The effect may change with time. Because of the potential variation in effect and ability to cope, staff should never presume that being told how a student is impaired tells them what a student can, or cannot do, or what they may be capable of. Always ask, tactfully, what effect an impairment has and how the individual copes. Remember that visual status may change and so it may be necessary to revise the position from time to time. The terms 'blind' and 'partially sighted', when used in a legalistic sense, are based upon the ability to read letters on a Snellen chart and relate to the right to be registered as either blind or partially sighted.
Registration then gives access to potential benefits.
In view of the fact that many people who could be on the registers are not, and that many who are registered as 'blind' do have usable residual vision, the two terms do not really help in either understanding the position of an individual or planning curriculum, or teaching strategy. What is important to remember is that just because a person is categorised as 'blind' or has a white cane or guide dog, does not necessarily mean that they have no vision at all. Partial sight can have additional complications, in that the degree of sight may vary in the same person with environmental conditions - a person with restricted field may use a cane for safety but read with relative ease, or somebody who has few problems in dull light may have considerable difficulty in bright light.