Hemeralopia

Also Day Blindness; A condition where it is difficult to see clearly in bright light (e.g. daylight). Hemeralopia is generally viewed as a less severe form of photophobia, but the two are sometimes used synonymously. There are several causes of hemeralopia, but are mostly concerned with the misfunction of Cone photoreceptors, such as:

• Cone Dystrophy – a progressive disease caused by the death of cone cells
• Achromatopsia (incomplete) – a congenital disease caused by several different genetic mutations

The opposite problem – the inability to see in dim light – is known as Nyctalopia (Night Blindness) and is a symptom of Rod Dystrophy, amongst other diseases.