Higher-Order Aberrations When Wearing Sphere and Toric Soft Contact Lenses

Abstract

Purpose To determine the on-eye effect of spherical and toric contact lens design on higher-order aberrations (HOA). Methods Thirty eyes (15 subjects) entered a masked, randomized, cross-over study. Each eye was fitted with the spherical and toric lens of the following brands in random order: Acuvue Advance, Biomedics 55, Frequency 55, and SofLens 66. HOAs were measured using the Zywave II Aberrometer over a 6-mm aperture up to fifth order. A linear model accounting for the fixed effect of lens type and random effects of subject and eye was created. Paired t-tests were completed between lens brands within the spherical and toric lenses and between the spherical and toric lens within each brand. Best-corrected visual acuity (VA) was measured and compared. Results No clinically meaningful differences in total HOAs were found between brands or between the spherical and toric lens within a brand. Positive spherical aberration (SA) was reduced by all spherical and toric lenses compared to wearing no lens by 0.07 to 0.23 μm (p<0.0001). Frequency toric induced the greatest change in SA. The thin-zone design lens (Acuvue Advance for Astigmatism) had a statistically different amount of vertical coma (−0.04 μm) than the three prism-balast toric lenses (0.11 to 0.23 μm; p<0.0001). SofLens toric had the greatest amount of vertical coma, but better VA than Acuvue Advance for Astigmatism and Frequency toric. With the exception of Acuvue Advance for Astigmatism, toric lenses had greater absolute magnitude of vertical coma than their sphere counterparts (all p<0.002). No other significant HOA differences were observed. Conclusions Toric contact lenses with prism-ballast designs demonstrated more vertical coma, but better VA. Positive SA was reduced by spherical and toric contact lenses. The visual quality effect of lens design and material on induced HOAs warrants further investigation.

Spherical aberration and higher order aberrations with Balafilcon A (PureVision) and Comfilcon A (Biofinity)

“…There were also no differences in subjective appreciation or clinical performance between lens designs or lens powers. Other studies found various effects on HOA with differing spherical soft contact lens brands [21][22][23][24][25][26][27][28][29], which presumably drove the development of aspheric or 'aberration-free' lenses, along with the reports of the possible benefits of aspheric lenses [30][31][32][33]. This study found no changes in spherical aberration, but it did find changes in other aberrations.…”

Tear Deformation Time and optical quality in eyes wearing silicone hydrogel contact lenses

“…The variation of optical aberrations during the lens wear can be attributed to many factors, including lens centration relative to the corneal center, lens-to-cornea fitting relationship, optical quality of the contact lens, and pre-lens tear film status 7, 8. The first two factors were controlled as much as possible during the measurements.…”

Non-Surgical Treatment of Astigmatism

“…Nowadays, improved lens designs and the availability of disposable toric contact lenses have resulted in improved health benefits and adaptation (10) Well-fitted hydrogel toric lenses can provide visual acuity and visual performance equivalent to that of spherical RGP lenses. (9) All the literature agrees that the best way to fit a soft lens is by considering the response to the trial lens fitting. By slit lamp, the physician observes centralisation, the movement of the lens and the lens-cornea relationship.…”

“…Additionally, decentration of spherical aberration correction has been shown to induce a coma-like aberration that is another distortion in image formation. (9) Visual acuity with toric lenses is better than with spherical or aspheric lenses, but initially lens quality and stability was a problem. Nowadays, improved lens designs and the availability of disposable toric contact lenses have resulted in improved health benefits and adaptation (10) Well-fitted hydrogel toric lenses can provide visual acuity and visual performance equivalent to that of spherical RGP lenses.…”

“…Spherical lenses failed to mask corneal toricity during topography, while toric lenses caused central neutralisation and a decrease in corneal cylinder in low and moderate astigmatic eyes. (9) Soft aspheric contact lenses have been recommended for low astigmatic patients because its design could decrease the level of spherical aberration that is a distortion in image formation. However, clinical studies have reported that non-toric aspheric soft contact lenses did not improve visual acuity significantly when compared to spherical lenses on low astigmats.…”