In this theoretical paper hypothetical situations and instruments were used to form, analyse and derieve an expression with the objective of filling loopholes in einstein’s theory of time dilation [1,2,3,4,10,12]. Time dilation as presented by albert einstein in 1905 is one of the most experimented and reviewed topic. time dilation states that time slows down in a moving object which is given by. ᵟ????’ = ᵟ???? √1 − ????2 ????2 Where: ᵟt’=dilated time elapsed v = speed of moving object ᵟt = actual time elapsed c = speed of light in vacuum The explanation and expression of time dilation works only when vacuum is the medium of object propagation. but, when a medium other than vacuum is present, then this equation falls short of an important factor that is, optical density[8,9]. My research paper here, presents an expression to measure time dilation considering this missing factor. light beam clocks[5,6,7] and the concept of closed and bounded systems have been used as a link connecting optical density to the original theory of time dilation. the new derivation has a potential to reduce errors in measurements in calculations which use the formula for time dilation. I