A naphthopyran compound represented by the formula (I): wherein: n1, n2, p, q is an integer comprised from 0 to 5 inclusive; m is an integer comprised from 0 to 4 inclusive; R1 and R2 represent a group selected from halogen, —Ra, —OH, —ORa, —SH, —SRa, —NH2, —NRaRa1, —NRbRc, —CO—Ra, and —CO2Ra1, wherein Ra, Ra1, Rb and Rc, are as defined in the description; R3 represents a group selected from halogen, —Ra, —OH, —ORa, —SH, —SRa, —NH2, and —NRaRa1; R4 represents a group selected from halogen, —Ra, —OH, —ORa, —SH, —SRa, —NH2, —NRaRa1, —CO—Ra, and —CO2Ra1; R5 represents a group selected from: halogen, —Ra, —OH, —ORa, —SH, —SRa, —NH2, and —NRaRa1, wherein Ra and Ra1 are as defined hereinbefore, or when q is equal to 2, then two R5 together represent further a group —O—(CH2)q1—O— wherein q1 represents an integer comprised from 1 to 3 inclusive.