Optic Disc Shape

Overview

The normal shape of the optic disc is slightly vertically oval.¹

Pearls

Vertical disc diameter is about 7%-10% larger than the horizontal disc diameter.
- Maximal disc diameter is nearly equal to vertical diameter; horizontal diameter is almost equal to the minimal diameter.
Glaucoma susceptibility is mostly independent of the shape of the optic disc.
- As a single variable, optic disc shape is not markedly important for diagnosis and pathogenesis of glaucoma in eyes with myopia <-8 D.
  - However, optic disc shape may affect the distance between the neuroretinal rim and the central retinal vessel trunk location on the lamina cribrosa surface (see Chapter 7).
  - Family history may play a role in optic disc shape.²
Disc shape is not correlated with age, sex, right eye, left eye, body weight, body height.
- High myopia (>-12 D)
  - Disc is more oval, elongated than any other group.
  - More obliquely oriented than any other group.
Disc shape is correlated with increased corneal astigmatism and amblyopia.
- Corneal astigmatism is significantly higher in eyes with tilted discs and significantly lower in eyes with more circular disc shapes.
- The orientation of the longest disc diameter can indicate the axis of the corneal astigmatism.
  - Consider keratometry and retinoscopy in children if the optic nerve is abnormal in shape.
    - Amblyopia is significantly associated with an elongated optic disc shape and high corneal astigmatism.

References

1. Jonas JB, Budde WM, Panda-Jonas S. Ophthalmoscopic evaluation of the optic nerve head. Surv Ophthalmol. 1999;43:293-320.

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Oct 13, 2018 | Posted by drzezo in OPHTHALMOLOGY | Comments Off