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Flash blindness is an either temporary or permanent visual impairment during and following exposure of a varying length of time to a light flash of extremely high intensity, such as a nuclear explosion, flash photograph, lightning strike, or extremely bright light, i.e. a searchlight, laser pointer, landing lights or ultraviolet light. [1]
As of 2015, there were 940 million people with some degree of vision loss. [5] 246 million had low vision and 39 million were blind. [1] The majority of people with poor vision are in the developing world and are over the age of 50 years. [1] Rates of visual impairment have decreased since the 1990s. [1]
Childhood blindness is an important contribution to the national prevalence of the disability of blindness. [3] Blindness in children can be defined as a visual acuity of <3/60 in the eye with better vision of a child under 16 years of age. [ 4 ]
The various cone cells are maximally sensitive to either short wavelengths (blue light), medium wavelengths (green light), or long wavelengths (red light). Rod photoreceptors only contain one type of photopigment, rhodopsin, which has a peak sensitivity at a wavelength of approximately 500 nanometers which corresponds to blue-green light. [ 6 ]
Nyctalopia (/ ˌ n ɪ k t ə ˈ l oʊ p i ə /; from Ancient Greek νύκτ-(núkt-) 'night' ἀλαός (alaós) 'blind, invisible' and ὄψ (óps) 'eye'), [1] also called night blindness, is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases.
Solar retinopathy or "eclipse blindness" is untreatable and can catch you by surprise. Here's what to look for.
A patient with cortical blindness has no vision but the response of his/her pupil to light is intact (as the reflex does not involve the cortex). Therefore, one diagnostic test for cortical blindness is to first objectively verify the optic nerves and the non-cortical functions of the eyes are functioning normally.
However, current literature has various definitions of both terms. Childhood blindness encompasses multiple diseases and conditions present in ages up to 16 years old, which can result in permanent blindness or severe visual impairment over time. [2] Congenital blindness is a hereditary disease and can be treated by gene therapy.