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PubMedDate not supplied

Corneal wound healing in monkeys 18 months after excimer laser photorefractive keratectomy.

Excimer laser keratomileusis (photorefractive keratectomy, direct corneal ablation) for myopic corrections of 2.00 diopters (n = 1), 4.00 D (n = 4), and 8.00 D (n = 3) was performed on eight corneas of four Rhesus monkeys. All animals were followed for 18 months. The ablations healed normally and no epithelial erosions occurred. Serial slit-lamp microscope examinations revealed that a variable amount of corneal haze developed in all animals; this haze progressively faded during the follow-up period. Histopathology revealed an epithelium of normal thickness, basement membrane abnormalities, increased number and activity of stromal keratocytes, and a variable amount of newly secreted extracellular matrix in the anterior stroma. These findings suggest that excimer laser keratomileusis induces a mild wound healing response in the anterior cornea which displays considerable individual variability and persists up to 18 months.

Animals↗
PubMed1994

Photorefractive keratectomy for myopic astigmatism: phase IIA of the Federal Drug Administration study (12 to 18 months follow-up). Excimer Laser Study Group.

Excimer laser photorefractive keratectomy was performed on eight eyes to investigate toric ablation of naturally occurring compound myopic astigmatism. Follow-up ranged from 12 to 18 months. In each surgical case, the spherical component was reduced. The cylindrical component was reduced or eliminated in seven of eight eyes and remained unchanged in one eye. However, six of eight eyes had some residual astigmatism and three had 0.75 diopters of cylinder or more. In six of eight eyes the change in axis in the postoperative cylinder varied between 5 and 10 degrees of the preoperative cylinder axis. In one eye with an eccentric ablation, the axis changed by 40 degrees. In two eyes with loss of best corrected visual acuity of one line each, from 20/20 to 20/25, irregular astigmatism and subepithelial haze persisted 18 months after treatment. One eye gained a line of best corrected visual acuity from 20/20 to 20/15. Two eyes were overcorrected. Twenty-five percent of patients achieved 20/20 or better uncorrected visual acuity, 62.5% achieved 20/40 or better uncorrected acuity, and 100% achieved 20/50 or better uncorrected acuity. These preliminary results of excimer laser photoastigmatic keratectomy compare favorably with reports of photorefractive keratectomy for myopia alone. There were no adverse reactions to treatment. The procedure was effective although some residual astigmatism was found in most patients.

Adult↗
PubMed2005

Enhancement outcomes after photorefractive keratectomy and laser in situ keratomileusis using topographically guided excimer laser photoablation.

PURPOSE: To evaluate the efficacy and safety of topographically guided excimer laser photoablation to retreat unsuccessful myopic and hyperopic photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). SETTING: Eye Clinic, San Salvatore Hospital, University of L'Aquila, L'Aquila, Italy. METHODS: At least 3 months after primary PRK (Group A) or primary LASIK (Group B), 48 eyes of 42 patients were submitted to PRK or LASIK enhancements. The eyes were treated with an excimer laser linked to a computerized videokeratography unit with a topographically supported customized ablation workstation. RESULTS: The mean follow-up was 27.8 months +/- 8.2 (SD). In Group A, the uncorrected visual acuity (UCVA) changed from 0.5 +/- 0.7 logarithm of the minimum angle of resolution (logMAR) (range 20/600 to 20/200) to 0.1 +/- 0.7 logMAR (range 20/60 to 20/20); the mean best spectacle-corrected visual acuity (BSCVA) changed from 0.1 +/- 0.7 logMAR (range 20/50 to 20/20) to 0 +/- 0.7 logMAR (range 20/50 to 20/20) after the enhancement. In Group B, the UCVA changed from 0.7 +/- 0.8 logMAR (range 20/600 to 20/40) to 0.1 +/- 0.7 logMAR (range 20/40 to 20/20); the mean BSCVA improved from 0.2 +/- 0.8 logMAR (range 20/30 to 20/20) to 0 +/- 1.3 logMAR (range 20/25 to 20/20) after surgery. CONCLUSIONS: The enhancements using topographically guided excimer laser photoablation with a topographically supported customized ablation method resulted in satisfactory and stable visual outcome with good safety and efficacy after unsuccessful PRK and LASIK.

Adult↗
PubMedDate not supplied

Excimer laser calibration system.

BACKGROUND: Excimer laser photoablation for refractive and therapeutic keratectomies has been demonstrated to be feasible and practicable. However, corneal laser ablations are not without problems, including the delivery and maintenance of a homogeneous beam. We have developed an excimer laser calibration system capable of characterizing a laser ablation profile. METHODS: Beam homogeneity is determined by the analysis of a polymethylmethacrylate (PMMA)-based thin-film using video capture and image processing. The ablation profile is presented as a color-coded map. Interpolation of excimer calibration system analysis provides a three-dimensional representation of elevation profiles that correlates with two-dimensional scanning profilometry. Excimer calibration analysis was performed before treating a monkey undergoing phototherapeutic keratectomy and two human subjects undergoing myopic spherocylindrical photorefractive keratectomy. Excimer calibration analysis was performed before and after laser refurbishing. RESULTS: Laser ablation profiles in PMMA are resolved by the excimer calibration system to .006 microns/pulse. Correlations with ablative patterns in a monkey cornea were demonstrated with preoperative and postoperative keratometry using corneal topography, and two human subjects using video-keratography. Excimer calibration analysis predicted a central-steep-island ablative pattern with the VISX Twenty/Twenty laser, which was confirmed by corneal topography immediately postoperatively and at 1 week after reepithelialization in the monkey. Predicted central steep islands in the two human subjects were confirmed by video-keratography at 1 week and at 1 month. Subsequent technical refurbishing of the laser resulted in a beam with an overall increased ablation rate measured as microns/pulse with a donut ablation profile. A patient treated after repair of the laser electrodes demonstrated no central island. CONCLUSIONS: This excimer laser calibration system can precisely detect laser-beam ablation profiles. The calibration system correctly predicted central islands after excimer photoablation in a treated monkey cornea and in two treated human subjects. Detection of excimer-laser-beam ablation profiles may be useful for precise calibration of excimer lasers before human photorefractive and therapeutic surgery.

Animals↗
PubMed2001

Excimer laser photorefractive keratectomy.

The excimer laser has proved to be a precise and versatile tool for treating refractive errors. Excimer laser photorefractive keratectomy for myopia is now an established safe and effective alternative to contact lenses and glasses, and should be part of the ophthalmologist's standard armamentarium for treating this condition. This article provides a brief overview of the basic principles underlying excimer laser technology, as well as the surgical technique and postoperative management of myopic correction.

Cornea↗
PubMed1997

Scanning laser polarimetry in corneal haze after excimer laser refractive surgery.

PURPOSE: We evaluate the technique of retinal nerve fiber layer thickness measurement using scanning laser polarimetry in cases of central corneal haze due to photorefractive keratectomy. METHODS: Nerve fiber layer thickness was measured using a Nerve Fiber Analyzer II (Laser Diagnostic Technologies, Inc., San Diego, CA, U.S.A.) in eight eyes of eight individuals with mild to pronounced corneal haze owing to earlier excimer laser refractive surgery, and in nine eyes of nine control volunteers. RESULTS: Neither total and sectorial nerve fiber layer thickness values, nor superior/ inferior quadrant thickness ratio differed in a statistically significant manner between the two groups (unpaired t test, p > 0.05). Reproducibility in the "haze" and control groups was 4.3% and 3.4%, respectively, for mean nerve fiber layer thickness calculated from all quadrants around the disc. The figures were 4.9% and 5.2%, respectively, for the superior quadrant thickness; 8.2% and 8.8%, respectively, for the temporal thickness values; 5.4% and 4.6%, respectively, for the inferior thickness values; and 4.1% and 5.0%, respectively, for the nasal quadrant thickness values. For the superior/inferior quadrant thickness ratio the reproducibility was 4.4% and 6.8%, respectively. None of the corresponding values for reproducibility differed significantly between the two groups (F-test, p > 0.05). CONCLUSIONS: Corneal haze did not cause an artificial increase of the thickness values measured with scanning laser polarimetry and did not diminish the reproducibility of the measurement. The results suggest that scanning laser polarimetry may be a suitable method for the precise measurement of the nerve fiber layer thickness even in eyes with persistent corneal haze after excimer laser refractive surgery.

Adult↗
PubMed2001

Laser in situ keratomileusis with a scanning excimer laser for the correction of low to moderate myopia with and without astigmatism.

PURPOSE: To evaluate the safety and effectiveness of and patient satisfaction with laser in situ keratomileusis (LASIK) performed with a scanning excimer laser by experienced surgeons to correct low and moderate levels of myopia and astigmatism. SETTING: Clinique Laservue, Montreal, Quebec, Canada. METHODS: A consecutive series of 125 patients (236 eyes) with myopia of -0.5 to -7.0 diopters (D) and cylinder less than 2.5 D were enrolled in this single-center prospective clinical trial. The patients were treated with LASIK and followed for 6 months. The System-ALK Automated Corneal Shaper microkeratome (Bausch & Lomb Surgical) with a 180 microm thickness plate and the Technolas 217 excimer laser (Bausch & Lomb Surgical) with PlanoScan software for the stromal ablation were used in all procedures. Since this version of PlanoScan tended to undercorrect, a mean of 14.7% was added to the standard nomogram. Patient satisfaction was assessed by questionnaires administered preoperatively and 1 and 6 months postoperatively. Retreatments for enhancement were not performed during the 6-month follow-up. RESULTS: Six months after LASIK (86.4% follow-up), the mean postoperative manifest spherical equivalent was +0.02 D +/- 0.64 (SD) compared with a preoperative mean of -4.01 +/- 1.59 D. The uncorrected visual acuity was 20/40 or better in 94.6% of eyes and 20/20 or better in 81.9%. A total of 91.2% were within +/-1.0 D of emmetropia and 73.0% were within +/-0.5 D. Only 2 eyes were overcorrected by >1.0 D. Of the eyes with astigmatic myopia, 86.8% were within +/-1.0 D of the intended cylinder correction (by vector analysis) and 73.0% were within +/-0.5 D. The refractions were generally stable after 1 month, and the change in refraction between postoperative examinations was within +/-0.5 D in 88.0% of eyes. A 1-line decrease in best spectacle-corrected visual acuity was seen in 11.3% of eyes, and no eye lost more than 1 line. An increase of 1 or 2 lines was seen in 45.1%. No intraoperative problems occurred, and the interface was clear in all eyes. At 6 months, most symptoms present significantly more frequently than preoperatively were "mild"; none were "marked" or "severe." A total of 90.5% of eyes were reported with marked to extreme improvement in the overall quality of vision, and 99.0% of patients said they would choose LASIK surgery again. CONCLUSIONS: Mild to moderate myopia, with and without astigmatism, was corrected safely, effectively, and predictably with a high degree of patient satisfaction using LASIK with a scanning excimer laser and the System-ALK Automated Corneal Shaper.

Adult↗
PubMed1996

Occurrence and magnitude of pressure waves during Er:YAG laser ablation of atherosclerotic tissue: comparison to XeCl excimer laser ablation.

BACKGROUND AND OBJECTIVE: Since excimer laser ablation has not shown advantages in comparison to conventional balloon angioplasty, the search for other laser light sources came up with the Er:YAG laser, operating at a wavelength of 2.94 microns. STUDY DESIGN/MATERIALS AND METHODS: Normal and atherosclerotic human vessel segments were irradiated in vitro, using pulsed Er:YAG laser systems. The laser beam was either focused onto the tissue in air or delivered via a fibre system onto the tissue being immersed in saline. Needle-type hydrophones were used for pressure pulse detection. RESULTS: Er:YAG laser irradiation results in effective tissue ablation of normal and calcified atherosclerotic vessel segments. In comparison to excimer lasers, ablation rates can be increased by a factor of 5 to 10 at least. Er:YAG laser ablation is also associated with a generation of pressure waves. On calcified plaque, the acoustic signals differ significantly from those on normal tissue. Histological tissue analysis reveals small zones of discoloration and tissue fissures that are found 100-200 microns lateral to the crater edge, depending on the energy density used. CONCLUSION: Er:YAG lasers generate pressure waves that are comparable to excimer laser ablation. Er:YAG lasers, however, show a markedly improved ablation efficiency, which may favour these systems as effectively cutting, less traumatic tools for removal of atherosclerotic plaque.

Aortic Diseases↗
PubMedDate not supplied

Laser trabeculodissection with a photopolishing scanning excimer laser.

A phase I study of nonpenetrating trabeculectomy (Zimmerman procedure) using a scanning excimer laser system was conducted to evaluate the ability of this laser system to achieve the deep dissection required to allow significant filtration without inadvertent penetration into the anterior chamber. A photopolishing, scanning 193 nm excimer laser system (LS 2000, LaserSight, Inc.) was used with a proprietary fluence, spot size, scanning pattern, and ablation shape to perform a trabeculodissection under a scleral flap with a limbal-based conjunctival flap in 8 cases of advanced glaucoma including 5 eyes that had a failed trabeculectomy. The laser trabeculodissection (LTD) was carried through Schlemm's canal and the juxtacanalicular trabecular meshwork, achieving vigorous aqueous outflow. No peripheral iridectomy was done. The scleral flap was closed loosely with a 10-0 suture. Mitomycin-C was used intraoperatively. In no case did inadvertent penetration into the anterior chamber occur. No peripheral iridectomy was performed. No intraoperative hyphema occurred. There was no postoperative iritis except minimal anterior chamber reaction in 1 eye with preoperative rubeosis. Postoperatively, a good filtering bleb was achieved in all 8 eyes with substantial reduction in the intraocular pressure without topical antiglaucoma therapy. No cases of postoperative shallowing (overfiltration) occurred. Gonioscopy, postoperatively, revealed no new peripheral anterior synechiae (PAS) to the filtration site and an intact inner trabecular meshwork. All eyes were followed for a minimum of 6 months. In this phase I study, laser trabeculodissection (LTD) with a 193 nm photopolishing, scanning system appears to be a promising alternative to full-thickness trabeculectomy, achieving significant filtration while perhaps avoiding much of the risk of filtration surgery. The laser system seemed to provide a more reliable, better-controlled dissection than a knife. The aqueous drainage seems to have acted as a self-regulating endpoint by absorbing UV energy, thus avoiding inadvertent penetration into the anterior chamber. More study is needed to establish the appropriate role of LTD in glaucoma therapy.

Chronic Disease↗
PubMed1990

[Experimental study of application of excimer laser to laser angioplasty].

The possible application of excimer laser to laser angioplasty was studied. In the first experiment, the ablative effects of excimer laser at wavelengths of 248 nm and 308 nm on the pig myocardium were examined in vitro at an air-tissue interface. Crater depth increased with total delivered energy and energy per pulse. Very clear cuts could be observed by histological examination. There was no evidence of thermal damage at a wavelength of 248 nm, at 10 pps. Above 10 pps, a thin bordering zone of suspicious thermal damage was noted with the wavelengths of 248 nm and 308 nm. Thermal damage increased with pulse repetition rate. In the second experiment, the effects of excimer laser irradiation on blood were examined. Five vials, each of which contained 3 ml of blood, were exposed to 37.5 mJ laser beam at 10 pps in repetition rate for 10, 20, 30, 40, 50 seconds. One vial was left untreated as a control. No change in hematocrit value was observed after excimer laser irradiation. In contrast, the level of plasma free hemoglobin rose progressively with each increased duration of exposure. This result indicates that the lysis of erythrocytes does not occur in the laser-exposed cells. However, the damage to erythrocyte membrane took place as it was evidenced by progressive hemoglobin leakage into plasma. In the third experiment, the excimer laser was coupled to a 400 microns quartz optical fiber and the laser energy transmitted through the fiber was measured. At a wavelength of 308 nm, pulse energies up to 9 mJ were noted at the tip of the fiber. At a wavelength of 248 nm, the fiber tip was destroyed. In the fourth experiment, acute and chronic healing responses of normal canine arteries to excimer laser irradiation were studied in 4 mongrel dogs. The artery healed completely at the 18th day after the excimer laser irradiation. There was no evidence of thrombus formation and intimal hyperplasia in these arteries. The results suggest the applicability of excimer laser to laser angioplasty.

Angioplasty, Laser↗
PubMed1992

Reactivation of latent herpes simplex virus by excimer laser photokeratectomy.

We tested whether excimer laser photorefractive and phototherapeutic keratectomy may reactivate latent herpes simplex and cause recurrent keratitis in mice. Two of ten latently infected mice that were treated with ten excimer laser pulses to the corneal epithelium shed herpes simplex virus type 1, as did four of ten mice that were treated with 50 excimer laser pulses. Ocular shedding of herpes simplex virus was detected in four of ten mice that were treated with ethylenediamine-tetraacetic acid (EDTA) scraping of the corneal epithelium without laser keratectomy, and in six of ten mice on which combined EDTA-facilitated epithelial removal was performed followed by the application of ten excimer laser pulses. In both EDTA-treated groups, viral shedding was prolonged and 18 of 20 mice developed marked corneal opacification or neovascularization, or both. Corneal photoablation with the excimer laser may induce reactivation of latent herpes simplex virus, even in mice with clear and smooth-appearing corneas, and should be considered in the differential diagnosis of humans with persistent corneal epithelial defects after refractive or therapeutic excimer procedures.

Animals↗
PubMed1997

Single-laser approach for fluorescence guidance of excimer laser angioplasty at 308 nm: evaluation in vitro and during coronary angioplasty.

BACKGROUND AND OBJECTIVE: Spectroscopic guidance of laser angioplasty has been attempted using a diagnostic He-Cd laser in addition to the therapeutic laser system. This study evaluated a single-laser approach for simultaneous ablation and fluorescence excitation. STUDY DESIGN/MATERIALS AND METHODS: A spectroscopy system was coupled to a clinical XeCl excimer laser. Ablation of 162 human aortic samples in saline and blood with 45 mJ/mm2 per pulse yielded 676 fluorescence spectra validated histologically. The same equipment was used in 16 patients for angioplasty of 18 coronary stenoses applying 500 to 1,725 pulses with 45 to 60 mJ/mm2 under saline flushing. A total of 783 spectra were recorded and validated by intracoronary ultrasound (categories: atheroma, fibrous plaque, calcified lesion). RESULTS: In vitro, 5 types of spectra could be differentiated: (1) atheroma, (2) fibrous plaque, (3) calcified lesion in saline, (4) media, and (5) calcified lesion in blood. Discriminant analysis prospectively classified 576 validation spectra with the following sensitivity and specificity for each type: (1) 83.5 and 97.1%, (2) 85.7 and 96.8% (3) 100 and 98.5%, (4) 98.1 and 99.3%, (5) 98.9 and 100%, respectively. In vivo type 1, 2, 3, and 5 spectra were also observed, but not the media spectrum. The predominant sonographic category also prevailed in spectroscopy. Calcified lesions yielded type 3 and 5 as well as mixed spectra. CONCLUSIONS: Using an excimer laser for angioplasty allows combining ablation and fluorescence excitation without a diagnostic laser. Principal types of atherosclerotic lesions and the media can be differentiated spectroscopically with this approach.

Adult↗
PubMed2002

Time course of changes in corneal forward shift after excimer laser photorefractive keratectomy.

BACKGROUND: Excimer laser refractive surgery has been reported to induce forward shift of the cornea, but its long-term sequelae remain unknown. OBJECTIVES: To prospectively investigate the time course of changes in corneal elevation after excimer laser photorefractive keratectomy (PRK). METHODS: We performed PRK on 65 eyes of 34 patients with refractive errors of -1.25 to -10.0 diopters. The anterior/posterior corneal elevation and corneal thickness were measured with a scanning-slit corneal topography system before and 1 week and 1, 3, 6, and 12 months after surgery. Twenty eyes of 10 healthy control subjects underwent similar measurements at 3-month intervals. RESULTS: The posterior corneal surface displayed a mean +/- SD forward shift of 36.6 +/- 25.3 microm 1 week after PRK, which gradually increased to 55.1 +/- 46.1 microm at 1 year. All postoperative values were significantly larger than those of healthy controls (2.4 +/- 8.9 microm; P<.001, Mann-Whitney test). The largest forward shift occurred within the first postoperative week. The progression thereafter was most pronounced from 1 to 6 months, and nearly stabilized at 6 months. The variance of postoperative data was statistically significant (P<.001, repeated-measures analysis of variance). Multiple postoperative comparisons demonstrated significant differences between measurements at 1 week and 6 months (P =.002, Tukey Honestly Significant Difference), at 1 week and 1 year (P<.001), at 1 and 6 months (P<.001), and at 1 month and 1 year (P<.001). Progression of forward shift was more prominent in eyes with less preoperative corneal thickness and greater myopia that required larger laser ablation. We observed no progressive thinning and expansion of the cornea during the 1-year follow-up, which refuted the occurrence of true ectasia. A statistically significant correlation was found between the amount of myopic regression and the forward shift of the cornea (Pearson correlation coefficient, r = -0.37; P =.005). CONCLUSIONS: Photorefreactive keratectomy induced forward shift of the cornea, which is not true corneal ectasia. The largest forward shift occurred within the first postoperative week. Changes were progressive up to 6 months postoperatively, but became almost stable thereafter. Eyes with thinner cornea and higher myopia, requiring greater photoablation, are more predisposed to progression. Forward shift of both corneal surfaces added to the tendency toward myopic regression after PRK.

Adult↗
PubMed2003

Corneal forward shift after excimer laser keratorefractive surgery.

The excimer laser keratorefractive surgery inevitably compromises structural integrity of the cornea by the surgical tissue subtraction and loss of integrity of Bowman's membrane. Forward shift of the cornea is commonly seen after both photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Antero-posterior movement of the cornea is evaluated by measuring the posterior corneal elevation with the scanning-slit corneal topography (Orbscan). Eyes with thinner cornea, higher intraocular pressure, and higher myopia requiring greater laser ablation were more predisposed to forward shift of the cornea. After PRK, there was a trend toward progressive forward shift of the cornea, but the progression stabilized 6 months after surgery. Because progressive thinning and expansion of the cornea were not observed during the one-year observation period after PRK, the forward shift of the cornea does not represent true ectasia. Forward shift of both corneal surfaces would add to the tendency toward myopic regression after excimer laser surgery.

Cornea↗
PubMed1992

Bone-cement removal with the excimer laser in revision arthroplasty.

The excimer laser was thought to be an appropriate tool for the removal of bone cement without damaging the bone. However, due to its low ablation rate, its clinical use in total hip revision arthroplasty proved to be impossible. This experimental study was designed to evaluate the maximal ablation rate by adjusting the laser's parameters. Energy density, frequency, pulse duration, radiation area, quantity of pulses, and environmental conditions were varied in the experimental setup. Even with the best set of parameters the excimer laser was about ten times slower than, e.g., the carbon dioxide laser. The removal of 10 g bone cement takes about 1 h. Thus, complete cement removal by means of the excimer laser alone is not possible. However, selective application of the excimer laser in combination with other techniques could be discussed.

Arthroplasty↗
PubMedDate not supplied

Design and development of a new 193-nanometer excimer laser surgical system.

BACKGROUND: The 193-nanometer excimer laser is used for photoablative reprofiling of the cornea to correct refraction errors and to treat corneal pathologies. To use the unique properties of the excimer laser, some technical features should be provided by the excimer laser system. A new excimer laser system is presented. METHODS: The instrument has a fluence sensor for precise measurement of the actual fluence just before surgery, a new delivery system including an integrator system to homogenize the laser beam, a steelband with apertures and a zoom optic to get the desired form of central reprofiling, and an alignment system to reduce the possibility to decenter the optical zone. RESULTS: The fluence before surgery can be measured very precisely with the fluence sensor. The ablation zone size is at least 8 mm in diameter with a homogenous laser beam profile resulting in a smooth surface of the treated material. Different forms of ablations can be created using the steelband with different forms of apertures. The center of the ablation zone can be found using the alignment system. CONCLUSION: The new excimer laser system fulfills some important technical features for optimal use of the excimer laser in corneal surgery.

Cornea↗
PubMed2006

Shack-Hartmann-Based wavefront analyzer for calibrating excimer lasers.

PURPOSE: Currently, refractive surgical excimer laser systems are calibrated by ablating plastic lenses, which are measured by lensometer and analyzed by a technician. The accuracy of this method is approximately 0.25 diopters (D) in sphere and cylinder power. Theoretically, objective calibration using wavefront technology would be significantly more accurate, thereby improving surgical outcomes. This study describes a Shack-Hartmann-based instrument, which has been developed to measure ablated plastic lenses for calibration and quality control of the excimer laser. METHODS: A calibration instrument comprising an LED source at 640 nm, a lenslet array, beam-guiding optics, and a CCD camera was designed to perform full wavefront analysis. The measurement plane is conjugate to the lenslet array plane, and the diameter of the pupil is 5 mm. Accuracy was determined by measuring a set of well-calibrated spherical and cylindrical glass lenses. Plastic lenses were ablated, and high-precision measurements were performed by surface profile scanner. RESULTS: In the power range of -6.00 to +4.00 D, repeatability exceeded 0.01 D, accuracy of measurement exceeded 0.04 D, and 10 for the axis of cylinder lenses. The measurement of excimer-ablated plastic lenses agreed with high-precision surface profile scanner measurements within 0.10 D, and repeatability exceeded 0.01 D. CONCLUSIONS: Wavefront technology-based, high-precision measurement of calibration lenses can more accurately set the energy of the excimer laser, which enhances the accuracy of refractive laser correction. In automating calibration, the new instrument removes operator subjectivity and decreases the time needed for calibration.

Calibration↗