The Differential Contribution of Macular Pigments and Foveal Anatomy to the Perception of Maxwell’s Spot and Haidinger’s Brushes

Round 1

Reviewer 1 Report

Review of “The role of macular pigment and foveal anatomy in the generation of Maxwell’s spot and Haidinger’s brushes”

Summary: The authors take subjective measurements of the size of Maxwell’s spot and Haidinger’s brushes and compare these with foveal morphometric measurements of various kinds and measures of macular pigment density. The finding that the parameters influencing the perception of Haidinger’s brushes are linked to foveal morphometry and that MS is not, is interesting.

I suggest the authors reconsider the title and revise it to be more specific and preferably to state the result. ‘The role’ implies mechanism rather than the correlations observed here. Similarly on line 84 the authors state that they aim to determine the ‘mechanism of generation’ but this study is about correlations not mechanism, so I suggest this is revised.

I am not sure the citation on line 37 is appropriate as both MS and HB have been associated with macular pigment for many years and referencing [6] at this point implies this is a new idea originating with these authors. Later this is unpacked but the order of the statements in the introduction should be adjusted to ensure the authors work is placed in the proper context.

The authors state ‘machine generated axial measures of retinal thickness were assumed to be consistent between cases’ on line 153 but is that a reasonable assumption given the importance of these measurements to the study? How are these generated by the machine? Is it possible that differences in corneal curvature could lead to both scaling errors in morphometry and altered perception of Haidinger’s brushes, and this explains the link, not foveal morphometry itself? If this is a possibility this should be addressed in the text.

Presenting the data in table form makes data interpretation very challenging for the reader. Is it possible to reconsider how the data is presented to convey the key results more directly. E.g if data is being compared between two groups perhaps a bar graph is more appropriate. Consider using supplementary tables.

The magnitude of the standard deviation should guide how many significant figures to include in the results. Currently there are too many significant figures in many cases.

Overall, the confusing presentation of the results is in my opinion the weakest aspect of the manuscript.

Minor comments on presentation:

The images are pixelated and appear to be screenshots from the software. In figure 1 explaining the method this may be appropriate but in figure 2 the axis text is unreadable and the images poorly cropped. Labels for panels are absent making it difficult to following in the figure legend.

There is an overreliance on unnecessary abbreviations which makes it difficult to follow the paper. Please replace the Parameter variable abbreviations with their real names unless absolutely necessary. Currently the paper reads more like computer code and there is plenty of space in the tables for the real terms.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript is very well written, presented in a well-structured manner and relevant to the field of ophthalmology/optometry. The finding that Maxwell’s Spot (MS) is more directly related to macular pigment density/volume compared with Hadinger’s Brushes is interesting and may certainly prove useful clinically in the future.

The manuscript can be considered for publication once the following minor comments are addressed.

Abstract & Manuscript

Throughout the manuscript macular pigment densities are compared with MS and HB’s. Can the authors comment on the use of macular pigment optical density (MPOD) vs macular pigment optical volume (MPOV), as is described in the paper by Green-Gomez et al 2019.

Introduction

In the manuscript it is mentioned that MS and HB radii were significantly correlated with macular pigment spatial profile radius, however, it is not very clear from the results how this was performed. A comment would help the reader to better understand this correlation.

Line 81-83 –‘’While secondary peaks in MP profile are associated with wider fovea’s and more likely in individuals with larger FAZ areas’’. Can the authors comment on possible differences in profiles between men and women, as it has been documented that females have a larger FAZ area.

Materials & Methods

Line 94 - A clarification on the assessment of eye health and visual acuity is needed. Also, as the study was carried out during the Covid period, can the authors comment on possible implications.

Line 96 - Monocular measurements of HS were made in 52 eyes. Can the authors clarify if ocular birefringence would interfere with the accurate measurement of HBs monocularly? See Temple et al 2019.

Line 97 -Can the authors comment on the mean age of the subjects.

Figure 2 – For ease of interpretation include A, B and C in Figure 2.           

Line 121- The macular pigment profiles were classified blind – i.e. Were authors shown category 1, 2 & 3 and asked to classify profiles into 0, 1, 2 or 3? Please clarify. What would happen if there was a disagreement between authors GM and SA for classification of the various MP profiles?

Results

Line 208 – Comment on the availability of data – why were three eyes excluded? 8 data sets excluded from experiment 2 yet n=40 in Table 6.

Line 214 - Was this carried out by the authors GM and SA or physically from OCT?

Line 284 – It would be clearer to say compare Table 6 with Table 2

Line 286 -288. It would be clearer if abbreviations were included as well i.e. Ft, Fh, Pr

Line 289 -296 Paragraph difficult to understand. Please rephrase.

Discussion

Line 298 – It is not clear what is used to support this statement.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

My concerns have largely been addressed by the authors responses. Two minor points remain:

1.) I don't think the authors are justified in their use of abbreviations in their tables and figures beyond the MPOD measurements. Their response to this point doesn't appropriately justify this choice - there is space for the terms and this would make the paper much easier to understand for those not invested in the abbreviations.

2.) The significant P values should be highlighted with an asterisk instead of yellow highlighter and the actual value should be given not rounded down to zero.

Author Response

1.1 Figure 3 has now been redrawn and is now explicitly annotated as requested.

1.2 Tables 2 and 3 have been replaced and now to include full names of the measurement parameters (beyond the MPOD measurement) as requested.

2 Both the reviewer’s points have been addressed in that significant p-values are marked with an asterisk and exact  p values are stated or, where appropriate, identified as p<0.001

 

Reviewer 2 Report

I have reviewed the manuscript and author's comments. I am happy that the manuscript has been sufficiently improved to warrant publication in Vision.

Author Response

Thank your