[Development and scientific rationale for a universal index for rapid assessment of readability]

The hygienic regulations of academic books, including teachware, for children and adolescents necessitate the performance of special studies to assess their readability by the unified procedure that would suggest a visual response while reading. This study has developed and warranted a universal readability index by the velocity of reading. There are significant regression correlations between the velocity of reading as the readability index and the degree of tiredness, detected by various visual functions. The parameters of accommodation and adaptive properties of the eye are most sensitive to visual load on reading. Reading velocity as an indicator of readability of illogical texts may be used as a rapid method under laboratory and natural conditions to determine the action of various textual loads on the visual system.