Original Article

Evaluating the Ectasia Risk Score System in Cancelled
Laser In Situ Keratomileusis Candidates

Mehrdad Mohamadpour1, MD; Masoud Khorrami-Nejad1,2, MS; Mohammad Yaser Kiarudi1, MD
Keivan Khosravi1, MD

1Translational Ophthalmology Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
2School of Rehabilitation, Shahid Beheshti University of Medical Sciences, Tehran, Iran

ORCID:
Mehrdad Mohamadpour: https://orcid.org/0000-0002-9383-6362

Abstract

Purpose: To evaluate the ectasia risk score system in cancelled laser in situ
keratomileusis (LASIK) candidates at an academic hospital.
Methods: LASIK candidates who had been cancelled by a surgeon considering the
patient age, preoperative central corneal thickness, residual stromal bed thickness, or
preoperative manifest refraction spherical equivalent were retrospectively reviewed, and
their Randleman ectasia risk score system score was calculated.
Results: The mean ectasia score of 194 eyes (97 patients) was 4.5 ± 2.67; 40 (20.6%),
46 (23.7%), and 108 (55.7%) eyes were classified as low-, moderate-, and high-risk eyes,
respectively. The topography was abnormal in 69% of the patients. The mean manifest
refraction spherical equivalent, central corneal thickness, and estimated residual stromal
bed thickness were 4 (+0.50 to –15.50) diopters, 520 (439 to 608) µm, and 312.38 (61.5
to 424.12) µm, respectively. The main cause of cancellation in low- and moderate-risk
patients (86 eyes) was the presence of unstable refractive error in the past year.
Conclusion: Although promising, some other criteria, such as stable refraction, should
be added to this scoring system to achieve greater practicality since a main cause of
cancelling LASIK candidates in this study was the presence of unstable refraction.

Keywords:

J Ophthalmic Vis Res 2020; 15 (4): 481–485

INTRODUCTION

Ectasia, progressive steepening, and thinning
of the cornea are uncommon but serious

Correspondence to:

Mehrdad Mohammadpour, MD. Translational
Ophthalmology Research Center, Farabi Eye Hospital,
Tehran University of Medical Sciences
Email: mahammadpour@yahoo.com
Received: 10-06-2019 Accepted: 27-07-2020

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DOI: 10.18502/jovr.v15i4.7788

complications of excimer laser corneal refractive
surgery that reduce uncorrected and often
corrected distance visual acuity (CDVA).
They occur commonly after laser in situ
keratomileusis (LASIK) and infrequently after
photorefractive keratectomy (PRK).[1] Because of
the significant medical and legal consequences

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How to cite this article: Mohamadpour M, Khorrami-Nejad M, Kiarudi MY,
Khosravi K. Evaluating the Ectasia Risk Score System in Cancelled Laser In
Situ Keratomileusis Candidates. J Ophthalmic Vis Res 2020;15:481–485.

© 2020 JOURNAL OF OPHTHALMIC AND VISION RESEARCH | PUBLISHED BY KNOWLEDGE E 481

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Evaluating the Ectasia Risk Score System; Mohamadpour et al

of this complication, studies have focused on this
issue.[2–9]

Ectatic changes can occur as early as one week
after LASIK or be delayed for up to several years
after the initial procedure.[10] Histologic findings
suggest that post-LASIK keratectasia results in
collagen fibril thinning and a decreased interfibrillar
distance within the residual stromal bed (RSB).[11]

Clinical and topographical findings of ectasia
are often indistinguishable from those of
keratoconus.[12] To date, no method can definitively
diagnose patients with ectasia. A practical task
for clinicians is to improve the sensitivity of
screening methods for identifying patients
with mild keratoconus to prevent iatrogenic
keratectasia. Randleman et al[1] developed a
scoring system to evaluate the risk of ectasia after
LASIK considering some parameters – such as
preoperative topography, RSB thickness, age,
preoperative corneal thickness, and degree of
myopia – to better identify patients with a high
risk for ectasia. They concluded that no single
characteristic identifies all at-risk patients. Instead,
various factors should be considered in a weighted
fashion. For all patients, special emphasis should
be placed on the topographic pattern, and factors
in addition to the inferior–superior value or
computer-generated indices should be considered
in the screening. For young patients, heightened
scrutiny is warranted, and other aspects of their
preoperative evaluation, particularly topographic
patterns and refractive stability, should be within
normal limits. The intraoperative corneal thickness
should be measured if the variability of flap
thickness is likely to put a patient at risk for ectasia.
In the initial series, this scoring system showed
a high sensitivity and specificity. Subsequently,
another study validated it and noted the ectasia
risk score system (ERSS) to be a valid and effective
method for detecting the eyes with ectasia after
LASIK.[13]

This study was aimed at retrospectively
evaluating the ERSS score in candidates for
refractive surgery who were cancelled by a
surgeon. We calculated the risk score of cancelled
LASIK candidates to evaluate the efficacy of ERSS
for the preoperative screening.

METHODS

Medical records of candidates for refractive surgery
who had been cancelled by a surgeon (MM) at

Farabi Eye Hospital, Tehran University of Medical
Sciences, Tehran, Iran, between 2011 and 2015
were reviewed. Causes of cancellation of these
candidates were based on conventional and
individual criteria, such as unstable refraction,
defined as an increase in the spherical or cylindrical
refractive error >0.5 diopters (D) in the past
year, age <9 years, or suspected or abnormal
topographical patterns, such as inferior steepening
>1.4 D, central corneal thickness <480 µm,
RSB <250 µm, or CDVA <20/30. The exclusion
criteria were a history of refractive or cataract
surgery, keratoconus, collagen vascular disease,
and diabetic retinopathy.

Data of all patients, including the age, sex,
preoperative manifest refraction spherical
equivalent, central corneal thickness, topographic
pattern, and predicted RSB thickness were
evaluated, and their Randleman ectasia risk
factor score was calculated. Based on the
Randleman ERSS, as described previously,[1] a
cumulative ectasia risk score was calculated for
all patients. Central corneal and RSB thicknesses
were measured using a Pentacam topographer
(Oculus, Wentzler, Germany). Regarding the
cumulative points, risk categories were as follows:
0–2 points, low risk; 3 points, moderate risk; and 4
points, high risk.

RESULTS

A total of 97 patients (194 eyes) were included in
this study, with the mean age of 26.4 years (range:
18–50 years). Sex distribution was approximately
equal (48 women and 49 men).

According to the Randleman ERSS for
preoperative refractive surgery, 40 (20.6%), 46
(23.7%), and 108 (55.7%) eyes had low-, moderate-,
and high-risk scores, respectively. The mean score
was 4.5 ± 2.67. The mean manifest refraction
spherical equivalent, central corneal thickness,
and estimated RSB thickness were 4 (+0.5 to –15.5)
D, 520 (439 to 608) µm, and 312.38 (61.5 to 424.12)
µm, respectively (Table 1). Refractive astigmatism
ranged from 0.5 to 6.25 D. Corneal astigmatism
ranged from 0.04 to 4.90 D. Internal astigmatism
ranged from 0 to 2.25 D. Unstable refraction was
found in 86 (44.3%) eyes.

Table 2 shows the topographic characteristics
of the patients. The symmetrical (normal) pattern,
asymmetrical bow tie, inferior steepening

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Evaluating the Ectasia Risk Score System; Mohamadpour et al

Table 1. Randleman ectasia risk score system for identifying eyes at high risk of developing ectasia after laser in situ
keratomileusis

Parameter Points

4 3 2 1 0

Topography Abnormal
topography

INF steep/SRA ABT Normal/SBT

RSB (µ) <240 240 to 259 260 to 279 280 to 299 ≥300
Age (yrs) 18 to 21 22 to 25 26 to 29 ≥30
CT (µ) <450 451 to 480 481 to 510 ≥510
MRSD (D) >–14 >–12 to –14 >–10 to –12 >–8 to –10 >–8 or less

Low risk (0–2 points), moderate risk (3 points), high risk (≥4 points)
ABT, asymmetric bowtie; CT, corneal thickness; D, diopters; INF steep, inferior steepening pattern; MRSE, manifest refraction
spherical equivalent; RSB, residual stromal bed thickness; SBT, symmetric bowtie; SRA, skewed radial axis; Yrs, years

Table 2. Characteristics of 97 patients (194 eyes)

Features Mean (range)

Age (years) 26.44 (18 to 50)

Gender Male Female 49 (50.5%) 48 (49.5%)

MRSE (D) 4 (0.5 to 15.5)

CCT (µ) 520 (439 to 608)

RSB (µ) 312.38 (61.5 to 424.12)

CCT, central corneal thickness; D, diopters; MRSE, manifest refraction spherical equivalent; RSB, residual stromal bed thickness

or skewed radial axis, and other abnormal
topographic (pellucid) patterns were seen in
65 (33.51%), 87 (44.84%), 39 (20.1%), and 3 (1.54%)
eyes, respectively.

DISCUSSION

In our study, a significant number of patients (86
eyes, 43.7%) who were not scheduled for LASIK
due to unstable refraction in the past year had
a low or moderate ERSS score (1–3). Therefore,
this method, which is applied for categorizing and
assessing the risk of ectasia, should be modified in
consideration of unstable refractive errors.

Reports on ERSS are incongruent.[13–16]
Previously, Randelman et al stated that this
system, which was developed from case reports
of ectasia, was more sensitive compared to
traditional screening strategies. In a subsequent
study, Randelman et al validated their risk scoring
system by applying it on 50 previously unpublished
ectasia cases matched to 50 normal eyes. The
sensitivity and specificity of their scoring system

for the initial and comparison populations were
91% and 92%, respectively.[13]

Binder et al[15] retrospectively reviewed a
surgeon’s LASIK database to assess Randleman
ectasia risk scores in eyes with normal
preoperative topography. Risk scores of 5 or
more, 4 or more, and 3 or more were found in
35 (2.1%), 92 (5.4%), and 208 (12.2%) eyes with a
normal topography, respectively. None of these
eyes developed ectasia. In their evaluation, three
eyes of two patients in the entire database of
9,813 myopic eyes with variable follow-up periods
developed ectasia. They noted that with this
risk score system, 5.4% of eyes with 4 or more
points would have been eliminated from LASIK
surgery, and an additional 6.8% of eyes with a
score of 3 indicating a “moderate risk” would
have required the surgeon to exercise caution.
Therefore, they concluded that in the eyes with
normal preoperative topographies, this scoring
system may not accurately predict an increased
risk for developing postoperative LASIK ectasia.
This is consistent with our findings of a significant
number of patients at a high risk whom the

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Evaluating the Ectasia Risk Score System; Mohamadpour et al

Table 3. Topographic patterns of 194 eyes of 97 patients

Topographic pattern Number (Percentage)

Normal/symmetrical 65 (33.51)

Asymmetric bowtie 87 (44.84)

INF steep/SRA 39 (20.11)

Abnormal 3 (1.54)

INF Steep/SRA, topographic pattern with inferior steepening and/or a skewed radial axis

surgeon cancelled, while the risk score was low or
moderate with ERSS.

Chan et al[14] retrospectively evaluated ERSS in
36 eyes with post-LASIK ectasia. A low risk was
seen in 25% of eyes. They reported the sensitivity
of this method to be only 56% and concluded that
ERSS can miss a significant proportion of patients
at risk of ectasia. Randleman et al[1] reported that
unstable refractions may predict corneal ectasia
after refractive surgery. This study suggests that
other criteria, such as stable refraction, should
be added to this scoring system for increased
practicality since a main cause of cancelled LASIK
candidates in this study was unstable refraction.

Hodge et al[16] presented a case of unilateral
keratectasia in a laser refractive surgery patient.
LASIK was performed in the first eye, but because
of the difficulty in lifting the femtosecond-created
cap in the fellow eye, PRK was performed in that
eye. In their report, the eyes had no risk factors
for keratectasia and identical low Randleman ERSS
scores. According to them, the procedure of
elevating the cap had a weakening effect.

Consistent with Sorkin et al’s study,[17] a highly
prevalent risk factor in our study was suspected
and abnormal topographic patterns were found in
approximately 64% of patients. This is consistent
with former reports. Nearly 50% of ectasia cases
in Randleman et al’s study and 69% in Chan
et al’s study had abnormal topographies. ERSS
relies exclusively on Placido-based images.
Recent topographic systems apply other corneal
imaging, including Orbscan II and Pentacam
imaging. The limitations of ERSS include starting
keratoconus from the posterior portion and the
lack of assessment of posterior elevation.

Another factor not included in our study for
ERSS was unstable refraction. Randleman et al[1]
considered refractive instability in borderline cases
that could increase the risk of ectasia. We defined it

as a spherical or cylindrical refractive error >0.5 D
in the past year and found it in 86 (44.3%) eyes. This
factor may be paramount for an effective refractive
surgical screening.

Dawson et al evaluated the histopathology and
ultrastructure of the corneas developing ectasia
after LASIK or PRK and found no significant
differences in any of the measurements in the
LASIK flap or interface wound; however, the
ultrastructure of RSB significantly differed between
the ectatic and non-ectatic regions. The primary
effect of the biomechanical failure process involves
the RSB (42% thickness reduction) compared to the
LASIK flap or hypocellular primitive stromal scar.[18]
In this regard, preservation of at least a 250-μm
thickness in the central stromal bed after ablation is
important for the prevention of ectasia,[19]although
the suggested range of minimum RSB varies from
200 to 318 μm.[20, 21] However, keratectasia can
occur after LASIK with an RSB thickness of >250
μm.[22] In our study, the mean RSB thickness of
cancelled patients was 312 μm above the widely
accepted 250 μm. Moreover, in Chan et al’s study,
the average RSB was >250 μm.[14] Therefore, it
cannot be an isolated risk factor.

We suggest considering refractive stability as
a factor with a significant weight in a modified
scoring system for the preoperative screening
for ablative refractive surgery. Validation of other
possible values, such as the degree of astigmatism,
between eye topographic asymmetry, and family
history of keratoconus should be evaluated.
Moreover, studies should include a control group
comprising the eyes that have undergone LASIK at
the same interval. In conclusion, Randleman ERSS,
although promising, is yet to be validated with a
population of ectasia cases and controls.

Financial Support and Sponsorship

None.

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Evaluating the Ectasia Risk Score System; Mohamadpour et al

Conflicts of Interest

There are no conflicts of interest.

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