Rods & cones

Looks like

Microscopic light-sensing cells lining the back of the retina: around 120 million rods and 6 million cones in each eye.

What it does

Rods see in dim light; cones see colour and detail in daylight.

Keeping it well

Inherited diseases such as retinitis pigmentosa cause night blindness first; vitamin A deficiency does the same. Colour blindness is a cone variant.

Related conditions

• Age-related macular degeneration
• Blepharitis & styes
• Cataract
• Colour blindness
• Conjunctivitis
• Diabetic retinopathy
• Eye melanoma (uveal melanoma)
• Hyperthyroidism & Graves' disease
• Jet lag
• Keratitis (corneal infection and ulcer)
• Keratoconus
• Onchocerciasis (river blindness)
• Presbyopia
• Retinal artery occlusion (eye stroke)
• Retinal detachment
• Retinal vein occlusion
• Retinitis pigmentosa
• Retinoblastoma
• Retinopathy of prematurity
• Seasonal affective disorder
• Short and long sight (refractive error)
• Sjögren's disease
• Squint & lazy eye
• Toxoplasmosis & CMV
• Uveitis & iritis