For weekly absorbing media such as water, the relationship between the intensity of the incident and detected optical beams is given by Beer-Lambert law:I(??)=I(??o)exp(???2??a(??)d) (1)Here ??a(??) is the wavelength dependent water absorption coefficient [Fig. 1(a)] and the factor of 2 in the exponent accounts for the double pass of the optical beam through the eye / water cell.