FULL PHOTOBIOLOGY WITH SUNSCREENS IN DETAIL

1. PHOTOBIOLOGY
DR. SHILPA SONI.

2. LIGHT
• Speed = 3x10^8 m/sec
Travels in straight line

3. ELECTROMAGNETIC SPECTRUM
• Consist of 7 components
– Radio waves
– Microwaves
– Infra-red radiation
– Visible light
– Ultra-violet waves
– X-rays
– Gamma rays
105 m
10-14 m
Wavelength
Rich Men In Vegas Use X-ray Goggles

5. PROPERTIES OF LIGHT
• Wavelength (λ)
• Energy of light (J) α 1
λ
• Power (W) – rate of flow of energy. (W or J/s)

6. • Irradiance – rate at which light energy is
delivered to a unit area is known as the
intensity of light or irradiance.
Irradiance = J/s/cm²
• Dose of light = it is the total amount of light
delivered to the skin & is equal to the product
of irradiance & time of exposure.
Dose = J/cm²

7. Fate of Light

8. SOLAR SPECTRUM

12. Application of Electromagnetic waves
Ultra-Violet (UV) Radiation (10-8 to 10-7)
• Sunlight is the main source of UV radiation
• Ultraviolet lamps are used in sunbeds for
artificial tanning.
• Used in hospital for sterilisation - kill bacteria
and viruses

13. Application of Electromagnetic waves
Visible Light (10-7)
• Only part of the EM spectrum that can be detected by
human eye.
• Wavelength: 400nm (violet) to 700nm(red)
• Laser can be used in industries
to weld metals together and in
medicine.
• Optical fibres in telecommunications

14. Application of Electromagnetic waves
Radio waves (10-1 to 105)
• Longest wavelengths
• Able to go around obstructions due to their
long wavelength
• Used in radio broadcasting,
telephone transmission, television,
radar, navigation system

15. Application of Electromagnetic waves
Microwaves (10-3 to 10-1)
• Microwave oven – cause the water molecules
in the food to vibrate. The vibration causes
friction at a molecular level which will heat up
the food.
• Satellite communication and television –
signals are transmitted through aerial dishes
to satellites in the space.

16. Application of Electromagnetic waves
Infra-red Radiation (10-7 to 10-3)
• All object emit infra-red radiation
• We experience infrared-radiation in the form of heat
• Ear thermometer: measure the amount of infra-red
radiation that emanates from the eardrum.
• Used in remote controls for electronic devices and
infra-red motion detectors.

17. Application of Electromagnetic waves
X-Rays (10-13 to 10-8)
• used to produce the X-ray images to examine
a person’s body or tooth decay
• used in X-ray scanners in airports
• can penetrate through all materials except
lead.

18. Application of Electromagnetic waves
Gamma Rays (10-14 to 10-10)
• It can be used to treat cancer by killing cancer
cells.
• Cause serious damages to living tissues.

19. PHOTOPROTECTION

20. Types of sun protection
• Natural
- Atmosphere
• Biological factors
- Melanin
- Stratum corneum
- Chromophores

21. Types of sun protection
• Physical factors
- Clothing
- Hats
- Make up
- Window glass

22. Types of sun protection
• Artificial photoprotection
• Systemic photoprotection

23. Types of sun protection
Artificial photoprotection
- Topical sunscreen
- SPF
- Substantivity
- Types
- Organic/chemical
- Inorganic/physical
- Combination sunscreen

25. Sunscreens
• Organic (chemical)
absorbers
- UVB absorbers
PABA derivatives
PABA
Cinnamates
Cinoxate
Salicylates
- UVA absorbers
Benzophenones
oxybenzone
dioxybenzone
Dibenzoyl methanes
avobenzone

26. Sunscreens
• Inorganic/physical/
sunblocks absorbers
- Titanium dioxide
- Zinc oxide
• Others/broad spectrum
chemical
- Mexoryl SX
- Tinosorb M
- Tinosorb S

28. Types of sun protection
• Systemic sun protection
- Beta – carotene
- Anti – malarial drugs
- Psoralens

29. Systemic sun protection
• BETA – CAROTENES
Mechanism of action
- Photo oxidised by UVR and this spares the cell
components from being photo damaged.
- Free radical scavenger & free radical quencher.

30. Beta carotene
• Uses
- Erythropoetic porphyria
- PLE
- SU
• Doses
- 30-120µgm in children
- 120-300µgm in adults

31. Antimalarials: Actions in Dermatology
• Bind to porphyrins and facilitate their
clearance in urine
• Solubilization and mobilization of hepatic
porphyrins and their clearance
• Ability to bind to melanin and antioxidant
activity: ?Role in photosensitive disorders
• Binds to melanin in retina leading to retinal
toxicity

32. Systemic sunscreen?
• Useful for diseases exacerbated by UVB (SCLE >
ACLE) as well as those exacerbated or induced by
UVA (polymorphous light eruption & its variants &
majority of photosensitivity dermatoses)
• Blocks effects of exposure on skin as well as other
organs esp. in LE
• Antioxidant effect & blockage of a cascade of
immunologic actions that follow light exposure

33. Anti - malarials
• Uses
- PLE
- SU
- PCT
- SLE & DLE
• Doses
- Chloroquine = 250-500mg/day
- Hydroxychloroquine = 200-400mg/day

34. Anti - malarials
• Monitoring
- Ophthalmic examination
- Visual acuity
- Perimetery
- Color vision
- Ophthalmoscopic avaluation
(at every 6 months interval)

35. Anti - malarials
• Toxicity
- Reversible corneal deposits
- Retinopathy
- Optic atrophy
- Pigmentary degeneration of macula.
(bull’s eye retinopathy)
- Arteriolar narrowing

36. Contraindications
• Hypersensitivity (cross reactions)
• Pregnancy and lactation
• Severe blood dyscrasia
• Severe hepatic dysfunction
• Retinal & Visual field changes

37. Systemic sun protection
• Psoralenes
- 8 MOP
- TMP
(in conjunction with carefuly controlled exposure to either
sunlight (PUVAsol) or an artificial source of UVA (PUVA) can
be effective method of increasing skin’s resistance to the
damaging effect of UVB component sun light)

38. Psoralenes
• Indications
- PLE
- SU
- AR

39. Psoralenes
• Doses
- 8 MOP = 0.6mg/kg
- TMP = 0.3mg/kg

40. Psoralenes
• Toxicity
- Gastric discomfort
- Insomnia
- Anxiety
- Depression
- Photo toxicity
- Risk of SCC

42. THANK YOU