Effect of decentration and tilt on in vitro optical quality of intraocular lenses with different focus designs

Objective  To observe the effect of different degrees of decentration and tilt on the optical quality of the intraocular lenses (IOLs) with different focus designs.

Methods  The UV 3300 PC UV-visible spectrophotometer was employed to measure the spectral transmittance of the monofocal IOL CT ASPHINA 509M (509M), bifocal IOL AT LISA 809M (809M), and trifocal IOL AT LISA Tri 839MP (839MP) within Zeiss MICS platform with a refractive power of + 20 D. The modulation transfer function (MTF) values at a spatial frequency of 50 lp/mm along with MTF curves and United States Air Force (USAF) resolution test charts for each IOL at the focal point were measured at apertures of 3.0 mm and 4.5 mm using the in vitro optical quality testing system OptiSpheric IOL R&D under centered, decentered (0.3, 0.5, 0.7, 0.9 and 1.1 mm) and tilted (3°, 5°, 7°, 9° and 11°) conditions.

Results  All three IOLs filtrated the ultraviolet (UV) spectrum below 400 nm.When each IOL was in the centered position, at the 3.0 mm aperture, the MTF values were 0.772 at the far focus of the monofocal IOL 509M, 0.467 and 0.282 at the far and near focus of the bifocal IOL 809M, and 0.416, 0.147, and 0.229 at the far, intermediate, and near focus of the trifocal IOL 839MP, respectively.Whereas at the 4.5 mm aperture, the monofocal IOL 509M MTF value at the far focus was 0.664, the bifocal IOL 809M MTF values at the far and near focus were 0.506 and 0.264, and the trifocal IOL 839MP MTF values at the far, intermediate, and near focus were 0.392, 0.107, and 0.210, respectively.Among the three centered IOLs, the 509M demonstrated the highest MTF value at the far focus, followed by the 809M and then the 839MP; at the near focus, the MTF value of the 809M surpassed that of the 839MP.For decentration and tilt, the difference in MTF values of the three IOLs at the far and near focus was consistent with the differences observed when they were centered.At the same degree of decentration and tilt, all three IOLs exhibited superior optical quality at the 3.0 mm aperture compared to the 4.5 mm aperture.The optical quality of all three IOLs exhibited an overall decline as decentration and tilt increased.All three IOLs demonstrated a decrease in optical quality at the decentration of 0.3 mm or the tilt of 5°.

Conclusions  The IOLs within the Zeiss MICS platform design exhibits identical spectral transmittance and UV filtering properties.Among the three IOLs, when centered, the 509M, the 839MP, and the 809M exhibit superior optical quality at the far, intermediate, and near focal points, respectively.Under decentered and tilted conditions, the 509M and the 809M demonstrate better resistance against decentration and tilt, respectively, at both far and near focuses.Additionally, all three IOLs demonstrate better optical quality at smaller apertures, given equivalent degrees of decentration or tilt.However, the optical quality at each focal point of the three IOLs decreases compared to the centered position when subjected to a decentration of 0.3 mm or a tilt of 5°.

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