description of effect of different radiations in eye

1. Effects of radiation
and glare in eye
Hira Nath Dahal
Optometrist
Drishti Eye Care System

2. Radiation
• Physical term defining the transfer of energy through space from and
emitter or radiator to a receiver
• Light emission and absorption
• Net transfer of energy

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Electromagnetic Spectrum

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Electromagnetic Spectrum
FG Figure 7-2
ULTRA-
VIOLET
RADIATION

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Electromagnetic Spectrum
FG Figure 7-2
ULTRA-
VIOLET
RADIATION
INFRARED
RADIATION

6. Radiation effects
• Mechanism of radiation hazards
• Molecular level
• Photo-absorption increased energy level unstable state  electron ejection 
combine with oxygen  superoxide molecule formation (free radical)disrupt cell
membrane, mitochondrial membrane and nucleic acid  tissue destruction
• Tissue level

7. Classification of radiation effects
• Draper’s law
• For an effect the radiation must be absorbed by the substance
• Vision??
• Effects of radiation
• Ionizing radiation
• Non-ionizing radiation

8. Ionizing radiation
• Interacts with matter to form ions
• High-energy electromagnetic radiation and particle radiation are
capable of producing ions in their passage through matter.
• Types
• Alpha and beta particles,
• X-rays, gamma rays
• Ionizing radiation thorough living tissue  wreaks havoc on the atoms
and molecules in its path  chain of events  destruction of living cells
with functional abnormality

9. Ionizing radiation: Effects
• Damage depends on
• Exposure time
• Concentration
• Type
• Direct effect
• Cellular anomalies or death
• Indirect effect
• Damage to blood vessels
• Low levels of radiation
• Engorged conjunctival vessels
• Loss of corneal lusture
• High levels of radiation
• Exfoliation of epithelial cells
• Keratitis
• Corneal ulcer
• Cataract
• Retinal degeneration

10. Non-ionizing radiation
• Electromagnetic radiation that is not of sufficient energy to
ionize matter, though it is capable of damaging the human body.
• Cause photochemical and thermal effects
• By exciting electrons in atoms to higher energy levels, and by
producing molecular excitation.
• Examples
• Lasers, radio-frequency and microwave radiation, IR radiation,
and UV radiation

11. Non-ionizing radiation: Effects
•Thermal effects
• Heating effect
• Solar retinopathy
•Photochemical effects
• Visual sensation
• Photokeratitis

12. Concentration of radiant energy by eye

13. Special consideration

14. Absorption of the radiation by the ocular
tissue
Tissue Ultraviolet (nm) Visible (nm) Infrared (nm)
Tear layer 290-380 380-760 760-3000
Cornea 290-380℗ 380-760 760-3000℗
Aqueous 290-380℗ 380-760 760-3000℗
Lens in child 310-380℗ 380-760 760-2500℗
Lens in adult 375-380℗ 380-760℗ 760-2500℗
Vitreous 290-380℗ 380-760 760-1600℗

15. Absorption of radiation by various ocularAbsorption of radiation by various ocular
tissuestissues

16. Effect of ultraviolet radiation (UVR)
•Pinguecula
• Small yellowish elevated concretion of bulbar conjunctiva
• Fibro-fatty degenerative change within the palpebral fissure
• Typically located nasally
• Due to light reflecting off the nose onto the nasal conjunctiva
• a/w long continued exposure to the solar radiation

17. Pterygium
 A fibrovascular growth which appears on the
cornea and looks as if it is continuous with the
conjunctiva
◦ ?Degeneration or proliferation
◦ Rich in blood vessel growth which appears to pull the
lesion toward he cornea.
◦ An orange-brown ferric deposition line (Stocker’s line)
may be seen at the leading edge of the pterygium on
the cornea
 More on nasal side

18. Pterygium
 Greater frequency in tropical areas near the equator rather than in
milder climates
◦ UVR as an risk factor
 Pathophysiology
◦ Elastoid degeneration of deep conjunctival tissue
◦ fibrovascular proliferation
◦ over growth of conjunctivally derived epithelium onto the limbus and
cornea

19. Band shaped keratopathy
 White or cream colored opacities b/w the
epithelium and Bowmann’s layer
◦ Distributed symmetrically in the inter-
palpebral portions of two cornea
 Spheroid degeneration or climatic droplet
keratopathy
 Limited geographic prevalence

20. Photophthalmia
◦ Absorption of UV<300 nm
◦ Photochemical damage to corneal epithelium
◦ Photokeratoconjuctivitis
◦ Latent periods of 30 minutes to 24 hrs
◦ Cumulative effects
◦ Intermittent exposure prevents healing

21. Photophthalmia
 Clinical features
◦ Foreign body sensation
◦ Photophobia
◦ Lacrimation and blepharospasm
◦ Redness
◦ Edema
◦ Similar features as in snow blindness
and welder’s keratitis
• Self limiting
• Symptomatic treatment
• antibiotic coverage
• NSAIDS

22. Uveitis
• UV wavelengths between 295nm and 310nm cause anterior
uveitis.
• Usually this is only a temporary problem.

23. Cataract
 Any form of lens opacity
◦ Adversely affecting vision or visual function
 Continuous exposure
 Cumulative effect
◦ Formation of lens pigments causing yellow coloration of the lens
nucleus
◦ Pigments mainly produced by the nucleus
◦ UV-B (290-320)
◦ Brown cataract
 Nuclear, PSCC and cortical cataract

24. Retinal damage
 Usually protected
◦ ? aphakia
 UVR absorption by RPE and choroid  potential photochemical
and thermal effect
 Cystoid macular edema
 Decline in short wavelength sensitive cones in rapid manner
 Retinal degenerative changes
◦ ARMD

25. Age related macular degeneration
• Prolonged sun exposure: risk factor

26. Tumors of eyelids and conjunctiva
• Basal cell carcinoma
• Mainly lower lids on medial sides
• More incidence in the countries with high sunlight
exposure (Australia)
• Squamous cell carcinoma
• Invasive epithelial malignancy showing keratinocytic
differntiation
• Lower lid

27. Tumors of eyelids and conjunctiva
• Sebaceous carcinoma
• Malignant melanoma
• Squamous cell carcinoma of the conjunctiva

28. Effects of visible radiation
 Transparent media
◦ Transmisssion of the visible spectrum
 Photoreceptors
◦ Absorption  visual sensation
 Higher level of visible light
◦ Harmful photochemical and thermal injury to the retina
◦ Converged radiation to the retina
◦ Even at normal level, prolonged exposure  undesirable visual effects such
as increased dark adaptation time

29. Effects of visible radiation
• Short wavelength
• Higher energy more photochemical damage
• Long wavelength
• Less energy  both photochemical and thermal damage
• Infra-red radiation thermal damage

30. Effects of visible radiation
• Age related macular degeneration
• Long term exposure to the visible radiation and UVR
• RPE and photoreceptor damage
•Solar retinopathy
•Eclipse burn
•Presentation
• Reduced vision
• Small dense central scotoma
• Chromatopsia and metamorphopsia

31. Effects of visible radiation
•Solar retinopathy
• Cause
• ?IR thermal burn
• Photochemical trauma (blue light hazard)- short term
exposure to the high energy short wavelength visible
spectrum (400-500nm)
• Thermal injury - Long term exposure to the long
wavelength visible radiation and IR radiation

32. Solar retinopathy

33. Effects of IR radiation
 Damage by 780-2000 nm
 >1400 nm absorbed by tear film and cornea
 Sources
◦ Solar radiation
◦ Carbon, tungsten and xenon lamps
◦ Photoflood lamps
◦ Some laser sources
 Immediate effects after IR exposure
 Population at risk
◦ Glass blowers
◦ Blast furnace operators

34. Effects of IR radiation
 Cornea
◦ Coagulation and opacification
 Iris
◦ Congestion
◦ Depigmentation
◦ Atrophy
 Lens
◦ Exfoliation of lens capsule
◦ Coagulation of lens protein
◦ Cataract production : ASCC, PSCC
 Retina
◦ Necrotic burns

35. Other forms of radiation
• Long wave microwaves
• Diathermy
• Ionizing radiation
• X-ray and gamma rays

36. Glare
 Refers to the presence of one or more areas in the field of vision
that are of sufficient brightness to cause discomfort in vision.
 Visual perception created by external light
 Glare source : Axial / Peripheral
 Reduces the quality of the image
◦ an unpleasant sensation
◦ a temporary blurring of vision
◦ a feeling of ocular fatigue

37. Classification
• Veiling or disability glare
• Discomfort glare
• Specular reflection glare

38. Veiling or disability galre
 Arises from stray light falling on the retina, usually from scatter
by the media of the eye.
 Scattered light falls as a patch of veiling illuminance on the fovea
◦ Reduces the contrast of the retinal image.
◦ Reduces visibility and visual performance.
 E.g. sky, sand, brightly illuminated walls etc.-
◦ the reflected images are large in angular subtense leading to reduction
in contrast observed in the visual field.

39. Glare in Cataract
Normal Cataract

40. Discomfort glare
• Occurs when the illumination in a part of the visual field is
much greater than the level of illumination for which the
retina is adapted.
• Highest level of illumination in the visual field and background
illumination exceeds a ratio of 3 :1
• During night driving-causes extreme discomfort.
• Importance of having background illumination while
watching television

41. Specular reflection glare
 Occurs when patches of bright light are
reflected form smooth, shiny surface into the
eye.
◦ Typical reflecting surfaces include expanses of
water, snowfields, roadways etc.
 Reflections are not only annoying but
interfere with visibility, at times seriously.
 Can be well controlled by using polaroid
glasses.

42. Glare testing
•Objective :
• quantify the deleterious effects of light scatter on visual
performance
• Reduce the effect on impairment of vision
•When?
• Corneal opacities
• Corneal dystrophies/ Degeneration
• Cataract

43. Indications for glare testing
 Pre-operative
◦ Cornea
 Infectious scarring
 Traumatic scarring
 Degenerative scarring
 Dystrophic scarring
◦ Lens
 Age-related cataract
 Traumatic cataract
 Drug-induced cataract
 Disease-induced cataract
 Post-operative
◦ Cornea
 PK
 Epikeratophakia
 Keratomileusis
 Repaired laceration
◦ Lens
 PCO following ECCE, IOL

44. Glare Testers
• Brightness Acuity Tester (BAT)
• Optec 1500 Glare Tester
• Terry Vision Analyzer (TVA)
• Miller-Nadler Glare Tester

45. Thank you