Visual Task Analysis and Spec Lens selection

1. During sight test- H&S, during refraction, at end

2. During CL- H&S, at end

3. Dispensing

Contrast Sensitivity Func

• darker tint= cut too much light in dull conditions

• indoors =1/10th light levels/ 30x lower than outdoor on cloudy day

• higher light levels needed for low contrast tasks

• Glare = different -ve effects of light sources on our vision

  2 Types:

  • Veiling glare

  • Scotomatic glare

• ** GLARE NOT REFLECTION - anti-reflection coatings reduce reflections, not glare

• Fire service

• Electricians

• Textile workers

• Armed forces

• train Drivers

• Pilots

• lifeboat crew

• moving targets closer increases angular subtense

Disads:

• increased accom demand is an issue if not enough accom reserve

• increase convergence demand is an issue if remote NPC

• books, newspapers, tablets and phones held below midline, so near add in lower part of specs

• desktops near midline intermed distance, , so correction at middle of lens

• laptops closer than desktops and lower angle of gaze

Natural light sources- UV ( enhanced with snow, sand and water)and IR( olten metals, glass, welding)

Prolonged viweing of any light source = damage

• any strong acid/alkali - cooking, cleaning, DIY

• sport balls- squash, garden,

  • ASK WHAT PX ACUALLY DO. eg DR is not enough.