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:-
- Nipple cone- <5mm with steep curvature
- Oval cone- 5-6mm with ellipse
- 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.
The patient presents with symptoms while a careful examination helps in assessing signs:
- Myopia (short-sightedness)
- Slit lamp examination- reveals thinning and dilatation of central cornea.
- 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.
- Distant direct ophthalmoscopy- oil droplet reflex is observed. (central and peripheral areas of cornea are separated by shadows)
- Keratometry- abnormal mires alignment
- Photokeratoscopy- distorted circles
- Placido disc examination- irregular circles
- 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.
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.
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.
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).
- 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:-
Keratoplasty is the only viable option, namely DALK (Deep Anterior Lamellar Keratoplasty) or PK (Penetrating Keratoplasty).