Radiation Cataract

Radiation cataract is lens opacity caused by ionising radiation, typically starting as posterior subcapsular opacity. It is a deterministic effect, and the lens is more radiosensitive than once believed, with opacity reported at doses of about 0.5 Gy or less.

Exposure. Interventional cardiologists, radiologists and their staff, radiographers, nuclear workers, radiotherapy patients with orbital or head fields, aircrew and astronauts, and accident survivors.

Latency. Months to decades, shorter with higher dose. Cataract surgery is usually needed in time.

Dose limit. The occupational limit for the lens is about 20 mSv/year averaged over 5 years, with no single year over 50 mSv. Annual dose to the eyes in interventional workers can exceed this without shielding.

Appearance. Posterior subcapsular opacity is typical, but cortical changes also occur. The appearance is not specific.

Pathophysiology.

Radiation damages lens epithelial cells at the germinative zone. Abnormal fibre differentiation and migration deposit aberrant cells at the posterior pole, producing opacity.

Oxidative stress and DNA damage contribute, and lens cells have limited ability to remove damaged cells.

• Glare, blurred vision especially in bright light, and reduced reading vision as the opacity forms near the visual axis.
• Monocular diplopia and fluctuating acuity.
• Often asymptomatic and found at screening.

Red flags.

• Sudden visual loss, pain or flashes (retinal detachment, glaucoma).

• Exposure history: dose records, personal dosimeter and eye dose, use of lead glasses, workload.
• Slit lamp examination with dilated pupils: posterior subcapsular opacity, with grading of opacity.
• Visual acuity and glare testing.
• Exclude other causes: age, steroid use, diabetes, uveitis, trauma and myopia.
• Baseline and periodic lens examination in exposed workers.

Differential diagnosis. Age related cataract, steroid induced cataract, diabetic cataract, uveitic cataract, traumatic cataract, myopic cataract, infrared cataract.

• Prevention: ceiling suspended shields, leaded glasses with side shields (can reduce eye dose by about 90% when correctly worn), distance, and reduced beam time; use eye level dosimetry.
• Reduce further exposure and review work practices.
• Observation with updated glasses and bright light management for mild opacity.
• Cataract surgery by phacoemulsification with intraocular lens implantation when visual function falls under the patient's needs. Postoperative drops and monitoring by ophthalmology.
• Long term review for retinal and glaucoma disease as usual.

Monitoring. Slit lamp examination every 1 to 2 years in exposed workers over the first years of exposure, and yearly once an opacity is present.

Referral and escalation. Ophthalmology for any lens opacity, visual symptoms or surgery planning; occupational physician for dose review and fitness assessment; notification and compensation where required.