Premium
Predicted accommodative response from image quality in young eyes fitted with different dual‐focus designs
Author(s) -
FariaRibeiro Miguel,
AmorimdeSousa Ana,
GonzálezMéijome José M.
Publication year - 2018
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1111/opo.12443
Subject(s) - dual (grammatical number) , focus (optics) , optometry , quality (philosophy) , image quality , computer science , image (mathematics) , psychology , computer vision , medicine , optics , art , physics , literature , quantum mechanics
Purpose To investigate the separated and combined influences of inner zone ( IZ ) diameter and effective add power of dual‐focus contact lenses ( CL ) in the image quality at distance and near viewing, in a functional accommodating model eye. Methods Computational wave‐optics methods were used to define zonal bifocal pupil functions, representing the optic zones of nine dual‐focus centre‐distance CL s. The dual‐focus pupil functions were defined having IZ diameters of 2.10 mm, 3.36 mm and 4.00 mm, with add powers of 1.5 D, 2.0 D and 2.5 D (dioptres), for each design, that resulted in a ratio of 64%/36% between the distance and treatment zone areas, bounded by a 6 mm entrance pupil. A through‐focus routine was implemented in MATLAB to simulate the changes in image quality, calculated from the Visual Strehl ratio, as the eye with the dual‐focus accommodates, from 0 to −3.00 D target vergences. Accommodative responses were defined as the changes in the defocus coefficient, combined with a change in fourth and sixth order spherical aberration, which produced a peak in image quality at each target vergence. Results Distance viewing image quality was marginally affected by IZ diameter but not by add power. Near image quality obtained when focussing the image formed by the near optics was only higher by a small amount compared to the other two IZ diameters. The mean ± standard deviation values obtained with the three adds were 0.28 ± 0.02, 0.23 ± 0.02 and 0.22 ± 0.02, for the small, medium and larger IZ diameters, respectively. On the other hand, near image quality predicted by focussing the image formed by the distance optics was considerably lower relatively to the other two IZ diameters. The mean ± standard deviation values obtained with the three adds were 0.15 ± 0.01, 0.38 ± 0.00 and 0.54 ± 0.01, for the small, medium and larger IZ diameters, respectively. Conclusions During near viewing through dual‐focus CL s, image quality depends on the diameter of the most inner zone of the CL , while add power only affects the range of clear focus when focussing the image formed by the CL near optics. When only image quality gain is taken into consideration, medium and large IZ diameters designs are most likely to promote normal accommodative responses driven by the CL distance optics, while a smaller IZ diameter design is most likely to promote a reduced accommodative response driven by the dual‐focus CL near optics.