Citation: Kang DH, Lee YW, Hwang KY, Koh KM, Kwon YA, Kim BY, Song
SW, Kim KY. Changes of tear film lipid layer thickness by 3% diquafosol
ophthalmic solutions in patients with dry eye syndrome. Int J Ophthalmol
2019;12(10):1555-1560.
DOI:10.18240/ijo.2019.10.06
·Clinical Research·
Changes
of tear film lipid layer thickness by 3% diquafosol ophthalmic solutions in
patients with dry eye syndrome
Dong-Hyun Kang, Yong-Woo Lee, Kyu-Yeon Hwang, Kyung-Min
Koh, Young-A Kwon, Byung-Yeop Kim, Sang-Wroul Song, Kook-Young Kim
Myung-Gok Eye Research Institute,
Department of Ophthalmology, Kim’s Eye Hospital, Konyang University College of
Medicine, Seoul 150-034, Korea
Correspondence to: Kook Young Kim. Department of
Ophthalmology, Kim’s Eye Hospital, Myung-Gok Eye Research Institute, Konyang
University, #156 Youngdeungpo-dong 4ga, Youngdeungpo-gu, Seoul 150-034, Korea.
md.kookyoung@gmail.com
Received:
Abstract
AIM: To evaluate the quantitatively changes in lipid layer thickness (LLT)
when 3% diquafosol eye drop is used for dry eye patients using the tear film
interferometer.
METHODS: A total 124 participants (32 males, 92 females;
mean age, 28.9y) diagnosed with dry eye disease (DED) received topical instillation
of 4 ophthalmic solutions in one eye: diquafosol, normal saline, 0.1% sodium
hyaluronate and 0.3% gatifloxacin, in a masked manner. LLT was measured using
an interferometer at baseline and 20min after the instillation of each
ophthalmic solutions.
RESULTS: Changes of LLT after instillation (nm, mean±
standard error) were as follows: 12.6±2.0 for diquafosol (P<0.001),
1.2±2.2 for normal saline (P=0.301), 1.5±2.0 for hyaluronate (P=0.495),
and 0.5±3.2 for gatifloxacin (P=0.884).
CONCLUSION: Topical instillation of diquafosol increases tear
film LLT in DED patients. Diquafosol 3% eye drop might be effective treatment
option of evaporative DED with meibomian gland dysfunction.
KEYWORDS: diquafosol ophthalmic solutions; dry
eye syndrome; tear film lipid layer thickness
DOI:10.18240/ijo.2019.10.06
Citation: Kang
DH, Lee YW, Hwang KY, Koh KM, Kwon YA, Kim BY, Song SW, Kim KY. Changes of tear
film lipid layer thickness by 3% diquafosol ophthalmic solutions in patients
with dry eye syndrome. Int J Ophthalmol 2019;12(10):1555-1560
INTRODUCTION
Dry eye disease (DED) is one of the
most difficult disease entities challenged by ophthalmologists. Globally, the
incidence of DED varies from 5% to 50%, especially in Asia, with an incidence
of over 30%[1]. DED is occurred by various causes,
characterized by the numerous ocular symptoms including ocular irritation and
visual disturbance, and which is accompanied by tear film instability,
increased tear osmolarity, and ocular surface inflammation[2-3].
Recently topical 3% diquafosol eye
drop can be one treatment option for an aqueous-deficient DED. Treatment using
diquafosol eye drop for 4-6mo improved significantly both subjective symptoms
and objective dry eye diagnostic parameters for aqueous-deficient type dry eye[4]. The long-term treatment of diquafosol reduced ocular
higher-order aberrations, as well as corneal epithelial healing and improved
tear film stability[5].
Diquafosol tetrasodium is an agonist
of P2Y2 purinergic receptor. It stimulates P2Y2 receptors
by activating fluid pump mechanism of lacrimal glands, causing tear component
secretion[6-8]. P2Y2
agonists are effective mucin secretagogues and stimulate the mucin secretion
from conjunctival goblet cells as well. The capability of the P2Y2
receptor activation to increase tear lipid component is not yet firmly proved,
but past animal studies showed the existence of P2Y2 receptor in the
meibomian gland[9-10].
Tear film interferometer is a
diagnostic device which evaluates tear film lipid layer thickness (LLT) by
measuring ocular surface interference[11-14].
In the preceding studies[14-15],
LLT was evaluated from grade 1 to grade 5 according to the patterns of color appearing
on tear film interference. Recently, in order to gain the quantitative
measurement of LLT, the LipiView (TearScience Inc, Morrisville, NC, USA) is
adopted.
This study was designed to evaluate
the changes of tear film LLT quantitatively after using 3% diquafosol
ophthalmic solution and control ophthalmic solutions by tear film
interferometer (Lipiview) in DED patients.
SUBJECTS AND METHODS
Ethical Approval This prospective study was carried
out at the Department of Ophthalmology, Kim’s Eye Hospital, Konyang University.
The study was approved by the Institutional Review Board (IRB number:
A-2015-004) at Kim’s Eye Hospital, Seoul, Korea. All procedures of study
followed the guidelines of the Declaration of Helsinki. Subjects were collected
at the cornea clinic of Kim’s Eye Hospital. To publish this study, informed
consent forms were filled out by the participants themselves.
Each subject received following
complete ophthalmic examinations: intraocular pressure with a applanation
tonometer; best-corrected visual acuity (BCVA) and refractive error evaluated
with autorefractor keratometer (TX-20P, Canon, Tokyo, Japan); anterior segment
(upper and lower eyelid, conjunctiva, cornea, etc.) screening by slit-lamp
microscopy. Dry eye screening examination was adopted to all subjects,
including ocular symptoms by questioning, tear break-up time (TBUT) and ocular
surface staining score by fluorescein dye.
The ocular surface was stained by
sterile fluorescein strip with drop of sterile saline into the conjunctival
sac. TBUT was recorded by measuring interval time between the last complete
blinking and the initial break up of the stained ocular surface. Ocular surface
staining score was graded from 0 to 3 onto the upper, middle, and lower third
of the cornea. The score was given according to the aspects of stained ocular
surface: 0, absent ; 1, minimal scattered stained dots; 2, moderate stained
spotty; 3, marked diffuse stained area.
The Ocular Surface Disease Index
(OSDI) by Allergan Inc, Irvine, CA, USA) is one of the most frequently used
questionnaires for evaluation of DED. This includes 12 questions which measure
the frequency of symptoms over the recent week, and the scores range from 0 to
100. According to the result, the patient’s symptoms were classified as normal
(from 0 to 12), mild (from 13 to 22), moderate (from 23 to 32), or severe (from
33 to 100) DED.
Meibomian gland expressibility was
scored by using digital compression to the central one third area of the lower
eyelid. The meibomian gland expressibility was classified into 0-3 score: 0
(clear meibum); 1 (cloudy meibum by mild compression); 2 (cloudy meibum by
moderate compression); and 3 (no expressed meibum or toothpaste-like meibum by
heavy compression)[16]. Higher meibomian gland
expressibility means a more obstructive meibum secretion.
LLT was evaluated using the Lipiview
interferometer by the principle of white light interferometry. The
interferometry color units (ICU) of the tear film which is an indicator of LLT
is assessed according to the mean interference color pattern through specular
reflection[17]. Subjects who their the chin and
brow were attached leaning forward against each stand were seated in front of
the Lipiview interferometer. The test was performed with visual fixation of
participants on the internal light-emitting diodes target. Experienced tester
performed camera adjustment until the central pupil position and the reflected
tear film image was in the targeting square area. During capturing images for
20s, tester allowed participants blink naturally. Meiboscore was also measured
using meibograph of Lipiview interferometer: 0 (no meibomian gland loss); 1
(gland loss appeared less than one third of the total area); 2 (gland loss
appeared between one third and two thirds); 3 (gland loss appeared more than
two thirds).
A total of 124 eyes of 124
participants were categorized randomly to the 4 treatment groups. All subjects
received four tests. One eye (left or right eye) was randomly selected and to
treated with four ophthalmic solutions (3% diquafosol eye drop, isotonic normal
saline, 0.1% sodium hyaluronate, 0.3% gatifloxacin). Investigators were masked
that treatment option of subjects remained unidentified status during the
study. All subjects used a single topical eye drop in randomized selected eye.
Participants were scheduled for a total of four visits and visited at
approximately 1mo intervals. The LLT was measured after instillation of
diquafosol eye drop, followed by normal saline, hyaluronate and gatifloxacin
(Figure 1). LLT was measured two times after 20min of subjects applied 1 drop
of each ophthalmic solution.
Figure 1 Flow chart of this study.
Inclusion criteria for screening DED
were BCVA>20/30, TBUT<5s, corneal fluorescein staining score >1 by
Oxford schema.
Exclusion criteria included allergic
conjunctivitis and anterior segment diseases, previous consecutive topical eye
drop user, contact lens wearer, those who has a history of ocular surgery
recent 3mo and systemic diseases that would correlated with tear film
dysfunction.
Statistical Analysis Paired t-test in SPSS version
18.0 (SPSS Inc, Chicago, Illinois, USA) was used for statistical analyses. If
the result was less than P-value 0.05, it was statistically significant.
RESULTS
The preoperative demographics of the
study population are described in Table 1. A total of 124 eyes of 124 participants
(32 male and 92 female) were registered. The mean age of subjects was
28.92±6.33 (range, 26-42 years). Before the instillation of the ophthalmic
solutions, all ocular examinations from all subjects, including TBUT
(4.80±2.14s), the corneal staining score (0.89±0.70), meibomian gland
expressibility (1.60±0.82), Meiboscore (0.78±0.66), OSDI score (33.67±19.11),
showed DED status of participants.
Table 1 Demographics of the subjects
|
Parameters |
Data |
|
Age, y |
28.92±6.33 (range, 26-42y) |
|
Sex |
32 males and 92 females |
|
Best corrected visual acuity |
0.16±0.08 logMAR |
|
TBUT |
4.80±2.14 |
|
Corneal staining score |
0.89±0.70 |
|
Meibomian expressibility |
1.60±0.82 |
|
Meiboscore |
0.78±0.66 |
|
OSDI score |
33.67±19.11 |
TBUT: Tear break-up time.
Changes of Average Lipid Layer
Thickness Figure 2 showed that change of LLT
measured by LipiView interferometer. Mean baseline LLT before ophthalmic
solutions measured by Lipiview interferometer were 61.50±2.57 for diquafosol,
62.23±2.64 for normal saline, 62.80±3.03 for hyaluronate, 62.96±3.25 for
gatifloxacin. Mean changes of LLT after instillation (nm, mean value ± standard
error) were 73.27±2.67 for diquafosol (P<0.001), 64.38±2.81 for
normal saline (P=0.301), 64.28±3.17 for hyaluronate (P=0.495),
63.48±3.34 for gatifloxacin (P=0.884; Table 2). LLT after instillation
of diquafosol was significantly increased (Figure 3).
Figure 2 Cases of LipiView
interferometer for 4 ophthalmic solutions
A: A
34-year-old female with 3% diquafosol eye drop; B: A 36-year-old male with
isotonic normal saline; C: A 27-year-old female with 0.1% hyaluronate: D: A
26-year-old female with 0.3% gatifloxacin.
Table 2 Changes of LLT measured by
LipiView interferometer
|
Treatment group |
Baseline |
After |
Pa |
|
Diquafosol eye drop 3% |
61.50±2.57 |
73.27±2.67 |
<0.0001 |
|
Isotonic normal saline |
62.23±2.64 |
64.38±2.81 |
0.3013 |
|
Gatifloxacin 0.3% |
62.96±3.25 |
63.48±3.34 |
0.8844 |
|
Hyaluronate 0.1% |
62.80±3.03 |
64.28±3.17 |
0.4954 |
LLT: Lipid layer thickness. aPaired
t-test.
Figure 3 Mean changes of LLT
measured with LipiView interferometer aStatistically significant in
3% diquafosol group (P<0.05).
DISCUSSION
Diquafosol eye drop contains
diquafosol sodium which is an agonist of P2Y2 receptor as the active
component. The P2Y2 receptors are widely distributed in various
organs throughout the body. Adenosine triphosphate (ATP) or uridine
triphosphate (UTP) conduct as endogenous agonists of the P2Y2
receptor. The P2Y2 receptor is existed in the cornea, conjunctival
goblet cells, and meibomian gland onto the ocular surface[9],
and it has been known that ATP and UTP induce aqueous component and mucin
secretion in the conjunctival tissue[18-20].
Diquafosol sodium which is a dinucleotide derivative as an agonist of P2Y2
receptor[21], promotes fluid transport
from the serosal to mucosal (tear film) side through chloride ion channel
activation after elevating intracellular calcium ion concentration in the
conjunctival epithelium[6,18].
In addition, diquafosol sodium activates the expression of membrane-associated
mucin on the corneal epithelium and conjunctival goblet cells, induces the
mucin secretion[22]. Previous study with healthy
subjects showed that diquafosol eye drop increased tear film volume for up to
30min[23]. Therefore, these effects of diquafosol
eye drop induce the tear film stability and relief for ocular symptoms.
Previous clinical studies showed the efficacy of 3% diquafosol eye drop for the
treatment of DED[24-25].
Yokoi et al[23] reported for the first time in human eyes that a
single topical eye drop of 3% diquafosol induced significant increasing of the
tear volume. In past prospective clinical study[26] indicated
that 3% diquafosol eye drop are effective in improving both subjective symptoms
and objective TBUT in patients with short TBUT. A study of 14 female DED with
Sjögren’s syndrome, 3% diquafosol eye drop may have efficacy for mild to
moderate DED patients[27].
The activation of the P2Y2
receptor to increase tear film lipid component on ocular surface is less well
studied in human species, but previous animal experiments proved the expression
of P2Y2 receptor in the meibomian gland[9-10].
Obstructive meibomian gland
dysfunction (MGD) which is the major cause of evaporative DED, is represented
stagnation of meibum secretion and it may or may not be accompanied by a
quantitative or qualitative changes in meibum[28-29]. Hyposecretion of tear film lipid component might
result in short TBUT, tear film instability, and aggravation symptoms of DED.
The change of meibomian gland directly affects LLT and tear stability. In this
study, we found that the meibomian dysfunction affects dry eye syndrome, as
seen in meibomian expressibility and meiboscore.
Arita et al[30] investigated the treatment effect of 3% diquafosol
eye drop for DED with obstructive MGD. Diquafosol 3% treatment was applied with
4 times daily, and clinical follow-up period persisted at least 4mo (range
4-16mo). Subjective symptoms, ocular surface inflammation, meibomian gland
status, TBUT, and tear meniscus height was improved in all 19 eyes of 10
patients. This study analyzed with quantitative noncontact meibography, showed
a significant improvement in meibomian gland coverage from 36.9%±10.1% to
41.5%±9.2% after 3% diquafosol eye drop treatment (P<0.0001). This
study suggests that 3% diquafosol eye drop might act on stimulating the P2Y2
receptor via the meibomian gland ductal epithelium.
Our study showed a statistically
significant increase in of LLT after 3% diquafosol eye drop instillation more
than other control ophthalmic solutions. Fukuoka and Arita[31]
was proved that a single topical eye drop of 3% diquafosol increase
significantly LLT in the healthy human eye. Participants showed TBUT, corneal
staining score was slightly decreased, ocular surface inflammation was not
severe dry eye status. Most participants showed a mild obstructive MGD pattern
with a decrease in meibomian gland expressibility and some damage on
meibograpy. This study is meaningful as that first paper demonstrated through
quantitative test it in dry eye patients with control ophthalmic solutions. We
thought that this study is significant as the research that will support the
result of the previous studies[30-31].
LipiView interferometer could
measure meibomian gland of the upper and lower lid. The lower eyelid is easy to
evaluate better than the upper eyelid by LipiView interferometer. In order to
evaluate meibomian gland from the upper eyelid, the eyelids must be eversion,
which in turn pushes the upper eyelid, which could lead to errors in the LLT
and affect the measurement of other parameters of DED. Meibomian gland loss in
upper eyelid was correlated with those in the lower eyelid, and both were
correlated with changes of LLT in the obstructive MGD patients. Thus, a single
measurement of LLT and meibography in lower eyelid might be enough for the
assessment of MGD status, not necessarily measuring both eyelids[32]. LLT has negative correlation with obstructive MGD in
upper and lower eyelid[14]. Increasing of LLT by
3% diquafosol ophthalmic solution could be a therapeutic effect on the MGD.
There are two possible mechanisms.
First, P2Y2 receptors on the ocular surface and the inner surfaces
of the eyelids activated by diquafosol tetrasodium, promotes the natural tear
secretion. It causes ocular surface hydration through the release of
electolyte, water, mucin and other components of the tear film[7,33]. Cowlen et al[9] proved the mRNA expression P2Y2 receptor in
the corneal, conjunctival epithelium and goblet cell, and meibomian gland
ductal epithelial cells using in situ hybridization analyses in the rabbit and
rhesus macaque. Tanioka et al[10] showed
that P2Y2 receptor expression was existed in the meibomian gland and
lacrimal gland ductal epithelium using the immunohistological examinations. Our
study suggests that diquafosol tetrasodium also directly activates P2Y2
receptors on the meibomian gland of the eyelids and leads to an increase in the
meibomian glands secretions. In animal experiments performed by the mouse
experiment, Fujihara et al[33] the area of
PAS-stained conjunctival goblet cells decreased significantly from 5min after
3% diquafosol eye drop instillation, and after 25min the cell area was normal.
Diquafosol instillation significantly increased sialic acid, a marker of
mucin-like substances, although the effect was transient at 5min (but not at
20min)[34]. Mucin secretion is known to be
induced rapidly from 5min after instillation. It is known that the increase in
LLT is maintained from 15min to over 60min after diquafosol eye drop
instillation in healthy human eyes[31]. In this
study, the time (20min after diquafosol instillation) of the increasing LLT
after 3% diquafosol eye drop instillation was longer than that in increasing
tear volume or sialic acid concentration. Thus, it suggests that the increasing
of the tear film lipid layer actually induced by diquafosol eye drop
instillation and it is thought to have worked independently of the role
associated with mucin secretion.
And diquafosol increase water and
mucin component on tear film through activation of P2Y2 receptors
and it may improve the tear film stability. Mucin is high-molecular weight
glycoproteins with a protein backbone and a high carbohydrate component. Mucin
has one important role which makes the tear film hydrophilic status. Mucin
decreases ocular surface tension and induced evenly stable tear film, allowing
the aqueous component of tear film to spread over the ocular surface. In animal
studies, immediate effects after diquafosol instillation showed increased
corneal wettability and increased MUC
There were some limitations in this
study. First, this study did not evaluate whether the increase in LLT was
maintained during clinical follow-up. However, it is meaningful that the
increase of LLT after the use of diquafosol was quantitatively evaluated using
a LipiView interferometer in human patients. Second, the patients were limited
to patients with DED with mild obstructive MGD. We need to study patients with
different types of MGD (like hyposecratoy and hypersecretory) in the same study
design. Third, this study did not evaluate the changes of subjective DED
symptoms correlated with changes in LLT. The study of the relationship between
the symptoms of patients with increased LLT will be needed. Fourth, study
participants are limited to younger age groups (26-42 years old). Although
there is an advantage of eliminating other age-related anterior segment
diseases, further studies are needed to see whether the same results are
obtained in the elderly.
In conclusion, diquafosol causes
lipid layer reinforcement, as well as aqueous and mucin layer of the tear.
Therefore, it is considered to be useful treatment option at evaporative dry
eye with meibomian dysfunction, as well as aqueous deficient dry eye.
Diquafosol eye drop might be the treatment options for MGD that have poor
response to conventional treatments, such as warm compression, lid scrub, and
using artificial tear or systemic anti-inflammatory medications.
ACKNOWLEDGEMENTS
Authors’ contributions: Study concept and design (Kim KY);
data collection (Kim KY, Koh KM); interpretation and analysis of data (Lee YW,
Koh KM, Kwon YA, Kim BY); drafting of the manuscript (Kim KY, Kang DH, Hwang
KY); critical revision of the manuscript (Kim KY, Kang DH, Song SW).
Conflicts of Interest: Kang DH, None; Lee YW, None; Hwang
KY, None; Koh KM, None; Kwon YA, None; Kim BY, None; Song
SW, None; Kim KY, None.
REFERENCES