Question

0. Ms Duffy is 28 years old and wears spectacles. Over the last three years her vision has been worsening even with spectacles. She was examined by an eye doctor and diagnosed to have thinner and steeper than normal corneas with vision impairment in both eyes but more in the left than right eye. Her corneal condition and vision were expected to continue to worsen without intervention. Thus, the eye doctor performed a negligibly invasive treatment procedure on her eyes, first in the left eye and six months later in the right eye. The treatment improved her vision in both eyes.

   Answer the following sub-questions separately.

   1. Which corneal disease did Ms Duffy develop? (1 mark)

   2. What could be the effect/s of this corneal disease on Ms Duffy’s vision and why? (1 mark)

   3. What are the two most common likely causes of this disease? (1 mark)

   4. From your understanding of the structure of the cornea, state primarily which part/s of the

      cornea is/are compromised in this disease? (1 mark)

   5. What are the main clinical and histopathological features of this disease?

   6. Which pathophysiological mechanisms are activated in this disease? Explain three of the

      mechanisms.

   7. Explain the basic principle underlying treatment of Ms Duffy’s disease. (1 mark)

Answer 1

-The corneal thinning and steeping are seen in disorder known as corneal keratoconus. This causes progressive thinning of the cornea which cannot be corrected with corrective lens.

Corneal keratoconus which causes corneal inthinning and steepness causes shortsightedness and astigmatism. This results in blurry vision and visual impairment.

Corneal keratoconus occurs due to two reasons :

1 genetic- the disease is inherited and runs in families

2. The disease can also be seen associated with other diseases such as Marfan syndrome

A bowman's layer lies between the corneal stroma and epithelium. The gradual thinning of bowman layer results in rubbing stroma and epithelium against each other which results in shape distortion of cornea

As the bowman's layer of cornea undergoes degenerative thinning it causes following clinical features -

1. Slow progressive visual impairment

2. Impaired night vision

3. Blurry vision

4. Chaotic spreading of image causing monocular polyopia.  

5. Flatting of image around a light source

The symptoms are seen due to bulging and scarring of the cornea which causes shape distortion of cornea.

The three mechanism that are seen are :

1. Genetic - the disease is inherited

2. Environmental factors that constantly irritate the eyes

3. Cellular effects arising from other diseases such as Marfan disease or down syndrome

The main principle lying behind the treatment is making the cornea appear smooth as in RGP lens. The hydrid lens or corrective lens are also used to manage the condition.

As the disease progress visual impairment cannot be corrected by lens. Corneal transplant is needed.