Page 101 - Pharmaceutics IV (02-06-01305)

Ophthalmic DD: Introduction

Anatomy & physiology

Nasolacrimal system: tear/lacrimal fluid
Tear fluid osmolarity:
• The concentration of salts in lacrimal fluids determines its osmolality.
• Tear fluid osmolarity has an average value

of 290 mOsm (0.9% NaCl).
• Higher than normal osmolality in the tear

fluid is often seen in patients with dry eye
syndrome (hypotonic eye drops!).

195

Ophthalmic DD: Introduction

Anatomy & physiology

Nasolacrimal system: tear/lacrimal fluid
Tear fluid viscosity:
• It is primarily controlled by the higher molecular weight proteins

dissolved in the lacrimal fluid.
• Tears are non-Newtonian fluids whose coefficient of viscosity is

shear dependent (shear-thinning).

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Salma E. EL-Habashy