Here we have another error in the 1841 British edition, the loss of the determiner their before sight. The 1920 LDS edition restored the original their to the LDS text. Parallel usage earlier in the text supports the expression “the blind to receive their sight”:
Remarkably, except for the verb in the summarizing statement at the end, we have the same sequence of verbs phrases: “heal the sick / raise the dead / cause the lame to walk / the blind to receive their sight / the deaf to hear”. Thus the use of their in 4 Nephi 1:5 is firm.
Summary: Maintain the use of their before sight in 4 Nephi 1:5, the earliest reading; the parallel language in Mosiah 3:5 provides strong support for the expression “the blind to receive their sight”.