๐ 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.
๐ 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 |
๐ WTW and HVID are essentially the same and Horizontal measurement is most commonly used.
๐ Normal Range
MeasurementNormal Value
| H-WTW / HVID | ~12 mm |
| V-WTW / VVID | ~11 mm |
๐งฌ Clinical Applications
- Congenital glaucoma diagnosis
- Sizing of anterior chamber intraocular lenses (AC-IOLs)
→ Lens size = WTW + 0.5 to 1.0 mm
๐ฌ 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 |
โ Summary
- Corneal size is defined by WTW or HVID
- ~12 mm (horizontal) is considered normal
- Important for lens implantation and glaucoma evaluation
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