Mechanisms of Action of Light-based Therapies in the Management of Dry Eye Disease and Meibomian Gland Dysfunction
Phase: NA
Conditions: Dry Eye Syndromes, Meibomian Gland Dysfunction
Sponsor: Aston University

 
 
 
 
 
 
 
 
 
 
Mechanisms of action of light-based therapies in the management 
of dry eye disease and Meibomian gland dysfunction 
 
 
Study Protocol 
 
 
 
Investigators: 
Dr Jeremy Chung Bo Chiang 
Professor James S Wolffsohn 
 
School of Optometry 
College of Health and Life Sciences

Background and purpose 
As the mechanisms of action underlying commonly prescribed light-based therapies are still 
not fully understood, our study aims to investigate clinical and physiological changes on the 
surface of the eyes and eyelids using clinically and readily available instruments. Two light-
based therapies commonly prescribed are intense pulsed light (IPL) and low-level light therapy 
(LLLT), often in combination (IPL+LLLT). While IPL+LLLT is becoming a more common 
treatment regimen worldwide, recent evidence has also shown that LLLT alone is more 
effective at alleviating dry eye signs and symptoms better than IPL (Giannaccare et al, 2023). 
The proposed study aims to investigate the short- and long-term morphological, functional and 
physiological changes in the eyelid skin and ocular surface following IPL+LLLT versus LLLT 
alone (with prior sham IPL) for the treatment of Meibomian gland dysfunction in dry eye 
disease. The findings from this study will contribute knowledge to eyecare practitioners 
regarding the cellular and molecular changes these treatments and strengthen clinical 
guidelines associated with the prescription of light-based therapies. Understanding the short- 
and long-term implications of these treatments will also enable eyecare practitioners to treat 
patients with a more evidence-based approach. 
 
Methods  
Materials and Instruments 
1. Light-based treatment protocol  
The Eye-light unit (Espansione Group Ltd, Funo, Italy) was used to deliver the light-based 
therapies. Prior to the intense pulsed light therapy (IPL), the highest meiboscore of either eyelid 
and the Fitzpatrick skin grading was inputted into the unit system. This automatically calibrated 
the optical radiance output of the IPL. Table 1 details the exact output for each combination of 
settings. 
 
Table 1. Optical radiance output of the intense pulsed light (IPL) therapy of the Eye-light unit 
(Espansione Group Ltd, Funo, Italy) according to inputted grading from the meiboscale and 
Fitzpatrick skin grading. 
Pult Meiboscale 
Fitzpatrick skin grading 
Optical radiance output (J) 
1 
1 
59 
2 
59 
3 
59 
4 
59 
2 
1 
60 
2 
62 
3 
62 
4 
60 
3 
1 
62 
2 
66 
3 
66 
4 
64 
4 
1 
65 
2 
69 
3 
69 
4 
67 
 

Figure 1 demonstrates the light-based treatment administration protocol used in this clinical 
trial for four treatment sessions. 
 
 
Figure 1. Intense pulsed light (IPL) protocol with (A) sequential placements of treatment cartridge for 
the five different regions involved, and (B) sham IPL placement of a disconnected empty cartridge 
along the same five different regions on the contralateral side but with the working IPL cartridge pointed 
away from the patient’s face to simulate a pulse. Low-level light therapy (LLLT) was then administered 
for 15 minutes (C) with placement of the mask consisting of a series of red light-emitting diodes 
(LEDs). These were conducted with the Eye-light unit (Espansione Group Ltd, Funo, Italy). 
 
2. Ocular assessment schedules and details 
The study was structured into multiple visits and all conducted at the Aston Dry Eye Clinic in 
Aston University, Birmingham, United Kingdom. Each visit lasted for about 1.5 hours, with 
the sequence of assessments detailed in Table 2: 
- 
Visit 1: Screening ± First treatment session 
- 
Visit 2 (2 to 3 weeks after Visit 1): Second treatment session  
- 
Visit 3 (2 to 3 weeks after Visit 2): Third treatment session 
- 
Visit 4 (2 to 3 weeks after Visit 3): Fourth and final treatment session 
- 
Visit 5 (2 weeks after visit 4): First follow-up 
- 
Visit 6 (3 months after visit 4): Second and final follow-up 
 
Table 2. The sequence of assessments for each visit 
Procedures 
Visits 
1 
2 
3 
4 
5 
6 
Screening with inclusion and exclusion criteria 
 
 
 
 
 
 
OSDI, DEQ5 and adapted SANDE questionnaires 
 
 
 
 
 
 
General medical and ocular history, and lifestyle 
questions 
 
 
 
 
 
 
Visual acuity assessment 
 
 
 
 
 
 
Oculus Keratograph 5M, Part 1 
- 
Number of total and partial blinks in 30 s 
- 
Tear meniscus height 
- 
Non-invasive tear break up time 
- 
Lipid layer pattern 
- 
Bulbar and limbal hyperaemia grading 
 
 
 
 
 
 
Laser Doppler flowmetry and multimodal spectroscopy 
at central lower eyelids 
 
 
 
 
 
 
Slit lamp biomicroscopy 
- 
Telangiectasia grading  
 
 
 
 
 
 

Procedures 
Visits 
1 
2 
3 
4 
5 
6 
- 
Number of blocked or capped Meibomian gland 
orifices 
- 
Demodex detection (2 lashes randomly chosen 
on either lid and assessed with lateral traction 
method) 
- 
Meibomian gland expression with Korb 
expressor 
Oculus Keratograph 5M, Part 2 
- 
Fluorescein sodium and lissamine green staining 
grading on ocular surface and lid wiper 
epitheliopathy 
 
 
 
 
 
 
Meibography 
 
 
 
 
 
 
In-vivo corneal confocal microscopy 
 
 
 
 
 
 
 
The following provides further details the instrumentation or procedures involved: 
i. 
OSDI and DEQ5 questionnaires 
These are validated questionnaires used to assess the severity and frequency of the dry 
eye symptoms experienced by the participants. OSDI consists of 12 questions regarding 
the frequency of symptoms and impact of daily activities over the past week. The scores 
range from 0 to 100 [1]. The DEQ5 assesses the severity and frequency of the 
discomfort, dryness and wateriness during a typical day in the past month. The scores 
range from 0 to 22 [2]. The adapted SANDE questionnaire is a visual analogue scale 
quantifying the severity and frequency of dry eye symptoms for each eye separately 
from 0 to 100 [3]. These were self-administered by the patient on a printed A4 sheet of 
paper. 
ii. 
Visual acuity assessment 
A standard vision chart mounted on the wall was used to assess high-contrast vision in 
logMAR units, calibrated at 3 m. 
iii. 
Oculus Keratograph 5M, Part 1 (Optikgerlite GmBH, Wetzlar, Germany) 
Number of total and partial blinks in 30 seconds, tear meniscus height measured using 
in-built calipers in the Oculus Keratograph 5M software (average of 3 measures), 
objective non-invasive tear break up time (average of 3 measures), subjective lipid layer 
pattern grading (1: Open meshwork; 2: Closed meshwork; 3: Wave pattern; 4: 
Amorphous pattern; 5: Colour fringe pattern) [4], and automated bulbar conjunctiva 
and limbal redness grading (0: none to 4: severe in 0.1 increments) were assessed using 
this instrument.  
iv. 
Laser Doppler flowmetry 
This is an instrument developed by the Aston Institute of Photonics Technology (Aston 
University, Birmingham, United Kingdom) which uses a small probe lightly touching 
the skin to analyse blood flow in small vessels [5, 6]. This was adapted and mounted 
on the slit lamp to assess the blood flow of the external cutaneous skin of the central 
lower eyelid of each side.  
v. 
Slit lamp biomicroscopy 
The number of blocked or plugged Meibomian gland orifices were assessed under white 
light of the slit lamp biomicroscope (CSO SL9900 Digital LED Slit Lamp, 
Worcestershire, United Kingdom). Subjective grading of telangiectasia in the lower lid 

margin (from 0 signifying no telangiectasia, to 3 representing telangiectasia crossing 
orifices across ≥ 50% of the lid margin) was also conducted [7]. The number of 
eyelashes with any presence of Demodex mite around the base of the lashes were 
assessed by random selection of two lashes from each eyelid and using a lateral traction 
method as described previously [8]. Diagnostic Meibomian gland expression was 
conducted using a Meibomian Gland Evaluator (TearScience, North Carolina, United 
States) across five glands temporally, five glands centrally and five glands nasally. The 
expressibility and meibum quality were graded with the Pflugfelder scale (0: all 5 
glands expressing; 1: 3 to 4 glands; 2: 1 to 2 glands; 3: no glands expressing) and Bron 
scale (0: clear fluid; 1: cloudy fluid; 2: cloudy particulate fluid; 3: inspissated), 
respectively [9], and averaged across the 15 glands assessed. 
vi. 
Oculus Keratograph 5M, Part 2 
This instrument was also used for imaging sodium fluorescein and Lissamine green 
staining, graded using the Oxford scale (from 0, absent to 5, severe) for the overall 
cornea and bulbar conjunctiva [10]. For each participant, a fluorescein sodium 
impregnated dry strip (Bio Fluoro, Bio-Tech Vision Care, Gujarat India) was moistened 
with a drop of saline solution (sodium chloride 0.9%), and the excess fluid shaken off, 
before applying on the lower temporal palpebral conjunctiva after slightly everting the 
lower eyelid. The same was done with a lissamine green impregnated dry strip 
(Contacare Ophthalmics and Diagnostics, Gujarat, India), but with the excess fluid 
allowed to fully coat the whole strip, before a large droplet was instilled in the same 
manner. Imaging was conducted following this using the in-built blue light and yellow 
filter, and then the white light for lissamine green staining. Following upper and lower 
lid eversion, lid wiper epitheliopathy was also assessed by grading the width (0: < 25 
%; 1: 25 to 50 %; 2: 50 to 75 %; 3: > 75 %) and length (0: < 2 mm; 1: 2 to 4 mm; 2: 5 
to 9 mm; 3: > 10 mm) of the staining [11], and an average of the width and length 
grading taken as the lid wiper epitheliopathy grading for each of the upper and lower 
eyelid. Meibography of the upper and lower lids were performed and graded using the 
meiboscale for the percentage area of gland loss or atrophy compared to the whole tarsal 
area (0: around 0%; 1: ≤ 25 %; 2: 26 to 50 %; 3: 51 to 75 %; 4: > 75 %) [12]. 
vii. 
In-vivo corneal confocal microscopy 
The Heidelberg Retinal Tomograph III with Rostock Corneal Module (Heidelberg 
Engineering GmbH, Heidelberg, Germany) was used to image the sub-basal nerve 
plexus of the central cornea and inferior whorl. One drop of anaesthetic eyedrop 
(proxymethacaine hydrochloride 0.5% minims, Bausch & Lomb, Surrey, United 
Kingdom) used routinely in clinical practice was administered in both eyes for comfort 
and to minimise blinking for image capturing. Analyses of the total corneal nerve length 
(in mm/mm2) using a semi-automated method in NeuronJ, a plugin of Image J (National 
Institutes of Health, Maryland, United States of America), and density of immune cells 
[cells/mm2 of putative epithelial T cells (small, immune cells with no visible dendrites) 
and of dendritic cells (larger cells with dendritiform shape and apparent dendrites)] [13] 
using the Cell Counter plugin within ImageJ, from the central corneal (4 images 
randomly selected) were conducted. Total inferior whorl nerve length was also 
measured using NeuronJ from 1 image of the inferior whorl, an anatomical landmark 
where the sub-basal corneal nerves traverse towards 1 to 2 mm inferonasal to the central 
cornea. 

Statistical Analysis 
Two-factor repeated measures analysis of variance (ANOVA) was used for statistical analysis 
to assess changes over time across the multiple visits between each treatment group. One-way 
repeated measures ANOVA was used to assess changes over time for overall measures 
including OSDI scores, DEQ-5 scores, visual acuity, and blink rate. The Greenhouse-Geisser 
correction was applied to the one-way and two-factor repeated measures ANOVA results to 
adjust for the lack of sphericity. Paired t-test for normally distributed data or Wilcoxon signed-
rank test for non-normally distributed data was used to assess differences between the two 
treatment modalities within the same visit. 
 
 
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