Here's how it works.
"Eyes" (עיניים) in Hebrew is a "dual" or "pair" word (צורה זוגי)1 like "ears" (אוזניים) and other parts of the body that generally come in pairs. These dual words are usually feminine gender. Exception to pairs objects are "teeth" (שיניים) and finger or toe nails (ציפורניים) that have a dual form but do not generally come in pairs.
These dual words have two forms: singular, pair. For these words the pair form also serves as the plural (many) form2. The pair form ends with "ayim" (ים pronounced as יים) which is not to be confused with the regular masculine plural form "eem" (ים) used in non-dual words of masculine gender.
When used in singular or plural compound possessive forms these pair words behave like any other word that does or does not have a pair form, and there is no indication in the compound that these words also have a pair form - it gets contracted out. So for "eye" we have:
- My eye עיני, short for העין שלי
- My eyes עיניי, short for העיניים שלי
- Your eye (masc.) עינך, and in verse final form עיניך, short for העין שלך
- Your eyes (masc.) עיניך, short for העיניים שלך
Note that without diacritics or context we have only the yod (י) between the nun (נ) and the final caf (ך) to distinguish between the singular and the plural. In some cases in the MT we don't even have this yod and we need to rely on the context to disambiguate.
Furthermore, the verse final form of the second person singular possessive singular is the same as the verse medial form of the second person singular possessive plural.
So, in Psalm 17:2, עיניך is simply second person possessive of plural objects (your eyes). The following verb, תחזינה which is feminine plural future isn't even needed to make the disambiguation.
- Yes, the term in Hebrew is "צורה זוגי", not "צורה זוגית"!