Abstract
Measurement of intraocular lens (IOL) alignment implanted in patients in cataract surgery is important to understand their optical performance. We present a method to estimate tilt and decentration of IOLs based on optical coherence tomography (OCT) images. En face OCT images show Purkinje-like images that correspond to the specular reflections from the corneal and IOL surfaces. Unlike in standard Purkinje-imaging, the tomographic nature of OCT allows unequivocal association of the reflection with the corresponding surface. The locations of the Purkinje-like images are linear combinations of IOL tilt, IOL decentration, and eye rotation. The weighting coefficients depend on the individual anterior segment geometry, obtained from the same OCT datasets. The methodology was demonstrated on an artificial model eye with set amounts of lens tilt and decentration and five pseudophakic eyes. Measured tilt and decentration in the artificial eye differed by 3.7% and 0.9%, respectively, from nominal values. In patients, average IOL tilt and decentration from Purkinje were 3.30±4.68 deg and 0.16±0.16 mm , respectively, and differed on average by 0.5 deg and 0.09 mm, respectively, from direct measurements on distortion-corrected OCT images. Purkinje-based methodology from anterior segment en face OCT imaging provided, therefore, reliable measurements of IOL tilt and decentration.
Highlights
Cataract is one of the major causes of vision loss in the aging population
The intraocular lens (IOL) is inserted in the capsular bag through a circular window in the anterior capsule, with the lens haptics pressing against the equatorial region of the capsular bag
We demonstrate the measurement of IOL tilt and decentration from optical coherence tomography (OCT) images, which used a Purkinjebased analysis
Summary
Cataract is one of the major causes of vision loss in the aging population. The common treatment for cataract is the replacement of the natural lens by an intraocular lens (IOL). The aimed correction of corneal HOA by aspheric IOLs may be compromised by the induction of other HOA by a tilted/decentered lens.[2] The performance of refractive M-IOLs (generally with concentric or segmented near/far regions) is critically affected by potential misalignments of the IOL.[3] tilts and decentrations occurring with the only U.S Food and Drug Administration (FDA)-approved A-IOL may play a role in its function.[4] Measurement of tilt and decentration of IOLs in pseudophakic eyes is important as an endpoint for treatment, with premium IOLs. On the other hand, in combination with biometrical and anatomical ocular data, knowledge of IOL and eye alignment is important in the development of customized computer eye models, which give insights into the relative contribution of different factors to optical performance with IOLs The method was validated on an artificial model eye (with set values of lens tilt and decentration) and tested in five pseudophakic eyes with implanted AIOLs (where the en face OCT Purkinje-based estimates of IOL tilt and decentration were compared to direct estimates from distortion-corrected 3-D OCT images)
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