Accuracy of vertical cup-to-disc ratio discrimination among clinical optometry trainees with different years of clinical experience.

PURPOSE: Accurate evaluation of the cup-to-disc ratio is crucial for optometrists and may be influenced by their clinical experience. The study's objective was to compare the thresholds for discriminating vertical cup-to-disc ratio (VCDR) between years 2, 3, and 4 clinical optometry trainees.
METHODS: One hundred fundus photos with various VCDR sizes were selected from a clinic database. The median VCDR (0.43) photo was assigned as the standard, while the other 99 were assigned as the test photos. The participant's task was to discriminate using a 2-alternate-forced-choice paradigm whether the test photos' VCDR were larger or smaller than the standard VCDR. Data were fit with a Weibull function, and three discrimination thresholds were determined: the point of subjective equality (PSE), the range of VCDR uncertainty, and the ability to judge VCDR that was 0.1 unit larger than the standard photo.
RESULTS: Year 4 trainees had better VCDR discrimination thresholds. However, the difference between the three participant groups was not statistically different for all measurements (PSE: F(2,27) = 0.43, p = 0.657; VCDR uncertainty range: F(2,27) = 0.12, p = 0.887), and thresholds for correctly discriminating VCDR 0.1 larger than the standard photo's VCDR: F(2,27) = 0.69, p = 0.512).
CONCLUSION: Although Year 4 optometry trainees performed slightly better at estimating VCDR than their Year 3 and Year 2 peers, the number of years of clinical experiences did not significantly affect their VCDR discrimination thresholds when 2-dimensional fundus photos were used as stimuli.

Introduction

The fundus of the eye can be examined using various methods such as direct ophthalmoscopy, fundus biomicroscopy, fundus photography, and optical coherence tomography [1, 2]. Its evaluation allows the detection of any changes that may indicate the occurrence of a pathology. For instance, the optic nerve head (ONH) evaluation is vital as it may be related to the presence of ocular diseases, such as glaucoma. Specifically for the ONH, features such as the optic disc’s size, shape and tilt, the optic cup’s shape and depth, cup-to-disc ratio (CDR), and neuroretina rim should be inspected during an eye examination [3].

CDR can be measured horizontally or vertically, giving the horizontal cup-to-disc ratio (HCDR) and vertical cup-to-disc ratio (VCDR), respectively. VCDR is usually used as an indication for glaucoma screening [1, 4–6]. An illustration of the ONH and VCDR is shown in Fig 1. VCDR equal to or larger than 0.8, or a difference in VCDR between eyes by more than 0.2, is pathological [7]. Such fundus findings may indicate glaucoma, characterized by damage to the optic nerve, resulting in irreversible blindness. As 6.6% of blindness among the elderly aged 50 years old and above is contributed by glaucoma [8], accurate VCDR evaluation is essential to aid clinical diagnosis.

Fig 1

An illustration of the optic nerve head (ONH) and the vertical cup-to-disc ratio (VCDR).

The technological development of sophisticated tools has helped in capturing high-quality fundus images. However, the judgement of any changes, normal or pathological, is still dependent on the subjective assessment of the clinician especially when automated estimation is not available. The estimation of VCDR can be subjective and a trainee’s ability is typically benchmarked against an examiner who has years of clinical experience [9]. As the accuracy of clinical judgements may be correlated with clinical experience [5, 10], it is hypothesized that trainees with more clinical experience are better at discriminating cup-to-disc ratio than their more junior peers. In addition, knowing how trainees with different clinical experiences judge CDRs would help examiners to devise a fairer way to evaluate their clinical judgement.

Therefore, the study’s objective was to determine the thresholds for discriminating VCDR between Year 2, 3, and 4 clinical optometry trainees. The thresholds were then compared between these three groups with a different number of years of clinical experience.

Methodology

Study participants

This cross-sectional study was carried out from February to July 2021 in the Optometry Clinic, Universiti Kebangsaan Malaysia (the National University of Malaysia) located in Kuala Lumpur. The study population was clinical optometry trainees in the Optometry and Vision Science Programme. They were in their second, third, and fourth year in the optometry programme. At the time of the data collection, all participants had at least two semesters of theoretical knowledge of the anatomy of the retina and practical experience in fundus examination techniques. All participants had a cumulative grade point average (CGPA) of at least 3.00 out of a maximum of 4.00. It is calculated as the mean of the total grade points for every semester divided by the total number of credits where ≥3.00 CGPA reflected an overall academic performance graded as ‘distinction’. Trainees who had resit for any modules or had postponed their studies were excluded.

Participant sampling

The population size (N) was 105 trainees. Using G*Power 3.1.9.4 [11], a sample size (n) of 30 would be able to detect a medium to a large effect size of 0.6 with a power of 80% and an error rate α of 0.05. The sample size was divided into three groups based on the participants’ study years (Years 2, 3, and 4). Ten trainees who fulfilled the inclusion criteria from each study year were selected using a simple random sampling method. Data were only collected after the Information Sheet was given to each participant and the Informed Consent Form was signed. The ethics of this study was approved by the institution’s Research Ethics Committee (project code: UKM PPI/111/8/JEP-2021-063).

Experimental stimuli and instrument

All fundus photos were captured with a Canon CR-2 PLUS AF Digital Non-Mydriatic Retinal Camera (Canon U.S.A., Inc.), located in Diagnostic Room 1 of the Optometry Clinic. The fundus photos were first compiled from the instrument’s database by author YRL, a final-year optometry student. They were then evaluated and selected by consensus by YRL, author MIH who was a registered optometrist and academician with a 15-year of experience, and another optometrist who was independent of the study. One hundred fundus photos with clear optic disc and optic cup contour, chosen from the Optometry Clinic database (from 2018 to 2020), were selected as stimuli. Fundus photos with any pathology (other than enlarged VCDR) and with apparent artefacts were discarded. Every fundus photo’s VCDR was determined using the Canon CR-2 Plus’s built-in software.

Psychophysical procedures

All of the photos were uploaded onto the PsychoPy software [12]. A custom-written program was created to display the stimuli and determine the participants’ threshold to discriminate VCDR accurately. The fundus photo whose VCDR was the median (0.43) was chosen as the standard from the 100 photos. The other 99 fundus photos were assigned as the test photos.

For measurements of discrimination thresholds, a test photo was displayed next to the standard photo. Using the 2-alternate-forced-choice (2AFC) method, the participant’s task was to indicate if the test photo’s VCDR was larger or smaller than the standard photo’s VCDR. The discrimination task was carried out for all 99 test photos. The viewing distance was set at 40 cm. At this viewing distance, the visible area of the fundus subtended 14.7 minutes of arc. The procedure was carried out binocularly. Viewing time was unlimited. The participant’ responses were collected using a keypress on a keyboard.

All participants underwent a training session to familiarize themselves with the study’s procedures. Data from the training session were not included in the analysis. All data collected after the training session were averaged from three experimental runs.

Determination of VCDR discrimination thresholds

The percent response for “test photo’s VCDR judged larger than standard photo’s VCDR” was plotted as a function of the test photos’ VCDRs in Igor Pro® software. The data was fit with a Weibull function with the formula: where th is the estimated VCDR threshold, corresponding to 50% percent response for “test photo’s VCDR judged larger than standard photo’s VCDR”; β is the slope of the psychometric function; and x is a given VCDR.

From the psychometric function, participants’ discrimination thresholds were determined in three ways:

The point of subjective equality (PSE), where the test photo’s VCDR was judged to be larger than the standard photo’s VCDR 50% of the time (Fig 2);

Fig 2

The percent of test photo’s VCDR judged to be larger than standard photo’s VCDR, plotted as a function of VCDR.

The data was fit with a Weibull function. The point of subjective equality was determined by finding the VCDR that corresponds to ‘50% larger’ response.

The range of VCDR discrimination uncertainty, which was determined by (a) estimating the test photo’s VCDR that was judged to be larger than the standard photo’s VCDR 75% of the time, and (b) estimating the test photo’s VCDR that was judged to be larger than standard photo’s VCDR 25% of the time, that is, the VCDR that the participants accurately judged to be 25% smaller than the standard photo’s VCDR. The range of VCDR discrimination uncertainty was calculated by subtracting (b) from (a) (Fig 3).

Fig 3

The range of VCDR discrimination uncertainty was calculated by subtracting the VCDR that was accurately judged to be 25% larger than the standard photo’s VCDR with VCDR that was accurately judged to be 25% smaller than the standard photo’s VCDR.

The percentage that the participants were able to discriminate that VCDR of test photo was 0.53, that is, 0.1 unit larger than the standard photo’s VCDR (0.43) (Fig 4).

Fig 4

Determination of % of times a VCDR of 0.53 judged to be larger than the standard photo’s VCDR (0.43), that is, when the test photo VCDR was larger by 0.1 unit.

Statistical analysis

Discrimination thresholds for 25%, 50%, and 75% responses, and for correctly discriminating 0.53 VCDR, were calculated for each participant and presented as mean and standard deviation using IBM Statistical Package for Social Sciences version 25 (IBM Corp., Armonk, NY, USA). One-way ANOVA was used to compare the mean discrimination thresholds between three participant groups. The value of significance was set at p<0.05 for all statistical tests.

Results

The mean age of the 30 participants was 22.17±0.91 years (age range: 21 to 24 years old). Five participants (16.7%) were males, and twenty-five (85.3%) were females. The characteristics of the participants are summarized in Table 1. There was no significant difference between the year groups’ CGPAs (one-way ANOVA [F(2,27) = 2.071, p = 0.146]).

Table 1

Participants’ sociodemographics and cumulative grade point average (CGPA).

Characteristics	Year 2 (n = 10)	Year 3 (n = 10)	Year 4 (n = 10)	Overall (n = 30)
Age	21.30±0.68	22.00±0.00	23.20±0.42	22.17±0.91
Gender
Male	2	2	1	5
Female	8	8	9	25
CGPA (out of 4)	3.58±0.34	3.42±0.25	3.35±0.15	3.45±0.27

The mean VCDR PSE for participants in Year 2, Year 3, and Year 4 was 0.44±0.04, 0.43±0.06 and 0.43±0.02, respectively. There was no statistically significant difference of PSE between the three groups (one-way ANOVA [F(2,27) = 0.426, p = 0.657]).

The VCDR uncertainty range was determined by subtracting the threshold for correctly discriminating a test photo’s VCDR that was 25% larger than the standard photo’s VCDR with the threshold for correctly discriminating a test photo’s VCDR that was 25% smaller than the standard photo’s VCDR. The VCDR uncertainty range for participants in Year 2, Year 3, and Year 4 was 0.18±0.06, 0.17±0.05, and 0.18±0.03, respectively. There was no statistically significant difference in the VCDR uncertainty range between the three groups (one-way ANOVA [F(2,27) = 0.121, p = 0.887]).

The percentage of correctly estimating a test photo with VCDR of 0.53 indicated the ability of the participants to discriminate VCDR that was 0.10 units larger than the standard photo’s VCDR (0.43). The mean percentage correct 0.53 VCDR estimation for participants in Year 2, 3, and 4 were 73.72%±11.61, 77.52%±14.23 and 79.56%±6.80, respectively. Although trainees with the most clinical experience (Year 4) tend to have higher percentages in judging the VCDR correctly, the differences in VCDR estimation between the participant groups were not statistically significant (one-way ANOVA [F(2,27) = 0.687, p = 0.512]).

Discussion

Despite technological advances in automated medical imaging, the competency in evaluating clinical findings by trainees in clinical courses such as optometry remains vital for the successful care of patients. This study assessed the ability to discriminate VCDR of the optic nerve head in clinical optometry trainees from three cohorts, each with different clinical experience and exposure. Generally, Year 2 participants had higher thresholds to achieve the point of subjective equality than Year 3 and Year 4 participants. Year 2 participants also had the lowest percentage correct to discriminate VCDR that was 0.10 larger than the median VCDR, compared to their Year 3 and Year 4 peers. However, all of these results were not statistically significant. In addition, the VCDR uncertainty range was also not significantly different between the cohorts. These results suggest that the assumed difference in the hands-on clinical training did not significantly influence the participants’ ability to discriminate VCDR.

The COVID-19 pandemic resulted in the suspension of face-to-face teaching, including hands-on practical sessions. The current study’s Year 2 participants spent significantly fewer hours in the teaching lab as most teachings were carried out online due to the COVID-19 lockdown. Despite spending less than a semester of hands-on clinical training, they were able to judge VCDR, based on fundus photos, just as well as their more senior peers. These findings suggest that online education and web-based teaching sessions, which replaced traditional teaching sessions, were effective, in line an earlier report for ophthalmology training [13]. Nevertheless, it can be argued that the lack of hands-on session could create a delay in the acquisition of necessary clinical skills such as ophthalmoscopy. It has been reported that that online tutorials were helpful in medical ophthalmic skill teaching [14]. However, these authors also reported that online teaching of direct ophthalmoscopy, one of the clinical procedures that allow VCDR evaluation, was challenging. As clinical competencies are found to be positively correlated with years of clinical experience [10, 15], the association between the ability to judge VCDR based only on fundus photos and the actual clinical competency to obtain it remains to be seen should be investigated in a future study.

This study’s findings were in line with an earlier report where the clinical accuracy in evaluating the glaucomatous optic nerve head characteristics by first- and third-year ophthalmology residents were compared [16]. It was found that the third-year residents only did better than the first-year residents in evaluating four out of ten optic nerve head characteristics. These findings were attributed to theoretical teaching that was primarily conducted in the first year of the residents’ training. Besides, another study reported no significant correlation between VCDR’s graders’ reliability and their years of experience in grading [6]. In our study, the clinical optometry trainees were taught about the ways to discriminate VCDR when they were in Year 2. In Years 3 and 4, more intensive practical training was conducted in order to improve clinical accuracy. Although the VCDR discrimination abilities of the current study’s participants were not statistically different, their actual clinical ability to conduct fundus examination, such as direct ophthalmoscopy, may not be equal.

The results of this study appear to be in contrast to a study that found that medical students performed better VCDR evaluation than non-clinical graders [5]. However, their non-clinical graders had no prior experience with VCDR grading nor with clinical care in general. However, the current study’s Year 2 participants did have some clinical training, albeit the least compared to their Year 3 and Year 4 peers. Therefore, it is reasonable to suggest that the experience that the Year 2 participants had contributed to their ability to discriminate VCDR.

For the current study’s participants, at least, it seems that clinical experience was not the primary factor that influences VCDR discrimination. Participants in this study had a maximum of two-year gap in their clinical experience. A larger gap in clinical experience probably would lead to a different outcome. A future study could be conducted to compare the discrimination of VCDR between optometry trainees and registered optometrists with at least 5 to 10 years of experience. Moreover, the lack of hands-on experience during the COVID-19 pandemic may have contributed to differences in the ability to judge VCDR, even though the participants’ clinical experiences were technically different. Across the three trainee groups, their ability to correctly discriminate 0.1 unit change in VCDR was similar at approximately 80%. Therefore, optimisation of the clinical ability may be achieved with additional lectures [17, 18] and clinical training [19, 20]. Indeed, the COVID-19 pandemic offers an opportunity for clinical teaching institutions to reshape medical training, with the use of new technology as part of educational tools [13]. Web-based teaching, clinical simulators, and remote mentoring offer the necessary flexibility to reverse any gaps in clinical skills due to the suspension of traditional teaching, while simultaneously be part of a future-ready curriculum.

This study has several limitations. One issue that arises is whether the judgements of the ONH and VCDR based on fundus photos, which lack depth cues, could accurately reflect the actual clinical ability of the trainees. However, some popular clinical methods of ONH observation also involve monocular or 2-dimensional observation, including the use of a monocular hand-held direct ophthalmoscope and evaluation of fundus photos captured with a fundus camera, which are relevant to the method employed in this study. Nevertheless, we also agree that there could be limitations on the transferability of the estimated 2D estimations of the VCDR, particularly when its examination involves binocular procedures such as the binocular indirect ophthalmoscopy and or with the Hruby lens. Secondly, although there were 99 test photos as stimuli, there were only a few fundus photos at the extreme ends of the VCDR values (n = 2 for 0.15 VCDR and n = 2 for 0.70 VCDR). Thirdly, the objective discrimination of VCDR was carried out by one person only (author LYR), which might have led to expectation bias.

Conclusions

Optometry trainees with different years of clinical training experience have similar thresholds for discriminating VCDR when 2-dimensional fundus photos were used as the stimuli.

(XLSX)

Click here for additional data file.

6 Jul 2022

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Alon Harris

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf  and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. We note that you have stated that you will provide repository information for your data at acceptance. Should your manuscript be accepted for publication, we will hold it until you provide the relevant accession numbers or DOIs necessary to access your data. If you wish to make changes to your Data Availability statement, please describe these changes in your cover letter and we will update your Data Availability statement to reflect the information you provide.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The main question that comes forward is qualifying as a technically sound manuscript. Following the description above "The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented." I am concerned that the research does not necessarily support the final conclusion statement as written, or at least a better description of how the conclusion is a leap from the data. It is well know that fundus photography does not show depth perception, thus to conclude that optometry trainees do or do not discriminate appropriately the VCDR off only 2 dimension photography seems to be a bit of scientific stretch. The conclusion only applies to whether optometry trainees discriminate the VCDR well in fundus photos, with lack of depth clues, not their performance clinically. There seems to be a leap of faith that the performance on the grading of photography (research data) will be the same as the trainees performance in clinic, per the conclusion. I encourage the authors to include a discussion on the limitations and transferability of measurements estimated 2 dimensional photography versus 3 dimensional clinically.

The figures and tables were accurately reported. Statistics seemed appropriate and accurate. There was a case for using an n=30 but study was conducted on a much larger number and should only make statistics stronger (line 70-76) if including additional subjects. Methods appeared to be sound (line 148-150). There were a few discussion points regarding COVID and training (line 199) that start to delve into some explanation behind the results, however, I think time spent on the conclusion on above relevant topics would be prudent and encourage authors to include further detail. Strong references (line 34, 204) were including. Overall, a interesting study that may further help guide Optometry curriculum.

Reviewer #2: The authors presented an interesting study evaluating the accuracy of vertical cup-to-disc ratio discrimination among clinical optometry trainees with different years of clinical experience. The manuscript is clear, its topic is original in content, and the conclusions are consistent with the evidence presented. The manuscript is with merit and the findings are worth reporting, but the authors should address the following comments before publication.

- Introduction/entire manuscript

o It would be helpful to have a graphical visualization of the optic nerve head and of the vertical cup to disc ratio for readers that are not experts in ophthalmology

o Revise the use of abbreviations: an abbreviation should be explained once in the manuscript and after only the abbreviation (and not the full explanation) should be used – revise the manuscript correspondingly (i.e. cup-to-disc ratio (CDR), horizontal cup to disc ratio (HCDR) and vertical cup to disc ratio (VCDR) are explained in the introduction: only the abbreviations should be used after in the entire manuscript – for example at line 84 “Every fundus photo's vertical cup-to-disc ratio (VCDR)” should be replaced by “Every fundus photo's VCDR” )

- Methodology

o Section “study participants”

�  The authors should provide the details of the name and location of the University/optometrist clinic where the study was conducted

�  The authors should provide a brief explanation of what the “cumulative grade point average (CGPA)” is, for readers who may not be familiar with such score

o Section “Experimental Stimuli and Instrument”: how was the selection of the one hundred fundus photos made? One or multiple operators and at which level of training? The authors should provide additional details in this section

- Discussion

o The authors should provide insight about the future directions of this research and discuss the significance (from a clinical/educational point of view) of their results

- Figures and Tables legends: the authors should provide the explanations of the abbreviations used in the legends

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

11 Jul 2022

Manuscript ID:

PONE-D-22-10365

Manuscript Title:

Accuracy of vertical cup-to-disc ratio discrimination among clinical optometry trainees with different years of clinical experience

Response to Reviewers

We thank both Reviewers for their helpful comments and suggestions. They have helped us significantly improved the manuscript. We address their comments point-by-point below.

Reviewer #1:

Reviewer #1 found that the study was interesting that may further guide the Optometry curriculum. They also found that our figures, tables, statistics, and methods sound and accurately reported. We agreed that our initial conclusion might have appeared like a leap between the ability to discriminate VCDR to clinical competency; however, we have addressed this concern by making the necessary changes as described in detail below.

Comment 1:

I encourage the authors to include a discussion on the limitations and transferability of measurements estimated 2 dimensional photography versus 3 dimensional clinically.

Our response:

We thank Reviewer 1 for their helpful comments, particularly when the study was found to be interesting and useful to further guide the relevant optometry curriculum.

We agree with Reviewer 1’s comment on the transferability of estimated measurements of VCDR based on 2-D photos vs. the 3D nature of the optic nerve head. Nevertheless, even clinically, some popular methods of ONH observation also involve 2D observation. These include the use of a monocular hand-held direct ophthalmoscope and evaluation of the fundus photos captured with a fundus camera, such as the one used in this study. The fundus-matching method proposed by Kwok et al 2017 , where ophthalmology residents were tasked to match real patients’ actual fundus with their corresponding 2D fundus photos, has been found to be effective in improving clinical judgement and skills.

Having said that, we also agree that there could be limitations on the transferability of the estimated 2D estimations of the ONH, particularly when its examination involves binocular procedures such as the binocular direct ophthalmoscopy and or using the Hruby lens. We address this as limitations in the revised manuscript, lines 255-263:

“One issue that arises is whether the judgements of the ONH and VCDR based on fundus photos, which lack depth cues, could accurately reflect the actual clinical ability of the trainees. However, some popular clinical methods of ONH observation also involve monocular or 2-dimensional observation, including the use of a monocular hand-held direct ophthalmoscope and evaluation of fundus photos captured with a fundus camera, which are relevant to the method employed in this study. Nevertheless, we also agree that there could be limitations on the transferability of the estimated 2D estimations of the VCDR, particularly when its examination involves binocular procedures such as the binocular indirect ophthalmoscopy and or with the Hruby lens.”

We have also revised the Conclusion:

(i) of the abstract (lines 17-19)

“Although Year 4 optometry trainees performed slightly better at estimating VCDR than their Year 3 and Year 2 peers, the number of years of clinical experiences did not significantly affect their VCDR discrimination thresholds when 2-dimensional fundus photos were used as stimuli.”

(ii) and in Conclusions (lines 266-267)

“Optometry trainees with different years of clinical training experience have similar thresholds for discriminating VCDR when 2-dimensional fundus photos were used as the stimuli.”

Comment 2:

There was a case for using an n=30 but study was conducted on a much larger number and should only make statistics stronger (line 70-76) if including additional subjects.

Our response:

As mentioned in the subheading Participant Sampling, the n=30 of the current study has adequate power (80%). Although n could have been made larger, the discrimination thresholds measured were based on a large number of observations, where each participant completed 297 trials (99 trials × 3 runs), excluding training sessions. Such a paradigm is said to be optimum for identifying systematic functional relationships in experimental designs with (relatively) small n (Smith & Little, 2018) . Thus, for the purpose of the study, n=30 is adequate although we do not disagree with Reviewer 1 that a larger sample size should make the statistics stronger.

Comment 3:

There were a few discussion points regarding COVID and training (line 199) that start to delve into some explanation behind the results, however, I think time spent on the conclusion on above relevant topics would be prudent and encourage authors to include further detail.

Our response:

Yes we agree that the impact of the pandemic on training is prudent to be discuss in detail. We have revised and added the point below in Discussion, lines 204-218:

“The COVID-19 pandemic resulted in the suspension of face-to-face teaching, including hands-on practical sessions. The current study’s Year 2 participants spent significantly fewer hours in the practical teaching lab as most teachings were carried out online due to the COVID-19 lockdown. Despite spending less than a semester of hands-on clinical training, they were able to judge VCDR based on fundus photos just as well as their more senior peers. These findings suggest that online education and web-based teaching sessions, which replaced traditional teaching sessions, were effective, in line with an earlier report for ophthalmology training (Ferrera et al., 2020). Nevertheless, it can also be argued that the lack of hands-on session could create a delay in the acquisition of necessary clinical skills such as ophthalmoscopy. It has been reported that online tutorials were helpful in medical ophthalmic skill teaching (Shih et al., 2020). However, these authors also reported that online teaching of direct ophthalmoscopy, one of the clinical procedures that allow VCDR evaluation, was challenging. As clinical competencies are found to be positively correlated with years of clinical experience (Barsuk et al., 2017; Kong et al., 2011), the association between the ability to judge VCDR based only on fundus photos and actual clinical competency to obtain it remains to be seen and should be investigated in a future study.”

In the same vein, we have also include the point on how clinical training can be enhanced, as part of the future direction after the COVID-19 pandemic, lines 249-254:

“Indeed, the COVID-19 pandemic offers an opportunity for clinical teaching institutions to reshape medical training, with the use of new technology as part of educational tools (Ferrera et al., 2020). Web-based teaching, clinical simulators, and remote mentoring offer the necessary flexibility to reverse any gaps in clinical skills due to the suspension of traditional teaching while simultaneously be part of a future-ready curriculum.”

Reviewer #2

We would also like to thank Reviewer2 for their valuable comments. They found that the manuscript to be with merit, and our findings worth reporting. The comments are addressed in detail below.

Comment 1:

It would be helpful to have a graphical visualization of the optic nerve head and of the vertical cup to disc ratio for readers that are not experts in ophthalmology

Our response:

We thank Reviewer2 for the suggestion. Indeed, a figure of the optic nerve head and of the VCDR calculation would be helpful. We have addressed this comment in the Introduction as Figure 1. As such, the numbering of all other figures has been modified accordingly.

Comment 2:

Revise the use of abbreviations: an abbreviation should be explained once in the manuscript and after only the abbreviation (and not the full explanation) should be used – revise the manuscript correspondingly (i.e. cup-to-disc ratio (CDR), horizontal cup to disc ratio (HCDR) and vertical cup to disc ratio (VCDR) are explained in the introduction: only the abbreviations should be used after in the entire manuscript – for example at line 84 “Every fundus photo's vertical cup-to-disc ratio (VCDR)” should be replaced by “Every fundus photo's VCDR” )

Our response:

We thank Reviewer2 for the suggestion. The manuscript has been revised where all abbreviations are used appropriately as suggested. These changes are tracked in the manuscript.

Comment 3:

The authors should provide the details of the name and location of the University/optometrist clinic where the study was conducted

Our response:

The name and location of the university where the study was conducted are now stated in the revised manuscript. The first line (line 62) of the Study Participants section now reads:

‘This cross-sectional study was carried out from February to July 2021 in the Optometry Clinic, Universiti Kebangsaan Malaysia (the National University of Malaysia) located in Kuala Lumpur.’

Comment 4:

The authors should provide a brief explanation of what the “cumulative grade point average (CGPA)” is, for readers who may not be familiar with such score.

Our response:

We have provided a brief explanation on the CGPA to aid understanding for readers who may not be familiar with the score. The Study Participants section has now been revised to address this point (lines 68-71):

‘All participants had a cumulative grade point average (CGPA) of at least 3.00 out of a maximum of 4.00. It is calculated as the mean of the total grade points for every semester divided by the total number of credits where ≥3.00 CGPA reflected an overall academic performance graded as ‘distinction’.’

Comment 5:

Section “Experimental Stimuli and Instrument”: how was the selection of the one hundred fundus photos made? One or multiple operators and at which level of training? The authors should provide additional details in this section

Our response:

The details on the selection of the fundus photos have been revised and are now described in Experimental Stimuli and Instrument as follows (lines 87-90):

‘The fundus photos were first compiled from the instrument’s database by author YRL, a final-year optometry student. They were then evaluated and selected by consensus by YRL, author MIH who was a registered optometrist and academician with a 15-year of experience, and another optometrist who was independent of the study.’

Comment 6:

The authors should provide insight about the future directions of this research and discuss the significance (from a clinical/educational point of view) of their results

Our response:

We have also added that the integration of new technology as an important tool to reverse any gaps in clinical skills, and also as part of a future ready curriculum in medical training (Discussion lines 249-254):

“Indeed, the COVID-19 pandemic offers an opportunity for clinical teaching institutions to reshape medical training, with the use of new technology as part of educational tools (Ferrera et al., 2020). Web-based teaching, clinical simulators, and remote mentoring offer the necessary flexibility to reverse any gaps in clinical skills due to the suspension of traditional teaching while simultaneously be part of a future-ready curriculum.”

Comment 7:

- Figures and Tables legends: the authors should provide the explanations of the abbreviations used in the legends

Our response:

The abbreviation used in the Figures (i.e. VCDR) is provided in the axis labels. Abbreviations are also now mentioned in full for Table 1.

END OF RESPONSE

Mohd Izzuddin Hairol

9 July 2022

Submitted filename: Response to Reviewers.docx

Click here for additional data file.

5 Sep 2022

Accuracy of vertical cup-to-disc ratio discrimination among clinical optometry trainees with different years of clinical experience

PONE-D-22-10365R1

Dear Dr. Mohd Izzudin Hairol,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Alon Harris

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Yes

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: Yes

Reviewer #3: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

Reviewer #3: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: The authors addressed all my comments to the best of their knowledge and the manuscript can be accepted for publication.

Reviewer #3: The authors addressed all the comments of the reviewers, and corrected and added accordingly the manuscript

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: No

Reviewer #3: No

**********

8 Sep 2022

PONE-D-22-10365R1

Accuracy of vertical cup-to-disc ratio discrimination among clinical optometry trainees with different years of clinical experience

Dear Dr. Hairol:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Alon Harris

Academic Editor

PLOS ONE