Corneal Size & White-to-White (WTW) / Visible Iris Diameter (VID)

👁 Corneal Size & White-to-White (WTW) / Visible Iris Diameter (VID)

The cornea makes up the anterior 1/6 of the eye,
with a radius of approximately 8 mm, forming part of the eye's spherical structure.

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🔍 How is corneal size measured?

From a front view, the horizontal distance from limbus to limbus (white sclera to white sclera)
is termed White-to-White (WTW) or Visible Iris Diameter (VID).

TermMeaning

WTW	White-to-white distance
VID	Visible iris diameter
HVID	Horizontal visible iris diameter

📌 WTW and HVID are essentially the same and Horizontal measurement is most commonly used.

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📏 Normal Range

MeasurementNormal Value

H-WTW / HVID	~12 mm
V-WTW / VVID	~11 mm

 

 

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🧬 Clinical Applications

• Congenital glaucoma diagnosis
• Sizing of anterior chamber intraocular lenses (AC-IOLs)
  → Lens size = WTW + 0.5 to 1.0 mm

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🔬 Study Examples

Study YearSubjectsResults

Korea 1988	314 adults	Male: 11.47mm / Female: 11.17mm
Global 2013	Multi-ethnic review	Average: ~11.5–12.0 mm

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✅ Summary

• Corneal size is defined by WTW or HVID
• ~12 mm (horizontal) is considered normal
• Important for lens implantation and glaucoma evaluation