Nanadassana-visuddhi

Ñānadassana-visuddhi: 'purification of knowledge and vision', is the last of the 7 purifications and a name for path-knowledge maggañāna i.e. the penetrating realization of the path of Stream-winning, Once-returning, Non-returning or Arahantship. Vis.M XXII furnishes a detailed explanation of it see: visuddhi.
In A. IV, 41 ñānadassana apparently means the divine eye dibbacakkhu abhiññā being produced through concentrating the mind on light.
==References==
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952. 
Category:Pali terms