Excimer Laser Photorefractive Keratectomy Research Articles

Excimer laser keratectomy for hyperopia in special needs children: longer-term outcomes

We report the results of excimer laser photorefractive keratectomy (PRK) for hyperopia in special needs children who are intolerant of spectacle wear or contact lenses.

Visual acuity, refractive error, and regression outcomes in 169 children with high myopia who were implanted with Ophtec-Artisan or Visian phakic IOLs

To analyze outcomes in a large cohort of spectacle-aversive children with high myopia who were treated by implantation of the Ophtec-Artisan or Visian phakic intraocular lens (pIOL). Outcome data were collated retrospectively in 78 children (115 eyes) implanted with the Ophtec-Artisan iris-enclaved anterior chamber pIOL and 91 children (154 eyes) implanted with the Visian ICL (intraocular collamer lens) sulcus pIOL. All children had difficulties with spectacle or contact lens wear. Mean age at surgery was 9.9years; mean follow-up was 3.9years (range, 0.6-14.1years). A total of 248 of 269 eyes (92%) were corrected to within ± 0.5 D of their target value. Spherical correction averaged 12.3±1.0 D. Refractive spherical regression was -0.04 D/year at last follow-up. Uncorrected distance visual acuity improved from an average logMAR 1.8 to 0.4; corrected distance visual acuity improved an average 0.3 logMAR. Of the treated children, 68% had a gain in binocular fusion. Neurobehavioral and/or visuomotor comorbidities were present in 87% of children. Five eyes (2%) developed retinal detachment an average 6years after implantation. Nine eyes (3%) implanted with the Ophtec-Artisan pIOL required repositioning after trauma. Implantation of pIOLs in children is an effective method for correcting high myopia in spectacle noncompliant children. Rates of myopic regression after pIOL surgery are substantially lower than those reported for children treated by excimer laser photorefractive keratectomy (PRK). The prevalence of major complications was relatively low in this high-risk population.

Intraocular Lens Power Calculations in Eyes with Previous Corneal Refractive Surgery: Review and Expert Opinion

Intraocular lens (IOL) power calculations are less accurate in eyes that have undergone corneal refractive surgery. A wide range of methods have been proposed. We reviewed the methods and outcomes of IOL power calculations in eyes with previous LASIK, excimer laser photorefractive keratectomy (PRK), or radial keratotomy (RK). The PubMed database was searched for articles that (1) discuss methods and outcomes of IOL power calculation in eyes with previous corneal refractive surgery and (2) evaluate the outcomes of toric, multifocal, or extended depth-of-focus (EDOF) IOLs in these eyes. We excluded review articles, case reports or case studies, and non-English reports. Seventy full-text articles were included in this review. Three categories of methods exist based on whether and how they use historical data acquired before the corneal refractive surgery. The American Society of Cataract and Refractive Surgery (ASCRS) postrefractive IOL calculator incorporates many commonly used methods. In eyes with previous myopic LASIK or PRK, hyperopic LASIK or PRK, and RK, 0% to 85%, 38.1% to 71.9%, and 29% to 87.5% of eyes, respectively, showed refractive prediction errors within ±0.5 diopter (D); in eyes with toric IOL implantation that met certain inclusion criteria, 80%, 84%, and 69% of eyes, respectively, achieved postoperative astigmatism of 0.50 D or less. Intraocular lenses with negative spherical aberration (SA) will reduce the positive corneal spherical aberration induced in eyes by myopic LASIK or PRK or by RK. Intraocular lenses with 0 SA on average best match corneal SA in eyes with prior hyperopic LASIK or PRK. Studies have reported excellent outcomes of postrefractive eyes implanted with multifocal or EDOF IOLs; however, corneal topographic enrollment criteria were not specified. Despite availability of new measurement technologies and development of new IOL calculation formulas, further advances are needed to improve outcomes of cataract surgery in eyes that have undergone corneal refractive surgery. Tools like the ASCRS postrefractive IOL calculator are useful for the clinician by incorporating a variety of formulas. Toric, EDOF, and multifocal IOLs may provideexcellent outcomes in selected cases that meet certain corneal topographic criteria.

Intraoperative optical pachymetry in photorefractive keratectomy

Tostudy the effect of variables on the accuracy and reliability of the optical pachymeter built into the WaveLight EX500 excimer laser during photorefractive keratectomy (PRK). John A. Moran Eye Center, University of Utah, Salt Lake City, USA. Retrospective case series. A chart review of 352 eyes (181 patients) that had excimer laser PRK was performed. Programmed excimer laser residual stromal bed (RSB) measurements, optical pachymeter measurements after ablation, and Scheimpflug pachymetry measurements (Pentacam) at the 1-year follow-up were compared. Variables included ablation time, preoperative spherical equivalent (SE), 1-year SE, mitomycin-C use, operating room temperature and humidity, and programmed monovision. The mean programmed RSB was 27μm greater than the optical pachymetry post-ablation measurement (P<.001). Of patients with a 1-year follow-up, the 1-year Scheimpflug pachymetry RSB was 24μm greater than the optical pachymetry post-ablation RSB (P<.001). Comparison of the programmed RSB with the optical pachymetry post-ablation RSB showed that the preoperative SE and ablation time had a Pearson correlation coefficient of -0.36 and 0.30, respectively (P<.001). There was no correlation between operating room temperature, humidity, or programmed monovision with these differences. The RSB post-ablation values measured by optical pachymetry during PRK were significantly lower than the programmed excimer laser RSB value and 1-year Scheimpflug pachymetry RSB value. Intraoperative pachymetry during PRK underpredicted the actual long-term RSB thickness. The greater temporary drying effect associated with increased ablation time in higher myopic corrections might have caused this error.

Intraocular lens power calculations in eyes with previous hyperopic laser in situ keratomileusis or photorefractive keratectomy

To evaluate the accuracy of 7 intraocular lens (IOL) calculation formulas in patients with previous hyperopic laser in situ keratomileusis (LASIK) or excimer laser photorefractive keratectomy (PRK). Retrospective case series. Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, and private practice, Mesa, Arizona, USA. The 7 formulas evaluated were the adjusted Atlas 0-3, Masket, Modified Masket, Haigis-L, Shammas-PL, Barrett True-K, and Barrett True-K No-History. The Masket and Modified Masket were calculated using the single-K version of Holladay 1 and Hoffer Q formulas; the adjusted Atlas 0-3 was calculated using the double-K version of Holladay 1 and Hoffer Q. The IOL power predicted by each formula was calculated by targeting the postoperative manifest refraction. The IOL prediction error was obtained by subtracting the predicted IOL power from the implanted IOL power. The mean IOL prediction error, median absolute refractive prediction error, and percentages of eyes within ±0.50 diopter (D) and ±1.00 D of the predicted refraction were calculated. Twenty-one eyes of 21 patients were evaluated. There were no significant differences in the median absolute refractive prediction error or percentages of eyes within ±0.50 D or ±1.00 D of the predicted refraction between formulas or methods. The IOL mean prediction errors were comparable between the Holladay 1 and Hoffer Q calculations for all formulas except for a greater error for the double-K version of the Hoffer Q of the adjusted Atlas 0-3. In eyes that had hyperopic LASIK or PRK, there were no significant differences in the accuracy between the 7 IOL calculation formulas.

Visual performance after excimer laser photorefractive keratectomy for high myopia.

PURPOSE:To evaluate the efficacy, safety, predictability, and visual performance of excimer laser photorefractive keratectomy (PRK) for myopia greater than −8 diopters (D).METHODS:Fifty-four patients (104 eyes) with myopia from −8D to −13D and cylinder up to −4D received surface ablation technique with the Allegretto wave version 1009-1 excimer laser to correct their refractive error. The patients were examined on days 1, 3, 7, and 14 and 1, 3, 6, and 12 months postoperatively. Visual acuity, manifest refraction, corneal haze, topography, intraocular pressure, contrast sensitivity, and wavefront aberration were evaluated.RESULTS:Twelve months postoperatively, 95% of eyes were within 1D of the intended correction. In addition, 94% of eyes had attained uncorrected distance visual acuity of 20/25 or better, and 98% of eyes had improved or remained their corrected distance visual acuity. All eyes exhibited barely detectable corneal haze which peaked during the 1st month with a gradual reduction in the 3rd month. Ninety-five percent of patients had no or only mild degree of night glare.CONCLUSIONS:Excimer laser PRK is an effective and predictive treatment for high myopia greater than −8D with or without astigmatism up to −4D. The incidence of complication is low. All patients who are candidates for laser in situ keratomileusis can be candidates for surface ablation, especially those with preoperative thinner cornea or higher risk of corneal flap complications.

Importance of rational drug use after corneal refractive surgery

Safety, efficacy and predictability of corneal refractive surgery have greatly improved as the advancement of the operating technology and equipment.Laser corneal refractive surgeries include excimer laser photorefractive keratectomy (PRK), laser-assisted subepithelial keratomileusis (LASEK), laser in situ keratomileusis (LASIK) and small incision lenticule extraction (SMILE). No matter what kind of operation method, its ultimate goal is to increase the comfort level and improve visual quality.With the surgery skills improving, retinal drug use is a primary factor affecting the safety of laser corneal refractive surgery.Ophthalmologists should strictly master indications and administration of commonly used drugs in postoperative eyes to prevent drug-related eye diseases.In addition, eye doctors also should understand the postoperative complications and topical administration of eye drops.It is important to pay attention to the standard surgical operation and rational drug use after corneal refractive surgery, which can enhance the visual quality and comfort and reduce the complication. Key words: Refraction, ocular/surgery; Lasers, excimer/therapeutic use; Postoperative complications; Ophthalmic solutions/administration d Ophthalmic solutions/adverse effects; Postoperative period; Administration, topical

Higher incidence of steroid-induced ocular hypertension in keratoconus.

BackgroundTo compare intraocular pressure (IOP) changes following topical dexamethasone administration for 1 month in keratoconic versus normal eyes.MethodsThis is a retrospective, single-center, non-randomized case series evaluation of 350 eyes. Two groups were formed: normal/control Group A (nA =73), eyes that underwent excimer laser photorefractive keratectomy; and keratoconic (KCN) Group B (nB =277), eyes that were subjected to partial laser photorefractive keratectomy combined with collagen cross-linking (The Athens Protocol). All eyes received the same post-operative regimen of topical dexamethasone 0.1 % for at least 1 month. Goldmann applanation tonometry IOP readings and central corneal thickness (CCT) measurements were monitored. Cases with induced ocular hypertension (OHT, defined as post-operative IOP higher than 21 mmHg), were identified and correlated to refractive procedure, gender, and corneal thickness.ResultsAt 4 weeks postoperatively, OHT was noted on 27.4 % (20 /73 eyes) in Group A, and 43.7 % (121 /277 eyes) in KCN Group B, (p <0.01). Six months post-operatively (following 5-months of discontinuing topical dexamethasone treatment and commencing treatment of IOP-lowering medications), OHT rate was 1.8 % in Group A and 3.9 % in the KCN Group B.ConclusionThis study demonstrates a potentially significant pre-disposition of keratoconic eyes to the development of steroid-induced OHT.

Eighteen-year follow-up of excimer laser photorefractive keratectomy

To evaluate the long-term efficacy of photorefractive keratectomy (PRK). University Hospital, London, United Kingdom. Prospective case series. One eye of patients who had PRK 18 years previously was examined. All had myopic corrections with a 6.0 mm optical zone. Forty-six patients were examined. The mean preoperative spherical equivalent (SE) refractive error was -4.86 diopters (D) (range -2.75 to -7.375 D). The mean programmed correction was -4.43 D (range -2.50 to -7.00 D). Between 1 year and 18 years, the mean change in SE was -0.31 D (P = .06) and a significant increase in variance occurred (P < .002). The mean change in SE was -0.54 D in patients younger than 40 years at the time of correction (P < .02) and -0.05 D in patients older than 40 years (P = .9). The mean SE change was -0.40 D in women (P < .04) and -0.08 D in men (P = .8). The efficacy index was 0.58. The safety index was 0.998. The corrected distance visual acuity (CDVA) improved significantly from 1 to 18 years (P < .01). Ninety-six percent of corneas were clear at 18 years, with a reduction in haze scores (P < .001). There was no evidence of ectasia. A significant increase in myopic SE occurred between 1 year and 18 years after PRK in patients younger than 40 years and in women. Predictability decreased between 1 year and 18 years. The procedure was safe with no long-term complications. The CDVA and corneal transparency improved with time. Dr. Marshall was a consultant to Summit Technology, Inc. No author has a financial or proprietary interest in any material or method mentioned.

Twenty-Year Follow-Up of a Randomized Prospective Clinical Trial of Excimer Laser Photorefractive Keratectomy

To investigate the 20-year efficacy and safety of photorefractive keratectomy (PRK). Long-term observational case series. In the setting of a university hospital, a study population of 42 patients (42 eyes) who had, as part of a randomized prospective trial, undergone PRK 20 years previously were studied. All had received -3.0 or -6.0 diopter (D) corrections with either 5.0 or 6.0 mm optical zones or a multizone treatment. The mean preoperative spherical equivalent refractive error (SEQ) was -5.13 D (range, -2.75 to -8.0 D). The outcome measures included visual acuity, refractive error, corneal topography and axial length. Between 1 and 20 years there was an increase in mean myopic SEQ of -0.54 D (P < 0.02). In patients younger than 40 years of age at time of correction, this increase was -0.92 D (P < 0.002) with an accompanying increase in variance (P < 0.02), whereas in those older than 40 it was -0.08D (P = 0.8). In female patients the change was -0.69D (P < 0.01), while in males it was -0.26D (P = 0.6). The efficacy index at 20 years was 0.49, and the safety index was 0.97. Corrected distance visual acuity improved between 1 and 20 years (P < 0.01); 93% of corneas were clear at 20 years; 3 eyes had trace haze. There was an improvement in haze scores between 1 and 20 years (P < 0.02). Cornea power remained unchanged between 6 months and 20 years (P = 0.4). Axial length increased by a mean of 0.84 mm (P < 0.0001). There was no ectasia. There was a slight but significant increase in myopic SEQ after PRK between 1 and 20 years, particularly in those under 40 at the time of treatment and in female patients. Corneal power remained unchanged, but axial length increased. The procedure was safe, with no long-term sight-threatening complications and with improvements in corrected distance visual acuity and corneal transparency with time.

Comparative evaluation of Comfilcon A and Senofilcon A bandage contact lenses after transepithelial photorefractive keratectomy

PurposeTo evaluate and compare Comfilcon A and Senofilcon A silicone hydrogel contact lenses used as a therapeutic bandage following transepithelial excimer laser photorefractive keratectomy (PRK). MethodsPatients undergoing transepithelial PRK for myopia were prospectively recruited. Included patients had a Comfilcon A silicone hydrogel lens inserted in one eye, with a Senofilcon A lens in the contralateral eye. Postoperative assessment of subjective pain, epithelial healing and visual recovery was at day 1, 3 and 7. Contact lens factors including centration, movement and deposits were assessed. Results48 eyes of 24 patients were included in the study. Mean age was 31 years (SD 11) and mean refractive error −4.5 D (SD 1.8). Mean pain score at day 1 was significantly higher in the Comfilcon group at 4.6 (SD 2.7) vs. 1.5 (SD2.5) in the Senofilcon group (P<0.005). Mean time to healing was 3.17 days (SD 0.37) in the Comfilcon group, and 3.21 days (SD 0.4) in the Senofilcon group, with no difference in defect size. There was a pronounced central raphe in 1 eye in the Comfilcon group vs. 5 eyes in the Senofilcon group (P=0.19). Significantly more eyes demonstrated no lens movement in the Senofilcon group (18 vs. 4, P=0.0001). ConclusionThe variation in material characteristics and lens geometry of different silicone hydrogel lenses affects their clinical characteristics in therapeutic roles. Other factors than oxygen permeability may affect pain and epithelial healing, with superior pain relief from the less permeable Senofilcon lens in this study.

Spectral OCT with speckle contrast reduction for evaluation of the healing process after PRK and transepithelial PRK.

We evaluate Spectral OCT (SOCT) with a speckle contrast reduction technique using resonant scanner for assessment of corneal surface changes after excimer laser photorefractive keratectomy (PRK) and we compare healing process between conventional PRK and transepithelial PRK. The measurements were performed before and after the surgery. Obtained results show that SOCT with a resonant scanner speckle contrast reduction is capable of providing information regarding the healing process after PRK. The main difference between the healing processes of PRK and TransPRK, assessed by SOCT, was the time to cover the stroma with epithelium, which was shorter in the TransPRK group.

Systemic absorption of mitomycin-C when used in refractive surgery

To determine whether corneal topical application of mitomycin-C (MMC) results in measurable plasma levels of systemic absorption. Madigan Army Medical Center, Refractive Surgery Center, Fort Lewis, Washington, and Micro-Constants Laboratory, San Diego, California, USA. Case-control study. The study comprised male and female active-duty soldiers having excimer laser photorefractive keratectomy with MMC. Patients who met inclusion criteria were asked to provide a blood sample immediately after being treated with MMC 0.2 mg/mL (0.02%) for 30 seconds. Human plasma samples were evaluated by liquid chromatography mass spectrometry to determine whether MMC was present. Thirty samples were submitted for evaluation. There was zero detection of MMC in the submitted samples. The quantifiable limit was greater than 10.0 ng/mL. All samples were below this. In this study of 30 patients with topical application of MMC for refractive surgery, there was no measurable evidence of systemic absorption. Although systemic absorption has been found with use in larger quantities, it was not known whether MMC toxicity concerns could be extrapolated to the refractive surgery population. This information allows counseling of patients on the extremely low likelihood of systemic absorption or toxicity following current techniques for refractive surgery. No author has a financial or proprietary interest in any material or method mentioned.

Excimer laser photorefractive keratectomy for low to moderate myopia using a 5.0 mm treatment zone and no transitional zone: 16-year follow-up

To evaluate the safety and efficacy of photorefractive keratectomy (PRK) 16 years postoperatively. Refractive Laser Suite, Mater Private Hospital, Dublin, Ireland. Cohort study. Myopic PRK was performed using the UV200 excimer laser with a 5.0 mm ablation zone. The following were evaluated in patients returning 16 years postoperatively: refractive stability, refractive predictability, corrected visual acuity, corneal haze, and subjective patient symptoms (eg, glare, halos). Most of the 120 eyes (80 patients) were followed for 2 years or more; 23 patients (39 eyes) were followed for 16 years. Preoperatively, the spherical equivalent (SE) ranged from -1.75 to -7.25 diopters (D) and astigmatism from 0.00 to 1.50 D. At 2 years, the mean SE was -0.25 D and at 16 years, -0.58 D. Overall, 31 eyes (79.5%) were within ± 1.00 D of emmetropia, with 6 eyes (15.4%) between 1.00 D and 2.00 D and 2 eyes (5.1%) between 2.00 D and 3.00 D. The final uncorrected distance visual acuity was 20/20 or better in 27 eyes (69.2%) and 20/30 or better in 36 eyes (92.3%). Eight eyes (20.5%) lost 1 line of corrected distance visual acuity. Four eyes (10.3%) had visible haze and 7 eyes (17.9%) had hemosiderin. All patients stated they would have the procedure again. Photorefractive keratectomy was safe and effective in the treatment of myopia up to -7.00 D, and all patients reported being satisfied. There appeared to be slight regression over the follow-up period. No author has a financial or proprietary interest in any material or method mentioned.

Collagen Crosslinking for Ectasia following PRK Performed in Excimer Laser–Assisted Keratoplasty for Keratoconus

To report the results of corneal collagen crosslinking (CXL) in a patient with corneal ectasia developed after excimer laser-assisted lamellar keratoplasty for keratoconus and a secondary photorefractive keratectomy (PRK) for residual refractive error. A 33-year-old woman, who had originally been treated for keratoconus in the right eye by excimer laser-assisted lamellar keratoplasty, subsequently had her residual ametropia treated by topographically guided, transepithelial excimer laser PRK. Five years after PRK, the patient developed corneal ectasia showing concomitant visual changes of best spectacle-corrected visual acuity (BSCVA) reduced to 20/33 with a refraction of -6.00 +6.00 × 30. The minimum corneal thickness at the ectasia apex was 406 µm. A treatment of riboflavin-UVA-induced corneal CXL was performed on the right eye. Two years after the CXL treatment, the right eye improved to 20/20 BSCVA with a refraction of plano +1.00 × 50 while exhibiting a clear lamellar graft. Corneal CXL provided safe and effective management of ectasia developed after excimer laser-assisted lamellar keratoplasty and PRK.

Simultaneous topography-guided PRK followed by corneal collagen cross-linking after lamellar keratoplasty for keratoconus

BackgroundThe purpose of this paper is to report the results of using combined treatment of customized excimer laser-assisted photorefractive keratectomy (PRK) and prophylactic corneal collagen crosslinking (CXL) for residual refractive error in a group of patients who had previously undergone lamellar keratoplasty for keratoconus.MethodsThe study included 14 eyes from 14 patients who had originally been treated for keratoconus in one eye by excimer laser-assisted lamellar keratoplasty (ELLK), and subsequently presented with residual ametropia (−6.11 D ± 2.48, range −2.50 to −9.50). After a mean 40.1 ± 12.4 months since ELLK they underwent combined simultaneous corneal regularization treatment with topographically guided transepithelial excimer laser PRK (central corneal regularization) and corneal CXL induced by riboflavin-ultraviolet A.ResultsAfter a mean 15 ± 6.5 (range 6–24) months, all eyes gained at least one Snellen line of uncorrected distance visual acuity (range 1–10). No patient lost lines of corrected distance visual acuity, and four patients gained three lines of corrected distance visual acuity. Mean manifest refractive spherical equivalent was −0.79 ± 2.09 (range +1 to −3.0) D, and topographic keratometric astigmatism was 5.02 ± 2.93 (range 0.8–8.9) D. All the corneas remained clear (haze < 1).ConclusionThe combination of customized PRK and corneal CXL provided safe and effective results in the management of corneal regularization for refractive purposes after ELLK for keratoconus.

Photorefractive keratectomy in treatment of refractive amblyopia in the adult population

To evaluate changes in corrected distance visual acuity (CDVA) after photorefractive keratectomy (PRK) in amblyopic cases. Ankara Ataturk Training and Research Hospital 1st Ophthalmology Clinic, Ankara, Turkey. Retrospective case series. The medical records of cases of anisometropic amblyopia treated by excimer laser PRK were reviewed. Inclusion criteria were no previous refractive correction, occlusion treatment, or chemical penalization before age 15 years. Anisometropic amblyopia was defined as a more than 2-line difference in CDVA and a refractive error difference greater than 3.00 diopters (D) between 2 eyes of the same patient. Final visual acuity measurements were performed at the end of the sixth postoperative month. The study enrolled 16 hyperopic patients and 34 myopic patients with a mean age of 33.3 years. The mean preoperative spherical equivalent was -7.46 D ± 2.90 (SD) in myopic eyes and +4.15 ± 2.56 D in hyperopic eyes. The differences between the preoperative and postoperative uncorrected distance visual acuity and CDVA were statistically significant (P=.001). The mean CDVA was 0.47 ± 0.17 preoperatively and 0.61 ± 0.19 postoperatively. The CDVA decreased in 3 cases (6%), stayed the same in 12 cases (24%), and increased in 35 cases (70%). There was no statistically significant correlation between the severity of amblyopia and the increase in CDVA (r = 0.20, P=.165). After PRK to eliminate and correct refractive errors in anisometropic amblyopia, visual acuity improved significantly in 70% of adult patients with no previous occlusion or chemical penalization treatment.

Treatment of Lisch Corneal Dystrophy With Photorefractive Keratectomy and Mitomycin C

To describe a case of Lisch dystrophy; review the clinical, histopathologic, and electron microscopic features of this entity; and discuss a novel treatment approach using photorefractive keratectomy (PRK) and mitomycin C (MMC). A 45-year-old man with a feathery, comet-shaped, right-sided, corneal lesion was treated with excimer laser PRK and 20 seconds of MMC. The uninvolved fellow eye underwent traditional PRK without the use of MMC. Epithelial scrapings were sent for histopathologic analysis. Histopathologic analysis showed vacuolated cells in the epithelial layer. Electron microscopy revealed empty intracytoplasmic vacuoles, electron-dense whorled inclusions, and reduced tonofilaments. Surface ablation and MMC was successful in treating the initial lesion, with only minimal recurrence noted in the affected eye. Surprisingly, a new asymptomatic lesion was noted in the unaffected eye but dissipated over time. Although the whorled inclusions represent a novel finding, the overall clinical and microscopic analysis was consistent with Lisch dystrophy. Surface ablation with MMC should be considered as a treatment option for this disease.

Contrast to wavefront optimized and wavefront guided excimer laser photorefractive keratectomy

Conventional excimer laser keratectomy have been proved to achieve better visual function,but the traditional therapy of corneal spherical cutting line generally flat profile will make the cornea more oblate shape and the contours of the cornea and lcad to spherical aberration.The alteration of non.spherical nature cause the increase of corneal spherical aberration,which further affects the night vision and contrast sensitivity and other visual quality.Wavefront optimization based on total number of adjustments are to retain the previous visual aberrations of eyes and optimize the non-spherical nature of cornea to create a ideal model based on individual adjustments.Ocular wavefront-guided measurement and ablation in exeimer laser keratectomy can achieve better visual outcome.In this paper,wavefront guided and wavefront optimized treatment outcome for the spherical aberration correction are reviewed. Key words: Excimer laser photorefractive keratectomy; Spherical aberration; Wavefront guided; Wavefront optimization; Corneal eccentricity

Simultaneous aspheric wavefront-guided transepithelial photorefractive keratectomy and phototherapeutic keratectomy to correct aberrations and refractive errors after corneal surgery

To evaluate the results of combined aspheric wavefront-guided transepithelial excimer laser photorefractive keratectomy (PRK) and phototherapeutic keratectomy (PTK) to correct aberrations and refractive errors after radial keratotomy (RK) or keratoplasty. Sekal Rovigo Microsurgery Centre, Rovigo, Italy. This retrospective noncomparative consecutive case series comprised eyes having corneal wavefront-guided transepithelial PRK to correct aberrations followed by PTK (60 to 70 mum depth) without masking fluid. Corneal wavefront topography and a flying-spot excimer laser were used. Complete preoperative and postoperative ophthalmic examinations were performed. The mean age of the 26 patients (35 eyes; 17 RK, 18 keratoplasty) at surgery was 47 years +/- 9 (SD) (range 29 to 72 years) and the mean follow-up, 7 +/- 2 months (range 6 to 15 months). Preoperatively, all eyes had irregular astigmatism ranging from 0.50 to 6.50 diopters (D). At the last postoperative follow-up, the uncorrected distance visual acuity was better than 20/40 in 21 eyes (60%) and better than 20/20 in 6 eyes (17%); 25 eyes (71%) were within +/-1.00 D of the attempted spherical equivalent manifest refraction (mean -0.58 +/- 1.06 D; range -3.50 to +1.50 D). No eye lost Snellen lines of corrected distance visual acuity; 8 eyes (23%) had an increase of more than 4 lines. Trace haze developed in 1 eye. Simultaneous corneal wavefront-guided transepithelial PRK and PTK using an excimer laser was safe and effective in correcting aberrations and refractive errors after RK or keratoplasty. Neither author has a financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes.