How to protect from sunlight?

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HOW TO PROTECT PATIENTS FROM

Mashhad University Of Medical SciencesOPTOMETRY CENTER

HARMFUL SUNLIGHT ?

HOSSEIN ALIMIRZAIE

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• We are largely cocerned with refraction of light in its design and use of corrective lenses

• Another aspect in prescribing and dispensing is

(absorption) of light

SELECTIVE FILTRATION

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• While fashion sunglasses fall into this category lenses that filter sunlight for eye protection fall into this category also

• As eye care professionals we are in an excellent position today to understand and to utilize these characteristics and advise our patients about the proper steps to reduce the risk of cataracts and age related macular degeneration (AMD)


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• Yet there is much confusion about how sunlight contribute to these two major eye diseases

• In this presentation we describe UV filtration with the recent concept of HEV light filtration


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INTRODUCTION:

Electromagnetic Radiation:

Visible Light(380-780nm)

UltraViolet Radiation(190-380nm)

……..

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UVR:

UVA(315-380nm)

UVB(280-315nm)

UVC (190-280nm)

Lowest energy level

Harmful, Destructive

Most Dangerous

Blocked by ozon layer

UVC lamps are used to kill bacteria in water


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Sources of UVR:

Incandescent and flourescent lamps

Welding arcs

Laser

Sun


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UV reaches the eye :

Directly

Indirectly

Sunlight reflected off the surface of water ,sand and snow reflects UV radiation to the eyes


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Cloudy days arenot safe from UV

Up to %80 of the UV is still present in the overcast days

Indoor workers receive %3 of the total ambient UVR

Outdoor workers receive %10 of the total ambient UVR


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Cornea (Epithelum)absorbs UVC and UVB (peak absorbtion at 270 nm)

Lens absorbs UVB (295-315nm)

with age it include UVA + some visible light

Vitreous & Aquous have no role in blocking UV


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Exposure to both UVA & UVB causes some ocular diseases:

Basal cell carcinomaSquamos cell carcinoma

PingueculaPterygiumKeratitis Snowblindness & welders flash

Solar retinopathyMacular edema

Skin cancer

Cataract

Wrinkling of the skin surounding the eyes AMD

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• The effects of UV radiation are cumulative and likelihood of contracting an eye maladi related to overexposure increases with age


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High Energy Visible Light (HEV)

HEV Violet – Blue(380-530nm)

Can cause damage to the eyes

Over exposure to HEV blue light may increase the risk of devloping age-

related macular degenration (ARMD)

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AMD

• AMD Leading cause of blindness over age 50

1 in 6 acquire AMD at 55

1 in 3 acquire AMD at 75

HEV causes photochemical damage to macula

Those who are at greater risk:

Those who spend extended time outside:

Drivers

Salesperson

Construction workers

Police

Farmers

Sports fan

laborers

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• Those around beach and fresh snow (reflects %88 of the stroken light)

• Those who live near equator

• Those who live in altitude


• Those who wear contact lenses ,soft lenses can transmit up to %50more UV light to the eye

• UV radiation increases %5every 1000 feet

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• Those who receive certain medication which increase absorbtion of UV radiation like tetracycline , oral cotraceptive . Retinoids and phenothiazines

• Children are at heightened risk • Greater amount of UV enters childerns eyes due to

clearer corneas and lenses


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• Eye protection:

• Most effective solution


Altering behaviour and avoiding the situations where

the risk is greater

The human eye is protected from UVR by several factors

The brows , nose.eyelids and cheeks act as barriers

A wide- brimmed hat or visor could reduce the amount of light reaches the eye by up to 30%

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Melanin

• Hair &skin color

• In the eye:Iris color + RPE

Melanin effects vision performance by reducing glare

Melanin reduces HEV portion of light particularly

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Melanin absorbs more UV than HEV and mor blue than green

Melanin provides vision protection by functioning as an antioxidant and by

selective filtration of light

Melanin along vitamin E and vitaminC serve as antioxidan and neutralize free radicals which

could lead to AMD


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• Melanin absorbs %90 of the light coming to the back of the eye preventing glare

Age = Melanin

About %15 of our original melanin is lost in the eye by the age 40, and %25 by 50


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• Syntethic melanin has been incorporated into sunwear to mimic the UV and HEV absorbtion achieved by the eye

• Melanin sun lenses eliminates all of the UV and then reduce much of the HEV violet and blue light


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• Melanin glasses with higher EPF values transmit less high energy visible light and provide more protection to the retina

• EPF= Eye Protection Factor


First proposed by DR.Eisner in 1993 provides a way to rate sun lenses for their protection against macular degeneration

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Melanin:

• Golden brown color selectively blocks the highest amounts of violet and blue light (termed high-energy visible light). Blocking high-energy light is believed to reduce the risk of macular degeneration. Melanin provides high contrast with true color perception for golf and low vision. Recommended for sports, driving and everyday situations

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• Sunglasses are one of our best lines of defense against damaging radiation from sunlight

• Well-designed , well-fitted sunglasses are a must for anyone going out of doors during day light hours

SUNGLASSES

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• Wellfitted glasses blocks %75 to %90 visible light , %100 UV and a significantly reduce HEV

• Quality sunglases must be free of distortion and imperfection

• Polarized lenses serve to reflect incoming horoizontal light and UV radiation


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• Materials like polycarbonate and high index lenses block UVB up to 380 nm and all UVA

• Photochromic lenses by companies such as Transitions and corning offer 100%UV protection

A clear UV absorbing coating can be applied to ophthalmic lenses to increase the range of protection


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• Donot fooled by the color or shade of the lenses

• A dark lens without appropiate UV protection will only welcoming the damaging radiation through like a open door


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• The type of frame is also an important consideration when choosing sun protection

• Wrap-around sunglasses arenot just fashion

• They are much better than conventional sunglasses


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• We neednot look straight into the sun to be at risk

• A significant amount of radiation comes to the eye via reflected light

• Too small or ill-fitted glasses will allow a significant amount of UV & HEV light into the eyes from periphery


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How to protect from sunlight?

Health & Medicine

Transcript of How to protect from sunlight?