TOPIC 5: ILLUMINATION AND GLARE

Question 1

Why do elderly need brighter illumination?

Answer 1

Ageing results in reduced retinal illuminance (less light getting to the retina) due to:
-Senile miosis
-Media opacity - 20-year old has 3x retinal illuminance of 60-year old
-Loss of neural function (age-related decline in the number of ganglion cells and axons

Question 2

What are the 2 types of glare and how to resolve them?

Answer 2

Discomfort glare - this causes visual discomfort but doesn’t impact vision (ability to see detail).

Disability glare - impairs the ability to see details. May or may not cause visual discomfort. This is associated with excessive light entering the eye
e.g. sun shining directly into the eye, headlights from oncoming cars, reflected, light from snow/water bodies/digital device screen

Solutions to glare:
-Remove the glare source
Position TVs and laptops away from windows

-Matte screen protector

-Use tinted lenses or polarising filters

Question 3

Is blue light protection necessary?

Answer 3

There are cells in the retina (intrinsically photosensitive retinal ganglion cells -ipRGC) that do
not contribute to vision like regular photoreceptors. These cells are sensitive to wavelengths
between 470 - 480nm (visible spectrum blue) and use the blue light to control pupil size,
regulate the circadian rhythm and regulate the secretion of melatonin hormone into the
bloodstream to aect the sleep/wake cycle.
Harmful blue light (<450nm wavelengths) has more energy than the ‘beneficial’ blue light.
With higher energy, it may cause oxidative stress to the retina. Some claims of the harmful
eects of blue light include
it can cause retinal cell damage (and lead to AMD).
it can cause visual discomfort or fatigue