Search

Purpose: To investigate the effects of toric and soft spherical contact lenses on the visual performance and wavefront aberrations in cases of low astigmatism. Material and Method: Twenty-four eyes of 14 contact lens users with cylindirical refractive error of -1.25 diopters or less were included in this prospective study. The subjects wore spherical (lotrafilcon B) and toric (galyfilcon A) lenses for eight hours with a one-week interval. The best-corrected visual acuity and contrast sensitivity were measured before and after 8 hours of contact lens wear. Corneal topography and wavefront analysis were also performed. Zernike coefficients were used to calculate the aberrations at a 6-mm pupil diameter. Total and higher-order root mean square (RMS) values as well as spherical and coma aberrations were measured. Result: The mean spherical refractive error of the cases was -2.52±1.25 (range: from -0.50 to -6.0) D. The mean best- corrected visual acuity was significantly higher with both types of contact lenses than with glasses (p=0.017), however, no statistical difference was observed between the two types of contact lenses (p=0.470). The mean high-frequency contrast sensitivity value was lower with toric lenses (p=0.038). The mean higher-order RMS value was higher with both types of contact lenses (p=0.021), but with no difference between them (p>0.05). The mean spherical aberration value did not differ among glasses, toric or soft spherical contact lenses (p>0.05). The mean coma aberrations were high with both types of contact lenses (p=0.041); no difference was observed between the two lens types (p>0.05). Discussion: In this study, it was demonstrated that in cases of low astigmatism, soft spherical and toric contact lenses increase visual acuity, total higher-order aberrations, and coma aberrations, but decrease high-frequency contrast sensitivity. There was no difference between the two types of contact lenses. [ABSTRACT FROM AUTHOR]

Purpose: To assess topography-assisted corneal wavefront excimer laser surface ablation for the correction of ametropia and irregular astigmatism after keratoplasty. Setting: Department of Ophthalmology, St. Thomas'' Hospital, London, United Kingdom. Methods: In this pilot study, 15 patients (16 eyes) who were intolerant of spectacle and contact lens correction due to astigmatic anisometropia after keratoplasty (15 penetrating and 1 lamellar) had topography-assisted customized excimer laser treatments. Corneal topographic data using a Keratron Scout, Placido disk system allowed for preoperative analysis of wavefront anomalies of the anterior corneal surface from which a customized excimer laser correction of both lower-order aberrations (LOAs) and higher-order aberrations (HOAs) was prepared (ORK software) for treatment with a Schwind Esiris flying-spot laser. All eyes had laser-assisted subepithelial keratectomy (LASEK) using 15% alcohol with a 20-second to 30-second application. Four eyes received an application of mitomycin-C (MMC) 0.2 mg/mL for 1 minute after stromal ablation. Results: The mean preoperative spherical equivalent (SE) was −3.50 diopters (D) ± 3.97 (SD) (range +1.625 to −9.25 D). The preoperative cylindrical error was −7.2 D (range −2.75 to −13.5 D). The programmed laser correction was −3.14 D (range +1.62 to −9 D) with a maximum attempted cylindrical correction of −7 D. Adherent LASEK epithelial flaps along suture lines and the graft–host junction were noted in 9 eyes (56%), although it was possible to obtain and replace a partial flap. A follow-up of 18 months was achieved in all eyes. At the final follow-up visit, the mean postoperative SE was −1.08 ± 1.85 D (range +3 to −4.78 D) (P<.01, F<.01). Ten eyes (62.5%) were within ±1 D of the intended correction. The mean postoperative cylindrical error was −2.72 D (range −0.5 to −6.5 D) (P<.001), with vector analysis demonstrating a mean 6.23 D correction. Analysis of HOAs using a 6.0 mm pupil size demonstrated a significant reduction of higher-order root mean square (RMS) (P<.002), trefoil (P<.005), and 4th-order spherical aberration (P<.02) at 18 months compared with preoperative values. Uncorrected visual acuity improved in all eyes (P<.0001). Best spectacle-corrected visual acuity was unchanged or improved in 13 eyes (81%) and worse in 2 eyes by 1 line; 1 eye lost 3 lines due to an increase in preexisting cataract. In eyes that did not receive MMC, corneal haze (grade II to IV) was encountered in 3 eyes (27%). One eye required phototherapeutic keratectomy with MMC application at 12 months. Of the 4 eyes treated with MMC, 1 had trace haze and 3 had no detectable haze. There were no reported cases of epithelial instability, ectasia, or graft rejection. Conclusions: Topography-assisted customized LASEK was effective in the correction of postkeratoplasty astigmatism. A significant improvement of both LOAs and HOAs was obtained with good refractive stability for over 18 months. Iatrogenic haze typically occurred but appeared to be minimized with adjunctive use of intraoperative MMC. [Copyright &y& Elsevier]

Although toric contact lenses have improved in design and development and their use is increasing, further consideration should be given to the alternative methods of astigmatism correction by contact lenses. Much can still be achieved by non-toric lens, both for a wide range of astigmatism and for ease of supply. A number of these alternatives are examined, their advantages and disadvantages reappraised, and the merits of lens correction compared with surgical methods considered. [ABSTRACT FROM AUTHOR]