Medical filters are dyed according to the transmission curve
MEDICAL FILTER LENSES caan be used for

• Age-related macular degeneration
• Albinism
• Diabetic retinopathy
• Retinitis pigmentosa
• Achromatopsia (colour blindness) Migraines
• Cone-rod-dystrophy
• Iris coloboma
• UV protection for pseudophakia and aphakia
• Photochemotherapy,

Medical filter lenses absorb short-wave blue light components more strongly than conventional sun protection lenses or contrast-enhancing lenses. Medical filters lenses can restrict peripheral vision due to the (almost) complete absorption of short-wave blue and violet light – which is extremely important in sports.

The short-wave violet and blue light causes scattering in the eye, which leads to glare and a reduction in acuteness of vision.
The contrast is increased by the difference between the strongly and less strongly exposed receptors.

Visual symptoms such as blurred vision, visual aura and photophobia can occur during migraine attacks, but not necessarily always.

Less than half of current migraine sufferers have been formally diagnosed, and about one-third are thought to receive appropriate treatment with prescription medications.

Colourimeter research data determines certain specific tints can help migraine sufferers whose migraines are triggered by pattern glare.

BPI manufactures the pink FL-41 dye is a mixture of colours that blocks the blue-green wavelengths.
BPI is the world’s largest manufacturer of optical tints.
Though the efficacy of Blue Light Blockers can vary, environmental exposure to blue light, including those from digital screen technology, does not cause significant damage to eyesight. Therefore, filtering out the blue light from screens is not essential but can be helpful.

The FL-41 tints in 25, 50 and 75% transmissions. (The % related to how dark the tint saturation is.) are sometimes prescribed for patients with migraine or brain trauma. 

Research shows that there is not one specific colour to treat migraine (or any condition) as peoples vision and brains react differently and need to be treated individually. This is the reason the Colorimeter has 110,000 different colour combinations. 
Pattern glare tests involve tints (that later can be prescribed) often but not always blue or yellow to reduce nausea that can arise from stripe patterns for some people by reducing or changing the contrast between black and white.

The theory is some people have a hyperactivity imbalance between their central and peripheral vision for light, flicker and specific spatial frequencies in stripes and patterns and can make reading difficult.

Optometrists do not treat “dyslexia” or even learning difficulties, but learning-related vision problems, and in the above cases treat people with pattern glare with tints when it affects reading.

Migraine is a complex and the most common neurological condition and classified by the World Health Organisation as the 7th most disabling disease worldwide, the 4th for women. It is three times more common in women than it is in men and is usually inherited. It is a very individual condition. Some people experience only an odd attack, while others suffer them regularly.