Effect of expanding the treatment zone of the Nidek EC-5000 laser on laser in situ keratomileusis outcomes

ArticleinJournal of Cataract and Refractive Surgery 30(11):2336-43 · December 2004with4 Reads
DOI: 10.1016/j.jcrs.2004.05.015 · Source: PubMed
Abstract
To evaluate the effect of expanding the treatment zone of the Nidek EC-5000 laser on postoperative visual acuity as well as night glare and halos after laser in situ keratomileusis (LASIK) using 4 ablation zone diameters. Division of Ophthalmology, Evanston Northwestern Healthcare and Northwestern University Medical School, Glenview, Illinois, USA. This prospective study comprised 301 eyes of 154 consecutive patients who had LASIK in 1 or both eyes using the Nidek EC-5000 laser by 1 surgeon with experience in keratomileusis and excimer laser refractive surgery. A 6.5 mm optical zone was used with a transition zone 1.0 mm larger than the pupil under scotopic conditions (7.5, 8.0, 8.5, or 9.0 mm). Targeted correction was calculated according to a customized clinical nomogram. All patients were queried about glare and halos preoperatively and 3 months postoperatively using a questionnaire assigning numeric values to the degree of perceived visual disturbance (0 = no glare or halos, 1 = minimal, 2 = moderate, 3 = severe). The baseline uncorrected visual acuity (UCVA) was 20/200 or worse in 293 eyes. The baseline best spectacle-corrected visual acuity was 20/20 or better. The mean preoperative refractive sphere was -6.33 diopters (D) +/- 2.80 (SD) (range -1.00 to -16.25 D) and the mean preoperative refractive cylinder, 0.86 +/- 0.83 D (range 0 to +3.25 D). Three months postoperatively, 78% of eyes had a UCVA of 20/20 and 99%, of 20/40 or better. Preoperatively, 94 eyes (31%) had glare and halos. At 3 months, glare, halos, or both were present in 19 eyes of 11 patients (6.3%) (P<.0001); in 14 eyes, patients reported less severe glare and halos postoperatively than preoperatively. The use of a peripheral transition zone 1.0 mm larger than the pupil under scotopic conditions resulted in a low incidence of glare and halos postoperatively and did not adversely affect visual acuity. There was no increase in postoperative complications including corneal ectasia.
    • "Transition zone can ensure that the curvature is continuous at the boundary between transition zone and untreated cornea and at the boundary between optical zone and transition zone. The use of transition zone during LASIK resulted in a low incidence of postoperative glare and ha- los [2] . In addition, a transition zone was used in photorefractive keratectomy for high myopia [3]. "
    [Show abstract] [Hide abstract] ABSTRACT: The analysis in the impact of transition zone on the optical performance of human eye after laser refractive surgery is important for improving visual correction technology. By designing the ablation profiles of aspheric transition zone and creating the ablation profile for conventional refractive surgery in optical zone, the influence of aspheric transition zone on residual aberrations was studied. The results indicated that the ablation profiles of transition zone had a significant influence on the residual wavefront aberrations. For a hyperopia correction, the profile #9 shows a larger induced coma and spherical aberration when the translation of the centre of pupil remains constant. However, for a myopia astigmatism correction, the induced coma and spherical aberration in profile #1 shows relatively larger RMS values than those in other profiles. Therefore, the residual higher order aberrations may be decreased by optimizing ablation profiles of transition zone, but they cannot be eliminated. In order to achieve the best visual performance, the design of ablation pattern of transition zone played a crucial role.
    Article · Dec 2014
    • "It connects the optical zone to the untreated cornea. The use of transition zone during LASIK resulted in a low incidence of postoperative glare and ha- los [11, 12]. Arbelaez et al. showed that a multidynamic aspheric transition zone was included in a cornea ablation profile in order to minimize the amount of induced optical rations [13]. "
    [Show abstract] [Hide abstract] ABSTRACT: To detect possible differences in residual wavefront aberrations between standard and customized laser refractive surgery based onmathematical modeling, the residual optical aberrations after conventional and customized laser refractive surgery were compared accordingto the ablation profile with transition zone. The results indicated that ablation profile has a significant impact on the residual aberrations.The amount of residual aberrations for conventional correction is higher than that for customized correction. Additionally, the residualaberrations for high myopia eyes are markedly larger than those for moderate myopia eyes. For a 5 mm pupil, the main residual aberrationterm is coma and yet it is spherical aberration for a 7 mm pupil. When the pupil diameter is the same as optical zone or greater, themagnitudes of residual aberrations is obviously larger than that for a smaller pupil. In addition, the magnitudes of the residual fifth orsixth order aberrations are relatively large, especially secondary coma in a 6 mm pupil and secondary spherical aberration in a 7 mm pupil.Therefore, the customized ablation profile may be superior to the conventional correction even though the transition zone and treatmentdecentration are taken into account. However, the customized ablation profile will still induce significant amount of residual aberrations.
    Full-text · Article · Sep 2013
    • "These diameters, as well as the customized blend zone, were thought to be enough to avoid the potential night vision disturbances after LASIK in these patients with large pupil sizes. Macsai et al51 found that the use of a peripheral transition zone 1.0 mm larger than the pupil diameter under scotopic conditions resulted in a low incidence of glare and halos postoperatively, and did not adversely affect the visual acuity. In our study, there was no negative effect of the selected optical zone on CDVA or CS. "
    [Show abstract] [Hide abstract] ABSTRACT: To investigate the efficacy and predictability of wavefront-guided laser in situ keratomileusis (LASIK) treatments using the iris registration (IR) technology for the correction of refractive errors in patients with large pupils. Horus Vision Correction Center, Alexandria, Egypt. Prospective noncomparative study including a total of 52 eyes of 30 consecutive laser refractive correction candidates with large mesopic pupil diameters and myopia or myopic astigmatism. Wavefront-guided LASIK was performed in all cases using the VISX STAR S4 IR excimer laser platform. Visual, refractive, aberrometric and mesopic contrast sensitivity (CS) outcomes were evaluated during a 6-month follow-up. Mean mesopic pupil diameter ranged from 8.0 mm to 9.4 mm. A significant improvement in uncorrected distance visual acuity (UCDVA) (P < 0.01) was found postoperatively, which was consistent with a significant refractive correction (P < 0.01). No significant change was detected in corrected distance visual acuity (CDVA) (P = 0.11). Efficacy index (the ratio of postoperative UCDVA to preoperative CDVA) and safety index (the ratio of postoperative CDVA to preoperative CDVA) were calculated. Mean efficacy and safety indices were 1.06 ± 0.33 and 1.05 ± 0.18, respectively, and 92.31% of eyes had a postoperative spherical equivalent within ±0.50 diopters (D). Manifest refractive spherical equivalent improved significantly (P < 0.05) from a preoperative level of -3.1 ± 1.6 D (range -6.6 to 0 D) to -0.1 ± 0.2 D (range -1.3 to 0.1 D) at 6 months postoperative. No significant changes were found in mesopic CS (P ≥ 0.08), except CS for three cycles/degree, which improved significantly (P = 0.02). Magnitudes of primary coma and trefoil did not change significantly (P ≥ 0.34), with a small but statistically significant increase in primary spherical aberration. Wavefront-guided LASIK provides an effective correction of low to moderate myopia or myopic astigmatism in large pupil patients without deterioration of visual quality.
    Full-text · Article · Dec 2012
Show more