Keratoconus: Window, Oil Droplet & Scissor Reflex in Cornea

In this blog, we will focus on Window reflex, Scissor reflex and Oil Droplet Reflex in cornea occurring in Keratoconus. Keratoconus is usually bilateral, non-inflammatory and along axial part of cornea. The disease starts around puberty and progresses slowly with further expansion of the disease.


Keratoconus or Conical cornea is bulging out of normal round cornea into a cone-like structure due to ectasia (dilatation) and thinning of the cornea.


Depending upon shape and size, there can be 3 variations as:-

  1. Nipple cone- <5mm with steep curvature
  2. Oval cone- 5-6mm with ellipse
  3. Globus cone- >6mm with round globe


Thinning and ectasia (dilation) is the major pathology which occurs due to defect in synthesis of mucopolysacchride and collagen tissue.

Clinical Features

The patient presents with symptoms while a careful examination helps in assessing signs:


  1. Myopia (short-sightedness)
  2. Astigmatism


  1. Slit lamp examination- reveals thinning and dilatation of central cornea.
  2. Retinoscopy- Scissor reflex of Cornea in Keratoconus- Action of two bands moving toward and away from each other like the blades of a pair of scissors. It occurs with Astigmatism.
  3. Distant direct ophthalmoscopy- oil droplet reflex is observed. (central and peripheral areas of cornea are separated by shadows)
  4. Keratometry- abnormal mires alignment
  5. Photokeratoscopy- distorted circles
  6. Placido disc examination- irregular circles
  7. Munsan’s sign- patient lower lid bulges when he is asked to look down

Reflexes in Cornea

Window Reflex in Keratoconus

Also known as Blink or Corneal reflex, Window Reflex in keratoconus is involuntary blinking of eyelids in response to stimuli. This reflex is distorted in this condition.

Window reflex in Keratoconus
Window reflex in Keratoconus
Corneal reflex pathway

Scissor Reflex in Keratoconus

Upon retinoscopy, we observe light reflex. Normally, it should be evenly distributed. It appears as dark center, thus creating Scissoring reflex on retinoscopy in keratoconus.

Scissor reflex in Keratoconus

Oil Droplet Reflex in Keratoconus

Also known as Charleux sign, Oil Droplet Reflex in Keratoconus refers to the Dark Reflex in the area of cone when cornea is observed in a dilated pupil by distant direct ophthalmoscopy.

Oil Droplet Reflex in Keratoconus


It may be associated with ocular conditions or systemic conditions:-

  • Ocular conditions- Ectopic lentis, congenial cataract, vernal keratoconjunctivits (VKC).
  • Systemic conditions- Down syndrome, marfan syndrome, atopy, osteogenesis imperfecta.


The rupture of descemet’s membrane can lead to acute hydrops, which with this condition, leads to corneal oedema, pain, vision loss, photophobia (light sensitivity) and lacrimation (excess tears).


Early Cases

  • Spectacles- for correction of vision
  • Contact lenses- for correction of vision
  • Intracorneal ring segments (Intacs)- for vision correction

To slow down degeneration

Corneal collagen cross linking can be done:-

Corneal collagen crosslinking keratoconus.

Late cases

Keratoplasty is the only viable option, namely DALK (Deep Anterior Lamellar Keratoplasty) or PK (Penetrating Keratoplasty).

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