocular (Table 1). Figure 2 show that 100% of the hyperopic patients, 80% of the emmetropic patients, and 70% of the myopic patients, i.e., 83% of all 30 patients, obtained a DUCVA of 0.1 logmar or better. Eighty percent of the hyperopic, 90% of the emmetropic and 80% of the myopic patients reached a NUCVA of 0.3 lograd or better, i.e., 83% of all patients received a sufficient near performance, e.g., for reading regular newspaper and magazine print. Figure 3 represents both the preoperative and the 6- month far and near uncorrected visual acuities. After treatment, the results are located almost only in the lower left corner, which contributes to a spectacle-free daily life for far and near vision with 0.3 or better logmar and lograd. Safety In hyperopic patients, one patient (10%) lost 2 lines, four patients (40%) lost 1 line, five were unchanged to the preoperative level, and no hyperope gained any line in DBCVA. The distribution in emmetropic patients was identical to the hyperopic group. In the myopic patients, one patient (10%) even lost 3 lines, one patient (10%) lost 2 lines, another patient (10%) lost 1 line, six patients remained unchanged, and one even gained a line. Figure 4 displays the monocular and binocular safety information of all eyes and patients. At 6 months, the distance safety index of the three treatment groups showed for hyperopes monocular 0.8 and binocular 0.9, for emmetropes monocular and binocular 0.9, and for myopes monocular and binocular 0.9. The near safety index (ratio between mean postoperative NBCVA versus mean preoperative NBCVA) counted for each of the three groups monocular and binocular 1.0 (Table 1). Accuracy 6 months postoperatively, the mean spherical equivalent for distance refraction for the hyperopes was 0.13±0.61 D (range: 1.50 to D, median 0.06), 0.68±0.42 D (range: 1.50 to D, median 0.63) for the myopic patients, and 0.43±0.35 D (range: 1.38 to 0.00 D, median 0.38) for the emmetropes.

5 Table 1 Summary of the visual indices Eff ind dm Eff ind db Eff ind nm Eff ind nb Safe ind dm Safe ind db Safe ind nm Safe ind nb Hyperopia Emmetropia Myopia All Efficacy index for monocular distance visual acuity (Eff ind dm), for binocular distance visual acuity (Eff ind db), and analogous for near visual acuity (Eff ind nm, Eff ind nb), and for safety (Safe ind dm, Safe ind db, Safe ind nm, Safe ind nb) Fig. 2 Six-month postoperative cumulative uncorrected visual acuities. Top: distance-uncorrected visual acuity. Bottom: near uncorrected visual acuity

6 Fig. 3 Visual acuity. Top: preoperative. Bottom: 6 months postoperative The scattergram in Fig. 5 shows the achieved versus attempted defocus for all treated eyes 1, 3, and 6 months after surgery. The slope of the best-fit line was 0.90 after 1 month and 0.87 after 6 months. The refractive deviation from target of 0.5 D for distance correction was within ±0.5 D in 60% of the hyperopes, 90% of the emmetropes and 70% of the myopes (Fig. 6). Fifty-seven eyes (95%) were within ±1.0 D of spherical equivalent from expected target (Fig. 6). The postoperative astigmatism was 0.41±0.30 D (range: 0.00 to 1.00 D, median 0.50 D) with no relevant difference between the groups. Stability Very stable conditions with regard to spherical equivalent refraction were found, with only a slight myopic shift from a short period after surgery until 6 months postoperatively: the mean defocus refraction of the hyperopic patients changed from 0.09±0.62 D (range: 1.63 to +1.0 D) 1 month after surgery to 0.13±0.61 D (range: 1.5 to +1.0 D) 6 months postoperatively. The myopic patients showed a mean change from 0.58±0.40 D (range: 1.38 to D) 1 month after treatment to 0.68±0.42 D (range: 1.50 to D) 6 months postoperatively. A change from 0.41± 0.51 D (range: 1.25 to 0.38 D) after 1 month to 0.43± 0.35 D (range: 1.38 to 0.00 D) after 6 months was seen in the emmetropic group. Contrast sensitivity There were only marginal differences in logarithmic contrast sensitivity values among the three treatment groups from preoperation to 6 months postoperatively. The mean logarithmic contrast sensitivity was calculated in the hyperopic group

7 Fig. 4 Change in lines for distance-corrected visual acuity for monocular and binocular assessment monocular with 1.82±0.16 preoperatively and 1.69±0.23 postoperatively, binocular with 1.94±0.13 preoperatively and 1.89±0.12 postoperatively. The emmetropic group showed a change in monocular performance from 1.85±0.16 preoperatively to 1.73±0.16 postoperatively, but binocular 1.92±0.09 with no change in preoperative versus postoperative performance. The myopic group received preoperative monocular 1.86±0.16 and postoperative monocular 1.74± 0.22, whereas preoperative binocular 1.95±0.00 compared to 1.89±0.12 at 6 months. In summary, all 60 eyes/30 patients performed preoperative monocular with 1.85±0.16 and binocular with 1.94±0.09 but postoperative monocular 1.72± 0.20 and binocular 1.90±0.11. The postoperative monocular performance was significantly reduced in all groups, whereas binocular values were comparable to preoperative ones. Higher-order aberrations As intended and expected, both the fourth-order and the sixth-order spherical aberration were significantly different Fig. 5 Scattergram for defocus. All eyes for 1 month, 3 months and 6 months

8 Discussion Fig. 6 6-month refractive deviation from target for distance correction to preoperative levels. Neither unwanted third-order trefoil nor coma terms were significantly changed preoperatively to 6 months postoperatively. The changes of third-order aberrations and spherical aberration terms are documented in detail in Table 2. A shift from a preoperative mean value of 0.38±0.11 D to -0.28±0.36 D of multifocality 6 months postoperatively was observed, while an addition of 1.87± 0.51 (range: 0.75 to 2.50 D) had been planned. The intended induction and shift of spherical aberration into negative direction can be obviously seen (Table 3). Root-mean-square (RMS) for higher order aberrations (HOA) showed the following changes: the preoperative mean of 0.42±0.12 μm at 6 mm analysis diameter remained almost constant with 0.47±0.15 μm at 6 months (Table 2). The top of Fig. 7 represents the impact of the amount of distance-corrected refractive error on the patient s multifocality, i.e., the spherical aberration expressed in dioptres. It is seen that with the software version used in this study, a hyperopic defocus preoperative goes along with some extra amount of negative spherical aberration post-surgery. Thus, unintentionally, the preoperative hyperope typically had some extra multifocality induced postoperatively, whereas patients with myopic defocus preoperatively behaved vice versa. The bottom of Fig. 7 displays the part of patient s multifocality that was achieved based on the addition that was entered to the treatment plan. The top and bottom graphics together result in the patient`s postoperative multifocality. It appears that the concept and the ablation profile have room to improve. At 6 months, the majority of patients were undercorrected in terms of the planned multifocality, i.e., the achieved multifocality was usually less than attempted. The near performance was especially supported by the distance aim of 0.50 D, which in individual eyes reached up to 1.50 D. Presbyopia (Greek word presbys (πρέσβυς), meaning old man, or elder, with Latin root -opia, meaning eye ) describes the condition where the eye exhibits a progressively diminished ability to focus on near objects with age. Although the ability to focus on near objects declines throughout life, the first symptoms are usually noticed between the ages of 40 and 50. Accommodation decreases from 5 diopter (ability to focus at 20 cm) to 2 diopter (ability to focus at 50 cm) in only 10 years, deteriorating near vision. When we are looking at a near object, the so-called near trias (convergence, miosis, and accommodation) occurs. Presbyopia is the loss of accommodation; however, the reflex of convergence and miosis are still functional [21, 22]. As presbyopia cannot yet be cured, there is no option to restore physiological dynamic accommodation, but the symptoms associated with it can be reduced. The methods most commonly used are reading glasses or bifocals or multifocal lenses, and refractive surgery with multifocal intraocular lens (MIOL) implantation. The use of contact lenses (or glasses) to correct one eye for near and one eye for far is called monovision (which can interfere with depth perception due to loss of focusing ability in the other eye). Also, LASIK is used especially in myopes to create a monovision [4, 5]. Different MIOL are also able to improve the uncorrected visual acuity in far and near distance, but contrast sensitivity is reduced [1, 2, 23]. The main goal of a surgical procedure to correct presbyopia is to enhance not only distance but also near visual acuity and the range of relatively clear vision. The first ablation to induce a multifocal cornea was performed in 1992, and since then various methods have been established [24]. The PresbyMAX software creates a multifocal corneal surface to reduce spectacle dependence for near and far vision. The centre of the cornea is purposefully corrected for near, and the pericentral region is corrected for distance. Thinking about the near trias with induction of miosis, it is consequent to create a near zone in the corneal centre. We want to clarify the use of the term multifocality in this context. Here spherical aberration and multifocality are considered synonymous wanted effects sought as a compensation for presbyopia (in a continuous progressive manner), and should not be mixed up with a stepwise multifocality generally termed bifocality, tri-focality used in reading spectacles or IOLs. Bifocal and multifocal techniques are simultaneous vision techniques that enhance the depth of focus. During the average lifetime, there is a near linear reduction in accommodation up to approximately 50 years of age, a reduction in pupil size, and a shift in the general pattern of ocular spherical aberration. The contribution of the negative

9 Table 2 Changes of third-order aberrations and spherical aberration terms (in μm) determined from the Corneal Wavefront Analyzer at 6 mm diameter C[3,-3] C[3,-1] C[3,+1] C[3,+3] C[4,0] C[6,0] RMS(HOA) Hyperopia Preop Median Mean ± SD 0.15± ± ± ± ± ± ±0.11 Range 0.40 to to to to to to to months Median Mean ± SD 0.06± ± ± ± ± ± ±0.18 Range 0.30 to to to to to to to 1.07 Emmetropia Preop Median Mean ± SD 0.08± ± ± ± ± ± ±0.07 Range 0.19 to to to to to to to months Median Mean ± SD 0.02± ± ± ± ± ± ±0.12 Range 0.20 to to to to to to to 0.65 Myopia Preop Median Mean ± SD 0.16± ± ± ± ± ± ±0.15 Range 0.44 to to to to to to to months Median Mean ± SD 0.08± ± ± ± ± ± ±0.11 Range 0.32 to to to to to to to 0.73 All Preop Median Mean ± SD 0.13± ± ± ± ± ± ±0.12 Range 0.44 to to to to to to to months Median Mean ± SD 0.05± ± ± ± ± ± ±0.15 Range 0.32 to to to to to to to 1.07 spherical aberration effect is described in different publications [25 29]. Pupil constriction, and in some individuals, the change in ocular spherical aberration will enhance the depth of focus of the eye, and offer some relief from the deficiencies in near vision due to the loss of accommodation [30 32]. Bifocal and multifocal surgical techniques tend to enhance these natural phenomena aimed at treating presbyopia [33]. It is the intention of the PresbyMAX profiles to induce negative spherical aberrations to a certain amount. This was achieved in the majority of eyes in our study, whereas the RMS of the higher order aberrations (HOA) showed a non-significant change from 0.42±0.12 μm preoperatively to 0.47±0.15 μm at 6 months postoperatively. Thus, the intention to change spherical aberration terms only without the induction of further higher order aberrations worked well in our study. In our clinical evaluation, we saw results with regard to the improvement of NUCVA and DUCVA comparable to other studies [18, 19, 33, 34]. The most satisfied group objectively and subjectively tested was the hyperopic one. From the patients point of view, this result is explained by reaching a level close to emmetropia after treatment, so that uncorrected distance and near vision increases. All patients are completely spectaclefree in daily life in this group. Causatively, we have to remember the age of our patients which was 53.90± 8.47 years in the hyperopic group, so apparently some physiological accommodation is still available as a reason for improved near visual acuity. Also, a slight overcorrection towards myopia, which is seen in some cases, should be responsible for improved near performance apart from central steepening. The hyperopic group showed also the best results with regard to the achieved multifocality. Over the period of 6 months, only a slight regression was noticed with regard to this achieved multifocality. Nonetheless, a longer follow-up should be considered for a final statement. Surprisingly, the NDCVA did not show a real change after the treatment of hyperopic presbyopia by the PresbyMAX ablation profile, but NUCVA increased in all cases, resulting in high satisfaction levels in our hyperopic study patients. With D additionally planned for distance refraction in hyperopes, or favouring the full cycloplegic refraction over the manifest refraction that was used in this study, the uncorrected visual performance for both distance and near could be even better. As we know from standard LASIK, the centration on the vertex, i.e., the patient s visual axis, is

10 Table 3 Planned addition vs achieved multifocality in dioptres. Achieved multifocality was obtained from the radial symmetric terms of the Corneal Wavefront Analyzer at 6 mm diameter PreOP 3 months 6 months Hyperopia Planned add (D) Median 1.75 Mean ± SD 1.82±0.56 Range 0.75 to 2.50 Multifocality (D) Median Mean ± SD 0.38± ± ±0.32 Range 0.22 to to to 0.08 Emmetropia Planned add (D) Median 1.88 Mean ± SD 1.95±0.52 Range 1.25 to 2.50 Multifocality (D) Median Mean ± SD 0.34± ± ±0.32 Range 0.17 to to to 0.05 Myopia Planned add (D) Median 1.75 Mean ± SD 1.83±0.47 Range 1.00 to 2.50 Multifocality (D) Median Mean ± SD 0.40± ± ±0.27 Range 0.15 to to to 0.49 All Planned add (D) Median 1.75 Mean ± SD 1.87±0.51 Range 0.75 to 2.50 Multifocality (D) Median Mean ± SD 0.38± ± ±0.36 Range 0.15 to to to 0.49 considered crucial, especially in hyperopes [35 38]. The induction of coma-like aberrations is less when vertex centration is taken into account. In the myopic group, the mean patient age was 51.00± 3.84 years. Most of the patients of the myopic group still described spectacle dependency in different situations in daily life 6 months postoperatively. This can be explained on one hand by a decreased NUCVA due to the correction of the myopic refractive error for far distance. On the other hand, the postoperative DUCVA increased but did not reach preoperative levels with best-corrected glasses or contact lenses. Myopic patients are typically used to high visual acuities for reading with near focus point close in front of the eye. In our study the NUCVA was still satisfactory for daily life, but higher demands in both distance and near vision resulted in situations where myopes still prefer spectacles. The myopic group showed on average less corneal multifocality than the hyperopic group. The reason for this can be explained by an aberration-free ablation profile which still induces a certain amount of unwanted (positive) spherical aberration based on the amount of myopic far distance refraction to be corrected. The patients that belong to the emmetropic group improved in DUCVA and also in NUCVA. With correction of the slight refractive errors for far distance that did not demand spectacles or disturb the patient before, postoperative DUCVA was equal to or even better than it was preoperative. The effect of the presbyopia treatment led to an increased NUCVA, although in most cases the attempted multifocality could not be fully reached. An ablation profile which is even closer to an aberration-neutral performance than today should be of benefit, especially for the achieved multifocality (in myopic refraction types), so that the attempted change into negative spherical aberration will not be compensated in part (or even total) by positive spherical aberration due to the ablation of a myopic refraction. Far vision is affected by the presenceofthecentral hyperpositive area when pupil miosis occurs [39]. The loss of lines for the DBCVA in some patients may be correlated to the light-distribution concept of the Presby- MAX software, which leads to a division of the light for near of 35 to 40%, for intermediate of 15%, and for far distance of 45 to 50%. The PresbyMAX concept is definitely pupil-dependent, so a further effect could be a pupil size which is closer to photopic light condition (e.g., 40 lux) during the measurement process of DBCVA rather than to mesopic low (e.g., 0.4 lux). In individual cases, a significant induction of asymmetrical aberrations or too much multifocality on the cornea with compromise in

11 Fig. 7 Multivariate analysis of the 6-month postoperative achieved multifocality (D). Top: achieved multifocality (D) correlated to planned spherical equivalent (D). Bottom: achieved multifocality (D) correlated to addition (D). Achieved multifocality was obtained from the radial symmetric terms of the Corneal Wavefront Analyzer at 6 mm diameter contrast sensitivity could reduce DBCVA. The time of adaptation to the multifocal cornea and the amount of spherical aberration that was induced might play a role in individuals too. Multifocal contact and intraocular lenses have been studied extensively for achieving dependence in presbyopia and pseudophakia. Refractive or diffractive principles increase the depth of focus and reduce contrast sensitivity [39]. As for ablative approaches [40], several theoretical studies have been published [41, 42]. They suggest that presbyopia can be corrected by creating asphericity in the optical path of the eye. In most cases, it is possible to obtain an optical surface that will optically compensate for presbyopia. The main requirement will normally be for extended binocular depth-of-focus to yield adequate distance and near vision with good retinal contrast at lower spatial frequencies, rather than the highest levels of acuity and modulation transfer function at a single distance. The targeted correction of wavefront aberrations should take into account the visual needs and preferences of the individual patient. Central presbylasik seems the most widely applied approach nowadays [18, 33, 43, 44]. Literature reports improvements in distance- and near-uncorrected visual acuities, with some decrease in contrast sensitivity associated with the increase in high-order aberration coma and negative induction of spherical aberration. Peripheral presbylasik has become some credit especially for myopic treatments [17, 24, 40, 45, 46]. Reports also show decreasing contrast sensitivity and increase in high-order aberration. Paradoxically, a negative induction of spherical aberration (suggesting central myopia) is commonly reported [47]. Peripheral presbylasik seems to have higher acceptance in myopic patients [24, 46]. The rationale of peripheral presbylasik is the target of central emmetropia with peripheral myopia, which is a conceptual description of induced positive spherical aberration. Myopic LASIK tends to induce positive spherical aberration. So it seems logical to take benefit of this induction and creating central emmetropia. Monovision is probably the oldest approach, yet still in use; the references report successful rates between 86% and 96% [4, 5, 15, 48 50]. Laser blended vision is the combination of monovision and modulation of the spherical aberration [51, 52]. 95% to

12 99% of patients achieved binocular uncorrected visual acuity of 20/20 and J5, but with a 22% retreatment rate. Other investigated approaches include semi-lunar inferior steepening (induction of negative vertical coma) [53], or residual myopic astigmatism [54]. With an increase of HOA, especially spherical aberrations, we expected a relevant decrease in contrast sensitivity. But the Pelli Robson Contrast Sensitivity Test that was used in this study showed in most of the patients, independent of patient group, very similar binocular outcomes preoperatively to 6 months postoperatively. An automated and more standardised contrast sensitivity device with defined environmental light conditions and intensities would probably be more reliable and highly accepted, but would not have been available at the time of the study. It was not our attempt to quantify contrast sensitivity on an absolute scale rather than comparing changes in contrast after treatment. In comparison to other surgical presbyopic treatments like the refractive lens exchange with MIOL, corneal multifocal surgery has the major advantage of being a less invasive technique, with decreased risk of severe complications, and with the possibility of additional correction of higher-order aberrations. The PresbyMAX method uses bi-aspheric multifocal ablation profiles which can be combined with the correction of low or moderate ametropia. Experience in higher diopters (more than ±4 diopters) is not given at this stage because it was not part of our study design. A target myopia of 0.50 D for far distance, in combination with the induction of spherical aberration on the cornea, creates a central steepening associated with increased pseudoaccommodation. Thus, two factors that help to improve near-vision performance. Reflecting our experience and 6-month outcomes, PresbyMAX seems to be an efficient, safe and stable technique. Nonetheless, the adaptation to the new visual impression takes a while. Near performance was very good from day one after surgery, but the distance vision improved slowly. Patients were usually satisfied with distance vision at the 3-month check-up, but satisfaction levels improved even further at 6 months. Retreatments have not been performed while preparing this publication, but due to the refractive outcome, four to six eyes out of 60 may require optimisation for the patient s real satisfaction. In general, retreatment rates two to three times higher than in regular LASIK cases should be considered as normal. The tighter the patient selection criteria, the closer the retreatment levels to regular LASIK procedures could be. 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