Download SLT at Addenbrooke`s Hospital A Clinically Apparent Finding Further

Acute Reversible Corneal Endothelial Changes
Associated With Selective Laser Trabeculoplasty
Andrew J. White1,2, Achyut Mukherjee1, Inderraj Hanspal1, Nicholas Sarkies1, Humma Shahid1, Madhavan Rajan1,3, Keith R. Martin1,2, Peter Shah4,5.
1Ophthalmology,
Cambridge University Teaching Hospitals NHS Foundation Trust, Cambridge, United Kingdom; 2NIHR Biomedical Research Centre, University of Cambridge, Cambridge,
United Kingdom;3Anglia Ruskin University, Cambridge, United Kingdom 4Ophthalmology, NIHR BRC for Ophthalmology, Moorfields Eye Hospital & UCL Institute of Ophthalmology, London,
United Kingdom; 5Ophthalmology, University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom.
Changes Are Seen Across the Cornea
Background
•
•
•
Central Cornea
Peripheral Cornea
Selective Laser Trabeculoplasty (SLT) is an increasingly popular treatment for
glaucoma and ocular hypertension using Q switched YAG laser pulses applied to the
trabecular meshwork applied via a gonioscopic lens
In vitro and cadaveric studies have largely focussed on changes induced in the
trabecular meshwork 1-4
There has been very little published on changes induced in the cornea by SLT with the
exception of a few isolated case reports 5,6
1:Alvarado JA, et al. Am J Ophthalmol. 2010;150:254-64.
2:Cvenkel B, et al. Lasers Surg Med. 2003;33:204-8.
3:Kramer TR, et al. Ophthalmology. 2001 Apr;108(4):773-9.
4:Wood JP, et al. Lasers Surg Med. 2010;42:326-37.
5:Holz H, et al. J Cataract Refract Surg. 2010;36:847-9.
6:Moubayed SP, et al. Ophthalmol. 2009;44:337-8.
SLT at Addenbrooke’s Hospital
• Over 140 patients treated in
the last 12 months
• Standard protocol is:
–
–
–
–
–
–
–
–
Figure 5: Representative confocal images of central cornea and peripheral cornea 3mm
from the visual axis in the same patient taken approximately 30 minutes post SLT
documenting endothelial changes across the cornea.
30
No Morphological Changes On Specular Microscopy
25
Pilocarpine 2%
Apraclonidine 1%
Proxymetacaine anaesthesia
Ellex Tango YAG/SLT with
Latina lens (previously
Goldmann)
180 degrees treatment
Power 0.6-1.0mJ (Latina Lens)
No preoperative or
postoperative steroid
Routine followup at 6 weeks
20
Preoperative
IOP
15
(mmHg)
6 Week Followup
10
5
0
PreSLT 6 weeks
6
9
12
months months months
Figure 1: IOP drop with SLT for 129
eyes in 129 patients
Postoperative
Confocal Postoperative
Figure 6: Specular microscopy
images of central corneal
endothelium taken
immediately pre treatment,
approximately 1hour post
treatment and 6 weeks post
treatment. Confocal
microscopy images taken of
the same region of cornea in
the same patient
approximately 1 hour post SLT
treatment.
A Clinically Apparent Finding
• Subtle endothelial changes noticed at 2 centres
immediately post SLT treatment
• One centre routinely pre treated with
dexamethasone (Birmingham), one did not
(Cambridge).
• Differing machines
• Ellex (Cambridge)
• Coherent (Birmingham)
• Changes appeared to resolve within 24hrs
Central Specular Microscopy Counts
Figure 7: Mean specular endothelial counts,
average cell size and corneal thickness taken
immediately pre treatment, 1hour post
treatment and 6 weeks later. Error bars
represent standard deviation.
Figure 2: Subtle endothelial changes (arrow)
noted approximately 30 minutes post SLT
Further Investigation
•
•
•
•
•
Routinely booked patients at one centre (Cambridge) consented to have additional imaging pre
and post SLT and at routine followup (n=9)
Patients to have preoperative confocal microscopy and endothelial cell counts with specular
microscopy
Standard treatment and followup
Confocal and specular imaging immediately postoperatively (within 30-60 mins) and at routine 6
week followup
Local IRB approval granted
What is Causing This?
•
•
•
•
Confocal Images Pre and Post SLT
•
Preoperative
Postoperative
Human donor cornea obtained from Bristol Eye Bank
unusable for transplant
Study covered by Eye Bank ethical approval
Mounted in artificial anterior chamber filled with
Balanced Salt Solution (BSS)
Confocal imaging of endothelium either:
– Removed from chamber and direct SLT laser applied
to endothelium (0.9mJ)
– 10% fresh blood with BSS washout
– 2mM hydrogen peroxide 30mins
Remounted in anterior chamber and re- imaged
6 Week Followup
Donor Cornea
Prior to Treatment
Donor Cornea
0.9mJ Laser
Donor Cornea
10% Blood
Donor Cornea
2mM Peroxide
Figure 3: Confocal imaging of corneal endothelium immediately pre SLT. Imaging of the
same patient approximately 30 minutes post SLT and 6 weeks post SLT
A Spectrum of Post SLT Changes
Figure 4:
Patient age ranged from 66-84.
Four patients had PXF, four had
previous cataract surgery and
one had previous retinal
detachment surgery. The was no
change in visual acuity post
proceedure (0.14 logMAR units,
(range -0.2 – 0.7, n =16 eyes)).
Changes observed post SLT
ranged from very mild (top left)
to marked and diffuse changes
(bottom right). Only 2 (12%)
eyes showed no obvious
abnormality post SLT.
Figure 8:
Human donor cornea prior to exposure and following direct exposure to laser, 10% blood
and 30 mins of 2mM hydrogen peroxide. The direct laser produced a crircular region of
endothelial destruction surrounded by increased endothelial blebs (white arrow). A
different cornea exposed to blood showed increased patches of hyperreflectivity on the
endothlium (red arrow) and the final cornea exposed to peroxide showed a widening of
intracellular spacing (blue arrow)
Summary
• SLT appears to cause transient endothelial changes immediately postoperatively
that appear to resolve within a few days and do not affect vision
• The cause is unknown but we are investigating potential mechanisms
• Endothelial changes do not appear to be caused by direct laser damage
• Further study is required to investigate this finding
Acknowledgements
We also acknowledge Guy Negretti and Anja Nessman for help auditing our
SLT outcomes and Elena Novitskya and George Voyatzis for help with
imaging of the donor cornea