Clinical Trial Details
— Status: Completed
Administrative data
| NCT number |
NCT03107000 |
| Other study ID # |
2915-001 |
| Secondary ID |
|
| Status |
Completed |
| Phase |
N/A
|
| First received |
|
| Last updated |
|
| Start date |
September 1, 2017 |
| Est. completion date |
October 14, 2022 |
Study information
| Verified date |
April 2023 |
| Source |
Sunnybrook Health Sciences Centre |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
|
| Study type |
Interventional
|
Clinical Trial Summary
Corneal endothelial cells health and pumping function is crucial to permit corneal optical
clarity by keeping cornea in relatively dehydrated state. Corneal endothelial damage has been
associated with most types of intraocular surgery. Trabeculectomy is the standard glaucoma
surgical intervention in management of progressive glaucoma despite of medical therapy which
can be performed in combination with Cataract surgery (Phacoemulsification and IOL
implantation) in patients with cataract-impaired visual acuity.
In this study, the investigators will investigate and compare the corneal endothelial cells
number and health status before and after trabeculectomy vs. combined surgery (at 1 month and
3 months post-op visits) using Specular microscopy which is a non-invasive technique to
access the structure and function of the corneal endothelium by permitting visualization of
the corneal endothelial mosaic to assess the effect of this surgical intervention on corneal
endothelial cells health and number.
Description:
Corneal endothelial cells health and pumping function is crucial to permit corneal optical
clarity by keeping the cornea in a relatively dehydrated state.1 The corneal endothelium is a
single layer of hexagonal cells with uniform size and shape in normal conditions. When
endothelial cell density diminishes, the remaining cells increase in size to cover the empty
spaces left by the dead cells, and therefore there is a change in the size (polymegathism)
and morphology (pleomorphism) of the remaining cells. Trauma or other insults often cause
endothelial cell death, which is irreparable because these cells lack division capacity.2,3,4
Corneal endothelial damage has been associated with most types of intraocular surgeries
including glaucoma and cataract surgeries.5,6,7,8 Cataract and glaucoma are the most common
causes of visual impairment worldwide.9,10
Phacoemulsification and Intraocular lens (IOL) insertion, the most commonly performed method
of cataract extraction in the developed world, was first described in 1967.11 This technique
allows rapid visual rehabilitation postoperatively and low induced astigmatism.11 The
reported average loss of central corneal endothelial cells after phacoemulsification vary
between 4% and 25%.8 Trabeculectomy, introduced by Cairns in 1968 12, is the most commonly
performed incisional glaucoma procedure worldwide and has become the glaucoma filtering
procedure of choice in glaucoma patients 5,13,14 with advanced glaucoma or poor tolerance or
uncontrolled IOP despite of multiple topical or systemic medications with the goal of
preserving vision and reducing the likelihood and rate of visual field loss and optic nerve
changes in susceptible patients by reducing the intra ocular pressure (IOP) as the major risk
factor.15,16 The use of anti-metabolites specifically Mitomycin C (MMC) as a supplement to
trabeculectomy with more favorable effect on the outcome was reported by Chen 17 and Palmer 6
in the early 1990s5 showing eyes treated with MMC-augmented trabeculectomy have lower
intraocular pressure (IOP) than eyes treated with trabeculectomy only.12 About 8.7% loss in
central endothelial cells was reported after 3 months follow up in patients with
Trabeculectomy with augmented Mitomycin C (MMC).7 Combined Trabeculectomy with Cataract
surgery (Phacoemulsification and IOL insertion) can be performed based on the need to restore
cataract-impaired visual acuity in trabeculectomy candidates.9,18 Given available results of
previous studies on the effects of each of above mentioned procedures on corneal endothelial
cells7,8, it is presumed that combined trabeculectomy with phacoemulsification and IOL
insertion would have a cumulative effect on central corneal endothelial cell loss.
Specular microscopy is a non-invasive technique to assess the structure and function of the
corneal endothelium by permitting visualization of the corneal endothelial mosaic.19 It is
the standard method of endothelial cell analysis worldwide. By counting the number of the
cells in measured areas of the cornea, an estimate of endothelial cell density can be made.
There is only one retrospective study available comparing central corneal endothelial cell
loss after Trabeculectomy versus combined Trabeculectomy, Phacoemulsification and IOL
insertion.2 There is also very limited data available to determine whether the expected
damage is a non-progressive short-term effect or a progressive consequence which can lead to
corneal endothelial decompensation. The investigator's aim is to evaluate and compare the
effects of above mentioned procedures on central corneal endothelial cells health and
density. The results of this study could help glaucoma surgeons make proper decisions in
performing combined versus single surgeries in patients with initial risk factors for corneal
decompensation.
3. Hypothesis The hypothesis of this study is that combined trabeculectomy,
phacoemulsification and IOL implantation has more effect on corneal endothelial cell loss
than trabeculectomy alone.
4. Research Plan 4.1 Study Design This is a prospective, interventional comparative clinical
study
4.2 Patients Patients for this study will be recruited from the John and Liz Tory Eye Centre,
Sunnybrook Health Sciences Centre (SHSC) in Toronto, Ontario, Canada. All patients will
require and have consented to incisional glaucoma surgery with or without cataract surgery
prior to being recruited. Subjects will be placed in one of two groups (Group A:
Trabeculectomy only and Group B: Combined Surgery) based on absence or presence of
cataract-impaired visual acuity. After achieving consent, for all patients undergoing the
study, baseline information including age, gender, number of anti-glaucoma medications and
medical history will be recorded. All patients will receive an ocular examination, including
best corrected visual acuity measurement (Snellen chart), slit lamp examination along with
tonometry (Goldmann applanation tonometry), central corneal thickness measurement
(Pachymeter) and specular microscopy photos at pre-op, 1 month and 3 month visits. Anterior
chamber depth will be measured by The IOLMaster® (Carl Zeiss Meditec, Jena, Germany) for all
patients on pre-op visit. Type of the cataract will be assessed and recorded for Group B in
pre-op visit. All achieved data will be recorded and saved on prepared data sheet for future
analysis.
4.2-1 Inclusion criteria
1. Age over 18 years old
2. Patients with well established Open Angle Glaucoma (OAG) including Primary open angle
glaucoma (POAG), Pseudoexfoliation Glaucoma (PXFG), Pigmentary Glaucoma (PG) and Steroid
induced Glaucoma (SIG) requiring incisional surgery for IOP (Intraocular pressure)
higher than target, despite receiving maximal tolerable medical treatment or were
intolerant to medications with progressive glaucoma related visual field defects or
optic nerve changes.
3. Patients with any of above types of glaucoma requiring cataract surgery.
4. Patients on which specular microscopy and IOLMaster can be performed without any delay
in their treatment (availability of a qualified operator).
5. Decision makers able to give informed consent. 4.2-2 Exclusion criteria
1. Unable to attend follow -up visits 2. Angle closure glaucoma 3. Secondary open angle
glaucoma other than PXFG, PG or SIG 4. Previous intraocular surgery or laser procedures other
than laser trabeculoplasty 5. Post operative complications (if any) including flat anterior
chamber, endophthalmitis and severe post op inflammation 6. Need to perform any other
intraocular surgery during the course of the study 7. Pre-operation corneal disease
The investigators may decide to remove a patient from this study for any of the following
reason(s):
• Need for any other ocular surgery known to have effects on corneal endothelial health
4.3 Surgical procedure
4.3 A: Trabeculectomy
The primary investigator and/or a glaucoma fellow will perform a standard trabeculectomy.
After receiving a peribulbar block on identified eye, the patient will be transferred to OR
and prepped and draped in the usual fashion.
A traction suture (6-0 silk) will be put in peripheral cornea after a lid speculum is
inserted. A superior conjunctival peritomy will be performed followed by bipolar cautery for
haemostasis. At this point 0.2 mg/ml Mitomycin-C will be applied using 3 soaked sponges
tucked under conjunctival flap which will be removed after 90 seconds while checking the time
by a digital timer. Copious irrigation with 20 cc sterile saline will be performed after.
A 4 in 4 mm scleral flap will be demarcated by a diamond blade at the depth of 0.25 mm. The
flap will be elevated and dissected through the clear cornea using a crescent blade. After
creating a side port to decompress the anterior chamber by a 25-gauge needle, sclerotomy will
be performed using a 15 degrees blade followed by a peripheral iridotomy. The scleral flap
will be sutured back into place using 4-8 interrupted and buried 10-0 nylon sutures.
Anterior chamber (AC) will be reformed by balanced sterile saline (BSS) which reveals
filtration through the flap. Conjunctival flap will be repositioned meticulously into the
limbus using either continuous alone or with combination of interrupted 8-0 Vicryl sutures.
6-0 silk traction suture and speculum will be removed after reforming AC again to confirm no
leak from the wound site. The eye will be patched using an eye patch and a plastic shield
after application of TobraDex® ointment and Atropine 1% eye drop (if Phakic).
4.3 B: Combined Trabeculectomy, Phacoemulsification and IOL implantation
The primary investigator and/or a glaucoma fellow will perform Combined trabeculectomy,
phacoemulsification and IOL implantation. After receiving peribulbar block on identified eye,
pt will be transferred to OR and prepped and draped in the usual fashion.
A traction suture (6-0 silk) will be put in peripheral cornea after a lid speculum is
inserted. A superior conjunctival peritomy will be performed followed by bipolar cautery for
haemostasis. At this point 0.2 mg/ml Mitomycin-C will be applied using 3 soaked sponges
tucked under conjunctival flap which will be removed after 90 seconds while checking the time
by a digital timer. Copious irrigation with 20 cc sterile saline will be performed after.
A 4 in 4 mm scleral flap will be demarcated by a diamond blade at the depth of 0.25 mm. The
flap will be elevated and dissected through the clear cornea using a crescent blade.
After the side port is made using 15 degree blade, the entrance to the anterior chamber (AC)
will be made using 2.4 mm keratome. Capsulorrhexis will be performed using a cyctotome after
filling the anterior chamber with viscoelastic (Viscost® and Provisc®). Lens material will be
extracted using phacoemulsification and completed by irrigation and aspiration of the cortex
material. The capsular bag will be inflated using Provisc and Posterior Chamber Intra-Ocular
Lens (PCIOL) will be inserted using the PCIOL dispenser in to the bag and dialed in place by
a Sinskey hook. Completion of sclerotomy and creation of a peripheral iridectomy will be
followed by using a 20 degree blade and Vannas scissors.
The scleral flap will be sutured back into place using 4-8 interrupted and buried 10-0 nylon
sutures. AC will be reformed by balanced sterile saline (BSS) which reveals filtration
through the flap. Conjunctival flap will be repositioned meticulously into the limbus using
either continuous alone or with combination of interrupted 8-0 Vicryl sutures. 6-0 silk
traction suture and speculum will be removed after reforming AC again to confirm no leak from
the wound site. The eye will be patched using an eye patch and a plastic shield after
application of TobraDex® ointment.
