Tear height is a hidden attribute that determines how far above the ground tears travel. A greater tear height effectively increases range, and a high enough tear height (around 3) can allow tears to fly over obstacles without spectral tears.
+2.25 range up. +1.5 tear height. Isaac's tears travel through walls and appear out of the opposite wall. Isaac's tears also travel over rocks and objects.
Randomly while firing tears, Isaac will stop firing and turn red, where he will charge and release a lot of 'tears' in one go. In the burst of tears is a kidney stone which deals a lot of damage.
Isaac will now fire tears automatically directed at a red target on the ground which is controlled by the player. This allows for a full 360-degree tear firing radius. It can be overridden by other tear modifiers such as Mom's Knife or Brimstone.
Boosts one of Isaac's stats depending on the color of the aura around him. The aura disappears upon taking damage and reappears with a random color upon entering a new room. Red boosts damage, blue boosts tears, yellow boosts speed, and orange boosts range.
In co-op, Long Baby will occasionally briefly increase range, shot speed, and tear height. Dark Baby will occasionally briefly increase all stats, including tear height.
Azazel starts with -1 tear height, though the stat does not affect his short-range Brimstone.
This knockback comes from Tears, most notably Isaac's. The knockback force is determined by the speed and direction of the tear, which itself is determined by Isaac's movement and stats, for example Ring Worm does not increase knockback stat but does affect knockback as the tear's speed hits extremes of very fast and very slow, hitting enemies with the fastest moment of its arc applies significant knockback. (Needs research and confirmation)
Directional knockback affects most enemies, including bosses (except for stationary ones like Pin or Round Worm). Items (both trinkets and pickups) cannot be moved by tears, except for bombs placed by Isaac.
Piercing shots from items like Sagittarius or Cupid's Arrow will remove the natural knockback from tears, but direct boosts still apply. Flat Worm increases only natural knockback and is thus nullified.
Knockback from tears provides minor crowd control for homing enemies like flies or Gapers, increasing the time it takes them to reach Isaac.
Be wary of the natural knockback from tears when trying to dodge charging enemies (like the smaller twin of Gemini, Gurglings, and Leeches): The tears can push them off-track and towards the direction you are planning to escape to.
This knockback is a little shockwave that's emitted at a certain radius in all directions, most prominently from explosives, like Bombs. Certain farts also create a (non-harmful) knockback. Some enemies, like the Fatty, can fart, and Isaac can also do so with the Butter Bean.
Pickups (including chests) are affected by circular knockback; items, however, are not.
A familiar that follows Isaac and blocks tears. If a tear hits Farting Baby, there is a high chance for it to fart, which will either knockback, poison, or charm all nearby enemies.
Continuum
Compound Fracture
Ring Worm does not increase knockback stat but does affect knockback as the tear's speed hits extremes of very fast and very slow, hitting enemies with the fastest moment of its arc applies significant knockback. (Needs research and confirmation)
Sagittarius or 
Cupid's Arrow will remove the natural knockback from tears, but direct boosts still apply. 
Flat Worm increases only natural knockback and is thus nullified.
The Binding of Isaac: Rebirth 
Achievements
Attributes
Bosses
Cards and Runes
Challenges
Chapters
Characters
Co-op
Items
Item pools
Monsters
Objects
Pickups
Pills
Rooms
Seeds
Transformations
Trinkets
