Lasers in Medical Science

, Volume 34, Issue 6, pp 1229–1234 | Cite as

Impact of lens density and lens thickness on cumulative dissipated energy in femtosecond laser–assisted cataract surgery

  • Mehdi Shajari
  • Vladimir Rusev
  • Wolfgang Mayer
  • Vasilios Diakonis
  • Kerstin Petermann
  • Thomas KohnenEmail author
Original Article


To evaluate the required cumulative dissipated energy (CDE) to fragment the crystalline lens in femtosecond laser–assisted cataract surgery (FLACS) in relation to lens density and lens thickness. Consecutive eyes that underwent FLACS between September 2014 and March 2017 by a single surgeon using in all cases the same femtosecond laser and phacoemulsification platform were included in our retrospective study. Prior to surgery, corrected distance visual acuity (CDVA), optical biometry corneal, and crystalline lens tomographies were performed to assess anterior chamber depth (ACD), axial length (AL), and crystalline lens parameters (i.e., lens density, thickness, and nucleus staging (NS)). After surgery, CDE was calculated and analyzed in relation to lens density (LD) and lens thickness (LT). Zero ultrasound expenditure cases were recorded and their occurrence analyzed. The chart review identified 236 eyes of 200 patients, 98 males and 102 females aged 65± 15 years which were included in the study. Mean LD was 11.26 ± 2.05 pixel intensity units (range 7.30–18.80), and the mean LT was 3417 ± 405.17 μm (range 2545–4701). LD and LT correlated moderately (r = 0.50, p < 0.001) and weakly (r = 0.23, p < 0.001), with post-laser CDE. Higher LD and LT were also associated with lower rates of zero phaco (eyes in which no phacoemulsification energy was necessary). Furthermore, NS (r = 0.528, p < 0.001) and CDVA (r = − 0.3524, p < 0.001) also correlated with CDE. Higher LD, LT, NS values, and low CDVA are associated with higher ultrasound expenditure (CDE—cumulative dissipated energy) and with lower rates of zero ultrasound expenditure during FLACS.


Pentacam Intraocular lens Lens density Lens thickness Zero phaco CDE Cumulative dissipated energy FLACS Femtosecond laser Cataract surgery 



Alison Rowan McEwan and Leon de’Lorenzo, Goethe University, Frankfurt, Germany, provided additional support in the proof reading and preparation of this manuscript.

Compliance with ethical standards

Ethical approval

The study was designed in compliance with the principles of the Declaration of Helsinki and approved by the local ethics committee. For this type of study, formal consent is not required.

Conflict of interest

Mehdi Shajari: Oculus, Zeiss, Staar, Santen, Oertli. Vladimir Rusev: none. Wolfgang Mayer: Consultant or Advisory Board—Alcon, Allergan, Polytech/Domilens, Zeiss Meditec, Ziemer. Vasilios Diakonis: none. Kerstin Petermann: none. Thomas Kohnen: Research Funding—Hoya, J&J Vision (Abbott), Novartis (Alcon), Oculentis, Oculus, Schwind, Zeiss. Consultant or Advisory Board—Geuder, J&J Vision (Abbott), Novartis (Alcon), Oculus, Santen, Schwind, STAAR, TearLab, Thea Pharma, Thieme Compliance, Ziemer, Zeiss. Consultant and Research for Abbott/J&J, Alcon/Novartis, Schwind, Zeiss. Consultant for Allergan, Bausch & Lomb, Dompe, Geuder, Med Update, Oculentis, Oculus, Rayner, Santen, Staar, Thea, Tear Lab, Thieme, Unimed Verlag, Ziemer. Research for Avedro, Hoya, Presbia.

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag London Ltd., part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of OphthalmologyGoethe-UniversityFrankfurt am MainGermany
  2. 2.Department of OphthalmologyLudwig Maximillian UniversityMunichGermany
  3. 3.Bascom Palmer Eye InstituteMiamiUSA

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