Effects of radiation  and glare on human eyes
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Effects of radiation and glare on human eyes

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The presentation I have made and uploaded provides you with an in-depth insight into whats and hows as regards the radiation hazards on human eyes....

The presentation I have made and uploaded provides you with an in-depth insight into whats and hows as regards the radiation hazards on human eyes.
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Amrit Pokharel

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  • 1. EFFECTSOFRADIATIONANDGLARE ON EYE Amrit Pokharel B Opt0metry, IIIrd year
  • 2. Radiation??? Radiation is an energy in the form of electro- magnetic waves or particulate matter, traveling in the air.
  • 3. Glare??? A relatively bright light that produces  Unpleasant or discomfort  A temporary blurring of vision, or  A feeling of ocular fatigue  Which interferes with vision
  • 4. Consequence? The only real consequence  Is the reduction in the quality of an image Any problem in  Corneal layers  Lens  Viterous, or  Retina Results into GLARE
  • 5. Radiation
  • 6. Electromagnetic Spectrum8 5/17/2012
  • 7. Electromagnetic Spectrum ULTRA- VIOLET RADIATION FG Figure 7-29 5/17/2012
  • 8. Electromagnetic Spectrum ULTRA- INFRARED VIOLET RADIATION RADIATION FG Figure 7-210 5/17/2012
  • 9. Types: Ionizing Radiation Non-ionizing Radiation
  • 10. Ionizing Radiation Definition “It is a type of radiation that is able to disrupt atoms and molecules on which they pass through, giving rise to ions and free radicals”.
  • 11. Ionizing Radiation Caused by the disintegration of atoms With the subsequent release of subatomic paricles The energy released is SO HIGH that the binding energy of the electron is broken down And then comes off an ejection of electrons, leaving behind a positively charged atom called cation
  • 12. Radioactive Atom Ionizing Radiation alpha particleX-ray beta particle gamma ray
  • 13. Ionizing Radiation Paper Wood Concrete Energy Alpha Low Beta Medium Gamma High
  • 14. How radiation brings aboutchange…
  • 15. Effect Draper’s law Damage depends on:  Exposure time  Concentration  Type Direct effect  Cellular anomalies or death
  • 16. Effect Indirect effect  Damage to blood vessels Low levels of radiation  Engorged conjunctival vessels  Loss of corneal lustre
  • 17. Effect High levels of radiation  Exfoliation of epithelial cells  Keratitis  Corneal ulcer  Cataract  Retinal degeneration
  • 18. Non ionizing Radiation Definition“ They are electromagnetic waves incapable of producing ions while passing through matter, due to their lower energy.”
  • 19. Non ionizing Radiation The radiation energy is lower than the binding energy of the electron Only states change  Ground ---excited
  • 20. Non ionizing Radiation The change to the irradiated is brought about as:  Thermal Effect  Photochemical Effect  Photoluminescence(fluorescence)
  • 21. Non ionizing Radiation Thermal Effect:  Heating effect  d/t the change in energy states of atoms  Solar retinopathy is an example that involves a thermal lesion
  • 22.  Solar retinopathy  Pathogenesis: thermal effects of solar radiation by directly or indirectly viewing the sun  Presentation is within 1-4 hours of solar exposure with unilateral or bilateral impairment of central vision and central positive scotoma
  • 23.  Solar retinopathy  VA is variable  Fundus: a small yellow or red foveolar spot that fades within a few weeks  The spot is replaced by a sharply defined foveolar defect with irregular borders or a lamellar hole
  • 24. Non ionizing Radiation Photochemical Effect:  When the radiant energy is absorbed, the molecule that absorbs may decompose or chemically react to produce a unique chemical product.  Photokeratitis is an example that involves a thermal lesion
  • 25. Photokeratitis Damage to the corneal epithelium  Due to the absorption of UV-rays below 300nm Also called  Photophthalmia  Photoconjunctivitis The damage tends to be cumulative
  • 26. Photokeratitis Pathogenesis: • After 4-5 hrs(latent period)of UV exposure • There occurs desquamation of corneal epithelium • Leading to the formation of multiple epithelial erosions
  • 27. Photokeratitis
  • 28. Photokeratitis The patients experiences:  Foreign body sensation  Photophobia  Lacrimation  Blepharospasm  Redness  Oedema
  • 29. Photokeratitis The above clinical picture is also seen in SNOW BLINDNESS Occurs due to exposure to UV radiation from large areas from snow Also found in Welder’s keratitis in welders who strike an arc before they wear a protective helmet
  • 30. Photokeratitis Prophylaxis:  Crooker’s glass  Itcuts off all the UV- and IR- rays  To be used by those who are prone to the radiation hazard  Cinema operators, welding workers
  • 31. Photokeratitis Treatment:  Cold compresses  Pad, bandage and antibiotic ointment for 24 hours  Oral analgesics
  • 32. Photokeratitis Photoluminescence (fluorescence):  Asthe property of fluorescence in inherent to the lens, the lens is capable of absorbing UV rays  Thisabsorption gives off the formation of material-fluoregens, that give the characterstic colouration(yellowish) to the lens.
  • 33. Concentration of the radiantenergy by the eye
  • 34. Spectrum…
  • 35. Transmission of the spectrum Cornea: 270nm-3000nm Aqueous: 290nm-2700nm Lens: 310nm(375nm old)-2500nm Vitreous: 290nm-1600nm
  • 36. Absorption of the spectrum Tear layer:  Absorbs only a small amount of radiation  Absorbs UV below 290 and IR above 3000 Cornea:  Has a similar absorption band  But partially transmits UV from 290 to 315 and IR from 1000 to 3000
  • 37. Absorption of the spectrum Aqueous humour:  Absorbs very little or no radiation at all Lens:  The lens of a child absorbs UV below 310nm and IR above 2500nm  The lens of an older adult absorbs almost all radiation below 375nm and therefore transmits very little UV radiation  No change in the IR absorption band with increasing age
  • 38. Absorption of the spectrum Vitreous:  Absorbs radiation below 290nm and above 1600nmThe retina receives the radiation transmitted by the vitreous. UV radiation received by the retina decreases with age
  • 39. Effects of Ultraviolet radiation Photophthalmia Pterygium Pingueculum Cataract Band-shaped keratopathy Macular degeneration
  • 40. Effects of Ultraviolet radiation Pterygium A triangular fibro-vascular subepithelial ingrowth of degenerative bulbar conjunctival tissue over the limbus onto the cornea  Shows elastoid degeneration in the subepithelial stromal collagen  Type I pterygium is most associated
  • 41. Effects of Ultraviolet radiation Pterygium  Management:  Tear substitute  Advisethe patient to wear sunglasses to reduce UV exposure and decrease the growth stimulus
  • 42.  Pinguecula(sing: pingueculum)  Elastoid degeneration of the conjunctival collagen stroma  Found adjacent to the limbus
  • 43. Effects of Ultraviolet radiation Band- shaped keratopathy  Histology shows the deposition of calcium salts in the Bowman layer, epithelial basement membrane and anterior stroma
  • 44. Effects of Ultraviolet radiation Cataract has been found to be associated with the UV band from the sun Anterior subcapsular opacities are most associated, as found by one study There is also an increase in the stromal haze
  • 45. Effects of Ultraviolet radiation The epidemiology of UV-induced cataract: The ophthalmic community has found it difficult to accept the cause-effect relationship of UV exposure in producing cataracts Role of UVR in Skin Cancer and Cataracts Any relationship b/w the surface ectoderm and UV exposure
  • 46. Effects of Ultraviolet radiation The National Health and Nutritional Examination Survey(HANES) and the Model Reporting Area for Blindness Statistics(MRA)  Found a strong positive association between UV rays and the senile cataracts
  • 47. Effects of Ultraviolet radiation Brilliant et al studied 27,785 Nepalese individuals from the plains, the hills, and the mountains who were rural village residents  The no of hours of daily sunlight were determined for each location.  They found that persons exposed to 12 h of sunlight daily were 3.8 times more likely to develop cataracts than those who were exposed to only 7 h of daily sunlight
  • 48. Effects of Ultraviolet radiation They also reported a 2.7 times higher prevalence at altitudes of 185 m and below than at 1000 m and above Similar study conducted by Chatarjee maintained that the Punjab population who lived at higher altitudes were less susceptible to cataract.
  • 49. Effects of Ultraviolet radiation Some other research work made out that  Cortical cataracts are in association with UV exposure And as yet no strong positive correlation has been established by researchers as regards the UV exposure and Nuclear Cataracts
  • 50. Effects of Ultraviolet radiation UV and Cataract  In summary, the data demonstrate a correlation between cortical senile cataract and UVB radiation  Andtherefore protection against the radiation may be achieved upon the use of protective glasses
  • 51. Effects of Ultraviolet radiation Retina  Ina normal eye, the retina is shielded from much of the UV radiation by the filtering action of the cornea and the lens  Under ambient conditions, the retinal damage is unlikely
  • 52. Effects of Ultraviolet radiation inthe retinaDuke Elder states, “On the whole, it is probably safe to say that the ultraviolet radiations which might harm the retina do not reach it, and those radiations of this spectral origin which DO reach it have not been shown to do organic or functional harm of any practical importance to this tissue”
  • 53. Effects of Ultraviolet radiation inthe retina When the lens has been removed  The aphakic eye is subjected to UV radiation in the range of 320-380 nm, which had previously been filtered out by the lens.  Inaddition, the amount of visible radiation also increases in the aphakes.  Cystoid macular oedema(CMO) is one of the complications that follow cataract surgery.
  • 54. Effects of Ultraviolet radiation inthe retina CMO:  Accumulation of fluid in the outer plexiform and the inner nuclear layers of the retina with formation of cyst-like changes  These cysts may later on progress to give rise to macular hole
  • 55. Effects of Ultraviolet radiation inthe retina
  • 56. Effects of Ultraviolet radiation Ultraviolet and photosensitisation  Photosensitisation is the enhanced chemical reaction to normally harmless radiation(particularly UVA and visible) that are induced by the presence of a photosensitiser.  The patients taking medications belonging to Quinolone group—Fluroquinolone such as ciprofloxacin, ofloxacin, etc are to be advised on UV exposure  as photosensitisation may occur
  • 57. Effects of Visible radiation Almost all of the radiation is transmitted upto the retina for processing. Not harmful as the structures have evolved to remain immune to the damage However, the long term exposure to visible spectrum has been found to be associated with macular degeneration, damage to the photoreceptors and the pigment epithelium
  • 58. Effects of Visible radiation Solar retinopathy has been found to be associated with damage from long term exposure to visible radiation, to the retina
  • 59. Effects of Infrared radiation Wavelengths longer than 3000 nm do not reach the earth’s surface because  They are absorbed by water and carbondioxide in the atmosphere  Damage from IR radiation covers only from wavelengths 780 nm to 2000 nm Mechanism:  Thermal damage to tissue leading to DENATURATION, unlike the UV radiation that involves photochemical, thermal damage.
  • 60. Effects of Infrared radiation Cornea:  Opacification, debris, haze, exfoliation  Burn, necrotic ulceration  The posterior corneal regions show more damage than the anterior regions  Dueto the cooling effect by the tearfilm to minimise anterior corneal defects Also found to raise the aqueus humour temperature Also was seen an increase in the IOP.
  • 61. Effects of Infrared radiation Iris:  Absorption depends on the pigmentation of the iris itself  It has been found that the iris is more sensitive to the IR  Pupillary miosis, aqueous flare and posterior synechiae  Congestion, depigmentation, and atrophy
  • 62. Effects of Infrared radiation Iris:  Inflammation results due to breakdown of blood- aqueous barrier, which allows leakage of the proteins in the AC and thus the AC flare.
  • 63. Effects of Infrared radiation Lens:  Themorphology of cataracts caused is poorly understood.  Posterior cortical opacity is in strong relation to the IR exposure
  • 64. Effects of Infrared radiation Lens:  Verhoeff and Bell suggested that the outer surface of the cornea was air-cooled and that the anterior capsule of the lens was cooled by the circulation of the aqueous humour  Thus,cataract formed on the posterior surface of the lens because of its elevated temperature  They further postulate that heat interferes with the function of the ciliary body which subsequently interferes with the metabolism of the lens
  • 65. Effects of Infrared radiation Lens:  In acute IR-induced cataracts, anterior subcapsular opacity is common  However, posterior subcapsular opacity is a delayed process of the anterior damage migrating posteriorly
  • 66. Effects of Infrared radiation
  • 67. Effects of Infrared radiation As is already known that the damage occurs via thermal mechanism  Heatingof the tissue above its normal temperature has been linked to an increase in the metabolism of the affected tissue  Therefore, the metabolic acceleration could lead to  Prematureaging as a result of an abnormal accumulation of metabolic by-products
  • 68. Effects of Infrared radiation  However, osmotic involvement has also been suggested in the development of senile cataracts, invoking  an accumulation of water-soluble substances as the means of loss of lenticular transparency
  • 69. Effects of Infrared radiation Retina:  Damage due to the indirect thermal injury to the neural elements of the retina secondary to IR absorption by the RPE.  Injuryoccurs in durations ranging from microseconds to several hours
  • 70. Effects of Infrared radiation Retina:  Two mechanisms have been proposed.  Thermal mechanism(long wavelength)  Due to the elevation of temperature of the irradiated tissue,eg Necrotic burn  Photochemical mechanism(short wavelength)  Due to phototoxicity
  • 71. Effect of Radiation
  • 72. Effect of Radiation
  • 73. Effect of Radiation
  • 74. Effect of Radiation Choroidal melanoma, iris tumours ,retinoblastoma have been linked to radiation, or mutation induced due to radiation that may pass onto new generations.
  • 75. GLARE
  • 76. Glare Is defined as “that condition of vision in which there is discomfort or a reduction in the ability to see significant objects, due to an unsuitable distribution or range of luminances or to extreme contrasts in space”
  • 77. Glare is a catch-all term that usually includes three separate effects:  Disability glare  Discomfort glare  Light adaptation glare  Specular reflection glare, previously thought to be glare when, in fact, it is not glare according to the current definition of glare
  • 78. Glare Disability glare  Due to stray light falling on the retina  Due to scatter from the media opacities  Which may include cataract, corneal dystrophy, translucent iris, iritis albinism, vitreous opacities
  • 79. Glare
  • 80. Glare Disability glare  As shown in the previous picture, light that should have contributed to the brightness of the retinal image is instead scattered to adjacent parts of the retina  This lowers the brightness of the retinal image and increases the brightness of the background, lowering contrast
  • 81. Glare Some calculation…  Assume a simple target with a luminance of 100 cd/m2 on a background with a luminance of 25 cd/m2.  Then this target would have a contrast of  And if disability glare adds a veiling luminance of 10 cd/m2 then
  • 82. Glare Disability glare  Itis the most commonly used clinical measure of glare
  • 83. Glare Discomfort glare  Illuminationin part of the visual field is much greater than the level of illumination to which the eye is adapted  Itis a sensation of irritation and pain from sources of light in the field of view
  • 84. Glare Discomfort glare  Unlikedisability glare, the cause of which is mostly understood, the physiologic basis of discomfort glare is unknown  Because so little is known about the origin and measurement of discomfort glare, there is little international agreement on how it should be specified
  • 85. Glare Discomfort glare  The most common measure of discomfort glare is the border between comfort and discomfort(BCD)  As an example, a person may be shown a range of lights of varying brightness and asked to evaluate each in terms of its discomfort by placing it on the following semantic scale
  • 86. Glare Discomfort glare  It is unnoticeable  It is just noticeably uncomfortable  It is uncomfortable  It is very uncomfortable  It is intolerable
  • 87. Glare Discomfort glare  Headache is one of the so many effects of glare  Nasociliary nerve- driven pathway is involved  Therapid fluctuations in the pupillary diameter would accompany continuous innervation to the CNIII and this causes a continuous relay offerent signals from the iris-ciliary body complex via the nasociliary division.
  • 88. Glare Light adaptation glare  Is the reduction in vision caused by the after image of a glare source producing a central positive scotoma after directly looking at a bright light  Lightadaptation glare can persist even when the source has already been removed from the observer’s sight unlike disability glare  Forms the basis of Macular Function Test>Photostress Test
  • 89. Glare Light adaptation glare Since this glare is due to light adaptation of the photoreceptors  Ithas a negative impact on patients with macular problems
  • 90. Glare Specular reflection glare  AkaVeiling Reflection  When patches of bright light are reflected by smooth, shiny surfaces  Then there occurs a reduction in the quality of vision via the reduction in the contrast Control: use of polaroid lenses
  • 91. References: Donald G Pitts, Robert N Kleinstein, Environmental Vision, Interactions of the Eye, Vision, and the Environment;Alan L Lewis,OD, PhD, Chapter Five:Basic Concepts in Environmental Lightning;Donald G Pitts, OD, PhD, Chapter Six: Ocular Effects of Radiant Energy William J Benjamin, Borish’s Clinical Refraction;David B Elliott, Contrast Sensitivity and Glare Testing
  • 92. References: Jack J Kanski, Brad Bowling, Clinical Ophthalmology A Systematic Approach Troy E Fannin, Theodre Grosvenor, Clinical Optics;Chapter Seven:Absorptive Lenses and Lens Coatings http://en.wikipedia.org/wiki/Glare_%28vision%2 9 http://www.allaboutvision.com/sunglasses/spf.ht m
  • 93. References: http://sdhawan.com/ophthalmology/lens&catara ct.pdf www.nei.nih.gov