Reliability analysis of subjectively graded real-image pterygium based on its translucence appearance between young and experi-enced clinicians

Abstract

Introduction: Pterygium is commonly subjectively evaluated via anterior segment assessments during slit-lamp examination. Thus, this assessment prones individual variations as it requires subjective grading and adequate experience to ensure consistency of diagnosis and management. Purpose: This study aimed to compare the reliability of subjectively graded real-image pterygium based on its translucence appearance between experienced clinicians. Design of study: Prospective randomized study. Materials and methods: Thirty (30) primary pterygium images from 30 pterygium patients were captured in a standardized magnification, illumination and formatting setting as previously de-scribed. All images were projected using PowerPoint presentation™ on a liquid crystal display (LCD) monitor with standard resolution. Two clinicians with different levels of experiences act as a grader and grade all images based on reference images provided. For reliability testing, intra-grader assessment was repeated twice with different sequences at least a month apart between each session. Both clinicians were given a set of 30 randomized pterygium images for all sessions. Reliability testing was evaluated using paired T-test and independent T-test. Results: Descriptive analysis revealed observer 1 obtained mean grade of 2.19 (SD = 0.670) and 2.23 (SD = 0.713) for session 1 and 2 respectively. Observer 2 obtained 2.04 (SD = 0.853) and 2.08 (SD = 0.894) for session 1 and 2 respectively. Paired T-test showed the difference for both observers in both sessions were not statistically significant (P = 0.776 and P = 0.583) respectively. Reproducibility testing using Independent T-test results showed the difference between observers was not statistically significant (P = 0.275). Subjectively graded pterygium clinical grading based on its translucence appearance was repeatable and reproducible. Conclusion: These findings could serve as a basis for future work on to evaluate performance of pterygium clinical grading based on its morphology with different levels of experience and larger number of samples.

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(ISSN: 2831-7459) Open Access
Journal of Ophthalmic Research and Vision Care
www.acquirepublications.org/JORVC
Reliability analysis of subjectively graded real-image pterygium
based on its translucence appearance between young and experi-
enced clinicians
Khairidzan Mohd Kamal2, Mohd Radzi Hilmi1,*, Mohd Zulfaezal Che Azemin1, Mohd Hafidz Ithnin1
1Department of Optometry and Visual Sciences, Kulliyyah of Allied Health Sciences, Inter-national Islamic University Malaysia (IIUM),
Kuantan, Pahang, Malaysia
2Department of Ophthalmology, Kulliyyah of Medicine, International Islamic University Malaysia (IIUM), Kuantan, Pahang, Malaysia
*Corresponding author: Mohd Radzi Hilmi, Department of Optometry and Visual Science, Kulliyyah of Allied Health Sciences, IIUM,
Jalan Sultan Ahmad Shah, 25200 Bandar Indera Mahkota, Kuantan, Pahang, Malaysia
Received date: 16 September, 2021 | Accepted date: 2 October, 2021 | Published date: 11 October, 2021
Citation: Kamal KM, Hilmi MR, Azemin MZC, Razak ZA, Ithnin MH (2021) Repeatability and Reproducibility of Pterygium Grading
Based on Clinical Translucence Appearance. J Ophthalmic Res Vis Care 1(1). doi https://doi.org/10.54289/JORVC2100101
Copyright: © 2021 Kamal KM, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Research Article Volume 1 – Issue 1
Abstract
Introduction: Pterygium is commonly subjectively evaluated via anterior segment assessments during slit-lamp
examination. Thus, this assessment prones individual variations as it requires subjective grading and adequate experience to
ensure consistency of diagnosis and management.
Purpose: This study aimed to compare the reliability of subjectively graded real-image pterygium based on its translucence
appearance between experienced clinicians.
Design of study: Prospective randomized study.
Materials and methods: Thirty (30) primary pterygium images from 30 pterygium patients were captured in a standardized
magnification, illumination and formatting setting as previously de-scribed. All images were projected using PowerPoint
presentation™ on a liquid crystal display (LCD) monitor with standard resolution. Two clinicians with different levels of
experiences act as a grader and grade all images based on reference images provided. For reliability testing, intra-grader
assessment was repeated twice with different sequences at least a month apart between each session. Both clinicians were
given a set of 30 randomized pterygium images for all sessions. Reliability testing was evaluated using paired T-test and
independent T-test.
Results: Descriptive analysis revealed observer 1 obtained mean grade of 2.19 (SD = 0.670) and 2.23 (SD = 0.713) for
session 1 and 2 respectively. Observer 2 obtained 2.04 (SD = 0.853) and 2.08 (SD = 0.894) for session 1 and 2 respectively.
Paired T-test showed the difference for both observers in both sessions were not statistically significant (P = 0.776 and P =
0.583) respectively. Reproducibility testing using Independent T-test results showed the difference between observers was
not statistically significant (P = 0.275). Subjectively graded pterygium clinical grading based on its translucence appearance
was repeatable and reproducible.
Conclusion: These findings could serve as a basis for future work on to evaluate performance of pterygium clinical grading
based on its morphology with different levels of experience and larger number of samples.

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Introduction
Pterygium is one of the most common ocular surface disorder
especially in hot climate regions. Pterygium can be defined as
defined as a fibrovascular encroachment of fibrous tissue of
conjunctiva which originates from bulbar conjunctiva and
progresses towards the central cornea [1]. It is an established
fact that pterygium has higher prevalence in tropical countries
which is also known as ‘Pterygium belt’ which is located
between 300 north and south of the equator. Ultraviolet (UV)
exposure has been dubbed as the main risk factor for its
growth. It is well-known fact that pterygium causes
significant reduction in visual acuity [2,3] and contrast
sensitivity [4,5] due to changes on corneal curvature [6-8] as
it progresses.
Pterygium has been evaluated in various approaches, with its
length in comparison with the corneal size is the common
one. However, the impact of pterygium on cornea somehow
not necessarily depending on its length. Thus, this suggest
new approach is needed. In 1997, Donald Tan and his co-
workers [9] had proposed a grading which classifies
pterygium based on its translucency into three groups: Grade
I - atrophy, Grade II - intermediate and Grade III - fleshy. This
grading has been widely used since its inceptions [1-5].
However, there is a lack of literature that addresses the
reproducibility of the clinical grading between clinicians.
Therefore, this study aims to determine the reproducibility of
subjectively graded pterygium based on its translucency
appearance using real images of pterygium.
Materials and Methods
A cross-sectional study was conducted to evaluate the
reliability of subjectively graded real-image pterygium based
on its translucence appearance between two clinicians with
different levels of experience. Sixty (60) primary pterygium
images from 60 eyes were captured in a standardized
magnification, orientation and illumination [10-12] by a
single operator. The inclusion criteria include established
diagnosis of primary pterygium, both genders were included
with age ranges from 20 to 70 years and free from any history
of ocular trauma, ocular surgery and history of contact lens
wear. Patients with significant ocular surface diseases such as
recurrent pterygium, corneal opacity or irregularity due to
diseases other than pterygium [1,3,13,14]. Participants were
recruited from a University eye-specialist ophthalmic centre
in order to obtain images which would display a wide range
of severity of pterygium patients. Ethical approval was
obtained by the International Islamic University Malaysia
(IIUM) research ethical committee (IREC)
(IIUM/310/G13/4/4-125) and this study conformed to the
tenets of the Declaration of Helsinki. All participants were
given adequate information regarding methods and risks of
this study. Written consent was obtained prior to acquisition
of images.
All images were acquired using a standardized protocol at 10
- 16X magnification, under diffuse white illumination and
oriented at 30 - 35⁰ to the corneal surface [1,3]. A high
definition (HD) digital camera was used to capture the images
through a SL-990 slit-lamp biomicroscope (Costruzione
Strumenti Oftalmici (CSO), Firenze, Italy). All images were
stored and processed using an image processing software,
Phoenix™ version 1.2 (Costruzione Strumenti Oftalmici
(CSO), Firenze, Italy) in the form of Joint Photographic
Experts Group (JPEG) files.
All primary pterygium images were carefully examined based
on Donald Tan’s grading by placed into a PowerPoint
presentation (Microsoft Corporation, Redmond, WA, USA)
and displayed on a monitor with 17- inch 1280 X 1024
resolution [3]. All images were randomly sorted using
randomization software [15]. The images were matched and
graded based on reference images as described in previous
study [9] as shown in Figure 1 by two clinicians with different
levels of experiences. The young clinician was defined as a
clinician with less than 5 years of exposure in ocular surface
field, while the experienced clinician was defined as a person
Keywords: terygium, Cornea; Conjunctiva; Grading Scale; Subjective Grading
Abbrivations: UV: Ultraviolet, IIUM: International Islamic University Malaysia,IREC: International research ethical
committee, HD: high definition, CSO: Costruzione Strumenti Of-talmici , JPEG: Joint Photographic Experts Group, SPSS:
Predictive analytics soft-ware.

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with more than 5 years’ experience in respective fields. The
experienced clinician is noted as observer 1 while the young
clinician was noted as observer 2.
Statistical analyses were performed using IBM SPSS
(Predictive analytics software) (Version 24, SPSS Inc.,
Chicago, IL, USA). Descriptive statistics were used to
determine the mean and standard deviation (SD) of image
graded by both observers. Reliability analyses were evaluated
via Paired and Independent T-test. Paired T-test was
employed to assess the difference in measurement between
two sessions. For intra-observer reliability testing, the process
was repeated twice with different sequences at least a month
apart between each session. The differences between two (2)
observers were evaluated using Independent T-test. Both
grading sessions were done simultaneously, but on different
occasions. The alpha significance level was set at P < 0.05.
Table1. Descriptive analysis results (n = 60)
Variables
Session 1 (mean ± SD)
Session 2 (mean ± SD)
Observer 1
2.19 ± 0.670
2.23 ± 0.713
Observer 2
2.04 ± 0.853
2.08 ± 0.894
SD: standard deviation
Table 2. Repeatability and reproducibility assessment of Tan’s pterygium clinical grading (n = 60)
Variables
Session 1 (mean ± SD)
Session 2 (mean ± SD)
P value
(95 % CI)
Observer 1
2.19 ± 0.670
2.23 ± 0.713
0.776*, (-0.214,0.190)
0.275#, ( -0.256, 0.364)
Observer 2
2.04 ± 0.853
2.08 ± 0.894
0.583*, (-0.321, 0.111)
*: Based on Paired T-test, P = 0.05 was set as the level of significance
#: Based on Independent T-test, P = 0.05 was set as the level of significance
Figure 1. Reference images of Tan’s pterygium clinical grading, (a) Grade I. (b) Grade II. (c) Grade III.
Results
Based on thirty (30) primary pterygium, descriptive analysis
revealed observer 1 obtained a mean grade of 2.19 (SD =
0.670) for session 1, and mean grade of 2.23 (SD = 0.713) for
session 2. Observer 2 obtained 2.04 (SD = 0.853) for session
1, and mean grade of 2.08 (SD = 0.894) for session 2.
Descriptive analysis results were summarized in Table 1.
Paired T-test results showed the difference for both observers
were not statistically significant for observer 1 (P = 0.776, 95
% CI: -0.214, 0.190) and observer 2 (P = 0.583, 95 % CI: -
0.321, 0.111). Reproducibility testing using Independent T-
test results showed the difference between observers was not
statistically significant (P = 0.275, 95 % CI: -0.256, 0.364).
Both repeatability and reproducibility findings were
summarized in Table 2.
Discussion
The purpose of this study was to evaluate the perceptual
relationship between two clinicians with different levels of

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experience in estimating the translucence appearance of
pterygium based on reference images by Tan’s clinical
grading [9]. Previous works have shown that reproducibility
for subjective clinical grading is frequently limited [16-19],
due to variations between individuals. Study by Fieguth and
Simpson (2002) has proved that individual variations can
extend to approximately 50 %. In this study, the difference in
the level of experiences could be translated based on the
standard deviation which is wider in less-experienced
clinicians compared to experienced clinicians.
The difference in inconsistency of measurement could
happen due to various reasons such as lack of standardization
of reference images, variations in methodology, technology
and experience of individuals involved in assessing its
reliability. With incorporations of reference image as the
benchmark of a clinical grading and a standardized protocol,
inter-observer performance improved, hence reducing
individual variations and bias. Recent work [3] has
demonstrated by inclusion of reference image in subjectively
grading pterygium redness, the clinical grading performance
is promising. Previous works [3,20,21] had demonstrated that
subjective grading is permissible and reliable provided a
standard protocol was employed. This study proves that using
a static image as a reference image with an approximate
experience between observers, the repeatability and
reproducibility are very good. However, it is worth to re-
evaluate the reliability of this grading on a bigger scale in
terms of more pterygium images, with inclusion of variations
in experience/training factor involved. Proper training could
further reduce individual variations.
Conclusion
Different levels of clinical exposure could provide
differences in reliability of the grading. However, it is worth
noting that subjective grading is reproducible and repeatable.
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