Delhi Journal of Ophthalmology

Classical signs of Keratoconus

Josephine S. Christy, Shivraj Tagare
Department of Cornea and Refractive Services, Aravind Eye Hospital, Pondicherry, India 

Corresponding Author:

Josephine S Christy (MS)
Consultant, Cornea and Refractive Services
Aravind Eye Hospital and Post graduate Institute of Ophthalmology, Thavalakuppam, Pondicherry, India
Email: josyfred@gmail.com

Received: 04-SEP-2021

Accepted: 10-SEP-2020

Published Online: 09-OCT-2020

DOI:http://dx.doi.org/10.7869/djo.580

Abstract
Keratoconus is a bilateral progressive disease of unknown etiology characterized by gradual corneal thinning, steepening and ectasia. Though corneal topography plays a significant role in its diagnosis, early identification with clinical signs can greatly improve the visual outcome with appropriate management. This PG snippet elaborates on the classical signs of keratoconus by clear demonstration with slit lamp pictures.

Keywords :

External Signs
  1. Munson’s sign: V-shaped conformation of the lower lid produced by the ectatic cornea in down gaze (Figure 1a).
  2. Rizzuti’s sign: Sharply focused conical beam of light near the nasal limbus, produced by lateral illumination of the cornea from temporal side, in patients with advanced keratoconus (Figure 1b).

Figures 1: 1(a) Munson's sign (1b) Rizutti's sign

Slit Lamp Signs
  1. Vogt’s striae: Fine vertical stress lines in the deep stroma and descemet’s membrane that are parallel to the steep axis of cone (Figure 2a). These lines disappear transiently on gentle digital pressure (Figure 2b).
  2. Fleischer ring: Deposition of iron in the basal epithelial cells in a ring shape at the base of the conical protrusion (Figure 3a). This ring is faint and broad in early keratoconus and becomes thinner and more discrete as the condition advances. It is best appreciated in cobalt blue or green filter (Figure 3b).
  3. Corneal thinning: Slit lamp examination in keratoconic eyes show central or inferior corneal thinning. Maximum corneal thinning corresponds to the site of maximum steepening. (Mild Keratoconus: Figure 4a) (Severe Keratoconus) (Figure 4b).
  4. Corneal apical scarring: Approximately 20 percent of eyes with moderate or severe keratoconus develop corneal scarring. It occurs as a part of natural progression of the disease but is worsened by the wearing of rigid contact lenses. It usually appears at the apex of the cone, starting as fine lines initially and then develop into nebular scarring as it progresses (Figure 5a).
  5. Hydrops: An acute rupture in Descemet’s membrane causing imbibition of aqueous into corneal stroma causing it to swell. It is a complication usually seen in patients with advanced keratoconus with associated allergy or eye rubbing (Figure 5b).
  6. Prominent corneal nerves: It is not likely that the nerve fibers are more numerous in keratoconic patients, but only that they are more easily seen due to changes in density. An increased visibility of the corneal nerve fibers cannot be considered a singular distinction of keratoconus. (Figure 6a)
  7. Rupture in Bowman’s layer: These are irregular superficial opacities that develop due to breaks in Bowman’s layer. They can cause significant visual loss due to scarring in advanced cases. (Figure 6b)

Figures 2: (2a) Vogt's striae (2b) Disappearance of striae on digital pressure


Figures 3: (3a) Fleischer's ring (3b) Brown ring in Green filter


Figures 4: (4a) Thinning in Mild Keratoconus (4b) Thinning in Severe Keratoconus


Figures 5: (5a) Apical corneal scarring (5b) Acute Hydrops


Figures 6: (6a) Prominent corneal nerves (6b) Bowmans rupture

Retroillumination Signs 
  1. Scissoring reflex: During retinoscopy, two bands of the light beam reflexed from the retina, moves like the blades of the pair of scissors, towards and away from each other. This sign is diagnostic of keratoconus.
  2. Oil droplet sign (“Charleaux” sign): Dark Reflex in the area of the cone on observation of cornea in dilated pupil by distant direct ophthalmoscopy. The total internal reflection of light due to conical cornea produces a dark, round shadow in corneal mid periphery, separating the central bright red fundus reflex from a red reflex in corneal periphery.

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Christy JS, Tagare SClassical signs of Keratoconus.DJO 2020;31:87-89

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Christy JS, Tagare SClassical signs of Keratoconus.DJO [serial online] 2020[cited 2020 Dec 5];31:87-89. Available from: http://www.djo.org.in/articles/31/1/Classical-signs-of-Keratoconus.html