In vivo laser-tissue interactions and healing responses from 20- vs 100-millisecond pulse Pascal photocoagulation burns.
OBJECTIVE
To compare in vivo burn morphologic features and healing responses of Pascal 20- and 100-millisecond panretinal photocoagulation (PRP) burns in proliferative diabetic retinopathy.


METHODS
Prospective randomized controlled trial with 24 eyes assigned to either 20- or 100-millisecond Pascal PRP. Fundus autofluorescence and Fourier domain optical coherence tomography (FD-OCT) were performed 1 hour and 2 and 4 weeks after treatment. Main outcome measures included burn morphologic features on FD-OCT and greatest linear diameter (GLD) of laser burns as evaluated in 6 standard Early Treatment of Diabetic Retinopathy Study photographic fields using autofluorescence.


RESULTS
The contemporaneous increase in autofluorescence is observed with increasing pulse duration. Differences in mean GLD between 100- and 20-millisecond burns were 63 mum at 1 hour and 198 mum at 4 weeks (P < .001 for both). At 4 weeks, all burns corresponded to defects at the junction of inner and outer segments of photoreceptors (JI/OSP) and apical retinal pigment epithelium. After 4 weeks, the GLD of 20-millisecond burns reduced significantly by 35% (P < .001), with no change in 100-millisecond burns.


CONCLUSIONS
All burns initially appear as equivalent square-edged, columnar foci of hyperreflectivity in the outer retina. Pascal 20-millisecond burns progressively reduce in size, and this suggests a novel healing response localized to the JI/OSP and apical retinal pigment epithelium. The higher-fluence 100-millisecond burns develop larger defects due to thermal blooming and collateral damage.
Muqit
Mahiul M K
MM
Manchester Royal Eye Hospital, University of Manchester, Manchester, England.
Gray
Jane C B
JC
Marcellino
George R
GR
Henson
David B
DB
Young
Lorna B
LB
Patton
Niall
N
Charles
Stephen J
SJ
Turner
George S
GS
Dick
Andrew D
AD
Stanga
Paulo E
PE
D000328:Adult; D003930:Diabetic Retinopathy / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D005451:Fluorescein Angiography; D005583:Fourier Analysis; D006801:Humans; D017075:Laser Coagulation / Q000379:methods*; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D008297:Male; D010781:Photography; D011446:Prospective Studies; D055211:Retinal Photoreceptor Cell Inner Segment / Q000473:pathology*; D055214:Retinal Photoreceptor Cell Outer Segment / Q000473:pathology*; D055213:Retinal Pigment Epithelium / Q000473:pathology*; D041623:Tomography, Optical Coherence; D014945:Wound Healing / Q000502:physiology*