Comparison of Four Methods for Measuring Heterophoria and Accommodative Convergence over Accommodation Ratio

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper compared phoria and AC/A ratio measurement by different four methods: OptoTab SERIES, Cover Test, Modified Thorington test and Von Graefe at near and far distance in 76 subjects.

 

 

The article is nicely written, result is presented well and support the conclusions. 

As authors stated in the text, there are various methods to measure phoria and most of these methods are not interchangeable. The findings of this study also support that. All the subjects were normal, so it could be better if they included some subjects with dysfunction and compared with normal ones. This study does not give any new verdicts; however, because of the large number of subjects, and some of the methods applied here are new, it can be helpful to some readers.

 

Some of the suggestions:

Methods :

Target for cover test could be better if a letter or point rather than a row of letters is used. (Line 122)

Clarify how prism bar and the flipper of +-1D were used simultaneously to measure the AC/A ratio and phoria. (137)

 

Results:

Hundred subjects participated initially and 24 were excluded due to different exclusion criteria. Did not some of them have two or more problems? Please verify this. (line 180)

 

Comments on the Quality of English Language

There are some minor English language typo/errors.

Author Response

Comments 1: This paper compared phoria and AC/A ratio measurement by different four methods: OptoTab SERIES, Cover Test, Modified Thorington test and Von Graefe at near and far distance in 76 subjects. The article is nicely written, result is presented well and support the conclusions. As authors stated in the text, there are various methods to measure phoria and most of these methods are not interchangeable. The findings of this study also support that. All the subjects were normal, so it could be better if they included some subjects with dysfunction and compared with normal ones. This study does not give any new verdicts; however, because of the large number of subjects, and some of the methods applied here are new, it can be helpful to some readers. Response 1: The authors would like to thank the reviewer for their detailed comments and suggestions about the manuscript. The comments have identified important areas that require improvement. Please find enclosed below the responses to the specific comments.   Comments 2: Target for cover test could be better if a letter or point rather than a row of letters is used.

Response 2: Thank you for pointing this out. The section of the methodology dedicated to the cover test has been updated to better clarify the instructions given to the participants. An additional sentence was included to clarify the point: in near vision, although the stick had a row of letters, participants were asked to look at one isolated letter on the top of the stick while the examiner measured heterophorias; on the other hand, in far vision, participants were asked to maintain fixation on one letter of the row for the measurement process.

Comments 3: Clarify how prism bar and the flipper of +-1D were used simultaneously to measure the AC/A ratio and phoria.

Response 3: Thank you for the comment. A sentence has been added to the section “2.2 Test Procedures” to clarify that participants were the ones holding the flipper while the examiner conducted the measurement by the OptoTab SERIES, the Cover Test, and the Modified Thorington Test. For Von Graefe test, the ±1D lenses were collocated on the phoropter.   Comments 4: Hundred subjects participated initially and 24 were excluded due to different exclusion criteria. Did not some of them have two or more problems? Please verify this. (line 180) Response 4: Thank you for the suggestion to revise that point. The reviewer is right, there was a participant who suffered both strabismus and amblyopia, and this was indicated in the manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents clinically valuable insights, but it would benefit from placing greater emphasis in the introduction on digital solutions such as the OptoTab Series, particularly since comparisons between clinical tests have already been extensively researched. Improvements in the consistency of terminology and additional clarity on methodological details (as outlined in the comments below) would further enhance the manuscript. Additionally, providing clearer explanations of clinically significant differences and more elaboration in the results and discussion sections would strengthen the overall impact of the work.

 

The manuscript should carefully consider what is clinically and diagnostically significant difference between methods. It could be beneficial to define this (before concluding about obtained results) based on previous research that has defined intra-examiner repeatability and inter-examiner reproducibility (reference [4], [3], [10] and [19] in manuscript and also consider this article: Rainey, B. B., Schroeder, T. L., Goss, D. A., & Grosvenor, T. P. (1998). Reliability of and comparisons among three variations of the alternating cover test. Ophthalmic & physiological optics, 18(5), 430–437). Also the smallest measurement step should be considered in all techniques used, for example, if the measurement is done with 1 ∆ step (or 0.50 ∆ step in OptoTab series and Modified Thorington test; and 2 ∆ step in cover test), could differences between 4 techniques that is below or equal to 0.50 PD be considered significant (for far distance the difference aligns with this value)?

Terminology:

1. Throughout the manuscript, there is inconsistent use of the terms "phoria" and "heterophoria." It is recommended to use "heterophoria" consistently throughout, including in the title.
2. The terminology regarding measurement distance is inconsistent. In Line 12, "far and near vision" is used, while Line 82 mentions "at distance and near."  It seems that referring to the distance at which the measurement was done might be more appropriate. Additionally, in Tables 2, 3, and 4, consider revising "Far vision" and "Near vision" to "Far distance" and "Near distance."
3. In Line 41, it could be reconsidered whether "devices" or "tests" should be used.
4. In several parts of the manuscript, the term "cover test" is used. It is recommended to specify whether this refers to the alternating cover test or the unilateral cover test each time where it has not already been done (e.g., Lines 63, 70, etc.).
5. In Table 3, an explanation should be provided for how esophoria and exophoria are noted (e.g., clarification on what a negative heterophoria value indicates). Additionally, for the AC/A ratio, it may be necessary to include measurement values  in Table 3.
6. The word "significative" should be replaced with "significant."
7. There is inconsistency in describing the results of Von Graefe method. "Average measurement" is used in some instances, while "medium measurement" is used in others (Lines 207, 225, 227, 228).
8. In Line 288, the phrase "can condition" requires rephrasing for clarity.
9. In Line 310, "patient lag" should be revised to "accommodation lag." Additionally, "higher accommodation lag" should be used instead of "patient lag" in the same line.
10. In Line 315, the term "pure phoria" is used; however, the word "pure" seems unnecessary.
11. In Line 320, "vergential visual dysfunction" should be corrected to "vergence dysfunction."

Formatting:

1. In Line 36, the manuscript refers to "some studies" in the plural, appropriate references should be added to support this statement.
2. In Lines 60-61, the authors mention newly developed technologies; this also requires references. Additionally, in Line 63, it is unclear how references [3, 4, 18] explain that the OptoTab SERIES has not undergone reliability testing.
3. In Line 132, reference [18] is missing brackets.
4. In Table 2, suggestion to improve the description to clarify the message: “Descriptive statistics for sample (n=76) meeting inclusion criteria.” The left column is missing measurement units for VA, AA, PFV, and NFV. Additionally, some explanation regarding PFV and NFV should clarify that values presented refer to the blur point/break point/recovery point.
5. In Table 3, for "far vision" and "near vision," p-values are displayed as merged cells with one p-value for both conditions, while for the AC/A ratio, the p-value seems to refer only to the OptoTab POCKET, as the cells are not merged.
6. Line 274 mentions "previous studies" but lacks references. Similarly, Lines 279 and 283 refer to "some authors," but no references are provided.
7. In Line 285, the statement "since the other tests have measurements from 0 Δ.27" lacks a reference, and there appears to be a typo. If this refers to 0.27 Δ, it should be specified which test produces measurements in such step size.

Content:

 

1)   In abstract, Lines 19-21, the author reported “ Significant differences were found  […] except for the Modified 19 Thorington test vs. Cover Test (Wilcoxon test, p = 0.024) and between OptoTab POCKET compared 20 with all the other tests (Wilcoxon test, all p ≤ 0.001) with -1.00 D lenses.” but contradicted that with clinically significant findings (p = 0.024 and p ≤ 0.001).

2)      The first sentence in abstract (Lines 11-12) indicates that both heterophoria and AC/A was measured in far and near distances, but it seems from results section that AC/A ratio was measured at near distance only. Please make sure that this has been clearly said here in this sentence and in Lines 117-119 (by mentioning measurement distance “at near”).

3)      Lines 117-119 description of AC/A measurement are repeating for each heterophoria technique (last 2 sentences in sections 2.2.1.; 2.2.2.; 2.2.3.; and 2.2.4.), therefore, it seems that it might be better to either create section 2.2.5. that describes in detail procedure of AC/A measurement or explain this at the end of section 2.2.

4)      Line 104 – provide more details on environment lighting used (lux)

5)      Please reconsider Lines 135-136, as there appears to be an error. In the alternating cover test, an inward movement indicating exophoria requires base-in prisms for neutralization, not base-out, and esophoria requires base-out prisms, not base-in.

6)      In Section 2.2.1, since there are no references to published articles regarding the OptoTab SERIES, it would be helpful to include more details about the heterophoria measurement technique this program use (for example if red/green glasses and polarized glasses are used – how the vertical line is formed?). A supporting figure from test illustrating the description in Lines 113-115 could help.

7)      In Line 176, please verify whether the p-value of ≤0.005 is correct, or if it should be 0.05. Additionally, in Line 243, it is unclear why significance has been set as p≥0.025 instead of the p≥0.05.

8)      In Table 2, the NPC values seem unusually small. Could you please clarify the procedure used for NPC measurement? Additionally, if the mean NPC is 1.20 with a SD of 2.6, it seems unlikely that the median would be 0.00 and IQR would be 0.00–0.00, also SD of 2.6 for mean 1.20 suggests that some of the NPC values fall below zero.

9)      The discussion in Lines 267-269 could be improved. It begins by discussing dissociation methods but then shifts to specific measurement techniques for each test. For example, stating that prisms are used in the Von Graefe method does not clearly explain the dissociation, it should be clearly said which techniques measure dissociated and which associated heterophoria.

10)  The conclusions should more directly address the Thorington test at far distance and the Von Graefe test at near distance, by explaining if these tests yield higher or lower results compared to the other three tests, which were concluded to be interchangeable?  

Additional comments:

1)      In section 2.1. additional info about the minimum and maximum heterophoria values observed in study sample might be useful, as well as the approximate distribution in % between participants having esophoria, ortophoria and exophoria.

2)      Von Graefe technique was repeated 3 times, could you explain why only this technique was repeated 3 times? And also could you include then information if the difference between 1^st and following measurements were significant? To support that it was meaningful to compare all methods with both Von Graefe 1^st measurement and average measurement. If it is meaningful to analyze separately, then for the AC/A measurements with ±1.00D, it is unclear whether the first or the average Von Graefe measurement was used for the calculations in Table 3.

Comments on the Quality of English Language

Some examples for language improvements have been described along with terminology comments. Overall language check should be done.

Author Response

The authors would like to express their appreciation to the reviewer for their thoughtful comments and suggestions. In response, most manuscript sections have been revised to enhance clarity. Additionally, the terminology and references have been carefully reviewed and updated to ensure consistency and accuracy.

 

Comments 1: The manuscript presents clinically valuable insights, but it would benefit from placing greater emphasis in the introduction on digital solutions such as the OptoTab Series, particularly since comparisons between clinical tests have already been extensively researched.

Response 1: Thank you for your suggestion. The introduction has been reorganised and expanded to include more detailed information about the OptoTab SERIES device. In addition, the interest in digital devices in daily clinical practice has been pointed out, as they allow the assessment of diverse aspects of binocular function in a time-efficient manner, utilising tests that are readily comprehensible to the patient.

 

Comments 2: Additionally, providing clearer explanations of clinically significant differences and more elaboration in the results and discussion sections would strengthen the overall impact of the work.

Response 2: Thank you for the comment. Revisions have been made throughout the results and discussion sections to address the distinction between statistically significant differences and clinical relevance. Additionally, considerations regarding the varying resolution of the tests, which may result in mathematically significant outcomes without clinical significance, have been incorporated. These changes aim to improve the clarity and impact of the manuscript.

 

Comments 3: The manuscript should carefully consider what is clinically and diagnostically significant difference between methods. It could be beneficial to define this (before concluding about obtained results) based on previous research that has defined intra-examiner repeatability and inter-examiner reproducibility (reference [4], [3], [10] and [19] in manuscript and also consider this article: Rainey, B. B., Schroeder, T. L., Goss, D. A., & Grosvenor, T. P. (1998). Reliability of and comparisons among three variations of the alternating cover test. Ophthalmic & physiological optics, 18(5), 430–437).

Response 3: Thank you for the suggestion. In the revised manuscript, a paragraph has been added to clarify the concept of clinically significant differences, drawing on prior research concerning intra-examiner repeatability and inter-examiner reproducibility. It is noted that the minimum discernible difference for the alternating cover test, often regarded as the gold standard for assessing distance vision, is 2Δ. As such, discrepancies of less than 2Δ may be deemed clinically insignificant. The discussion emphasizes that the interpretation of results can vary depending on the assumption of this minimal clinically noticeable difference. It has been acknowledged that the differences observed between tests for far vision may lack clinical relevance. Furthermore, the importance of the 2Δ threshold in understanding the variability between test results has been reiterated, with references to studies recommended.

 

Comment 4: Also the smallest measurement step should be considered in all techniques used, for example, if the measurement is done with 1 ∆ step (or 0.50 ∆ step in OptoTab series and Modified Thorington test; and 2 ∆ step in cover test), could differences between 4 techniques that is below or equal to 0.50 PD be considered significant (for far distance the difference aligns with this value)?

Response 4: Thank you for the suggestion. Variations in the resolution of different tests may lead to slightly different results. This phenomenon has been addressed in the discussion section with the objective of emphasising its potential impact on the outcomes of statistical tests and the interpretation of the results.

 

Comment 5: Throughout the manuscript, there is inconsistent use of the terms "phoria" and "heterophoria." It is recommended to use "heterophoria" consistently throughout, including in the title.

Response 5: Thank you for the suggestion. The terminology throughout the manuscript has been updated to consistently use the term “heterophoria”.

 

Comment 6: The terminology regarding measurement distance is inconsistent. In Line 12, "far and near vision" is used, while Line 82 mentions "at distance and near."  It seems that referring to the distance at which the measurement was done might be more appropriate. Additionally, in Tables 2, 3, and 4, consider revising "Far vision" and "Near vision" to "Far distance" and "Near distance."

Response 6: Thank you for the suggestion. The terminology throughout the manuscript has been updated to consistently refer to the distance.

 

Comment 7: In Line 41, it could be reconsidered whether "devices" or "tests" should be used.

Response 7: Thank you for the suggestion. The typo was corrected.

 

Comment 8: In several parts of the manuscript, the term "cover test" is used. It is recommended to specify whether this refers to the alternating cover test or the unilateral cover test each time where it has not already been done (e.g., Lines 63, 70, etc.).

Response 8: Thank you for the suggestion. The terminology ‘alternating’ or ‘unilateral’ to Cover Test was added in the entire manuscript in places where it was not specified.

 

Comment 9: In Table 3, an explanation should be provided for how esophoria and exophoria are noted (e.g., clarification on what a negative heterophoria value indicates). Additionally, for the AC/A ratio, it may be necessary to include measurement values in Table 3.

Response 9: Thank you for the comment. Following clinical notation, negative values represent exophoria, whereas positive values indicated esophoria. The authors had added a sentence explaining this before table 3. Moreover, measurements of the AC/A ratio using +1.00 and -1.00 D lenses are shown in the same table.

 

Comment 10: The word "significative" should be replaced with "significant."

Response 10: Thank you for the comment The terminology “significative” has been replaced by “significant”.

 

Comment 11: There is inconsistency in describing the results of Von Graefe method. "Average measurement" is used in some instances, while "medium measurement" is used in others (Lines 207, 225, 227, 228).

Response 11: Thank you for your comment. The terminology in all the manuscript with the words “average measurement” has been updated.

 

Comment 12: In Line 288, the phrase "can condition" requires rephrasing for clarity.

Response 12: Thank you for the suggestion. The sentence has been rewritten for a better understanding.

 

Comment 13: In Line 310, "patient lag" should be revised to "accommodation lag." Additionally, "higher accommodation lag" should be used instead of "patient lag" in the same line.

Response 13: Thank you for the suggestion. The authors have done the indicated change.

 

Comment 14: In Line 315, the term "pure phoria" is used; however, the word "pure" seems unnecessary.

Response 14: Thank you for the comment. The authors agree with the reviewer. The term “pure” was deleted.

 

Comment 15: In Line 320, "vergential visual dysfunction" should be corrected to "vergence dysfunction."

Response 15: Thank you for the comment. The typo was corrected.

 

Comment 16: In Line 36, the manuscript refers to "some studies" in the plural, appropriate references should be added to support this statement.

Response 16: Thank you for the comment, the authors agree with the reviewer. A new reference to a meta-analysis analysing the relationship between ocular problems and learning disorders has been added.

 

Comment 17: In Lines 60-61, the authors mention newly developed technologies; this also requires references. Additionally, in Line 63, it is unclear how references [3, 4, 18] explain that the OptoTab SERIES has not undergone reliability testing.

Response 17: Thank you for the comment. The manufacturer's website (smarthings4vision.com) has been added, as it is the only available source for information on the newly developed technologies. Several studies, including those by Consejo A. et al., Marcellin M. et al., and Diaz-Gomez et al., also rely on this website as their sole reference for OptoTab. Additionally, references [3, 4, 18] are related to the previous statement. To avoid confusion, the sentence has been accordingly revised.

 

Comment 18: In Line 132, reference [18] is missing brackets.

Response 18: Thank you for pointing it out, it was a mistake. The error has been corrected.

 

Comment 19: In Table 2, suggestion to improve the description to clarify the message: “Descriptive statistics for sample (n=76) meeting inclusion criteria.” The left column is missing measurement units for VA, AA, PFV, and NFV. Additionally, some explanation regarding PFV and NFV should clarify that values presented refer to the blur point/break point/recovery point.

Response 19: Thank you for the suggestion. A new sentence before table 2 along with modifications in the table title has been made.

 

Comment 20: In Table 3, for "far vision" and "near vision," p-values are displayed as merged cells with one p-value for both conditions, while for the AC/A ratio, the p-value seems to refer only to the OptoTab POCKET, as the cells are not merged.

Response 20: Thank you for the comment, it was a formatting mistake, cells would to be combined. It has been corrected.

 

Comment 21: Line 274 mentions "previous studies" but lacks references. Similarly, Lines 279 and 283 refer to "some authors," but no references are provided.

Response 21: Thank you for pointing this out. References were added in both places.

 

Comment 22: In Line 285, the statement "since the other tests have measurements from 0 Δ.27" lacks a reference, and there appears to be a typo. If this refers to 0.27 Δ, it should be specified which test produces measurements in such step size.

Response 22: Thank you for the comment. It should be noted that the “27” was a typographical error; it should have been presented as a reference and placed within brackets. This has been corrected accordingly.

 

Comment 23: In abstract, Lines 19-21, the author reported “Significant differences were found […] except for the Modified 19 Thorington test vs. Cover Test (Wilcoxon test, p = 0.024) and between OptoTab POCKET compared 20 with all the other tests (Wilcoxon test, all p ≤ 0.001) with -1.00 D lenses.” but contradicted that with clinically significant findings (p = 0.024 and p ≤ 0.001).

Response 23: Thank you for the comment. As explained in the section “Statistical analysis”, to avoid type I errors arising from multiple comparisons, statistical significance for the Wilcoxon test was divided by the number of comparisons performed to give a p ≤ 0.005 (Bonferroni adjustment). Therefore, this adjustment was applied only during the performance of this specific analysis and not across the entire set of analyses. Thus, the reported significance in the abstract is not an error.

 

Comment 24: The first sentence in abstract (Lines 11-12) indicates that both heterophoria and AC/A was measured in far and near distances, but it seems from results section that AC/A ratio was measured at near distance only. Please make sure that this has been clearly said here in this sentence and in Lines 117-119 (by mentioning measurement distance “at near”).

Response 24: Thank you for the comment. The authors had rewritten the sentence in the abstract to clarify that the heterophoria was measured at distance and near and AC/A ratio only at near.

 

Comment 25: Lines 117-119 description of AC/A measurement are repeating for each heterophoria technique (last 2 sentences in sections 2.2.1.; 2.2.2.; 2.2.3.; and 2.2.4.), therefore, it seems that it might be better to either create section 2.2.5. that describes in detail procedure of AC/A measurement or explain this at the end of section 2.2.

Response 25: Thank you for the suggestion. The authors agree with the reviewer. A new sentence was added to the end of section 2.2 explaining that AC/A was measured always after heterophoria assessment.

 

Comment 26: Line 104 – provide more details on environment lighting used (lux)

Response 26: Thank you for the comment. Light conditions were the same for all participants, with all overall lights on and supplemented by a standup light which was especially helpful for near vision heterophorias measurements.

 

Comment 27: Please reconsider Lines 135-136, as there appears to be an error. In the alternating cover test, an inward movement indicating exophoria requires base-in prisms for neutralization, not base-out, and esophoria requires base-out prisms, not base-in.

Response 27: Thank you for pointing it out. It was indeed a mistake, which has now been corrected by the author.

 

Comment 28: In Section 2.2.1, since there are no references to published articles regarding the OptoTab SERIES, it would be helpful to include more details about the heterophoria measurement technique this program use (for example if red/green glasses and polarized glasses are used – how the vertical line is formed?). A supporting figure from test illustrating the description in Lines 113-115 could help.

Response 28: Thank you for the suggestion. A new sentence was added to clarify that both polarized and red/green glasses create a dissociation in which one eye sees the cross with the scale and the other sees the line, thus quickly obtaining the magnitude of the heterophoria. Additionally, a supporting figure of the test was added as you suggested.

 

Comment 29: In Line 176, please verify whether the p-value of ≤0.005 is correct, or if it should be 0.05. Additionally, in Line 243, it is unclear why significance has been set as p≥0.025 instead of the p≥0.05.

Response 29: Thank you for the comment. This situation is similar to the one addressed in Comment 23. As explained in the "Statistical Analysis" section, the threshold for statistical significance was adjusted using the Bonferroni correction, with a p-value threshold set at p < 0.005. Consequently, the reported p-values are correct and reflect this adjustment.

 

Comment 30: In Table 2, the NPC values seem unusually small. Could you please clarify the procedure used for NPC measurement? Additionally, if the mean NPC is 1.20 with a SD of 2.6, it seems unlikely that the median would be 0.00 and IQR would be 0.00–0.00, also SD of 2.6 for mean 1.20 suggests that some of the NPC values fall below zero.

Response 30: Thank you for the comment. The NPC values being close to 0 can be attributed to the sample comprising healthy young adults without any convergence-related issues or symptoms. The data have been thoroughly reviewed and confirmed as accurate. While these values may lack clinical significance, they are mathematically plausible, with some values deviating from 0 despite 0 being the most frequently observed value. Given that NPC values are non-parametric, it is appropriate to utilize non-parametric statistical measures, such as the median and interquartile range, for a more accurate representation.

 

Comment 31: The discussion in Lines 267-269 could be improved. It begins by discussing dissociation methods but then shifts to specific measurement techniques for each test. For example, stating that prisms are used in the Von Graefe method does not clearly explain the dissociation, it should be clearly said which techniques measure dissociated, and which associated heterophoria.

Response 31: Thank you for the comment. The authors have improved the explanation of the Von Graefe technique for obtaining the dissociation.

 

Comment 32: The conclusions should more directly address the Thorington test at far distance and the Von Graefe test at near distance, by explaining if these tests yield higher or lower results compared to the other three tests, which were concluded to be interchangeable?

Response 32: Thank you for the comment. The authors have specified that Modified Thorington test offered more esophoric values than all others whereas Von Graefe offered more exophoric values than all others in the conclusions.  

 

Comment 33: In section 2.1. additional info about the minimum and maximum heterophoria values observed in study sample might be useful, as well as the approximate distribution in % between participants having esophoria, ortophoria and exophoria.

Response 33: Thank you for the suggestion. Determining precise percentages for esophorics, orthophorics, and exophorics is challenging due to the variability in results obtained from different techniques. Consequently, it is not possible to provide exact percentages. Instead, the maximum and minimum values from all tests have been reported to convey the range of results. Apologies are extended for any confusion this may have caused.

 

Comment 34: Von Graefe technique was repeated 3 times, could you explain why only this technique was repeated 3 times? And also could you include then information if the difference between 1^st and following measurements were significant? To support that it was meaningful to compare all methods with both Von Graefe 1^st measurement and average measurement. If it is meaningful to analyze separately, then for the AC/A measurements with ±1.00D, it is unclear whether the first or the average Von Graefe measurement was used for the calculations in Table 3.

Response 34: Thank you for the comment. Similarly to other studies and because it was the most difficult test for the participant to understand, we decided to measure it three times and average it in case the first measurement was biased by the patient's lack of understanding. However, after comparing the first Von Graefe measurement vs. the average Von Graefe measurement no significant differences were found neither for far distance heterophoria (Wilcoxon test; p = 0.328) nor for near distance heterophoria (Wilcoxon test; p = 0.418). Moreover, the correlation between those two measurements was strong, as it is indicated in the manuscript. For the AC/A ratio, knowing that the two measurements were no significantly different, the first Von Graefe measurement was chosen to compare with the other methods, as indicated in table 3.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This present study investigates four measurement approaches of heterophoria and AC/A ratio. The authors concluded that all the distance tests are interchangeable except for Modified Thorington test, and all near tests are interchangeable except for Von Graefe test. Interestingly, the application of +/-1.00 D lenses would render most tests uninterchangeable when assessing the AC/A ratio. The author attributes this observation to the different dissociation methods, stimuli, quantification methods, patient conditions, and examiner skills. The manuscript is generally well written, but it is not clear why the authors chose not evaluate the Howell phoria test even though it is mentioned in the introduction section. Although the participants wore their habitual refractive correction in this present study, line 105-6 claims that the participants wore their “best refractive correction” which seems to contradictory. In the methods section, the authors mentioned that the OptoTab is based on the principles of the Modified Thorington test, but this is not true since their dissociation approaches are different. Insufficient information on the methods: what kind of occluder was used during cover test? It is mentioned in the discussion section that an opaque occlude is used, but it is not clearly stated in the methods section. The authors should explain the “environmental lighting” too.  The abstract is actually quite confusing to readers, so the authors may need to make substantial changes to it. Minor comments: One decimal place is sufficient for age. It is not clear what the author meant on line 35-36 when they said that the “phoria measurement is a useful indicator not only in diagnosis but also in a choice of treatment”. It is also not clear what the authors meant on line 40-42 when they said that “proper diagnosis based on reliable devices may generate decompositions which can have consequences such as amblyopia etc.”

Comments on the Quality of English Language

As mentioned above

Author Response

Comments 1: This present study investigates four measurement approaches of heterophoria and AC/A ratio. The authors concluded that all the distance tests are interchangeable except for Modified Thorington test, and all near tests are interchangeable except for Von Graefe test. Interestingly, the application of +/-1.00 D lenses would render most tests uninterchangeable when assessing the AC/A ratio. The author attributes this observation to the different dissociation methods, stimuli, quantification methods, patient conditions, and examiner skills.

Response 1: The authors wish to express their gratitude for the reviewer’s diligent efforts throughout the revision process and for highlighting important aspects of the study. The necessary clarifications and modifications have been made in response to the comments. The authors trust that the revised manuscript now fulfills the requirements for publication.

 

Comments 2: The manuscript is generally well written, but it is not clear why the authors chose not evaluate the Howell phoria test even though it is mentioned in the introduction section.

Response 2: Thank you for pointing this out. In the introduction section the authors mentioned a wide number of tests available for heterophoria measurement. However, considering the time burden on the patient and the bias caused by a multiple test approaching in only one session, a selection of tests was made for the following reasons stated on the reported literature of the manuscript: alternating Cover Test is considered the reference method for measuring heterophorias at distance, Modified Thorington test is considered the reference for measuring heterophorias at near, Von Graefe is a method widely used in daily clinical practice, and OptoTab SERIES is a new technology about which there is not yet much information.

 

Comments 3: Although the participants wore their habitual refractive correction in this present study, line 105-6 claims that the participants wore their “best refractive correction” which seems to contradictory.

Response 3: The authors would like to apologize for the ambiguity. Each participant's subjective refraction was assessed by an optometrist, and the participant's habitual refractive correction was only used if it was consistent with the assessment. A clarification has been provided in section 2.1 Participants; adittionally, it also has been pointed out in the line provided by the reviewer for enhanced clarity.

Comments 4: In the methods section, the authors mentioned that the OptoTab is based on the principles of the Modified Thorington test, but this is not true since their dissociation approaches are different.

Response 4: Thank you for the comment. The authors agree with the reviewer’s observation. A clarification has been made to the text to accurately reflect the distinction between the dissociation methods employed by the OptoTab and the Modified Thorington test.

 

Comment 5: Insufficient information on the methods: what kind of occluder was used during cover test? It is mentioned in the discussion section that an opaque occlude is used, but it is not clearly stated in the methods section.

Response 5: Thank you for the comment. The reviewer is right in pointing out the lack of information regarding the type of occluder used in the present study. The authors would like to apologize for this oversight. An opaque occluder was used in all cases. This information has been updated in the Cover Test section of the methodology.

 

Comment 6: The authors should explain the “environmental lighting” too.

Response 6: Thank you for the suggestion. All tests were performed under constant environmental lighting conditions, ensuring optimal visibility of the near distance optotypes. The standard overhead lighting in the examination room was used, supplemented by a standup light to maintain constant and appropriate illumination throughout the testing process.

 

Comment 7: The abstract is actually quite confusing to readers, so the authors may need to make substantial changes to it.

Response 7: Thank you for the indication. The abstract has been revised and reorganised to enhance readability and comprehension.

 

Comment 8: One decimal place is sufficient for age.

Response 8: Thank you for the suggestion. The age of the participants has been updated to one decimal place in the manuscript.

 

Comment 9: It is not clear what the author meant on line 35-36 when they said that the “phoria measurement is a useful indicator not only in diagnosis but also in a choice of treatment”.

Response 9: The statement regarding phoria being a useful indicator not only in diagnosis but also in treatment selection is supported by the findings of Abraham et al. (2015, doi:10.4103/0974-620X.149856). According to this research, phoria provides valuable insights into binocular disorders and aids in determining the most appropriate treatment approach. To clarify this point, additional information has been added to the text.

 

Comment 10: It is also not clear what the authors meant on line 40-42 when they said that “proper diagnosis based on reliable devices may generate decompositions which can have consequences such as amblyopia etc.”

Response 10: Thank you for the comment. With this statement, the authors aim to indicate that inadequate diagnosis resulting from the use of unreliable tests can lead to further complications. These complications may include conditions such as amblyopia, loss of binocular function, and reduced stereopsis. Modifications have been made to simplify the text and clarify the underlying concept.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Every thing is fine.

Author Response

Comment 1: Every thing is fine.

- Response 1: The authors would like to thank the reviewer for their detailed comments and suggestions throughout the review process. These have highlighted important areas for improvement, and the authors believe that the revisions have strengthened the manuscript. The authors appreciate the reviewer’s effort in enhancing the quality of the work.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have carefully and adequately addressed the reviewer comments, and only a few minor issues remain to be addressed:

In Line 198, it is stated that for PFV and NFV, two values are indicated (break/recovery), but in Table 2, three values are shown, most likely representing blur/break/recovery. It might also improve Table 2 if it were widened slightly and formatted so that, where possible, blur/break/recovery appear on one line for PFV and NFV.

Regarding the NPC measurement, there seems to be some methodological variation around the reference point used. The outer canthus is the commonly used reference point with the push-up technique where a typical NPC break point for a sample of healthy young adults without convergence-related issues would usually be between 5 cm and 8 cm (consistent with the NPC break norm value in Table 1 (<10 cm), as the nose limits measurements closer than 3-5 cm. To avoid any further confusion regarding the NPC values, could you kindly include a short sentence clarifying the reference point and technique used for NPC measurement?

The newly added references (Lines 214, 284, 287, 291, and 293) need to be formatted in line with the manuscripts style.

Once these minor points are addressed, the manuscript will be ready for further processing. Thank you for your careful attention to the reviewers comments.

Author Response

Comment 1: The authors have carefully and adequately addressed the reviewer comments, and only a few minor issues remain to be addressed:

- Response 1: The authors would like to thank the reviewer for their thoughtful feedback and for helping to improve the manuscript. The authors have discussed carefully all reviewer comments and believe the manuscript is ready for publication. However, if further clarifications are needed, we are happy to provide additional details. Please find our specific responses to the remaining minor issues below.

 

Comment 2: In Line 198, it is stated that for PFV and NFV, two values are indicated (break/recovery), but in Table 2, three values are shown, most likely representing blur/break/recovery. It might also improve Table 2 if it were widened slightly and formatted so that, where possible, blur/break/recovery appear on one line for PFV and NFV.

- Response 2: Thank you for the suggestion. The reviewer is right in pointing out the discrepancy between the values indicated in the text and those shown in the table. Table 2 has been adjusted as much as possible, in accordance with the journal's formatting guidelines, to ensure that the blur/break/recovery values appear on a single line where feasible.

 

Comment 3: Regarding the NPC measurement, there seems to be some methodological variation around the reference point used. The outer canthus is the commonly used reference point with the push-up technique where a typical NPC break point for a sample of healthy young adults without convergence-related issues would usually be between 5 cm and 8 cm (consistent with the NPC break norm value in Table 1 (<10 cm), as the nose limits measurements closer than 3-5 cm. To avoid any further confusion regarding the NPC values, could you kindly include a short sentence clarifying the reference point and technique used for NPC measurement?

- Response 3: Thank you for the suggestion. Clarifications have been included within Table 1, explaining the technique used for measuring NPC. The push-up technique was employed, where participants were asked to follow the fixation point and report as soon as they saw it double. The reference point for measuring the distance was the outer canthus, as the reviewers indicated, following the standard procedure. The authors apologize for any part of the manuscript that may have caused misunderstandings.

 

Comment 4: The newly added references (Lines 214, 284, 287, 291, and 293) need to be formatted in line with the manuscripts style.

- Response 4: Thank you for the suggestion. These references have already been changed to match the format of the manuscript. The authors want to apologize for the typo during the formatting process.

 

Comment 5: Once these minor points are addressed, the manuscript will be ready for further processing. Thank you for your careful attention to the reviewers comments.

- Response 5: Thank you for the suggestion. The authors have addressed all minor points as requested and believe the manuscript is now ready for further processing. We sincerely appreciate your recommendations in both this and the previous review, and we are available for any additional clarifications if needed.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This present study compared four techniques in measuring heterophoria and AC/A ratio. The authors found significant differences between Modified Thorington and the rest of the techniques in the distance, and between Von Graefe and the rest of the techniques at near. The authors concluded that all methods are interchangeable except Modified Thorington in the distance and Von Graefe at near. While the article is well written and presented, there are two concerns with the author’s conclusion. Firstly, the authors should clearly mention that these conclusions are only applicable for the normal visual system but not the abnormal visual system. Secondly, it is not clear if the sample size is adequately powered to find a significant difference. In terms of methods, it seems that the authors have taken each measurement once only rather than taking an average from a few measurements. They have not mentioned how they deal with situations where there is large variability in the measurements. For example, it is well known that the measurement may tend to fluctuate if the participant is tired. Minor comments: Does the author mean “strabismic” and “non-strabismic” instead of “strabic” and “non-strabic” in the discussion section?

Author Response

Comment 1: This present study compared four techniques in measuring heterophoria and AC/A ratio. The authors found significant differences between Modified Thorington and the rest of the techniques in the distance, and between Von Graefe and the rest of the techniques at near. The authors concluded that all methods are interchangeable except Modified Thorington in the distance and Von Graefe at near. While the article is well written and presented, there are two concerns with the author’s conclusion.

- Response 1: The authors appreciate the reviewer’s thoughtful feedback and positive remarks regarding the manuscript. The insights provided highlight crucial aspects that warrant further clarification and refinement. The authors acknowledge the need to address specific concerns raised in the review. Below, responses to each of the reviewer’s comments are presented.

 

Comment 2: Firstly, the authors should clearly mention that these conclusions are only applicable for the normal visual system but not the abnormal visual system.

- Response 2: Thank you for the suggestion. A clarifying sentence has been added at the end of the conclusions to highlight that these findings are specific to a young, healthy population, and further research is required to generalize the results to individuals with binocular vision disorders.

 

Comment 3: Secondly, it is not clear if the sample size is adequately powered to find a significant difference. In terms of methods, it seems that the authors have taken each measurement once only rather than taking an average from a few measurements. They have not mentioned how they deal with situations where there is large variability in the measurements. For example, it is well known that the measurement may tend to fluctuate if the participant is tired.

- Response 3: Thank you for the suggestion. You are correct that fatigue can influence heterophoria values. To minimize this effect, all tests were performed in a random order for each participant, and all measurements were taken on the same day, so any potential impact of fatigue would be consistent across tests. While each measurement was taken only once, this approach was chosen to reflect real-world clinical practice. However, we acknowledge that taking multiple measurements and averaging them could reduce variability, and this is a limitation of the current study. The authors have added this point to the Methods section and included it as a limitation in the Discussion (lines 371-376).

 

Comment 4: Minor comments: Does the author mean “strabismic” and “non-strabismic” instead of “strabic” and “non-strabic” in the discussion section?

- Response 4: Thank you for the suggestion. It was a typographical error, and the authors apologize for the mistake. It has now been corrected.

 

Author Response File: Author Response.pdf