1. Grace Carolan-Rees Arek Mazurek, Brian Western, Chris Edwards
Are LED sources suitable for light testing in photosensitivity disorders?
Grace Carolan-Rees
Arek Mazurek, Brian Western, Chris Edwards

2. What is photosensitivity?
Skin disorder. Allergy to sunlight
UVB, UVA, visible light or a combination may be responsible

3. Skin conditions Polymorphic Light Eruption (PLE)
Chronic Actinic Dermatitis (CAD)
Solar Urticaria
Drug Induced Photosensitivity

4. Polymorphic Light Eruption (PLE)
Affects 10% – 20% of population, predominantly females, usually in first 3-4 decades of life
Delayed onset (hours), pruritic erythematous papules, vesicles and plaques. Usually confined to sun-exposed sites
Light testing, if positive nearly always shows a sensitivity in the UVA, but occasionally in UVB

5. PLE

6. Chronic Actinic Dermatitis (CAD)
80% of sufferers are male, 50+ years old
Presentation varies but eczematous, often palpable appearance on light exposed sites is common
Light testing positive results usually to UVA and UVB, sometimes UVA alone, occasionally visible light

7. CAD

8. CAD light test results

9. Solar Urticaria Rare and extremely disabling
Immediate weal and flare reaction on light exposed areas
Anaphylaxis possible if solar urticaria patient exposed to phototherapy – death possible!!!
Reactions usually last 1-2 hours and resolve completely
All wavelengths including visible light can induce reaction

10. Solar Urticaria test result

11. Typical testing regime
Wavelengths tested:
300nm, 5nm BW 5 – 120 mJ/cm2 ( 10 steps)
320nm, 10nm BW 686 – 5166 mJ/cm2 (7 steps)
350nm, 20nm BW 3.5 – 28 J/cm2 (7 steps)
370nm, 20nm BW 30 J/cm2
400nm, 20nm BW 50 J/cm2
450nm, 20nm BW 30 J/cm2
Read immediately, 24 hours

13. The problem Time consuming - full test >1 hour per patient
Expensive and bulky equipment
Technical expertise to run the equipment
Lamp ageing

14. LED skin sensitivity tester
ENFIS UNO light engine at 460nm
Claimed O/P 4400 mW/cm2
AIM: To develop prototype LED device and measure its optical properties
SolidWorks v2007 CAD package
Bentham DM150 Spectroradiometer

16. MED Tester

18. Device characterisation
Position of collimating lens
Beam profile
Total power output
Construction and end-product characterisation

19. Beam profile 4 source-lens separations (3,6,7,8 mm)
For each separation, beam profile at 7 axial points (4.3, 5,6,7,8,9,10 cm)
At each axial distance, beam profile of +/- 4 cm
Detector attenuation required due to intensity of output

21. Pin Hole System

26. LED device O/P
254 mW.cm-2
Monochromator O/P
41 mW.cm-2

27. Conclusion
The LED device had a good beam profile across the device output port
Bandwidth 23 nm (FWHM)
Output exceeds existing arc lamp + monochromator system
Future work – clinical trials, development of LED devices at other wavelengths