Infrared Radiation Cataract

Infrared radiation cataract is lens opacity caused by repeated or prolonged exposure to infrared radiation (heat radiation) at work. It affects workers near furnaces, molten metal and glass, and is a thermal injury to the lens.

Exposure. Steel, foundry and forging workers, furnace and kiln operators, blacksmiths, glassworkers, and some welders. Infrared A (760 to 1400 nm) penetrates to the lens.

Epidemiology. Reported after about 10 to 15 years of heavy exposure in older studies. Dose thresholds are uncertain. Occupational limits for long exposure are about 10 mW/cm2 (100 W/m2) at the lens.

Appearance. Posterior subcapsular or cortical opacity, sometimes with anterior capsule change. The picture is not specific.

Aggravating factors. Combined ultraviolet exposure, age, smoking, diabetes and steroid use.

Pathophysiology.

Infrared radiation is absorbed by iris pigment and ocular tissue, raising the temperature of the aqueous humour and lens by several degrees. Direct infrared absorption adds to this.

Heat denatures lens crystallins and damages epithelial cells, and repeated injury accumulates because the lens does not renew.

• Gradual glare, blurred vision and reduced contrast, often asymmetrical.
• Dry or irritated eyes from heat.
• Often asymptomatic early.

Red flags.

• Sudden visual loss, eye pain or a red eye.

• Work history: heat source, distance, hours, years, eyewear and ultraviolet exposure.
• Slit lamp examination with dilated pupil; visual acuity and glare testing; intraocular pressure.
• Exclude other causes (age, steroids, diabetes, uveitis, trauma).
• Measure radiant exposure in the workplace when possible.

Differential diagnosis. Age related cataract, steroid induced cataract, diabetic cataract, ionising radiation cataract, uveitic cataract, traumatic cataract, glassblower's cataract.

• Control exposure: shielding of heat sources, remote handling, reduced exposure time and cooling of surfaces.
• Eye protection: infrared absorbing filter lenses with side shields, or full face shields, of shade suited to the source; combine with ultraviolet filtering.
• Mild opacity: observation, updated glasses and glare management.
• Cataract surgery by phacoemulsification with intraocular lens implantation when function limits work or daily tasks; postoperative care by the operating surgeon.
• No drug treatment prevents or reverses the opacity.

Monitoring. Slit lamp examination every 1 to 2 years in exposed workers, and yearly when opacity is present.

Referral and escalation. Ophthalmology for any lens opacity, visual symptoms or surgery planning; occupational physician for workplace exposure assessment and compensation where required.