Optimization of the Spot Spacings for Reducing Roughness in Laser-Induced Optical Breakdown Processes for Corneal Laser Vision Correction

Round 1

Reviewer 1 Report

This proposed paper is entitled « Optimization of the spot spacings for reducing roughness in laser

induced optical breakdown processes for corneal laser vision correction ». This manuscript deals with methods and optimization for ophthalmology surgery. This involves specifying the level of errors on a tool, linked to the use of optics. It is quite exciting to read this article. The paper can be read quite easily because it is written quite logically. But...

There are many problms with the form of this manuscript indeed:

Remark 1. There are still some minor mistakes in the text. For instance, page 1, ligne 6, it is written «

Independet » instead of « Independant » . Please, check your manuscript and correct all little mistakes.

Remark 2. However, reading the first page, in particular, leaves me with some questions. I think the authors could have better written their abstarct and not include some words like Purpose, Methodes, Results, Conclusion, Layman abtract. The abstract is too long, and not well presented.

Remark 3. Figures are not well placed on pages 5 and 6. To be modified.

Remark 4. Authors contributions, Funding and all other corresponding fields pages 9 and 10 are not filled.

The rest of the article is interesting and each set of figures is relevant. I find that the authors have synthesized their research well, and that the results obtained are particularly well explained.

To conclude this review, I would really like that authors submit a corrected version of their manuscrip before to be well reviewed It is not acceptable as it is. I encourage authors to verify their manuscript again abefore submitting it. Then it will be much apreciable.

Some mistakes in the manuscript should be corrected.

Author Response

This proposed paper is entitled « Optimization of the spot spacings for reducing roughness in laser

induced optical breakdown processes for corneal laser vision correction ». This manuscript deals with methods and optimization for ophthalmology surgery. This involves specifying the level of errors on a tool, linked to the use of optics. It is quite exciting to read this article. The paper can be read quite easily because it is written quite logically. But...

• Thank you for the overall positive score

There are many problms with the form of this manuscript indeed:

• We try to address all of them promptly

Remark 1. There are still some minor mistakes in the text. For instance, page 1, ligne 6, it is written «

Independet » instead of « Independant » . Please, check your manuscript and correct all little mistakes.

• We try to address all of them promptly

Remark 2. However, reading the first page, in particular, leaves me with some questions. I think the authors could have better written their abstarct and not include some words like Purpose, Methodes, Results, Conclusion, Layman abtract. The abstract is too long, and not well presented.

• The abstract has been accordingly revised and is now presented in a compact form as a single paragraph

Remark 3. Figures are not well placed on pages 5 and 6. To be modified.

• Figures are always shortly introduced and called in the results and subsequently presented and described in full

Remark 4. Authors contributions, Funding and all other corresponding fields pages 9 and 10 are not filled.

• We try to address all of them promptly
• This has been accordingly rewritten
  • Supplementary Materials: None
  • Author Contributions: Conceptualization, SAM; Methodology, SAM and HA; Software, HA; Validation, SAM and HA; Formal Analysis, SAM and HA; Investigation, HA; Resources, SAM; Data Curation, HA; Writing – Original Draft Preparation, SAM and HA; Writing – Review & Editing, SAM; Visualization, HA; Supervision, SAM; Project Administration, SAM; Funding Acquisition, None
  • Funding: None
  • Institutional Review Board Statement: Not applicable, the study does not involve humans or animals
  • Informed Consent Statement: Not applicable, the study does not involve humans or animals
  • Data Availability Statement: Data are not public, but can be made available upon reasonable request
  • Acknowledgments: None
  • Conflicts of Interest: SAM is employee of SCHWIND eye-tech-solutions

The rest of the article is interesting and each set of figures is relevant. I find that the authors have synthesized their research well, and that the results obtained are particularly well explained.

• Thank you for the overall positive score

To conclude this review, I would really like that authors submit a corrected version of their manuscrip before to be well reviewed It is not acceptable as it is. I encourage authors to verify their manuscript again abefore submitting it. Then it will be much apreciable.

• Thank you for the overall positive score

Reviewer 2 Report

The paper discusses the increasing importance of femtosecond lasers in ophthalmology, particularly in refractive surgery. It emphasizes the advantages of femtosecond lasers over mechanical microkeratome, highlighting their precision and minimal complications. The paper introduces an algorithm that simulates an idealized cutting surface using femtosecond lasers, exploring various parameter settings and their impact on the roughness of the cut. The results suggest that lower pulse energies combined with asymmetric spacings may reduce the roughness of femtosecond corneal surgery. The study also examines the optimization of laser energy, spot distance, and track distance to achieve smoother cuts. Moreover, the paper discusses the importance of low laser-induced optical breakdown (LIOB) threshold and the potential negative implications of reducing roughness by increasing dose. The findings highlight the need for further investigation into the interaction of various parameters and their impact on the roughness of the cut. Additionally, the paper recommends future empirical tests to validate the simulation results. The study provides insights into the optimization of femtosecond laser parameters for achieving minimal roughness and emphasizes the need for careful consideration of various factors in laser-based ophthalmic surgeries. The authors propose potential settings for optimizing femtosecond laser parameters to achieve smoother cuts in corneal surgeries.

The paper is well written in its own right, but the reviewer suspects that there are many similar works out there. Since the field covered by this paper is far from the reviewer's area of expertise, the reviewer cannot provide suitable examples. He encourages authors to self-check.

English quality is satisfactory, but needs to be double-checked to avoid possible typos.

Author Response

The paper discusses the increasing importance of femtosecond lasers in ophthalmology, particularly in refractive surgery. It emphasizes the advantages of femtosecond lasers over mechanical microkeratome, highlighting their precision and minimal complications. The paper introduces an algorithm that simulates an idealized cutting surface using femtosecond lasers, exploring various parameter settings and their impact on the roughness of the cut. The results suggest that lower pulse energies combined with asymmetric spacings may reduce the roughness of femtosecond corneal surgery. The study also examines the optimization of laser energy, spot distance, and track distance to achieve smoother cuts. Moreover, the paper discusses the importance of low laser-induced optical breakdown (LIOB) threshold and the potential negative implications of reducing roughness by increasing dose. The findings highlight the need for further investigation into the interaction of various parameters and their impact on the roughness of the cut. Additionally, the paper recommends future empirical tests to validate the simulation results. The study provides insights into the optimization of femtosecond laser parameters for achieving minimal roughness and emphasizes the need for careful consideration of various factors in laser-based ophthalmic surgeries. The authors propose potential settings for optimizing femtosecond laser parameters to achieve smoother cuts in corneal surgeries.

• Thank you for the overall positive score

The paper is well written in its own right, but the reviewer suspects that there are many similar works out there. Since the field covered by this paper is far from the reviewer's area of expertise, the reviewer cannot provide suitable examples. He encourages authors to self-check.

• Thank you. We have searched for similar works and could simply not find them.  We cannot ensure they are not published, but despite our efforts we could not find them.  We have found a few works “loosely” related to the topic, and include those in the references, e.g.,
  • Roland Ackermann et al. \Optical side-effects of fs-laser treatment in refractive surgery investigated by means of a model eye". In: Biomed. Opt. Express (2013) on the effects of periodically patterned structures on vision
  • Shwetabh Verma, Juergen Hesser, and Samuel Arba Mosquera. \Optimum Laser Beam Characteristics for Achieving Smoother Ablations in Laser Vision Correction". In: Investigative Ophthalmology and Visual Science (Apr. 2017) but applied to excimer laser ablations in the cornea
  • \Lower Laser Energy Levels Lead to Better Visual Recovery After Small-Incision Lenticule Extraction: Prospective Randomized Clinical Trial". In: American Journal of Ophthalmology (2017), indirectly inferring that the improvement in vision may be due to reduction in roughness
  • Arba-Mosquera S, Naubereit P, Sobutas S, Verma S. Analytical optimization of the cutting efficiency for generic cavitation bubbles. Biomed Opt Express. 2021 Jun 4;12(7):3819-3835. doi: 10.1364/BOE.425895. PMID: 34457382; PMCID: PMC8367260 suggesting already parallel benefits of asymmetric spacings
  • Ji YW, Kim M, Kang DSY, Reinstein DZ, Archer TJ, Choi JY, Kim EK, Lee HK, Seo KY, Kim TI. Effect of Lowering Laser Energy on the Surface Roughness of Human Corneal Lenticules in SMILE. J Refract Surg. 2017 Sep 1;33(9):617-624, clinically inferring that the improvement in vision may be due to reduction in roughness
  • Pradhan KR, Arba Mosquera S. Comparing high and low energy outcomes on day one for SmartSight myopic-astigmatism treatments with the SCHWIND ATOS: a retrospective case series. BMC Ophthalmol. 2023 Jul 18;23(1):328. doi: 10.1186/s12886-023-03076-z. PMID: 37464345; PMCID: PMC10354973, clinically inferring that the improvement in vision may be due to reduction in roughness
  • Donate D, Thaëron R. Lower Energy Levels Improve Visual Recovery in Small Incision Lenticule Extraction (SMILE). J Refract Surg. 2016 Aug 1;32(9):636-42. doi: 10.3928/1081597X-20160602-01. PMID: 27598734, indirectly inferring that the improvement in vision may be due to reduction in roughness
  • Hamilton DR, Chen AC, Khorrami R, Nutkiewicz M, Nejad M. Comparison of early visual outcomes after low-energy SMILE, high-energy SMILE, and LASIK for myopia and myopic astigmatism in the United States. J Cataract Refract Surg. 2021 Jan 1;47(1):18-26. doi: 10.1097/j.jcrs.0000000000000368. PMID: 32769749, indirectly inferring that the improvement in vision may be due to reduction in roughness

Reviewer 3 Report

In this manuscript, the authors conducted a numerical investigation on reducing the roughness in the Laser Induced Optical Breakdown process for Corneal Laser Vision Correction. The obtained results suggest a tighter pulse spacing, lower pulse energy and asymmetric scanning setting are beneficial in reducing the roughness. This topic is interesting to the broad readership of Photonics, and this manuscript has the potential to be published. However, this manuscript is not organized well. Lots of key information and discussion are missed. To make this manuscript acceptable, the authors are required to address the following comments well.

1. The abstract part is too wordy and should be refined.

2. In the abstract part, the authors mentioned that the roughness in all cases is multiple times larger than equivalent simulations for ablative procedures. However, I didn’t find such a comparison and discussion. Please clarify it.

3. Keywords are missed.

4. There are lots of statements repeated in the abstract, introduction and discussion part. Please use different sentences or descriptions for those contents.

5. Reference citation format should be modified. Please check the format requirement of this journal.

6. In line 59, please add “femtosecond” between “The” and “laser”.

7. The literature review is not sufficient. Self-citation ratio is too high.

8. What is the novelty of this work? I am confused about it.

9. Equation/table/figure format should be modified. Please check the format requirement of this journal.

10. Please add figures and more descriptions to your model. It’s difficult to understand how the roughness is captured, especially for the roughness @overlapped region.

11. Author contributions, funding, institutional review board statement, informed consent statement, data availability statement, acknowledgment, and conflicts of interest are incomplete.

Based on the abovementioned comments, this manuscript is recommended for major revision. A revised manuscript is required.

Author Response

In this manuscript, the authors conducted a numerical investigation on reducing the roughness in the Laser Induced Optical Breakdown process for Corneal Laser Vision Correction. The obtained results suggest a tighter pulse spacing, lower pulse energy and asymmetric scanning setting are beneficial in reducing the roughness. This topic is interesting to the broad readership of Photonics, and this manuscript has the potential to be published. However, this manuscript is not organized well. Lots of key information and discussion are missed. To make this manuscript acceptable, the authors are required to address the following comments well.

• Thank you for the overall positive score

1. The abstract part is too wordy and should be refined.

• Abstract has been accordingly rewritten, concise and as a single paragraph

2. In the abstract part, the authors mentioned that the roughness in all cases is multiple times larger than equivalent simulations for ablative procedures. However, I didn’t find such a comparison and discussion. Please clarify it.

• This has been added now
  • Lowering pulse energies combined with asymmetric spacings may be effective to reduce the roughness of femtosecond corneal surgery while keeping a safe dose low. The optimized roughness remains, however, manyfold larger (rougher) above equivalent simulations for ablative procedures.2 The simulations by Verma et al.2 showed induced roughness of 50nm or less (down to 10nm), whereas in this work the best simulations only reach slightly less than 100nm induced roughness. In a real scenario one must bear in mind, that ablative procedures work by removing the volume, thus (as described in the work by Verma et al.2) roughness will likely increase with ablation depth and volume.  On the contrary, lenticule extraction procedures are based on delineating the contour of an enclosed volume, and so induced roughness will be largely independent of the enclosed volume (but only the contribution of the anterior and posterior surfaces of the cut).

3. Keywords are missed.

• This has been added now
  • Keywords: Ophthalmology; refractive surgery; femtosecond laser; Optimization; roughness; laser induced optical breakdown; cornea; laser vision correction; pulse energy; waviness; homogeneity; simulation;

4. There are lots of statements repeated in the abstract, introduction and discussion part. Please use different sentences or descriptions for those contents.

• This has been accordingly rewritten

5. Reference citation format should be modified. Please check the format requirement of this journal.
6. In line 59, please add “femtosecond” between “The” and “laser”.

• This has been accordingly rewritten

7. The literature review is not sufficient. Self-citation ratio is too high.

• Thank you. We have searched for similar works and could simply not find them.  We cannot ensure they are not published, but despite our efforts we could not find them.  We have found a few works “loosely” related to the topic, and include those in the references, e.g.,
  • Roland Ackermann et al. \Optical side-effects of fs-laser treatment in refractive surgery investigated by means of a model eye". In: Biomed. Opt. Express (2013) on the effects of periodically patterned structures on vision
  • Shwetabh Verma, Juergen Hesser, and Samuel Arba Mosquera. \Optimum Laser Beam Characteristics for Achieving Smoother Ablations in Laser Vision Correction". In: Investigative Ophthalmology and Visual Science (Apr. 2017) but applied to excimer laser ablations in the cornea
  • \Lower Laser Energy Levels Lead to Better Visual Recovery After Small-Incision Lenticule Extraction: Prospective Randomized Clinical Trial". In: American Journal of Ophthalmology (2017), indirectly inferring that the improvement in vision may be due to reduction in roughness
  • Arba-Mosquera S, Naubereit P, Sobutas S, Verma S. Analytical optimization of the cutting efficiency for generic cavitation bubbles. Biomed Opt Express. 2021 Jun 4;12(7):3819-3835. doi: 10.1364/BOE.425895. PMID: 34457382; PMCID: PMC8367260 suggesting already parallel benefits of asymmetric spacings
  • Ji YW, Kim M, Kang DSY, Reinstein DZ, Archer TJ, Choi JY, Kim EK, Lee HK, Seo KY, Kim TI. Effect of Lowering Laser Energy on the Surface Roughness of Human Corneal Lenticules in SMILE. J Refract Surg. 2017 Sep 1;33(9):617-624, clinically inferring that the improvement in vision may be due to reduction in roughness
  • Pradhan KR, Arba Mosquera S. Comparing high and low energy outcomes on day one for SmartSight myopic-astigmatism treatments with the SCHWIND ATOS: a retrospective case series. BMC Ophthalmol. 2023 Jul 18;23(1):328. doi: 10.1186/s12886-023-03076-z. PMID: 37464345; PMCID: PMC10354973, clinically inferring that the improvement in vision may be due to reduction in roughness
  • Donate D, Thaëron R. Lower Energy Levels Improve Visual Recovery in Small Incision Lenticule Extraction (SMILE). J Refract Surg. 2016 Aug 1;32(9):636-42. doi: 10.3928/1081597X-20160602-01. PMID: 27598734, indirectly inferring that the improvement in vision may be due to reduction in roughness
  • Hamilton DR, Chen AC, Khorrami R, Nutkiewicz M, Nejad M. Comparison of early visual outcomes after low-energy SMILE, high-energy SMILE, and LASIK for myopia and myopic astigmatism in the United States. J Cataract Refract Surg. 2021 Jan 1;47(1):18-26. doi: 10.1097/j.jcrs.0000000000000368. PMID: 32769749, indirectly inferring that the improvement in vision may be due to reduction in roughness

8. What is the novelty of this work? I am confused about it.

• Thank you. We have searched for similar works and could simply not find them.  We cannot ensure they are not published, but despite our efforts we could not find them.  We have found a few works “loosely” related to the topic, and include those in the references, e.g.,
  • Roland Ackermann et al. \Optical side-effects of fs-laser treatment in refractive surgery investigated by means of a model eye". In: Biomed. Opt. Express (2013) on the effects of periodically patterned structures on vision
  • Shwetabh Verma, Juergen Hesser, and Samuel Arba Mosquera. \Optimum Laser Beam Characteristics for Achieving Smoother Ablations in Laser Vision Correction". In: Investigative Ophthalmology and Visual Science (Apr. 2017) but applied to excimer laser ablations in the cornea
  • \Lower Laser Energy Levels Lead to Better Visual Recovery After Small-Incision Lenticule Extraction: Prospective Randomized Clinical Trial". In: American Journal of Ophthalmology (2017), indirectly inferring that the improvement in vision may be due to reduction in roughness
  • Arba-Mosquera S, Naubereit P, Sobutas S, Verma S. Analytical optimization of the cutting efficiency for generic cavitation bubbles. Biomed Opt Express. 2021 Jun 4;12(7):3819-3835. doi: 10.1364/BOE.425895. PMID: 34457382; PMCID: PMC8367260 suggesting already parallel benefits of asymmetric spacings
  • Ji YW, Kim M, Kang DSY, Reinstein DZ, Archer TJ, Choi JY, Kim EK, Lee HK, Seo KY, Kim TI. Effect of Lowering Laser Energy on the Surface Roughness of Human Corneal Lenticules in SMILE. J Refract Surg. 2017 Sep 1;33(9):617-624, clinically inferring that the improvement in vision may be due to reduction in roughness
  • Pradhan KR, Arba Mosquera S. Comparing high and low energy outcomes on day one for SmartSight myopic-astigmatism treatments with the SCHWIND ATOS: a retrospective case series. BMC Ophthalmol. 2023 Jul 18;23(1):328. doi: 10.1186/s12886-023-03076-z. PMID: 37464345; PMCID: PMC10354973, clinically inferring that the improvement in vision may be due to reduction in roughness
  • Donate D, Thaëron R. Lower Energy Levels Improve Visual Recovery in Small Incision Lenticule Extraction (SMILE). J Refract Surg. 2016 Aug 1;32(9):636-42. doi: 10.3928/1081597X-20160602-01. PMID: 27598734, indirectly inferring that the improvement in vision may be due to reduction in roughness
  • Hamilton DR, Chen AC, Khorrami R, Nutkiewicz M, Nejad M. Comparison of early visual outcomes after low-energy SMILE, high-energy SMILE, and LASIK for myopia and myopic astigmatism in the United States. J Cataract Refract Surg. 2021 Jan 1;47(1):18-26. doi: 10.1097/j.jcrs.0000000000000368. PMID: 32769749, indirectly inferring that the improvement in vision may be due to reduction in roughness

9. Equation/table/figure format should be modified. Please check the format requirement of this journal.
10. Please add figures and more descriptions to your model. It’s difficult to understand how the roughness is captured, especially for the roughness @overlapped region.

• This has been accordingly rewritten
  • To obtain the depth in the achieved surface in the overlapping regions, the maximum value of all corresponding overlapped bubbles (single depths) is taken. This is a simplification of the model. In reality, the depth created by the overlapping laser pulses onto previous cavitations bubbles, may show cumulative effects.
  • On the other hand, the fact that the radius of the bubble and consequently the overlap of the bubble increases for higher energies if the spot distance and track distance remain the same confirms or explains that higher dose (either for a constant pulse energy with tighter spacings, or constant spacings with higher pulse energies) results in lower roughness, but also that for a constant dose (E/(ds*dt)=constant) roughness increases for higher pulse energies.
  • Due to the fact that a higher laser dose means that laser pulses are closer to each other, it is obvious, that the roughness decreases for higher laser dose. For the same laser dose, smaller spot distances ds lead to higher track distances dt (eventually leaving a gap between consecutive turns) and the optimum is achieved for lower pulse energies combined with larger spot distances (asymmetric spacings with ds>dt) since consecutive turns statistically/pseudo-stochastically tend to “fill the gaps” and place pulses nearby (small dt) in between pulse positions (separated by large ds) of the neighbouring turns.
  • To obtain the depth in the achieved surface in the overlapping regions, the maximum value of all corresponding overlapped bubbles (single depths) has been taken. This is a simplification of the model. In reality, the depth, created by the overlapping laser pulses onto previous cavitations bubbles, may show cumulative effects. Most likely, these cumulative effects are neither linearly additive (unlike for the excimer laser ablation), nor governed by the max function. Yet likely closer to the max function concept, so that the max function represents a reasonable simplification.

11. Author contributions, funding, institutional review board statement, informed consent statement, data availability statement, acknowledgment, and conflicts of interest are incomplete.

• This has been accordingly rewritten
  • Supplementary Materials: None
  • Author Contributions: Conceptualization, SAM; Methodology, SAM and HA; Software, HA; Validation, SAM and HA; Formal Analysis, SAM and HA; Investigation, HA; Resources, SAM; Data Curation, HA; Writing – Original Draft Preparation, SAM and HA; Writing – Review & Editing, SAM; Visualization, HA; Supervision, SAM; Project Administration, SAM; Funding Acquisition, None
  • Funding: None
  • Institutional Review Board Statement: Not applicable, the study does not involve humans or animals
  • Informed Consent Statement: Not applicable, the study does not involve humans or animals
  • Data Availability Statement: Data are not public, but can be made available upon reasonable request
  • Acknowledgments: None
  • Conflicts of Interest: SAM is employee of SCHWIND eye-tech-solutions

Based on the abovementioned comments, this manuscript is recommended for major revision. A revised manuscript is required.

• Thank you for the overall positive score

Reviewer 4 Report

In general, the publication is interesting, but several questions arose:

1. What is the goal of the optimization process? 

2. How was the roughness evaluated in the simulations?

3.What are the main findings of the optimization process?

4. What is the significance of the asymmetry ratio (ds/dt) in the optimization process?

5. How can the findings of this study be applied in real-world applications of laser ablation? 

Author Response

In general, the publication is interesting, but several questions arose:

• Thank you for the overall positive score

1. What is the goal of the optimization process? 

• the spot distance ds, track distance dt and the laser energy E are optimized to achieve a smooth profile, i.e., to minimize the roughness (while respecting relevant boundary conditions).

2. How was the roughness evaluated in the simulations?

• For determining the roughness, critical points are selected such that the difference/distance between the depth of ideal target profile and the depth of the simulated profile is locally a maximum in these points.

3.What are the main findings of the optimization process?

• Tighter pulses (spacings) using constant pulse energies lead to lower roughness
• Lower pulse energies for the same dose lead to lower roughness
• Asymmetric settings with spot distance larger than track distance, for the same pulse energies and treatment dose, lead to lower roughness
• For a given dose, lower pulse energies are more important than asymmetric settings

4. What is the significance of the asymmetry ratio (ds/dt) in the optimization process?

• Asymmetric settings with spot distance larger than track distance, for the same pulse energies and treatment dose, lead to lower roughness
• For a given dose, lower pulse energies are more important than asymmetric settings

5. How can the findings of this study be applied in real-world applications of laser ablation?

• In our simulations we have considered 2 different LIOBth (Eth as 65nJ and 47nJ), but due to the lengthy simulations, just a single bubble size factor (k = 1.5). This value is similar to what has been used in previous publications,5 but it is also compatible (and to some extent explains and supports) the minimum doses used for different commercial devices  (as well as Ivan Gabric, personal communication).  According to this, Visumax (Carl Zeiss Meditec, Germany) would have a Eth value close to 73nJ (using k = 1.5, leading to a bubble diameter of 4.5µm for 100nJ as in the cited work, leading to 494mJ/cm2 as minimum dose), whereas ATOS (SCHWIND eye-tech-solutions, Germany) would have a Eth value close to 49nJ (using k = 1.5, leading to a bubble diameter of 4.7µm for 80nJ, leading to 360mJ/cm2 as minimum dose as in the personal communication (80nJ in 7.4µm (ds) * 3.0µm (dt))).
• Higher Dose is „bad“ for the biology of the cornea (overdose, more severe insult to the tissue) even if formally this may lead to lower roughness. Further, lower Pulse E is more important than Asymmetry (yet with Pulse E > 1.5*LIOBTh, as per previous works).
• Finally, for already optimized low Pulse E (~1.5*LIOBTh), asymmetric spacings with ds >> dt induces less roughness than symmetric (ds ~ dt, e.g., VisuMax), and both of them induce less roughness than asymmetric with ds < dt (Z8 by Ziemer (Switzerland) or ELITA by Johnson & Johnson Vision (USA)). This is also consistent with recent publications in lenticule extraction.
• Further, the primary role of lowering pulse E in reducing roughness makes it all the more important that LIOBTh (Eth) remains low (as low as possible). Because roughness is dependent on the amount of E exceeding LIOBTh (E-Eth), and actually independent of Eth (Bubble=K*(E-Eth)^(1/3)); yet optimum E ~ 1.5*Eth.  Then, only low LIOBTh makes that 1.5*Eth-Eth=Eth/2 (i.e., the optimum amount of E exceeding LIOBTh), and that grows with LIOBTh.  Thus, the more important that LIOBTh stays low (as low as possible).
• According to this, we would actually recommend the following settings: E ~ 1.6x Eth; Asymmetry Ratio = ds/dt > 2; with optimum dose as published before.5 Leading to exemplary valid settings of 80nJ in 5.9µm (ds) * 2.8µm (dt) in ATOS (484mJ/cm2) or 100nJ in 4.5µm (ds) * 3.5µm (dt) for VisuMax (635mJ/cm2) (115nJ in 6.0µm (ds) * 3.5µm (dt) for VisuMax (548mJ/cm2) would have been better but is not possible to parametrize in the commercial VisuMax system).
• For Z8 according to this model (estimated Eth = 27nJ), settings of 43nJ in 4.7µm (ds) * 2.2µm (dt) (416mJ/cm2) would be optimum, whereas 57nJ in 5.1µm (ds) * 2.5µm (dt) (447mJ/cm2) for ELITA (estimated Eth = 36nJ) (yet, apparently, both settings are not possible to parametrize in these commercial systems, which further seem to use the opposite asymmetry, with ds << dt).

Reviewer 5 Report

This paper presents an innovative approach to improving the precision and safety of femtosecond laser-based refractive surgery in ophthalmology. The authors introduce a novel algorithm that simulates an idealized cutting surface, incorporating laser-induced optical breakdown (LIOB). The study systematically explores various parameter settings, including LIOB threshold, pulse energies, and spot spacings, to determine their impact on the roughness of the simulated cut. The results reveal valuable insights, such as the effectiveness of tighter pulse spacings and lower pulse energies in reducing roughness. The conclusions drawn from the simulations emphasize the importance of lower pulse energies and asymmetric spacings in minimizing roughness while maintaining a low LIOB threshold. The paper's findings offer valuable guidance for optimizing femtosecond corneal surgery, contributing significantly to the advancement of laser-based refractive techniques in ophthalmology. It is an interesting work and I think it can be accepted and published.To improve the manuscript, I consider there are still some issues that need to be addressed.

1.         “It needs to be considered that the femtosecond laser has other parameters and cannot be directly compared to excimer laser systems.” Can you provide more details regarding other parameters?

2.         “Certain critical points are considered (such as treat ment dose or cutting time) and the difference between achieved and ideal cut is determined.”How are these critical points determined?

3.         The absence of markers (a), (b), and (c) in Figures 1, 2, and 3 is an oversight that needs correction.

4.         The term "ideal cut" is frequently referenced in the paper. Could you elaborate on the meaning of ideal cut?

Author Response

This paper presents an innovative approach to improving the precision and safety of femtosecond laser-based refractive surgery in ophthalmology. The authors introduce a novel algorithm that simulates an idealized cutting surface, incorporating laser-induced optical breakdown (LIOB). The study systematically explores various parameter settings, including LIOB threshold, pulse energies, and spot spacings, to determine their impact on the roughness of the simulated cut. The results reveal valuable insights, such as the effectiveness of tighter pulse spacings and lower pulse energies in reducing roughness. The conclusions drawn from the simulations emphasize the importance of lower pulse energies and asymmetric spacings in minimizing roughness while maintaining a low LIOB threshold. The paper's findings offer valuable guidance for optimizing femtosecond corneal surgery, contributing significantly to the advancement of laser-based refractive techniques in ophthalmology. It is an interesting work and I think it can be accepted and published.To improve the manuscript, I consider there are still some issues that need to be addressed.

• Thank you for the overall positive score

1. “It needs to be considered that the femtosecond laser has other parameters and cannot be directly compared to excimer laser systems.” Can you provide more details regarding other parameters?

• This has been added now
  • It needs to be considered that the femtosecond laser has other parameters and cannot be directly compared to excimer laser systems (to highlight the most important ones, excimer laser systems work in the ultraciolet regime vs. the infrared regime of femtosecond systems (directly affecting spot size), the pulse duration changes from ns (excimer) to fs (femtosecond systems), the pulse energy changes from mJ (excimer) to nJ (femtosecond systems), or the total number of pulses for a general procedure change from thousands of pulses (excimer) to millions of pulses (femtosecond systems)). For commercial femtosecond laser systems used for corneal laser vision correction, it has been worked out that laser energies lower than 115nJ lead to faster recovery after surgery. Though it is also stated that further research has to be done for detailed explanations of the interaction of parameters.

2. “Certain critical points are considered (such as treat ment dose or cutting time) and the difference between achieved and ideal cut is determined.”How are these critical points determined?

• This has been added now
  • The algorithm includes the definition of possible positions for the laser pulses and calculation of the roughness for different parameter settings (including LIOB threshold, pulse energies, and spot spacings). Certain critical points are considered (such as treatment dose or cutting time, which are determined in the simulation and the simulation is “rejected” is those parameters do not meet the boundary conditions) and the difference between achieved and ideal cut is determined. Furthermore, optimizations of specific variables, such as spot distance (along the pathway), track distance (between lines/tracks) and pulse energy, are performed.

3. The absence of markers (a), (b), and (c) in Figures 1, 2, and 3 is an oversight that needs correction.

• This has been added now

4. The term "ideal cut" is frequently referenced in the paper. Could you elaborate on the meaning of ideal cut?

• This has been added now
  • (the ideal target cut is defined as the simplest surface (free of waviness) that meets the cutting requirements, in its simplest form the ideal target cut is a 3-dimensional surface placed at known distances from the corneal surface). Furthermore, optimizations of specific variables, such as spot distance (along the pathway), track distance (between lines/tracks) and pulse energy, are performed.

Round 2

Reviewer 1 Report

The paper is still poor.

In the bibliography, reference 13 must absolutly be deleted (there is no information).

It should be improved.

Author Response

The paper is still poor.

• We are sorry to read that opinion. We tried our best to present an interesting and novel work

In the bibliography, reference 13 must absolutly be deleted (there is no information).

• Thank you we have corrected it now

Reviewer 3 Report

The authors have answered most comments well. I just have one more comment:

Please modify the font format of the equations and figures to make them consistent with the font format in the paragraphs.

Author Response

The authors have answered most comments well. I just have one more comment:

• Thank you for the overall positive score

Please modify the font format of the equations and figures to make them consistent with the font format in the paragraphs.

• This has been corrected now