This study looked at the relationship between myopia and mercury from dental fillings. Hair mercury levels were found to be significantly higher in 25 nonmyopic children compared to 25 myopic children. The researchers hypothesized that if mercury was leaching from the silver dental fillings, then subjects without dental fillings would have a higher degree of myopia and poorer acuity. A study comparing 51 subjects without amalgams to 50 subjects with amalgams confirmed this hypothesis. The non-amalgam group had a 59 percent higher degree of myopia and significantly poorer acuity. Two additional studies also found that subjects without amalgams had a higher degree of myopia. All three studies found that significantly more subjects without amalgams wore glasses for distance when compared to subjects with amalgams. The authors hypothesize that mercury may increase the collagen fibrils of the sclera and thereby retard the progression of myopia.