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PubMedDate not supplied

Algorithm to correct hyperopic astigmatism with the Nidek EC-5000 excimer laser.

BACKGROUND: The efficacy of a new ablation algorithm for the correction of hyperopic astigmatism with the Nidek EC-5000 excimer laser was evaluated. METHODS: Twenty-five eyes with mean preoperative hyperopia of +3.76 +/- 1.70 D and a mean hyperopic cylinder of 2.20 +/- 0.80 D underwent photorefractive keratectomy (PRK) using a new algorithm with the Nidek EC-5000 excimer laser (software version 3.0). The new algorithm differed from previous algorithms in that less tissue was removed for the same amount of diopters, and there was less of a dioptric gradient between the optical zone and the transition zone. Mean preoperative spectacle-corrected visual acuity was 0.8 +/- 0.09. Minimum follow-up was 6 months. RESULTS: Mean postoperative spectacle corrected visual acuity (geometric mean) increased significantly to 0.89 +/- 0.1. The mean sphere decreased by 3.08 D and the mean cylinder by 1.60 D. CONCLUSION: Hyperopic PRK using the Nidek EC-5000 excimer laser with this new algorithm for hyperopic astigmatism appears to be safe and effective.

Adult↗
PubMedDate not supplied

Photorefractive keratectomy with an ablatable mask for myopic astigmatism.

PURPOSE: To evaluate efficacy, safety, and stability of photoastigmatic keratectomy (PARK) carried out with a Summit Apex Plus laser using an ablatable mask. METHODS: Forty-one eyes of 41 patients with myopic astigmatism with follow-up of 12 months were evaluated. Treatment efficacy was compared in groups with high (>6.00 D) versus low (< or =6.00 D) preoperative spherical equivalent subjective manifest refraction, in groups with high (>2.00 D) versus low (< or =2.00 D) preoperative cylindrical component and in groups divided according to preoperative axis of cylinder. RESULTS: At 12 months after surgery, mean spherical equivalent manifest refraction in all 41 eyes was -0.30 +/- 0.90 D. Mean cylinder component was 0.60 +/- 0.70 D. Mean reduction in astigmatic component was 67 +/- 47%. Uncorrected visual acuity of 0.5 or more was achieved in 79% of eyes; 71% of eyes achieved 0.8 or more. At 1 month after surgery, 49% of eyes had a loss of 2 or more lines of spectacle-corrected visual acuity. This loss was restored at 12 months. No statistically significant differences were found between the different subgroups. CONCLUSION: Photoastigmatic keratectomy with ablatable mask gives satisfactory results. No relation in efficacy was found when taking into account the amount of preoperative spherical component, the cylindrical component, or the cylinder axis direction.

Adult↗
PubMedDate not supplied

Photorefractive keratectomy with customized segmental ablation to correct irregular astigmatism after laser in situ keratomileusis.

PURPOSE: To correct irregular astigmatism after laser in situ keratomileusis (LASIK) with customized segmental ablation using the Nidek OPD-Scan (ARK-10000) to guide the Nidek EC-5000 excimer laser with the Final Fit software. METHODS: One eye of a patient that had undergone LASIK and one enhancement was treated using photorefractive keratectomy (PRK) with customized segmental ablation. OPD-Scan maps were analyzed before and after surgery. The Final Fit software was used to link the OPD-Scan to the EC-5000 laser to guide the customized ablation. RESULTS: At 1 month postoperatively, best spectacle-corrected visual acuity had improved from 20/20-2 to 20/15-2, the patient's subjective evaluation of vision was markedly improved, and the postoperative OPD-Scan maps appeared more regular. CONCLUSION: Customized segmental ablation can be performed using the Nidek OPD-Scan and Final Fit software to improve best spectacle-corrected visual acuity and minimize irregular astigmatism, which may result from prior surgical procedures.

Astigmatism↗
PubMedDate not supplied

Nomogram for treatment of astigmatism with laser in situ keratomileusis.

PURPOSE: Laser in situ keratomileusis (LASIK) is a mainstay in refractive surgery. Myopes and compound myopic astigmats generally have a good result after LASIK. However, simple myopic astigmats are sometimes not as pleased with their visual outcome. METHODS: We analyzed 40 patients who underwent LASIK with the Nidek EC-5000 excimer laser and the Hansotome microkeratome. The key to successful LASIK in these patients was proper analysis of corneal topography. RESULTS AND CONCLUSION: We found that 37 of the 40 patients studied had an excellent result, but poor topographic interpretation gave a poorer result in the remaining three patients. We discuss how to correctly interpret corneal topography and proper case selection and patient counseling.

Adolescent↗
PubMedDate not supplied

Changes in intraocular pressure after laser in situ keratomileusis for myopia, hyperopia, and astigmatism.

PURPOSE: Reports have shown that photorefractive keratectomy changes intraocular pressure (IOP) in myopic eyes by changing the thickness and curvature of the cornea. Changes in intraocular pressure after laser in situ keratomileusis (LASIK) for hyperopia led the authors to evaluate IOP after LASIK for various refractive errors. METHODS: The measurement of intraocular pressure with a Goldman applanometer in the central cornea was evaluated before and 3 months after LASIK in 100 eyes of 55 patients with various refractive errors. Corneal thickness (pachymetry) and corneal topography were evaluated. RESULTS: After LASIK, a significant decrease of intraocular pressure was observed in most eyes: mean 11.9 +/- 3.2 mmHg before and 9.8 +/- 2.6 mmHg at 3 months after surgery (P < .001). Mean decrease in IOP was 2.75 +/- 3.3 mmHg (P < .0001) for myopic eyes, 2.28 +/- 2.43 mmHg (P < .001) for hyperopic eyes, and 1.47 +/- 2.5 mmHg (P < .0012) for astigmatic eyes. IOP reduction was not significantly correlated to the amount of ablation (r = 0.05) or to corneal thickness. CONCLUSION: Intraocular pressure decreased in myopic, hyperopic, and astigmatic eyes after LASIK. The reduction was not correlated to the amount of tissue removed or to flattening or steepening of the central cornea.

Adolescent↗
PubMedDate not supplied

Laser in situ keratomileusis for hyperopia and hyperopic and mixed astigmatism with LADARVision using 7 to 10-mm ablation diameters.

PURPOSE: To evaluate the results of laser in situ keratomileusis (LASIK) performed to correct hyperopia, and hyperopic and mixed astigmatism using wider ablation diameters (optical zone diameter and overall ablation diameter) than those commonly used with the same and other lasers. METHODS: After flap creation using an Alcon SKBM microkeratome set for a 10-mm flap diameter, 53 eyes (33 patients) with a mean spheroequivalent attempted correction of +2.34 +/- 2.09 D underwent LASIK (Alcon LADARVision 4000) using a 7-mm optical zone diameter and a 3-mm transition zone for an overall 10-mm total ablation diameter. The nasal hinge was prevented from undesired ablation by the use of proprietary hinge protector software. Eyes were followed for 6 months after surgery. RESULTS: Six months after surgery, mean spheical equivalent refractive error was -0.22 +/- 0.41 D. There were 79.2% of eyes within +/- 0.50 D, and 98.1% within +/- 1.00 D of intended correction. Uncorrected visual acuity of 20/20 or better was achieved by 28 eyes (53%) and 20/40 or better by 50 eyes (94.3%). No meaningful visual complaints during nighttime hours, such as haloes or glare, were subjectively reported by patients. CONCLUSION: The use of larger ablation diameters in LASIK for hyperopia, and hyperopic and mixed astigmatism produced accurate results, early refractive stability, and good visual performance.

Adult↗
PubMedDate not supplied

Expanded range customcornea algorithms for myopia and astigmatism: one-month results.

PURPOSE: To evaluate the early clinical results achieved with an algorithm adjusted for an expanded range of correction in wavefront-guided customized ablation with the LADARVision4000 (Alcon Laboratories Inc, Fort Worth, Tex). METHODS: Fifty-five consecutive eyes from 31 patients underwent wavefront-guided, customablation laser in situ keratomileusis (LASIK) (Hansatome and BD 4000 microkeratomes, LADARWave aberrometer, LADARVision4000 laser system). These were normal myopic and astigmatic eyes that had never been operated on. The spherical equivalent refractive error was +0.30 to -8.13 diopters (D) (mean -4.26 +/- 2.14 D) and the astigmatism ranged from 0 to -3.75 D (mean -0.97 +/- 0.96 D). eyes were treated according to the CustomCornea protocol using the commercial LADARVision4000 platform. Patients were followed for at least 2 months and standard visual measurements were taken and recorded at 1 day and 1, 3, and 6 months after treatment. The results of treatment were assessed using the following parameters: uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA); manifest spherical equivalent refractive error; wavefront measurement of high order aberrations; and subjective reports of visual symptoms by patients. RESULTS: One month after LASIK, the mean manifest spherical equivalent refractive error was -0.18 +/- 0.41 D. Seventy-eight percent and 96% of eyes had manifest spherical equivalent refractive error within +/-0.50 D and +/-1.00 D of attempted correction, respectively, with 78% of eyes with 20/20 or better UCVA. Eyes with 20/16 and 20/12.5 BSCVA were 89% and 36%, respectively (55% and 7% preoperatively). The mean high order aberrations root-mean-square was 0.34 +/- 0.10 microm preoperatively and 0.35 +/- 0.09 microm postoperatively (6.0-mm pupil size). High order aberrations were either reduced, unchanged, or increased by <10% in 58% of eyes. Subjectively, patients reported no visual symptoms and had no complaints regarding the quality of their vision. CONCLUSION: The new optimized algorithm for higher refractive errors appears to be effective in improving BSCVA, and a minority of patients demonstrated an increase in the magnitude of high order aberrations when compared to preoperative aberrometry. A slight spherical equivalent refraction undercorrection will be addressed with future nomogram adjustments.

Adult↗
PubMedDate not supplied

Implantation of Artisan toric phakic intraocular lenses for the correction of astigmatism and spherical errors in patients with keratoconus.

PURPOSE: To evaluate the correction of astigmatism and spherical ametropia in patients with keratoconus through implantation of an Artisan toric phakic intraocular lens (PIOL) (Ophtec, Groningen, The Netherlands). METHODS: Artisan toric PIOLs were implanted uneventfully in both eyes of three patients with keratoconus with clear central corneas and contact lens intolerance. RESULTS: Best spectacle-corrected subjective visual acuity after lens implantation was unchanged in one eye and improved in five eyes. Spherical equivalent refraction was significantly reduced in all eyes (P=.03). The safety index was 1.49. CONCLUSIONS: The implantation of an Artisan toric PIOL may be an alternative for treating astigmatism and myopia in contact lens intolerant patients with keratoconus with clear central corneas. Especially in patients with associated myopia, this procedure is worth considering before planning a penetrating keratoplasty.

Adult↗
PubMedDate not supplied

Wavefront-guided LASIK with the NIDEK NAVEX platform for the correction of myopia and myopic astigmatism with 6-month follow-up.

PURPOSE: To assess safety, efficacy, predictability, stability, and change in higher order aberrations after wavefront-guided LASIK for myopia and myopic astigmatism using the NIDEK NAVEX platform. METHODS: Wavefront-guided LASIK was performed in 93 eyes in a 6-month trial with a goal of emmetropia. Treated eyes had a mean subjective manifest spherical equivalent refraction of -4.08+/-1.99 D diopters (D), with a range of -9.50 to -0.38 D of myopia and -4.50 to 0.00 D of astigmatism. An early nomogram with the OPDCAT software program provided by the manufacturer was used in all procedures. Safety, efficacy, predictability, stability, and change in higher order aberrations were evaluated at 6 months. RESULTS: At 6 months, 100% eyes were within +/-1.0 D of emmetropia and 95% eyes were within +/-0.5 D. Uncorrected visual acuity (UCVA) of > or = 1.0 was achieved in 89% of eyes, and 38% of eyes achieved UVCA of > or = 1.2. No eyes lost > or = 2 lines of best spectacle-corrected visual acuity (BSCVA), 25% of eyes gained 1 line, 3% gained 2 lines, and 1% gained > or = 2 lines of BSCVA. Higher order root-mean-square (RMS) values increased by 19% on average between pre- and postoperative measurements. Eyes treated with higher order aberrations of < 0.3 RMS showed on average an increase of 40% on preoperative values, whereas eyes with significant aberrations showed a decrease in aberrations following wavefront treatment. CONCLUSIONS: Wavefront-guided ablation using the NIDEK NAVEX platform is safe, effective, and predictable. However, patients with low amounts of aberrations showed an increase in aberrations following wavefront treatment, therefore, wavefront treatment may not be indicated or beneficial to every patient.

Adult↗
PubMed2006

Wavefront-supported photorefractive keratectomy with the Bausch & Lomb Zyoptix in patients with myopic astigmatism and suspected keratoconus.

PURPOSE: To evaluate the safety, efficacy, and visual outcome of wavefront-supported photorefractive keratectomy (PRK) for the correction of myopia and myopic astigmatism in patients with suspected keratoconus. METHODS: Forty eyes of 20 patients with myopia -4.0 to -8.0 diopters (D) (mean: -6.25 +/- 1.04 D), cylinder -1.0 to -2.50 D (mean: -1.61 +/- 0.71 D), and corneal thickness 440 to 488 microm were treated with wavefront-supported PRK. Corneal topography evaluation revealed a significantly irregular cylinder (inferior-superior difference > 1.5 D) with possible mild or forme fruste keratoconus. Aberrometry was performed with the Hartmann-Shack aberrometer, and corneal data were evaluated with the Orbscan system. Eyes were treated with the Technolas 217z Bausch & Lomb excimer laser and followed for a minimum of 40 months. RESULTS: Following surgery, mean spherical equivalent refraction was +0.33 +/- 0.8 D. It was within +/- 0.5 D of the intended refraction in 95% of eyes and within +/- 1.0 D in 100% of eyes. Mean uncorrected visual acuity improved from 20/400 preoperatively to 20/25 postoperatively. Mean best spectacle-corrected visual acuity (BSCVA) remained unchanged (20/20) or improved to 20/20 in 92.5% of eyes and to 20/25 in 7.5% of eyes. Individually, BSCVA did not change in 28 (70%) eyes and increased by > or = 2 Snellen lines in 9 (22.5%) eyes; 3 (7.5%) eyes lost 1 Snellen line because of corneal haze. Laser treatment induced a significant flattening of the preoperative inferior corneal steepness in all eyes. Wavefront analysis demonstrated a significant decrease in high order aberrations (total root-mean-square and coma). CONCLUSIONS: Wavefront-supported PRK appears to be effective for the treatment of myopia and astigmatism in patients with suspected keratoconus and thin, irregular corneas. Longer follow-up is needed to prove the safety of the procedure in this patient population.

Adult↗
PubMedDate not supplied

[An experimental study of the role of present-day suture materials in the forming of postoperative astigmatism in a penetrating corneal wound].

Tolerance of suturing materials ethylon 10/0, mersilene 11/0 (Ethycon), and nylon 10/0 (Alcon) by rabbit corneal tissue is studied. Mersilene and ethylon caused the least irritation of the eyes, while use of nylon and capron led to vascularization of cornea and rejection of the material (capron) in remote periods. Assessment of the effects of the above-listed materials on postoperative astigmatism showed that mersilene and ethylon caused a lesser astigmatism than nylon and capron.

Animals↗
PubMedDate not supplied

[Eximer laser correction of complex myopic astigmatism by centered and decentered keratoablation].

Reviews the results of correction of complex myopic astigmatism with asymmetric form of disposition on the cornea by two methods, with centered and decentered photokeratoablation. Analyzes the results of 80 laser keratomileusis operations for medium and high myopia. Describes a method of calculations and keratotopographic detection of asymmetric astigmatism and a method for transferring it into symmetrical form in computer-aided keratotopography. Two types of interventions brought about a good refraction result (sphere equivalent -0.66 +/- 0.54 diopters) and high resolving capacity of the eye (0.88-0.99). Decentered keratoablation led to a significant increase in visual acuity without correction, this indicating a better adequacy of this method, discussed in this paper.

Adult↗
PubMed2000

Clear lens extraction to correct hyperopia in presbyopic eyes with or without arcuate keratotomy for pre-existing astigmatism.

This retrospective study evaluates visual (functional) and refractive outcome of correcting hyperopia (i.e. 2.5 D or more) by means of a cataract procedure and simultaneously the pre-existing clinical significant astigmatism (1.5 D or more with the rule; 1 D or more against the rule), if present, by means of an arcuate keratotomy. Nine eyes undergoing clear lens extractions with intraocular lensimplantation (IOL) in combination with arcuate keratotomy (group one) and 29 eyes without arcuate kertotomy (group two) are included in the study. The mean age at the time of surgery was 62.89 years (range, 50 to 83) in group one and 68.17 years (range, 53 to 86) in group two. For calculation of the lens power a modified SRK II program, aiming at emmetropia was used. In only one highly hyperopic patient the Holladay I formula was used to calculate two piggyback lenses. A modified Istre nomogram was used to determine the surgical parameters of the arcuate keratotomy. The Cravy formula and the Holladay, Cravy, Koch vector analysis were used to determine the change in refractive cylinder results. Patients were followed postoperatively for a mean of 2.8 months in group one and 7.5 months in group two. In group one, 6 out of 9 eyes achieved a postoperative refraction within +/- 0.5 D of intended refraction and 8 out of 9 were within +/- 1 D of intended refraction. In group two, it was 15/29 and 24/29 respectively. Postoperatively, the uncorrected visual acuity was 20/40 or better in all eyes of group one (9/9) and in 27/29 eyes of group two. None of the eyes in both groups lost two or more lines of the best corrected visual acuity. Clear lens extraction with IOL is an effective and safe procedure for the correction of hyperopia in a presbyopic age group. In combination with an arcuate keratotomy, pre-existing astigmatism can be corrected simultaneously.

Aged↗
PubMed2000

Step-along vergence procedures in stigmatic and astigmatic systems.

The traditional step-along vergence procedure applies to stigmatic systems, that is, systems that are not astigmatic. Computation is disrupted when a focus coincides with a thin lens or refracting surface. A small change to the procedure results in a modified procedure which overcomes the computational problems. The modified procedure is easier to execute than the traditional procedure and allows one to write down useful equations directly. Among the formulae are those for back-vertex power. A step-along vergence procedure also exists for astigmatic systems. It makes use of the dioptric power matrix and the reduced vergence matrix. Computational problems arise when a point or line focus coincides with a thin lens or refracting surface; however they are not overcome by an analogous modification to the procedure. Nevertheless the modified procedure has some advantages including the fact that, as for stigmatic systems, it allows one to write down useful formulae directly. Stepwise calculations of vergence are sometimes performed backward through a system; the advantages and disadvantages described for step-along procedures holds for such step-back procedures as well.

Astigmatism↗
PubMed2001

[Analysis on three-year follow-up results of excimer laser photorefractive keratectomy in treatment for myopia and myopic astigmatism].

OBJECTIVE: To evaluate the efficacy of excimer laser photorefractive keratectomy(PRK) on myopia and myopia astigmatism. METHODS: PRK was performed with VISXC20/20 on 377 eyes of 209 patients. Treated eyes were divided into two groups, according to their conditions before operation: Group I included 238 eyes (-1.50 to -6.00 D); Group II, 139 eyes (-6.25 to -16.00 D). All patients were followed-up for more than three years. RESULTS: Percentages of uncorrected visual acuity (UCVA) > or = 10/20 and 20/20 were 99.6% and 85.3% in Group I, and 79.9% and 48.2% in Group II respectively. Percentage of diopter < +/- 1.00 in Group I was 94.5%, and 61.9% in Group II. The rate of corneal haze of grade 0 was 100% in Group I, and 98.6% in Group II, but corneal haze of grade 2 was found in 1.2% of eyes in Group II. The postoperative intraocular pressure (IOP) of all operated eyes was normal. CONCLUSION: The results suggest that excimer laser PRK is an effective method for treating myopia and myopic astigmatism, especially for low and moderate myopia.

Adolescent↗
PubMedDate not supplied

[Influence of surgical technic in cataract operation. (Postoperative astigmatism, type of iridectomy)].

The authors have made a statistical study of the influence of surgical technique on the anatomical (astigmatism) and functional results in cataract surgery. They have taken into consideration whether the incision is made under a conjunctival flap or not, with a keratome or Gillette blade, with a sector or peripheral iridectomy. Their conclusions are that when performed by the same surgeon the different surgical techniques do not give rise to significant variations in astigmatism or in the eventual functional result.

Aged↗
PubMed2003

[Experimental correction of irregular astigmatism in patients with keratoconus using diode laser thermal keratoplasty].

OBJECTIVE: To evaluate the potential of diode laser thermokeratoplasty (DTK) in the correction of irregular astigmatism in patients with keratoconus. GROUP AND METHODS: The coagulation of deep layers of cornea stroma was made on four eyes of four patients suffering from advanced keratoconus at the mean age of 31 years by means of the infrared contact cw laser Prolaser Rodenstock 1.9 DTK. The aim of the treatment was to increase the curvature of cornea in flat meridians and to compensate flattening of cornea in steep meridians by way of forming traction strips between the contracted tissue of individual coagulation points. The changes on the cornea topography and changes of visual functions were determined. RESULTS: The diode laser keratoplasty is capable to induce sector increase of cornea curvature and thereby improve symmetry pictures of irregular astigmatism in keratoconus. For a definitive inclusion of DLK into the spectrum of clinically applicable procedures, other therapeutic studies are needed as well as larger groups with relatively homogeneous pre-operation pictures.

Adult↗
PubMed1992

[Surgical correction of astigmatism after perforating keratoplasty].

Microsurgical control of astigmatism after perforating keratoplasty has widely remained an unsolved problem in spite of many sophisticated suggestions and inventions. The frequent irregularity in the recipient cornea and poor predictability with respect to wound healing are the major obstacles. If spectacles or contact lenses cannot provide useful vision, postoperative surgical correction is needed. Ablative or thermal laser techniques have not been sufficiently tried for such cases to be justified, and one may hesitate anyway to apply destructive methods in transplants. We therefore still use T-incisions and wedge resections, which are said to be rather imprecise. Only 3 out of more than 700 keratoplasties performed in our clinic from 1987 through July 1991 required such procedures. Two more cases were referred by surgeons outside the hospital. All five surgical corrections resulted in a good longterm effect with considerable improvement of vision. Thus, as long as alternative methods for surgical correction of postkeratoplasty astigmatism have not proved to be superior, we should continue to practice these "old" methods, which, indeed, are not bad if properly applied.

Adolescent↗