Purpose of 9-Point Pachymetry

Diagnosing Corneal Disorders:

• Identifies thinning or thickening patterns associated with conditions like keratoconus, pellucid marginal degeneration, or corneal edema.

Refractive Surgery Planning:

• Ensures sufficient corneal thickness before procedures like LASIK or PRK.
• Detects asymmetries to prevent complications like ectasia.

Monitoring Corneal Health:

• Tracks corneal changes after surgery, trauma, or disease.

Glaucoma Evaluation:

• Central corneal thickness (CCT) is a critical factor in interpreting intraocular pressure (IOP).

Points Measured in 9-Point Pachymetry

The nine points include:

1. Central Point: The thickness at the central cornea (CCT).
2. Superior: Located 3 mm above the central point.
3. Inferior: Located 3 mm below the central point.
4. Nasal: Located 3 mm nasally from the central point.
5. Temporal: Located 3 mm temporally from the central point.
6. Superior-Nasal: Located diagonally between the superior and nasal points.
7. Superior-Temporal: Located diagonally between the superior and temporal points.
8. Inferior-Nasal: Located diagonally between the inferior and nasal points.
9. Inferior-Temporal: Located diagonally between the inferior and temporal points.

This distribution ensures a comprehensive assessment of corneal thickness and detects regional irregularities.

Procedure

Preparation:

• The patient is seated comfortably, and the pachymeter is calibrated.
• Topical anesthetic drops may be used for contact pachymetry.

Measurement:

• The pachymeter probe (contact method) or an optical device (non-contact method) is used to measure thickness at nine specific points.

Data Recording:

• Measurements are recorded and displayed, often as a thickness map or a table.

Analysis:

• Compare thickness values across all points to identify asymmetry or abnormalities.

Interpretation of 9-Point Pachymetry

Normal Corneal Thickness:

• Central corneal thickness (CCT): Typically 540–560 µm.
• Peripheral cornea is usually thicker than the center.

Abnormal Findings:

• Thinning Patterns:
  • Seen in keratoconus (inferior thinning) or post-refractive surgery ectasia.
• Thickening Patterns:
  • Indicates corneal edema or early signs of endothelial dysfunction.
• Asymmetry:
  • Irregular distribution of thickness suggests localized corneal disease.