Wavefront-Optimized Technology in Hyperopic Correction Stability Using Different Optical Zones

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1 Med. J. Cairo Univ., Vol. 78, No. 1, December , Wavefront-Optimized Technology in Hyperopic Correction Stability Using Different Optical Zones ADNAN M.H. AL-MARZOUKI, F.R.C.S.C. The Department of Ophthalmology, King Abdul Aziz University, Jeddah, Saudi Arabia Abstract Purpose: To follow-up the visual and refractive outcomes of laser in situ keratomileusis (LASIK) to correct hyperopia using Wavelight Allegretto Wave since Setting: Eye Care Private One-Surgery Centre, Jeddah, Saudi Arabia. Methods: This retrospective study comprised 50 eyes of high hyperopia patients having spherical equivalence of +4.0 diopters (D) or more, treated with LASIK Wavelight Allegretto Wave. Outcomes are evaluated over follow-up visits. Patients underwent retreatment are excluded form this registry. Results: The mean patient age was ± 11.4 years. Fifty eyes were evaluated and followed-up over duration 56.76±8.62 weeks. No eye was retreated during the study. The mean manifest refraction spherical equivalent was +4.97±0.92 D preoperatively and ±0.47 D postoperatively. Fifty percent of eyes are within ±0.5 D while 94% were within ± 1.0 D The preoperative best corrected visual acuity ranged decimal scale (20/30-20/20 Snellen) and postoperative uncorrected visual acuity ranged decimal scale (20/30-20/20 Snellen). Conclusion: This registry had shown overall success in correcting high hyperopia using Allegretto Wavefront- Optimized Technology. The optical zone of 7.0 D of Wavefront optimized technology is providing better efficacy and stability in hyperopic patients especially after the age 45 years. Key Words: LASIK Hyperopic correction stability Different optical zones. Introduction IN 2003 LASIK Wavelight Allegretto Wave got the US FDA approval to be marketed in US. The device modified to be marketed under the trade name ALLEGRETTO WAVE EYE-Q Excimer Correspondence to: Dr. Adnan M.H. Al-Marzouki, The Department of Ophthalmology, King Abdul Aziz University, Jeddah, Saudi Arabia. Laser System and is indicated for laser assisted in situ keratomileusis (LASIK) for: (1) for reduction or elimination of hyperopic refractive errors up to +6.0 diopters (D) of sphere with and without astigmatism refractive errors up to 5.0 D at the spectacle plane, with maximum manifest refraction spherical equivalence (MRSE) +6.0 D, (2) in patients who are 18 years age or older; and 3) In patients with documentation of stable manifest refraction defined as 0.5 D of preoperative spherical equivalent shift over one year prior to surgery, exclusive of changes due to unmasking latent hyperopia [1-4]. This new technology is thought to have the potential to provide better postoperative quality of vision in patients, especially in contrast sensitive conditions such as scotopic and mesopic vision, than older conventional excimer laser technology or wavefront-guided technologies. With the technological discovery of wavefrontoptimized technology, ophthalmologists were able to quantify and potentially treat ocular higher order aberrations (HOAs) by excimer laser surgery [3]. Hence, the concept of wavefront-optimized ablation should improve the image quality, improving patients visual acuity, as can be observed with adaptive optics [1-4]. Material and Methods A retrospective nonrandomized patient retrieval has been done identifying 50 eyes of 25 patients received wavefront-optimized LASIK. Inclusion criteria: The age should lie between years old. Patient should show stable status of hyperopia. Our routine policy is to treat patients with hyperopia with appropriate spectacle correction and to assess their visual acuity VA at followup visits at least six month apart. 559

2 560 Wavefront-Optimized Technology in Hyperopic Correction Stability Surgical procedure: The laser operated at a 200 khz treatment rate with fast correction rate 4 seconds per diopter. The spot size was 0.68mm (FWHM), with Gaussian beam profile. The Wavefront-optimized excimer laser treatment with the Wavefront OptimizedTM refractive treatments (WaveLight Standard) [4-6]. The optical zone was set to the following values 6.5 or 7.0. The Moria M2 had been used with the following settings (single 90µ head)110µ flab [1-3]. Postoperatively, patients were instructed to instil gatifloxacin 4 times daily for 7 days and prednisolone acetate 1%, 4 times daily for 7 days. Statistical analysis: Statistical package used was NCSS version, Kaysville, Utah, United States, released April 2008 running on Widows Vista. Statistical significance was calculated using the Student t-test (p<0.05). Data are expressed as means ± standard deviation and ranges. Correlations were calculated using linear regression model. Difference in paired continuous variables is calculated and tested using two-side paired t-test. Graphical package used is Sigmaplot windows version 11.0, San Jose, California, United States. Results 25 patients were eligible with 50 eyes. Recorded patients mean age was 37.4 ± years. The mean manifested preoperative spherical equivalence is +4.97±0.92 (range D). The optical zones used are 6.5 and 7.0mm. Patients baseline best corrected visual acuity BCVA is 0.89 ±0.11 (range ) decimal scale (20/30-20/20 Snellen Scale). The follow-up period was ±8.62 weeks (range weeks). During the follow-up period the recorded spherical equivalence was ± 0.47 D while the uncorrected visual acuity UCVA was 0.89±0.11 (range ) decimal scale (20/30-20/20 Snellen Scale). Fig. (1) is illustrating the linear regression between preoperative BCVA and postoperative UCVA. The analyses suggested the following model: Postoperative UCVA= (0.783 *preoperative BCVA) where the regression coefficient was (p-value <0.001). The resulted difference in spherical equivalence SPE was 4.32 ±0.75 D (p-value <0.001) using 2-sided paired t-test. Fig. (2) is showing the postoperative correction where 50% of eyes are within ±0.5 D and 49% of eyes ± 1.0 D. Fig. (3), is illustrating the relationship among the difference in SPE, optical zones and observation period. From the graph the SPE stability can be pointed out after week 50 of follow-up with optical zone 7.0mm. Upon comparing the SPE profile of optical zone 6.5mm with optical zone 7.0mm during the period after week 50, the optical zone 7.0mm had more plantar profile ranging from 4.0 to 3.0mm. Fig. (4), is profiling the relationship of patients age during the operation and the change in the SPE during the follow-up period. Although the relationship profile is complex however the inner corner of the graph is showing more stable SPE performance. This inner corner is located at the age of 45 years and above crosscutting week 55 and above. In this corner the SPE change is lying between 3.0 to 2.0 D Visual Acuity (Decimal Scale) 3 Spherical Equivalence Postop UCVA Acheived Preop BCVA Attempted Fig. (1) Fig. (2)

3 Adnan M.H. Al-Marzouki 561 Fig. (3) Fig. (4) Discussion The routine pre-operational comprehensive ophthalmologic examination includes: Visual acuity with and without correction: Although best-corrected VA (BCVA) is typically determined in any comprehensive eye examination. Pupil examination with documentation of scotopic pupil size: Because increasing pupil size may be correlated with increased postoperative vision disturbances as haloes and glare [5-7]. Ocular motility and alignment assessment: An unrecognized, minor strabismus controlled with a prism in glasses can be associated with an exacerbation of diplopic symptoms after LASIK surgery. Refractions both manifest and cycloplegic conditions should be examined where the difference should be+1.00 D or less: Patients should also have no amblyopia. Slit-lamp biomicroscopy with careful attention to the cornea, anterior chamber depth, and lens: Because patients who undergo LASIK for hyperopia are, on average, older than their myopic counterparts, the presence of cataracts may be more likely. Anatomically narrow angles may be more frequent because of hyperopia and older age. Examination of the cornea is intended to detect any pathology that may represent a contraindication to LASIK. Patients with anterior basement membrane dystrophy have an increased risk of epithelial sloughing at the time of surgery and later epithelial in-growth and diffuse lamellar keratitis, which may be an indication for photorefractive keratectomy rather than LASIK [8,9]. Significant blepharitis should be treated preoperatively to decrease the risks of infection and interface inflammation after surgery. The ocular surface should be evaluated carefully before surgery, and patients should be warned about the potential postoperative development or exacerbation of dry eye symptoms [5,9-10]. Fundus examination: Although retinal detachments are less common in the hyperopic patient group than in myopic patients, the retina should be evaluated before any LASIK procedure. Corneal topography: Corneal topography measurement to assess corneal shape is a critical feature of the pre-lasik evaluation. It can detect irregular astigmatism, whether from contact lens warpage or from other causes, which, if significant, is a contraindication to spherocylindrical LASIK. Additionally, corneal topography is used to screen for keratoconus or asymmetrical steepening, which may be associated with unpredictable refractive outcomes and progressive ectasia after LASIK [11]. Inferior corneal steepening, sometimes designated as forme fruste keratoconus, is a frequent finding in corneas that appear normal on slit-lamp biomicroscopy. Mathematical indices to detect subtle keratoconus topographically have been developed [12]. Flat corneas are important to note preoperatively, because they are associated with small microkeratome flaps and free caps, and steep corneas are associated with flap buttonholes [13]. Corneal topography is also useful in predicting the final keratometry after refractive surgery. Central keratometry steeper than 49 to 50 D after LASIK may be associated with a decrease in quality of vision. Corneal pachymetry: Although the depth of the ablation is a rare problem in hyperopic patients, normal corneas may be as thin as 450mm centrally. In these thin corneas it may be unsafe to make a corneal flap.

4 562 Wavefront-Optimized Technology in Hyperopic Correction Stability Since the evolution of Allegretto Wave Light device, the manufacturer had claimed. 1- The Gaussian beam profile ensures a smooth ablation without grooves or ridges, while the tiny 0.68mm (FWHM) spot size provides a precise ablation of corneal tissue and very small transition zones. 2- The beam path is completely sealed and flushed with nitrogen. This prevents the creation of ozone and leads to perfect and constant laser beam supply at the cornea. We started to use this device in our centre since This experience is facilitating long-term assessment of this device [1,14]. Efficacy: SPE had been reduced by average 4.32 ±0.75 D which represents a substantial percentage of the baseline SPE which was +4.97±0.92 D. This confirms the efficacy of the device where 90% of the corrected SPE were within ± 1.0 D. Outcome stability: The stability in hyperopic patients is multifactorial [15-17]. A lot of precautions should be considered before taking the decision of doing any correction. The collected data in this registry enables the assessment of stability based on the optical zone utilized during correction. The device model utilized can be configured on right optical zone 5.5, 6, 6.5, 7 and 7.5mm where fractional configuration of optical zones are not present. In the included patients the optical zones of choice were 6.5 and 7mm. Results had shown that the use of 7D is more stable than 6.5 generally and more specifically after the week 50 of observation as it is present in both Figs. (3,4). Upon correlating the stability as well with age, the collected data had shown that patients doing correction after the age 45 years are stable compared to younger ones. Although the impact of age is phenomenal feature of hyperopic patients but the device is required to be tested also for this parameter. Safety: In all our retrieved data, no single case had been reported with any adverse event for either the device or the peri-operative medication. During the course of this registry we encountered two drawbacks which are: Patients are not complying with the follow-up schedule and no control group since only one device is present in the centre. Conclusion: This registry had shown overall success in correcting high hyperopia using Allegretto Wavefront- Optimized Technology. The optical zone of 7.0m of Wavefront optimized technology is providing better efficacy and stability in hyperopic patients especially after the age 45 years. References 1- United States Food and Drug Administration, Wave Light ALLEGRETTO WAVETM Excimer Laser System- P From website [ eviceapprovalsandclearances/recently-approveddevices/ucm htm]. Accessed 25 May, Wave Light Laser Technologie AG, Allegretto Wave Scanning Spot LASlK Laser System Procedure Manual Information for professional use. Procedure Manual 1008 Rev 13-Myopia, July, page 13-4, United States Food and Drug Administration, April 2007 PMA Approvals. From website [ MedicalDevices/ProductsandMedicalProcedures/Device- ApprovalsandClearances/PMAApprovals/ucm htm]. Accessed 25 May, OSHIKA T., KLYCE S.D., APPLEGATE R.A., et al.: Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis. Am. J. Ophthalmol., 127: 1-7, VARLEY G.A., HUANG D., RAPUANO C.J., SCHALL- HORN S., BOXER WACHLER B.S. and SUGAR A.: Ophthalmic Technology Assessment Committee Refractive Surgery Panel, Ameican Academy of Ophthalmology. LASIK for hyperopia, hyperopic astigmatism, and mixed astigmatism: A report by the American Academy of Ophthalmology. Ophthalmology. Aug, 111 (8): , Pub. Med. PMID.: POP M. and PAYETTE Y.: Risk factors for night vision complaints after LASIK for myopia. Ophthalmology, 111: 3-10, KLYCE S.D.: Night vision after LASIK: The pupil proclaims innocence. Ophthalmology, 111: 1-2, STULTING R.D., CARR J.D., THOMPSON K.P., et al.: Complications of laser in situ keratomileusis for the correction of myopia. Ophthalmology, 106: 13-20, WILSON S.E.: Laser in situ keratomileusis-induced (presumed) neurotrophic epitheliopathy. Ophthalmology, 108: , YU E.Y., LEUNG A., RAO S. and LAM D. S.: Effect of laser in situ keratomileusis on tear stability. Ophthalmology, 107: , AMOILS S.P., DEIST M.B., GOUS P. and AMOILS P.M.: Iatrogenic keratectasia after laser in situ keratomileusis for less than 4.0 to 7.0 diopters of myopia. J. Cataract. Refract. Surg., 26: , RABINOWITZ Y.S. and RASHEED K.: KISA% index: A quantitative videokeratography algorithm embodying minimal topographic criteria for diagnosing keratoconus. J. Cataract. Refract. Surg., 25: , 1999.

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