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Authors are the souls of any journal, and deserve much respect. To publish a journal manuscripts are needed from authors. Authors have a great responsibility for producing facts of their work in terms of number and results truthfully and an individual honesty is expected from authors in this regards. Both ways its true "No authors-No manuscripts-No journals" and "No journals–No manuscripts–No authors". Reviewing a manuscript is also a very responsible and important task of any peer-reviewed journal and to be taken seriously. It needs knowledge on the subject, sincerity, honesty and determination. Although the process of reviewing a manuscript is a time consuming task butit is expected to give one's best remarks within the time frame of the journal.
Salient features of the JCDR: It is a biomedical, multidisciplinary (including all medical and dental specialities), e-journal, with wide scope and extensive author support. At the same time, a free text of manuscript is available in HTML and PDF format. There is fast growing authorship and readership with JCDR as this can be judged by the number of articles published in it i e; in Feb 2007 of its first issue, it contained 5 articles only, and now in its recent volume published in April 2011, it contained 67 manuscripts. This e-journal is fulfilling the commitments and objectives sincerely, (as stated by Editor-in-chief in his preface to first edition) i e; to encourage physicians through the internet, especially from the developing countries who witness a spectrum of disease and acquire a wealth of knowledge to publish their experiences to benefit the medical community in patients care. I also feel that many of us have work of substance, newer ideas, adequate clinical materials but poor in medical writing and hesitation to submit the work and need help. JCDR provides authors help in this regards.
Timely publication of journal: Publication of manuscripts and bringing out the issue in time is one of the positive aspects of JCDR and is possible with strong support team in terms of peer reviewers, proof reading, language check, computer operators, etc. This is one of the great reasons for authors to submit their work with JCDR. Another best part of JCDR is "Online first Publications" facilities available for the authors. This facility not only provides the prompt publications of the manuscripts but at the same time also early availability of the manuscripts for the readers.
Indexation and online availability: Indexation transforms the journal in some sense from its local ownership to the worldwide professional community and to the public.JCDR is indexed with Embase & EMbiology, Google Scholar, Index Copernicus, Chemical Abstracts Service, Journal seek Database, Indian Science Abstracts, to name few of them. Manuscriptspublished in JCDR are available on major search engines ie; google, yahoo, msn.
In the era of fast growing newer technologies, and in computer and internet friendly environment the manuscripts preparation, submission, review, revision, etc and all can be done and checked with a click from all corer of the world, at any time. Of course there is always a scope for improvement in every field and none is perfect. To progress, one needs to identify the areas of one's weakness and to strengthen them.
It is well said that "happy beginning is half done" and it fits perfectly with JCDR. It has grown considerably and I feel it has already grown up from its infancy to adolescence, achieving the status of standard online e-journal form Indian continent since its inception in Feb 2007. This had been made possible due to the efforts and the hard work put in it. The way the JCDR is improving with every new volume, with good quality original manuscripts, makes it a quality journal for readers. I must thank and congratulate Dr Hemant Jain, Editor-in-Chief JCDR and his team for their sincere efforts, dedication, and determination for making JCDR a fast growing journal.
Every one of us: authors, reviewers, editors, and publisher are responsible for enhancing the stature of the journal. I wish for a great success for JCDR."
Thanking you
With sincere regards
Dr. Rajendra Kumar Ghritlaharey, M.S., M. Ch., FAIS
Associate Professor,
Department of Paediatric Surgery, Gandhi Medical College & Associated
Kamla Nehru & Hamidia Hospitals Bhopal, Madhya Pradesh 462 001 (India)
E-mail: drrajendrak1@rediffmail.com
On May 11,2011
Dr. Shankar P.R.
"On looking back through my Gmail archives after being requested by the journal to write a short editorial about my experiences of publishing with the Journal of Clinical and Diagnostic Research (JCDR), I came across an e-mail from Dr. Hemant Jain, Editor, in March 2007, which introduced the new electronic journal. The main features of the journal which were outlined in the e-mail were extensive author support, cash rewards, the peer review process, and other salient features of the journal.
Over a span of over four years, we (I and my colleagues) have published around 25 articles in the journal. In this editorial, I plan to briefly discuss my experiences of publishing with JCDR and the strengths of the journal and to finally address the areas for improvement.
My experiences of publishing with JCDR: Overall, my experiences of publishing withJCDR have been positive. The best point about the journal is that it responds to queries from the author. This may seem to be simple and not too much to ask for, but unfortunately, many journals in the subcontinent and from many developing countries do not respond or they respond with a long delay to the queries from the authors 1. The reasons could be many, including lack of optimal secretarial and other support. Another problem with many journals is the slowness of the review process. Editorial processing and peer review can take anywhere between a year to two years with some journals. Also, some journals do not keep the contributors informed about the progress of the review process. Due to the long review process, the articles can lose their relevance and topicality. A major benefit with JCDR is the timeliness and promptness of its response. In Dr Jain's e-mail which was sent to me in 2007, before the introduction of the Pre-publishing system, he had stated that he had received my submission and that he would get back to me within seven days and he did!
Most of the manuscripts are published within 3 to 4 months of their submission if they are found to be suitable after the review process. JCDR is published bimonthly and the accepted articles were usually published in the next issue. Recently, due to the increased volume of the submissions, the review process has become slower and it ?? Section can take from 4 to 6 months for the articles to be reviewed. The journal has an extensive author support system and it has recently introduced a paid expedited review process. The journal also mentions the average time for processing the manuscript under different submission systems - regular submission and expedited review.
Strengths of the journal: The journal has an online first facility in which the accepted manuscripts may be published on the website before being included in a regular issue of the journal. This cuts down the time between their acceptance and the publication. The journal is indexed in many databases, though not in PubMed. The editorial board should now take steps to index the journal in PubMed. The journal has a system of notifying readers through e-mail when a new issue is released. Also, the articles are available in both the HTML and the PDF formats. I especially like the new and colorful page format of the journal. Also, the access statistics of the articles are available. The prepublication and the manuscript tracking system are also helpful for the authors.
Areas for improvement: In certain cases, I felt that the peer review process of the manuscripts was not up to international standards and that it should be strengthened. Also, the number of manuscripts in an issue is high and it may be difficult for readers to go through all of them. The journal can consider tightening of the peer review process and increasing the quality standards for the acceptance of the manuscripts. I faced occasional problems with the online manuscript submission (Pre-publishing) system, which have to be addressed.
Overall, the publishing process with JCDR has been smooth, quick and relatively hassle free and I can recommend other authors to consider the journal as an outlet for their work."
Dr. P. Ravi Shankar
KIST Medical College, P.O. Box 14142, Kathmandu, Nepal.
E-mail: ravi.dr.shankar@gmail.com
On April 2011 Anuradha
Dear team JCDR, I would like to thank you for the very professional and polite service provided by everyone at JCDR. While i have been in the field of writing and editing for sometime, this has been my first attempt in publishing a scientific paper.Thank you for hand-holding me through the process.
Dr. Anuradha
E-mail: anuradha2nittur@gmail.com
On Jan 2020
Original article / research
Full Version
Correlation Between Axial Length and Peripapillary Retinal Nerve Fiber Layer Thickness Determined by Spectral Domain Optical Coherence Tomography: A Cross-sectional Study
Correspondence Address :
Nikhil Parashar,
House No. 55, Sector 16A, Faridabad-121002, Haryana, India.
E-mail: parasharnikhil94@gmail.com
Introduction: Peripapillary retinal nerve fiber layer (pRNFL) thickness is an important indicator for the diagnosis and monitoring of glaucoma. Optical Coherence Tomography (OCT) allows for accurate assessment of pRNFL thickness, but previous studies have shown that axial length can affect pRNFL thickness. Hence, this study aimed to confirm this hypothesis.
Aim: To determine the correlation between axial length and pRNFL thickness in healthy adults.
Materials and Methods: This was a cross-sectional study conducted on 200 eyes of healthy adults aged 18-30 years. All subjects underwent a complete ophthalmic evaluation. Average pRNFL thickness and quadrant pRNFL thickness were recorded using Topcon Spectral Domain OCT (SD-OCT) in all subjects. Axial length measurements were performed using optical biometry with the Topcon IOL Master, and subjects were divided into three groups according to axial length: Group 1 (<23.5 mm), Group 2 (23.5-25.5 mm), and Group 3 (>25.5 mm). pRNFL thickness values were subjected to Littmann’s correction for ocular magnification. Data was analysed using a one-way ANOVA test, and the correlation between pRNFL thickness and axial length, before and after correction for ocular magnification, was determined using the Pearson correlation coefficient.
Results: There was a significant negative correlation between uncorrected pRNFL thickness and axial length in the average pRNFL (r=-0.05, p<0.001), superior quadrant (r=-0.26, p<0.001), nasal quadrant (r=-0.44, p<0.001), and inferior quadrant (r=-0.48, p<0.001). Uncorrected temporal quadrant pRNFL thickness showed a positive correlation with axial length (r=0.17, p=0.015). After applying Littmann’s formula, the negative correlation between uncorrected pRNFL thickness and axial length disappeared in the average, superior quadrant, and inferior quadrant.
Conclusion: A negative correlation was established between pRNFL thickness and axial length, but this correlation disappeared after applying correction for ocular magnification. Thus, to avoid misdiagnosis of glaucoma in individuals with varying axial lengths, the authors recommend using correction methods for the effects of ocular magnification induced by axial length when considering pRNFL thickness values obtained from OCT.
Glaucoma, Ocular magnification, Ophthalmic evaluation
Glaucoma is one of the leading causes of irreversible blindness worldwide. It leads to progressive damage to retinal ganglion cells, resulting in changes in the optic disc structure and thinning of the Retinal Nerve Fiber Layer (RNFL) (1),(2). Numerous studies have demonstrated that loss of peripapillary RNFL occurs before the development of Optic Nerve Head (ONH) and Visual Field (VF) abnormalities (3),(4). Imaging devices such as Optical Coherence Tomography (OCT) enable quantitative and objective assessment of peripapillary RNFL thickness, aiding in the early diagnosis of glaucoma (5). RNFL thickness is also influenced by age, gender, race, and ethnicity (6),(7).
Several studies have investigated the relationship between RNFL thickness, axial length, and refractive error in both adults and children (8),(9),(10). While some studies have found a negative correlation between axial length and peripapillary RNFL thickness, recent research has reported no effect of axial length variation on peripapillary RNFL thickness after correcting for the magnification effect induced by axial length variation (11),(12),(13),(14). However, there are discrepancies in the findings of these studies and in the methods used to correct for ocular magnification (6),(13),(15).
Considering the diverse results from previous studies (13),(16),(17), the present study aims to examine the correlation between peripapillary RNFL thickness and axial length in normal healthy subjects, taking into account various variables. Littmann’s formula is utilised in this study to correct for the effect of ocular magnification induced by axial length variation (18),(19),(20). The objective is to establish a definitive correlation by addressing the limitations and inconsistencies observed in previous research.
This cross-sectional study was conducted at the Department of Ophthalmology, Bharati Hospital and Research Centre, Pune, Maharashtra, India, from August 2020 to October 2022. Written informed consent was obtained, and the procedures followed were in accordance with the Declaration of Helsinki and the standards of the Ethical Committee of Bharati Vidyapeeth Deemed to be University (BVDUMC/IEC/37).
Inclusion criteria: The study included healthy participants aged between 18 and 30 years.
Exclusion criteria: Those participants with astigmatism greater than 1.5 D, visual acuity less than 20/20, Intraocular Pressure (IOP) lower than 21 mm Hg, a history of ocular trauma, prior intraocular/refractive surgery, retinal lasers, glaucoma or ocular hypertension, anterior or posterior segment pathology, neurological disorders, uncooperative individuals, and cases with poor OCT image quality were excluded.
Sample size: Sample size estimation was performed based on the correlation coefficient (r) between axial length and pRNFL thickness, which was found to be 0.201 in a previous study by Kausar A et al., (13). With a power of 80% and a confidence interval of 95%, a minimum sample size of 192 was calculated (13). Hence, a sample size of 200 eyes was chosen for this study.
Procedure
The study included 200 eyes from 104 healthy adults aged 18-30 years. Each eye was considered as a separate subject. Out of the 208 eyes initially considered, four eyes had undergone refractive surgery, and four eyes had undergone retinal laser treatment, so they were excluded. All subjects underwent a comprehensive ophthalmic evaluation, including visual acuity testing, refraction, slit lamp examination, fundus examination, and intraocular pressure evaluation using Goldmann applanation tonometry.
Average pRNFL thickness, as well as superior, inferior, nasal, and temporal quadrant pRNFL thickness, were recorded using spectral domain OCT (Topcon 3D OCT-1 Maestro) imaging in all participants (Table/Fig 1). Uncorrected pRNFL thickness values were then subjected to Littmann’s correction to account for the magnification induced by different axial lengths, resulting in corrected pRNFL thickness values.
Axial length measurements were performed using the Topcon IOL Master (Topcon, Tokyo, Japan). Participants were divided into three subgroups based on axial length as follows:
Group 1: <23.5 mm
Group 2: 23.5 to 25.5 mm
Group 3: >25.5 mm (16).
Correction for ocular magnification was done using Littmann’s formula:
t=p×q×s
where t is the actual fundus dimension, p is the magnification factor of the imaging system (3.394 for Topcon 3D OCT-1 Maestro), q is the magnification factor for the individual eye, and s is the value obtained from the imaging device. The value of q is calculated as 0.01306×(axial length-1.82) (20).
Statistical Analysis
The data analysis was performed using IBM SPSS Statistics for Windows, Version 25.0 (Armonk, NY: IBM Corp). Descriptive statistics were used to present the results for continuous variables, while frequency and percentages were used for categorical variables. One-way analysis of variance (ANOVA) was used to compare the variables among the three groups. The Karl Pearson correlation coefficient was employed to determine the correlations between axial length and peripapillary RNFL thickness. A significance level of 5% was used throughout the analysis. A p-value less than 0.05 was considered statistically significant.
In this study, the mean age of the participants was 24.28±2.37 years. Among the participants, 50 were males (48.07%) and 54 were females (51.93%). The mean axial length was 24.4±1.5 mm. The majority of eyes belonged to Group-2 of axial length, with a mean length of 24.5±0.6 mm (Table/Fig 2).
The average uncorrected pRNFL thickness was 103.73±9.29 μm. On inter group comparison of mean values of pRNFL parameters, the mean average pRNFL thickness and thickness values in three quadrants were significantly different among the three groups, except for the Temporal quadrant (p=0.052) (Table/Fig 3).
After correction for the effect of ocular magnification by applying Littmann’s formula, the inter group comparison revealed that the mean average pRNFL thickness and thickness values in two quadrants, Superior and Temporal, were significantly different among the three groups (p<0.001) whereas, in the Inferior and Nasal quadrants, the difference was not statistically significant (p>0.05) (Table/Fig 4).
Analysing the correlation between pRNFL thickness and axial length using Pearson’s correlation coefficient revealed a statistically significant negative correlation in uncorrected pRNFL thickness (r=-0.05, p<0.001) and axial length in the average as well as in all quadrants (Table/Fig 5).
However, analysing the correlation between corrected pRNFL thickness and axial length using Pearson’s correlation coefficient revealed a positive correlation that was statistically significant in the average (r=0.26, p<0.001), superior (r=0.35, p<0.001), and temporal (r=0.48, p<0.001) quadrant values. The correlation was statistically insignificant in the inferior quadrant value (r=0.12, p=0.103). There remained a statistically significant negative correlation between corrected pRNFL thickness and axial length in the nasal quadrant (Table/Fig 5).
Scatter plots showing the correlation between average pRNFL thickness and axial length before and after correction for the effect of ocular magnification are shown in (Table/Fig 6).
The aim of this study was to investigate the correlation between axial length and pRNFL thickness in healthy adults. The average axial length was 24.39±1.46 mm, ranging from 19.8 mm to 27.6 mm, which is consistent with findings from other studies conducted in Indian populations (21),(22),(23). The largest number of subjects belonged to the axial length subgroup of 23.5 to 25.5 mm (n=86), which can be attributed to the random selection of subjects.
The average uncorrected pRNFL thickness in the present study was 103.73±9.29 μm, and the quadrant-wise uncorrected pRNFL thickness followed the ISNT (inferior-superior-nasal-temporal) rule, with the inferior quadrant having the highest thickness, followed by the superior, nasal, and temporal quadrants (24). Similar studies conducted on healthy Indian populations by Ramakrishnan R et al., and Dhami A et al., reported mean pRNFL thicknesses of 105±38.79 μm and ranging from 104.9±59.89 μm to 108.58±8.55 μm, respectively (11),(25). These findings are comparable to the present study.
The pRNFL thickness is measured by the OCT machine at a fixed angular distance (approximately 12°) centered on the optic disc. The location of the measurement circle on the peripapillary retina is influenced by the ocular optical system’s magnification. A longer eye will result in a larger measurement circle diameter, which will shift the RNFL measurement away from the center of the optic disc. Conversely, for smaller eyes, the opposite effect occurs (26),(27). Therefore, higher axial length can lead to falsely low pRNFL thickness measurements, while lower axial length can result in falsely high pRNFL thickness measurements.
To correct for this error caused by ocular magnification resulting from variations in axial length, Littmann’s formula was applied to all pRNFL thickness values. Littmann’s formula has traditionally been used to correct ocular magnification in OCT measurements (18). This formula can be used to calculate both the actual scan radius and the RNFL thickness measurement, as used in the present study (19).
In the present study, a significant negative correlation was found between uncorrected average pRNFL thickness and axial length, as well as for all quadrant-wise pRNFL thickness except the temporal quadrant. Similar results of a negative correlation between axial length and pRNFL thickness have been reported in studies conducted by Nagai-Kusuhara AN et al., (r=-0.20, p=0.011) and by Chen CY et al., who also reported that global RNFL thickness decreases by 3.086 μm for each additional millimeter of axial length (β=-3.086; p<0.001) (6),(28).
According to Dhami A et al., who also grouped the samples based on axial length, RNFL thinning increased with increasing axial length from 22.50 mm to >25.51 mm in all quadrants (11). Porwal S et al., also found a negative correlation in all quadrants, except for the temporal quadrant (p=0.75) (15). In this study, a positive correlation between axial length and uncorrected pRNFL thickness was observed in the temporal quadrant (r=0.17, p=0.015). It has been found that the Ganglion Cell Complex (GCC) thickness value in OCT is least affected by the ocular magnification error induced by axial length (29). Since the temporal pRNFL is closer to the macula, its value may be less affected by the magnification error induced by axial length. This could explain the absence of a negative correlation between uncorrected temporal quadrant pRNFL thickness and axial length (30),(31). It is important to note that all the aforementioned studies did not apply correction for the ocular magnification error induced by axial length.
In this study, after applying Littmann’s formula for the correction of ocular magnification, the previously observed negative correlation between uncorrected pRNFL thickness and axial length disappeared in the average, superior quadrant, and inferior quadrant. However, a statistically significant negative correlation between corrected pRNFL thickness and axial length persisted in the nasal quadrant. This can be attributed to the fact that the nasal side of the disc is maximally distant from the macula, where the readings of OCT are least affected by ocular magnification induced by axial length (30),(31).
In a study conducted on 120 children in Turkey using RTVue SD-OCT, it was found that a negative correlation existed between axial length and pRNFL (r=0.818, p<0.001), which was eliminated after applying Littmann’s formula (p>0.05) (9). In another study conducted in Pakistan on 93 adult subjects using Topcon SD 1-Maestro OCT, similar results were found. RNFL thickness was negatively associated with axial length in the average as well as all four quadrants. However, after applying Littmann’s formula for ocular magnification, the negative correlation was eliminated (all p>0.05) (13).
A major study conducted by Savini G et al., in Italy included 45 eyes from individuals aged 25 to 55 years. The eyes were divided into three categories: short (<22.5 mm), medium (22.51 to 25.5 mm), and long (>25.51 mm) axial lengths. They found a statistically significant negative correlation (r=-0.69, p<0.001) between axial length and RNFL thickness, which disappeared after applying Littmann’s formula (16).
Another study conducted in Turkey with 154 subjects using Stratus OCT also found similar results. They observed a negative correlation between RNFL thickness and axial length in myopic individuals (r=-0.763, p<0.001) and hypermetropic individuals (r=-0.266, p<0.05). However, after applying Littmann’s formula, the correlation disappeared (17).
A comparative assessment of similar studies is presented in (Table/Fig 7) (6),(9),(11),(13),(15),(16),(17),(28).
Limitation(s)
The subjects were not evenly distributed among the three axial length subgroups due to the random selection criteria used in this study.
A negative correlation was established between average pRNFL thickness and axial length. However, after applying correction for ocular magnification induced by axial length to the OCT pRNFL thickness measurements, there was no longer a negative correlation between average pRNFL thickness and axial length. The authors recommend the use of correction methods to account for the effect of ocular magnification induced by axial length before considering peripapillary retinal nerve fiber layer thickness values from OCT, in order to avoid misdiagnosis of glaucoma in individuals with varying axial lengths.
Further studies with larger sample sizes and greater variability in axial lengths are needed to improve our understanding of the correlation between pRNFL thickness and axial length. Additionally, it would be beneficial for newer OCT machines to have built-in software for correction of the effect of ocular magnification.
DOI: 10.7860/JCDR/2023/65264.18785
Date of Submission: May 06, 2023
Date of Peer Review: Aug 08, 2023
Date of Acceptance: Oct 07, 2023
Date of Publishing: Dec 01, 2023
AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. NA
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