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A-scan ultrasound in ophthalmology: A simulation tool

Petrella, L. I. ; Perdigão, F. ; Duarte, L. ; Santos, M ; Lopes, M. ; Gomes, M. ; Santos, J

Medical Engineering and Physics Vol. 97, Nº -, pp. 18 - 24, November, 2021.

ISSN (print): 1350-4533
ISSN (online):

Scimago Journal Ranking: 0,53 (in 2021)

Digital Object Identifier: 10.1016/j.medengphy.2021.09.005

In the present study, we developed a computational tool for simulating the ophthalmological applications of A-
scan ultrasound, including cataract characterisation and biometry. A-scan biometry is used to measure the axial
length (AL) of the eye before cataract surgery to calculate the refractive power of the intraocular lens to be
implanted. Errors in the measurement of the AL lead to post-surgical refractive errors. The simulation tool was
developed using the k-Wave Matlab toolbox, together with a user-friendly interface developed in Matlab.
Diverse error sources were evaluated. Constant ultrasound speed assumptions may introduce refractive errors
of up to 0.6 D; by contrast, probe positioning errors had a lower impact, of up to 0.11 D. The correct identifi-
cation of the Bruch’s membrane is limited not only by axial resolution constraints but also by the low reflection
coefficient at the retina/choroid interface. Regarding cataract characterisation, the amplitudes of the echoes
reflected at the lens interfaces are sensitive to diverse cataract types and severities, and a more realistic repre-
sentation could be obtained by using a higher resolution in the eye grid; however, the required computational
times would make simulations impracticable when using personal computers. The simulation tool shows good
versatility for evaluating diverse aspects of A-scan biometry.