keratoconus

Question 1

What is Keratoconus?

Answer 1

A form of corneal ectasia characterized by:
* Non-inflammatory, progressive, usually bilateral
* Cone shape at the inferior part of the cornea
* Associated with congenital weakness

Keratoconus involves thinning of the cornea and abnormal shape due to various factors.

Question 2

List the clinical features of Keratoconus.

Answer 2

• Myopic astigmatism
• Hallmark: Stromal thinning (Central paracentral → Inferior to the centre)
• Munson’s sign: Bulging of lower eyelid on downgaze
• Rizzut’s sign: Arrowhead pattern of light over nasal limbus
• Scissoring reflex on retinoscopy
• Oil droplet reflex on ophthalmoscopy
• Vogt’s striae: Stromal stress lines

These features help in the clinical diagnosis of Keratoconus.

Question 3

What is Munson’s sign?

Answer 3

Bulging of the lower eyelid on downgaze

This sign is indicative of Keratoconus.

Question 4

What does Rizzut’s sign indicate?

Answer 4

Light from the temporal side creates an arrowhead pattern of light over the nasal limbus

Rizzut’s sign is a clinical feature associated with Keratoconus.

Question 5

What is the hallmark feature of Keratoconus?

Answer 5

Stromal thinning (Central paracentral → Inferior to the centre)

This thinning is critical for diagnosis and understanding the progression of the disease.

Question 6

What is the diagnostic method for Keratoconus?

Answer 6

Corneal topography

This method provides detailed mapping of the cornea’s surface.

Question 7

What is the scissoring reflex observed during?

Answer 7

Retinoscopy

This reflex is a characteristic finding in patients with Keratoconus.

Question 8

What does the oil droplet reflex indicate?

Answer 8

A finding on ophthalmoscopy in Keratoconus

This reflex is associated with the abnormal shape of the cornea.

Question 9

What is the etiology of Keratoconus?

Answer 9

• Congenital weakness
• Associated with conditions like Down syndrome
• Vernal keratoconjunctivitis

These factors contribute to the development of Keratoconus.

Question 10

What is the shape of the cornea in Keratoconus?

Answer 10

Cone shape

The abnormal shape typically occurs at the inferior part of the cornea.

Question 11

What is keratoplasty?

Answer 11

Transplantation of the cornea

It is a surgical procedure to restore vision.

Question 12

What does C3R stand for?

Answer 12

Corneal collagen cross linking using riboflavin and UVA radiation

This procedure strengthens corneal tissue.

Question 13

What causes Band shaped Keratopathy?

Answer 13

Deposits of calcium in Bowman’s layer

This condition affects the cornea’s appearance.

Question 14

What is the treatment for Band shaped Keratopathy?

Answer 14

Chelation with EDTA

This helps remove calcium deposits.

Question 15

What is Arcus senilis?

Answer 15

Lipid deposition on Descemet’s membrane near periphery

It commonly occurs in old age.

Question 16

What is the lucid interval of Vogt?

Answer 16

Clear zone of cornea between arcus and limbus

This is a distinguishing feature in corneal examination.

Question 17

What is Interstitial Keratitis?

Answer 17

Inflammation only of corneal stroma

It can be caused by various conditions.

Question 18

Name two causes of Interstitial Keratitis.

Answer 18

• Congenital syphilis
• Cogan syndrome (interstitial Keratitis + deafness)

Other causes include tuberculosis and Herpes Simplex Virus (HSV).

Question 19

What are the types of Keratoplasty?

Answer 19

• Penetrating Keratoplasty (Full thickness)
• Lamellar Keratoplasty (Partial thickness)
• DSEK (Descemet’s stripping endothelial keratoplasty)
• DALK (Deep anterior lamellar Keratoplasty)

These types vary in the extent of corneal tissue replaced.

Question 20

What is the indication for Penetrating Keratoplasty?

Answer 20

• Pseudophakic bullous Keratopathy
• Acute hydrops in severe Keratoconus

Penetrating Keratoplasty involves removal of corneal tissue from epithelium to endothelium (i.e., all 5 layers).

Question 21

What does DSEK involve in corneal transplantation?

Answer 21

• Only endothelium and Descemet’s membrane (i.e., posterior layers)

DSEK stands for Descemet Stripping Endothelial Keratoplasty.

Question 22

What does DALK stand for in corneal procedures?

Answer 22

• Deep Anterior Lamellar Keratoplasty

DALK involves corneal tissue from epithelium up to stroma (i.e., anterior 3 layers).

Question 23

What is the procedure for corneal transplantation ?

Answer 23

• Host cornea cut using a trephine
• Implant the graft cornea (Diameter: 7.5mm, 0.25mm larger than host opening)

The trephine is used to create an opening in the host cornea.

Question 24

What is the main type of graft rejection in corneal transplantation?

Answer 24

• Endothelial rejection

This type of rejection is characterized by the formation of a Khodadoust line, which is diagnostic.

Question 25

What is the **storage media** for corneal transplantation for short term?

Answer 25

* mk media * 4°C, moist chamber/mccarey Kaufman medium ## Footnote This storage method is effective for less than 48 hours.

Question 26

What is the **intermediate term** storage duration for corneal transplantation?

Answer 26

< 2weeks ## Footnote This duration allows for corneal preservation before transplantation.

Question 27

What is the **long term** storage method for corneal transplantation?

Answer 27

* Cryopreservation (-70°C) ## Footnote Although the cornea loses its viability to a large extent, it can still be preserved for up to 35 days.