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In Vivo Confocal Microscopy (IVCM)

A practical guide to interpreting corneal nerve structure, immune activity, and pathological patterns. Focused on real-world findings such as nerve loss, microneuromas, and inflammation markers.

1. What is Confocal Microscopy?

In vivo confocal microscopy (IVCM) is a high-resolution imaging method that allows visualization of corneal nerves, immune cells, and epithelial structure at near-cellular resolution. It is commonly used in neuropathic corneal pain and dry eye disease evaluation.

In Vivo Confocal Microscopy
The use of confocal microscope in practice. Source

The human cornea is a transparent, avascular tissue that serves as the eye's outermost layer. It is composed of five distinct layers, each with unique structural and functional properties:

  1. Corneal Epithelium: ~ 50 μm deep. This outer, fast-regenerating layer is 5 to 7 cells thick and makes up roughly 10% of the total corneal thickness.
  2. Bowman's Layer (Membrane): ~ 8–14 μm deep. A very thin, dense, and tough fibrous sheet of connective tissue that protects the underlying stroma.
  3. Stroma (Substantia Propria): ~ 400–500 μm deep. The thickest layer, constituting roughly 80–90% of the total corneal depth. It is composed of precisely arranged collagen fibers that provide structural strength and transparency.
  4. Descemet's Membrane: ~ 5–15 μm deep (thickens with age). A thin, elastic basal lamina that separates the stroma from the inner endothelium.
  5. Endothelium: ~ 4–10 μm deep. A single, specialized layer of cells on the innermost surface that pumps fluid out of the stroma to keep the cornea clear.

Human cornea layers
Live histological cross-section representation of a normal cornea by IVCM. Source

Typical Epithelium:

Epithelium.
Basal epithelial cells of a human cornea observed with the corneal confocal microscopy HRT II. Source

Typical Subbasal Nerve Plexus:

Subbasal Nerve Plexus.
Sub-basal corneal nerves of a human cornea observed with corneal confocal microscopy, using the HRT II. Source

Typical Field of View of IVCM is 400 μm x 400 μm (0.16 mm²) which corresponds to a small fraction of the corneal surface area. The following image shows the scale of the cornea and the field of view of IVCM.

Confocal microscopy size scale.
1 square represents 400 μm × 400 μm field of view of one confocal image in a typical average adult human sized cornea.
And with an overlay of the healthy corneal nerve morphology, which is typically observed in the sub-basal nerve plexus layer of the cornea.
Confocal microscopy size scale with nerve morphology.
An overlay of the healthy corneal nerve morphology.
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