Light and Laser Injury

Dr . Hilal Mohamed Hilal

Light and Laser InjuryStructural damage to the retinaproduced by any type of light source.

Mechanism of damage

Photochemical &Thermal retinal damage possible

Potential causes1 solar eclipse

2 welding arc 3 lightning ,

4 ophthalmic instruments, 5 Laser

LIGHT INTERACTION WITH THE RETINAThe eye primarily perceives radiation in the optical spectrum, comprised of the visible (400–760 nm) Ultraviolet (UV; 200–400 nm), andInfrared (IR; > 760 nm).

Radiation in this region can be produced by the sun, ophthalmic instruments, and lasers

Associated features

■Delayed appearance of the lesion after the injury by hours to days

■Variable recovery of vision

■Severity of damage proportional to increased duration and intensity of exposure

Mechanisms to reduce retinal light exposure.

The cornea absorbs most UV-B (280–315 nm) andUV-C (< 280 nm), as well as some IR radiation, and reflects up to 60%of incident light that is not perpendicular to its surface.

The lens absorbs most UV-A (315–400 nm) and visible blue wavelengths .

Retinal xanthophyl absorption of near-UV and blue light to protect the photoreceptors,

Choroidal circulation control temperatureIntracellular moleculardetoxification of free radicals and toxic molecules.

Physiologicalprotective mechanisms include the eyebrow ridge, squint and blink reflexes, the aversion response, and pupillary miosis .

Light damage to the retina may occur when

Protective mechanisms are impaired

.Deliberate gazing at a light sourceمتعمد

Young patients may be at increased risk due to efficient light transmission through ocular media.

PHOTIC RETINOPATHYDamage disorder of RPE and photoreceptorTemporally Permanent;

Recovery noted in solar retinopathy welding arc maculopathy , and operating microscope phototoxicity.

Mild sever

Retinal injury and the visual recovery depend on multiple factorsThe location and area exposded , the duration, intensity, and spectrum of the light source, and host susceptibility factors, such as age, nutritional status, ocular pigmentation, core temperature, clarity of ocular media, and pre-existing retinal disease.Emmetropes and hyperopes may be at increased risk caused by effective focusing of light on the retina. Systemic photosensitizing agents, such as tetracycline, hematoporphyrins, and psoralen, may predispose to photochemical damage.

Solar (eclipse)Retinopathy Religious sun gazing, solar eclipse,,sunbathing,

psychiatric disorders,Solar radiation damages the retina through photochemical effects ,

Symptoms develop 1 to 4 hours by decreased vision. usually improves within 6 monthsA small yellow spot with a gray margin may be noted in the foveolar or parafoveolar area FA reveal transmission defects due to RPE irregularity OCT, demonstrates disrupted reflectivity in the outer retina, or fragmentation of the highly reflective layer corresponding to the junction between the IS OS Oral corticosteroids treat acute lesions ,

Welding Arc Exposure اللحام

keratitis due to cornea UV absorption.A yellow edematous lesion occurs acutely in the fovea which is replaced over time by an RPE irregularity or a pseudomacular hole.Vision usually improves with time

LightningالبرقRetinopathyLesions described include macular edema,macular hole, cyst, or a solar retinopathy-like picture, cataract, retinal detachment, retinal artery occlusionsVisual recovery often occurs over time, even with severe maculopathy.High-dose intravenous methylprednisolone treatment may play a role in recovery of vision

Retinal Phototoxicity fromOphthalmic Instruments

Retinal injury has been described following exposure to light produced by the operating microscop

7% of patients having cataract operations demonstratedoperating microscope phototoxicityThe mechanism ofintraoperative phototoxicity is photochemical but may be thermallyafter 60 minutes ofoperating microscope light exposure, despite the presence of UV and IRfilters,

The lesion is yellow roundFA of the acute lesion reveals fluorescein leakage at the level of the RPE which may simulate the appearance of choroidal neovascularization .

Subsequent weeks, the yellow lesion fades and is replaced by permanent areas of RPE clumping and atrophyFA blocking and transmission defects, respectively Long-term squealRetinal surface wrinkling. - Choroidal neovascularization

Measures to avoid this complication

1-Minimizing length of surgery2-Minimizing light output ,

3-Using filters,4-Rotation of the globe by a superior rectus suture ,

5-Maximizing light pipe distance from the retina 6-using eccentric and variable endoillumination

techniques7-Placement of an air bubble corneal cover

9-Retinal examinations be performed withthe minimal illumination required

LIGHT EXPOSURE AND AGE-RELATEDMACULAR DEGENERATION

An association between long-term solar exposure and AMD was consideredwhen AMD was found to be less common in patients who have nuclear cataract Solar observation acutely damages the RPE and produces RPE pigmentary irregularities, which are similar in appearance to those in AMDThe use of hats and sunglasses to filter UV was inversely associated with the prevalence of soft, indistinct drusen.

LASER INJURYLaser applications in industrial, military, and laboratory situationsaccount for accidental retinal injury.

-Subtle lesion -Macular hole-Hemorrhage -Foveal cyst–

-Yellow RPE irregularities-Epiretinal membrane

-Macular hole - Gliosis. Recovery of vision is variable and is related to the extent and location of the initial injury.Corticosteroids have been used to treat laser-induced and laser pointerretinal injuries.

Foveal cyst

In the ophthalmology setting

Lasers operators slit lamp or operating microscope contain filters to protect the operator Decreased color discriminatio has been noted in ophthalmologists who used the argon blue-green.

Persons in the laser areaare at risk from laser light scattered from optical interfaces such as contact lenses and mirrors

The risk is related to their distance from the laser, Protective goggles should be worn .

LASER POINTERS

Laser pointers are portable low energy devices that emit a very narrow coherent low-powered laser beam of visible light .

These devices are used to illuminate an item of interest with a spot of brightly colored light

Laser used by ophthalmologists for retinal therapy generate between 5 and 500mW The FDA specifies that laser pointers between 1–5 mW

LASER POINTERS Cont.There is misuse of these handheld lasers .

.The mechanism of injury is thermal chorioretinal damage

There is visual abnormalities and scotom. FA demonesterat perimacular hyperfluorescence correspond to RPE window defect

Visual acuity improved to 20/20 and visual field returned to normal within8 weeks, but a subjective decrease in brightness and foveal RPE

These pointers that exceed recommended standards may produce permanent retinal injury and visual impairment with resultant photoreceptor damage

COMPLICATIONS OF THERAPEUTIC RETINAL LASER PHOTOCOGULATION

Inadvertent photocoagulation of the fovea, cornea, iris, or lens can be minimized with use of careful techniqueand appropriate laser settings

Cont. COMPLICATIONS OF THERAPEUTIC RETINAL LASER PHOTOCOGULATION

panretinal photocoagulationspread over multiple sessions

Decreases in laser intensity and duration, avoid smaller spot sizes (50 μm),

with the use of the krypton red laser

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