Retinal damage is not always obvious. In general damage caused by visible lasers will be noticeable because the damage will have occurred around the fovea, the main focal point when someone is intentionally focusing on an object. If, however, the angle of incidence is high, damage may occur around the periphery of the fovea and would generally only be noticeable during dim conditions or during the intentional use of the peripheral vision.
As mentioned above temporary blindness is a result of bleaching where the retina, in an attempt to recreate the brightness of the light to the brain, dumps its entire complement of neurotransmitter pigments.
Permanent damage occurs when cells are lysed due to focused laser light. The light is absorbed by the cell membrane and ruptures. This occurs at any given point during the exposure. For pulsed operation the damage is generally limited. For CW operation the focused beam can extend across the retina depending on the actions of the victim. Reflexes tend to minimize the damage.
The results of such damage are spots in the visual field that are dark. Far infrared lasers such as CO2 are much less forgiving regarding eye damage. Because 10600 nm is not focused by the lens and cornea the damage occurs on the surface of the eye generally ablating the cornea and lens leaving permanent damage. The amount of damage is also complicated by the fact that CO2 lasers are generally much more powerful than visible lasers (at least for hobbiests). Cataract surgery and corneal transplants have been successful in restoring vision to some damaged eyes.
Moral of the story. Wear your eye protection.
