Original Article
Initial Experience of Corneal
Collagen Cross Linking in Progressive Keratoconus
Munira Shakir, Faiza
Rameez, Shakir Zafar, Muhammad Ahsan Sulaiman
Pak J Ophthalmol 2018, Vol. 34, No. 2
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See end of article for authors affiliations …..……………………….. Correspondence to: Munira
Shakir Liaquat National Hospital,
Stadium Road, Karachi, Pakistan Email: dr_munirasz@yahoo.com |
Purpose: To assess the outcome of
Corneal Collagen Cross-linking (CCXL) in patients with progressive
Keratoconus in terms of satisfaction. Study Design: Descriptive case series. Place and Duration of Study: This study was conducted at Liaquat National Hospital, Karachi,
Pakistan. It documents a process that is spread on one year. Material and Methods: This
prospective study is comprised of 34 patients who had bilateral Corneal Cross
linking (CXL) treatment for progressive Keratoconus. Analysis was performed
in terms of amount of corneal flattening (observed through topography),
effect on vision (observed through Snellen’s Chart) and satisfaction of patient
(assessed by filling of proforma 6 months post-operatively). Results:. Findings of 31 cases were
analyzed as 3 cases missed the follow-up. Mean age was 23.2 ± 5.5 years.
61.3% of the cases were males while 38.7% were females with respective
frequency of 19 and 12. Mean post-operative BCVA on Snellen’s Chart improved
on average by more than one line. Post-operative mean of change in steepest K
reading was 1.29 ± 0.52D. 16.13% of the cases were happy after treatment,
while 64.52% were satisfied. However, 19.35% of the cases were unhappy. Conclusion: This study shows that CXL
retards progression and generally brings satisfaction among the participants. Keywords: Corneal
Collagen Cross linking, Keratoconus, Corneal Topography. |
Keratoconus is a condition characterized by
corneal steepening typically inferior to central cornea with corneal thinning,
induced myopia and both regular and irregular stigmatism. It is usually a
bilateral condition and is non-inflammatory1.
The onset is around puberty with slow
progression until third and fourth decades of life. Many treatment options are
available including conservative options such as spectacles and rigid contact
lenses. Surgical options for the treatment include: intra-corneal ring segments;
Phakic Intra Ocular Lens (IOL); Refractive Lens Exchange (RLE); Anterior
Lamellar Keratoplasty (ALK); and Penetrating Keratoplasty (PK)1-3.
A disturbed cross-linking within or among
the collagen molecule has been observed in Keratoconus. By photo-oxidative
collagen cross-linking with riboflavin and ultra violet light, additional
covalent bindings between the collagen molecules is achieved which stabilizes
the collagen scaffold1.
Eberhard Spoesi and Theo Sieler developed Corneal
Cross linking (CXL) procedure in late 1990s4. Wollensak et al5 believed that collagen cross-linking
was becoming a standard treatment for Keratoconus.
The aim of this case
series is to evaluate the results of CXL in the patients with progressive Keratoconus
and the index of patient satisfaction is being used as a main gauge for proving
its effectiveness.
MATERIAL AND METHODS
This study documents an ongoing case
series, which was conducted in Liaquat National Hospital, Karachi, Pakistan. 34
cases of more than 10 years with central corneal ectasia and having commitment
to follow up of six months were included in the study. Each patient was first
time assessed at day one, then after a week, then monthly for 6 months and corneal
topography was repeated at 3 and 6 months. Patients filled a proforma after
topography. Exclusion criteria for this study was; any patient having corneal thickness
less than 400μm6; corneal scarring in the eye to be treated; loss to follow-up;
prior history of corneal surgery.
This study was conducted after getting an informed
written consent of all the participants. It was carried out under the supervision
of an advisory committee.
Pre-operative complete
ocular checkup was done including: Visual Acuity; Best Corrected Visual Acuity
(BCVA) through Snellen’s Chart; IOP through Goldman Applanation Tonometer;
Corneal Topography by Pentacam; and Pachymetry (Ultrasonic and Pentacam). Further
relevant information was collected, using a proforma, on follow ups. The CXL
was done as a day-care procedure under sterilized environment. The inclusion
criteria for this study, which is similar to O’bart et al7 included; Age between 16 – 35, no prior
history of ocular surgery, steepest K value between 48 D and 60 D, corneal
thickness > 400 μm, patient must meet the diagnostic criteria for
Keratoconus8, progression verified by corneal topography i.e.:
Change of max. K by 1D9.
CBM VEGA X-linker – device that emits UV
radiation at 365-370nm after proper calibration to direct 5.4 J/cm2
to the cornea – was used on all the participant of this study. Pre-operative
antibiotics were given after the instillation of anesthetic drops. Seiler or
epi-off technique was used. A lid speculum was applied. After removing the
epithelium, drops of riboflavin 0.1% (Vitamin B2) were given at 1-5 minutes for
30 minutes or until it is visible in the anterior chamber. After riboflavin
absorption, the participant was exposed to the UV light which was placed closer
i.e. 1-5 cm from the corneal apex. A small digital video camera was included in
the Ultra-Violet A (UVA) array in order to monitor the aiming beam. Following
irradiation, cornea was rinsed with chilled saline, drops of antibiotic were
applied and Bandage Contact Lens (BCL) was placed.
Post-operatively, topical antibiotics,
topical steroids (4 times a day), artificial tears, painkiller and oral
vitamin-C were given. BCL was removed after 3-4 days. This post-operative
regimen was in line with Sherif et al10.
Data were analyzed using
Minitab. Mean and standard deviation (SD) were used to define the variables.
Frequency and percentage were used to define variables such as satisfaction
index (ordinal variable) and gender. Descriptive statistics were developed and
presented in the section of Results. P-value < 0.05 was considered as
significant for normality testing of data. Correlation of the two interval
variables (Vision Improvement and Flattening) was further determined using
Pearson Coefficient.
RESULTS
34 cases were studied for this research;
however, three cases were lost for follow-up. Analysis of the remaining 31
cases, who completed the follow-up, was carried out. All cases had progressive
Keratoconus, and other ectasias were excluded from this study. For corneal
stabilization, pre- and post-operative topographic readings were taken as
criteria. In addition, BCVA was carried out through Snellen’s Chart and was
taken as another criterion. 61.3% of the cases were males while 38.7% were
females with respective frequency of 19 and 12. Mean age was 23.2 ± 5.5 years.
Mean post-operative BCVA on Snellen’s Chart
improved by more than one line. Specifically, the mean of change in vision
improvement on Snellen’s Chart was additional 1.5 ± 0.62 lines. Post-operative
mean of change in steepest K reading was 1.29 ± 0.52D as shown in Table 2. This
shows improvement as the topographic findings showed lesser steepening
post-operative. Normality test was applied on each variable’s distribution,
which were found to be non-normal (p < 0.1); therefore, parametric
statistical methods cannot be used and the scope was limited to descriptive
statistics.
At 6 months
post-operative, a proforma (placed as appendix) was filled for each case to gage
the satisfaction. It had three options: happy, satisfied and unhappy; thus
making it an ordinal variable. 16.13% of
Table 2: Post-operative description of
Variables.
Variables |
Mean* |
SD |
p-value for
Normality** |
Flattening |
1.2903 |
0.5211 |
< 0.006 |
Vision Improvement |
1.5145 |
0.6151 |
< 0.005 |
*Mean: for flattening read’ mean decrease
in steepening’, and; for vision improvement read’ mean additional lines on
Snellen’s Chart’
**Anderson-Darling
Normality Test was used. As the p-values are lower than 0.1 significance level,
the data do not follow the normal distribution
Fig. 1: Satisfaction Response (n = 31).
the cases were happy
after treatment, while 64.52% were satisfied. However, 19.35% of the cases were
unhappy, as shown in Figure-1. None of the cases developed any complications.
DISCUSSION
We have found a significant flattening in
the steepest K value in all the patients similar to the results of Wollensak et
al5 in whose study the decrease of mean Keratometer value was by 2.01
D.
As compared to other therapeutic measures
used for the treatment of Keratoconus such as: intra-corneal ring1,11; and epi-keratoplasty1; Hovkimyan et al12, showed that CXL can be regarded as a useful approach to reduce
number of keratoplasties. Wollensak et al13, in their study showed that mechanical rigidity increases in
porcine corneas, while they reported greater increase in human corneas.
Figure-2 visually describes the mean flattening and mean vision improvements in
our cases. Both distributions were found to be uni-modal and negatively skewed
(as shown by the box plots as well). Furthermore, figure-3 presents the scatter
plot developed between these two interval variables. It manifests a marginal
positive correlation, which can be testified by the value of 0.779 of Pearson’s
Correlation Coefficient.
The findings of our study are in agreement
with several earlier studies4,5,14-16 that
proved the significant improvement in visual acuity and maximum keratometry as
well as retarding progression after CXL. However, our study further takes into
account the satisfaction of the patients who went through the procedure. This
was carried out using a designed proforma.
Wolensak et al.17 in their study showed that riboflavin/UVA treatment is safe for
endothelium only when the dose is below 0.65 J/cm2 and cornea should
not be less than 400 μm thick. Adverse
(a) (b)
Fig. 2(a): Description of Flattening
(Mean Line). Fig. 2(b): Description of Vision
Improvement (Mean D)
Fig. 3: Scatter plot of Vision (Mean D) versus Flattening (Mean Line).
outcomes have also been
reported in different studies. Wolensak et al.18 reported dose dependent keratocyte damage after riboflavin/UVA treatment,
which can be expected in human corneas down to a depth of 300 μm using a
surface UVA dose of 5.4 J/cm2. Wolensak et al19, indicated that combined riboflavin/UVA treatment leads to 10
fold lower threshold for keratocyte cytotoxicity at 0.5 mW/cm2
compared to 5 mW/cm2 after UVA irradiation alone.
CONCLUSION
CXL has proved to be a safer
and an effective procedure in the treatment of progressive Keratoconus and it
usually results in satisfaction of the patient in terms of improvement of
vision and retardation of the progression. Other studies have similar
conclusions20.
Author’s Affiliation
Dr. Munira Shakir
FCPS, FRCS Ophthalmology
Associate Professor
Liaquat National Hospital, Karachi.
Dr. Faiza Rameez
MBBS, R5 Ophthalmology
Liaquat National Hospital, Karachi.
Dr. Shakir Zafar
FCPS Ophthalmology
United Medical & Dental College, Karachi.
Muhammad Ahsan Sulaiman
Final Year Medical student
Liaquat National Hospital, Karachi.
Role of Authors
Dr. Munira Shakir
Surgeon who provided all the cases and who did all the surgeries.
She is also a major contributor in writing this paper.
Dr. Faiza Rameez
She assisted the surgeon in the surgeries. Majorly wrote the paper
along with data collection and carrying out all descriptive statistics.
Dr. Shakir Zafar
Surgeon whose experience was highly beneficial in analysis and
conclusions of the findings.
Dr. Muhammad Ahsan Sulaiman
Data collection and all data entry.
REFERENCES
2. Kanski
JJ. Clinical Ophthalmology: A Systematic Approach: Elsevier; 2007.
9. Bikbova
G, Bikbov M. Transepithelial corneal collagen cross‐linking by
iontophoresis of riboflavin. Acta Ophthalmol. 2014; 92 (1).
16. Sykakis
E, Karim R, Evans JR, Bunce C, Amissah‐Arthur KN, Patwary
S, et al. Corneal collagen
cross‐linking for treating keratoconus. Cochrane Libr.2015.