Assessment of the Orbital and Auricular Asymmetry in Italian and Sudanese Children: A Three-Dimensional Study

Round 1

Reviewer 1 Report

The authors present results of the asymmetry of orbital and auricular asymmetry in height and width of two populations of children. Some differences were detected. There are a number of issues that I have which need further attention. A point by point list is given below. The list is not in order of importance of the comment, but rather goes from start to finish of the manuscript.

1) Abstract: Effect sizes are given in mm, while they should be dimensionless. In any case, as a surgeon (which I am not) I would be more interested in the actual dimensions instead of effect sizes and percentages.

2) I would remove all the content where the degree of asymmetry is put in classes, it adds no extra relevant information. Why report data that are less accurate when you have the raw data

3) I actually wonder why a surgeon would be interested in the amount of asymmetry present in a population. If I would need a reconstruction of my left ear, I would be perfectly happy if it would be the mirror image of my right ear, irrespective of the amount and range of asymmetry in the Belgian population. The clinical relevance is not convincing for me.

4) why is it clinically relevant that children (and NOT adults) are studied. I agree to include children as well, but I would, perhaps naively, think that reconstructive surgeries happen more in adults. It would also be interesting to see if the differences in children are still in the adult and fully grown population. And again, why would one do a reconstruction asymmetrically?

5) The authors briefly mention it, but how can one compare populations if different techniques are used to measure the asymmetry? They need an extensive argument to make their point that both techniques are comparable.

6) There is a total lack of study of measurement error, which has been regarded as extremely important in studies of FA. If not corrected for, asymmetry measurement are biased upward.

7) Why did the author's not use the data of the full scans as well. Their argument seems to be that obtaining scans and going through the hassle of GM analysis is to cumbersome to apply, but if they would compare GM with the linear measurements approach, they can actually show that most variation in asymmetry is in size and not shape (which I doubt, but it is up to the authors to convince the readers).

8) The authors use the absolute value of the signed asymmetry as a measure of fluctuating asymmetry. However, in doing so, they did not correct for DA, and thus their FA is confounded with DA. This is actually also the case when a simple correction is applied. The authors may consult a recent paper by Ekrami and coworkers in this journal for a discussion and possible solution. The authors claim to separate directional asymmetry from fluctuating asymmetry, but they do NOT. Taking the absolute value of the signed asymmetry is creating confounding between DA and FA. For linear measurements, DA is a population level measure, not an individual measure. If the authors would have used a 3D GM approach, they would be able to separate FA and DA at the individual level. A recent paper by Omid Ekrami has just shown that.

9) I would replace fig 2 by a table with descriptive statistics, and replace table 2 by a graph

10) What I mis in the discussion is what we have learned from this paper with respect to reconstructive surgery. Would the authors now advice that worldwide a kind of reference data set would be collected on the asymmetry of all traits that might require reconstructive surgery, and that surgeons would consult this to treat patients and introduce some asymmetry while reconstructing a face after a trauma or for congenital abnormalities? I would also like to see the clinical relevance here in a broader perspective.

11) I miss the clinical relevance entirely. The authors end their conclusions with the following sentence: 'Surgical treatment planning and the industrial design of protective equipment should consider these findings.' How should reconstructive surgery move forward? Suppose someone has had a severe car accident and got part of his ear thorn off. Should surgeons then reconstruct the ear to match the population level asymmetry, or should they aim for perfect symmetry? I do not know the answer, and it will probably end up with reconstructing it as good as possible with the available tissue. Or should glasses be made asymmetric with an average equal to the population level of asymmetry? I agree that glasses made to fit one's head would be ideal, but then you would ideally need a 3D scan anyway to make it fit in all dimensions.

11) the lack of information on ME, especially for the two different measurement techniques remains a problem

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

Journal

Symmetry (ISSN 2073-8994)

Manuscript ID

symmetry-1242859

Type

Article

Number of Pages

12

Title

Assessment of the orbital and auricular asymmetry in Italian and Sudanese children: a help for reconstructive facial surgery

Authors

Claudia Dolci , Fadil Elamin , Annalisa Cappella , Luisa Barni , Daniele Maria Gibelli , Chiarella Sforza *

 

 

1. There were studies on facial Directional Asymmetries (DA) in humans that the eye is programmed to disregard, while Fluctuating Asymmetry (FA) we consider less attractive. I miss that in the introduction. It is important for the context.
2. I cite from the introduction: "Moreover, data about symmetry in populations of different geographical origin are 65 still scarce in literature:" That is correct. Thus, literature on the ecological and evolutionary context is important. Herve Seligmann published many papers on digit asymmetry and tail injury in Lepidosauria, starting from 1998. In 2015 and in 2020, an evolutionary mechanism was suggested to all vertebrates, that explains left dominance (in comparison to right dominance) as stress related, thus population dependent. In 2015 it was with a facial trait (eye asymmetry) of lizards. In 2020, a paper on digit ratio in lizards, linked the digit asymmetry of Seligmann to brain laterality to explain the stress manifested in asymmetry and risk behavior.
3. Using this literature can also explain why the asymmetry indices are weakly related with age
4. Another paper on facial asymmetry of a vertebrate (snakes) and indirectly stress (via tail injury) and left dominance asymmetry (Razzetti et al. 2007).
5. Sadly, there was no reference of minor directional asymmetry (Werner et al, 1991).
6. The mean of FA is not significantly different from zero, while DA is significantly different from zero. I can't find such a test, or a justification for failing this test.
7. I disagree with the conclusion in the discussion that: "the different level of socioeconomical conditions 270 between Italy and Sudan and the possible effect of a larger developmental instability in 271 the Sudanese subjects". I think that (read the literature I added to understand) it is a directional asymmetry and an adaptation to higher stress. But the comparison of the mean to zero is missing. You do not have to agree with me. But you have to address it in the discussion.

 

 

 

Seligmann, H. (1998). Evidence that minor directional asymmetry is functional in lizard hindlimbs. Journal of Zoology, 245(2), 205-208.

Sion, G. (2015). Inter-relations among behavior, physiology, morphology and directional asymmetry in the gecko Ptyodactylus guttatus (Dissertation for PhD). The Hebrew University, Israel. 

 

Razzetti, E., Faiman, R., & Werner, Y. L. (2007). Directional asymmetry and correlation of tail injury with left-side dominance occur in Serpentes (Sauropsida). Zoomorphology, 126(1), 31-43.

 

Sion, G., Tal, R., & Meiri, S. (2020). Asymmetric behavior in Ptyodactylus guttatus: Can a digit ratio reflect brain laterality?. Symmetry, 12(9), 1490.

 

I think it is a good paper, worth to be published after addressing the issues I mentioned.

Author Response

Please see the attachment

Author Response File: Author Response.docx