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L. N. Davies, G. A. Gibson, A. L. Sheppard, J. S. Wolffsohn; In vivo Biometric Evaluation of Phakic and Pseudophakic Eyes During Accommodation With Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3777. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the relationship between refractive and anterior segment biometric changes in phakic and pseudophakic eyes during accommodation with Optical Coherence Tomography (OCT).
Refractive and biometric data were taken from 32 phakic human eyes (aged 18 to 36 years old; mean ± SD, 19.9 ± 3.6 years). Mean relative change in anterior chamber depth (ACD), lens thickness (LT), lens centriod (LC = ACD + (LT/2)), anterior segment length (ASL = ACD +LT) and in objective refraction were assessed while subjects viewed an accommodative target between 0 D and 4 D in 1 D steps. Mean relative change in ACD was also measured in 15 eyes implanted with the Kellen Tetraflex KH3500 AIOL (aged 44 to 85 years old; mean ± SD, 69.4 ± 10.0 years). In both cohorts, mean accommodative responses were measured with the Shin-Nippon NVision-K 5001 autorefractor, while biometric parameters were assessed subsequently with the Zeiss Visante anterior segment OCT.
In the phakic cohort, mean LT increased by 72.6 µm/D, ASL increased by 18.2 µm/D, while there was a mean anterior shift in LC of 18.0 µm/D. Mean ACD decreased by 52.8 µm/D, and increased by 353.8 µm/D for the phakic and psuedophakic eyes, respectively. The correlation between biometric changes for both accommodative demand and response in the phakic group followed a non-linear biphasic profile. The forward movement of the anterior crystalline lens surface was the primary correlate to ~1.5 D response, thereafter, the backward shift in the posterior surface also contributed to the accommodative response. The posterior shift in AIOL position with increasing accommodative demand corresponded with the concurrent change in refractive error.
The biometric and refractive changes of the human crystalline lens, particularly the posterior lens surface, appears to be biphasic and non-linear in function; however, this relationship with AIOLs is absent. Indeed, rather than the proposed anterior shift, the AIOL is displaced posteriorly with accommodation.
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