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Related Concept Videos

Ophthalmic Drug Delivery Systems01:23

Ophthalmic Drug Delivery Systems

Ophthalmic drug delivery faces major limitations due to poor absorption across the corneal membrane. This process is primarily driven by diffusion and is influenced by two main factors: the physicochemical properties of the drug and tear drainage. Most ophthalmic drugs, such as pilocarpine, epinephrine, atropine, and local anesthetics, are weak bases. They are typically formulated at an acidic pH to enhance chemical stability. However, this leads to high ionization, reducing their ability to...
Osmosis01:30

Osmosis

Osmosis is the movement of free water molecules through a semipermeable membrane.  The water's concentration gradient across the membrane is inversely proportional to the solutes' concentration. Whereas diffusion transports material across membranes and within cells, osmosis transports only water across a membrane, and the membrane limits the diffusion of solutes in the water. Osmosis is a special case of diffusion.
Water, like other substances, moves from a high concentration of free water...
Osmosis00:47

Osmosis

Approximately 60% to 95% of the weight of living organisms is attributed to water. Therefore, maintaining appropriate water balance within cells is of paramount importance. Osmosis is the movement of water across a semipermeable membrane, such as a cell’s plasma membrane. In living organisms, water plays a crucial role as a solvent—a molecule that dissolves other molecules.Diffusion Versus OsmosisBoth diffusion and osmosis are types of passive transport—cellular transport that does not require...
Osmosis and Osmotic Pressure of Solutions02:40

Osmosis and Osmotic Pressure of Solutions

A number of natural and synthetic materials exhibit selective permeation, meaning that only molecules or ions of a certain size, shape, polarity, charge, and so forth, are capable of passing through (permeating) the material. Biological cell membranes provide elegant examples of selective permeation in nature, while dialysis tubing used to remove metabolic wastes from blood is a more simplistic technological example. Regardless of how they may be fabricated, these materials are generally...
Microbiome of the Eye01:22

Microbiome of the Eye

The human eye has a specialized microbiota that reflects its unique anatomical and immunological environment. This low-biomass microbial community predominantly colonizes the conjunctiva and eyelid margins, playing a vital role in ocular surface homeostasis and defense. Despite its proximity to the richly colonized facial skin, the ocular surface maintains a distinct microbial profile due to continuous mechanical and biochemical defense mechanisms.The conjunctival surface hosts fewer microbial...
Osmotic Pressure01:26

Osmotic Pressure

Osmosis is a process where solvent molecules move toward a solution through a semipermeable membrane. As the solution dilutes due to the entry of solvent, it expands. This expansion increases the hydrostatic pressure of the solution. When the hydrostatic pressure equals the osmotic pressure, osmosis stops.Osmotic pressure, denoted by Π, is the minimum pressure needed to prevent the solvent from passing into the solution by osmosis. The van 't Hoff equation calculates the osmotic pressure of an...

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Effects of Systane(®) Balance on noninvasive tear film break-up time in patients with lipid-deficient dry eye.

Clinical ophthalmology (Auckland, N.Z.)·2014
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Related Experiment Video

Updated: Jun 25, 2026

Establishment of A Mouse Model of Aqueous Deficiency Dry Eye
05:21

Establishment of A Mouse Model of Aqueous Deficiency Dry Eye

Published on: November 1, 2024

[Tears osmolarity in dry eye].

Alejandro J Aguilar1

  • 1Departamento de Superficie Ocular Grupo Médico Las Lomas, San Isidro, Buenos Aires, Argentina. aguilara@arnet.com.ar

Arquivos Brasileiros De Oftalmologia
|March 11, 2009
PubMed
Summary

Dry eye disease is a complex condition affecting the ocular surface, causing discomfort and visual issues due to tear film instability and inflammation. This instability leads to increased tear osmolarity, damaging eye tissues and creating harmful feedback cycles.

Area of Science:

  • Ophthalmology
  • Tear film dynamics
  • Ocular surface disease

Context:

  • Dry eye disease is a prevalent condition characterized by multifactorial causes impacting tear film stability and ocular surface health.
  • Symptoms include discomfort, visual disturbances, and potential ocular surface damage.
  • Key pathological features involve increased tear film osmolarity and ocular surface inflammation.

Purpose:

  • To elucidate the complex pathophysiological mechanisms underlying dry eye disease.
  • To highlight the role of tear film instability and hyperosmolarity in disease progression.
  • To explain the neurophysiologic disturbances contributing to the chronic nature of dry eye.

Summary:

  • Dry eye disease involves tear film instability, leading to increased osmolarity and ocular surface inflammation.

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Effect of Artificial Tear Formulations on the Metabolic Activity of Human Corneal Epithelial Cells after Exposure to Desiccation
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Effect of Artificial Tear Formulations on the Metabolic Activity of Human Corneal Epithelial Cells after Exposure to Desiccation

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Last Updated: Jun 25, 2026

Establishment of A Mouse Model of Aqueous Deficiency Dry Eye
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Establishment of A Mouse Model of Aqueous Deficiency Dry Eye

Published on: November 1, 2024

Optimizing Tear Collection in Mice for mRNA and Protein Analysis
09:04

Optimizing Tear Collection in Mice for mRNA and Protein Analysis

Published on: July 19, 2024

Effect of Artificial Tear Formulations on the Metabolic Activity of Human Corneal Epithelial Cells after Exposure to Desiccation
06:29

Effect of Artificial Tear Formulations on the Metabolic Activity of Human Corneal Epithelial Cells after Exposure to Desiccation

Published on: May 2, 2020

  • This hyperosmolarity can cause epithelial osmotic lesions, exacerbating inflammation.
  • Disruptions in ocular surface homeostatic mechanisms create vicious cycles that worsen the condition.

    • Impact:

    • Understanding these mechanisms is crucial for developing targeted therapeutic strategies for dry eye.
    • This research provides insights into the chronic and progressive nature of dry eye disease.
    • Identifying key pathophysiological pathways can lead to improved patient outcomes and quality of life.