1. The following specimen is taken from a patient who has bilateral abnormal corneal
    appearance. Similar corneal changes are also seen in some of his relatives. True 
    statements include:
 

a. this is an autosomal recessive condition
b. glaucoma occurs in 50% of the cases
c. corneal decompensation is common by 40 years of age
d. the slit-lamp examination may be similar to figure1 (below)
e. the electron microscopy may show changes similar to figure 2 (see below)

Figure 1

Figure 2

Answer
a.F    b.F    c.F    d.T    e.T
The condition is posterior polymorphous dystrophy, an endothelial dystrophy which is autosomally inherited and affect both cornea.
The specimen shows multiple-layered endothelium (normal endothelium is single-layered).
Visual disturbance is uncommon. However, in some patients the abnormal endothelium may grow over the trabecular meshwork giving rise to glaucoma. Involvement of the iris may give an appearance indistinguishable from iridocorneal endothelial (ICE) syndrome except that ICE is an unilateral condition.
The slit-lamp shows multiple vesicles in the endothelium which can coalesce to form geographical lesions with time.
Electron-microscopy revealed microvilli on the endothelium resembling the epithelium.

2. The following corneal appearance belongs to a patient who had had blunt ocular 
    trauma::
 

 
a. it is commoner in secondary hyphaema than primary hyphaema
b. high intraocular pressure favors this appearance
c. histology will reveals red blood cells in the stroma
d. clearing of the opacity usually begins in the periphery
e. visual disturbance is usually minimal

Answer
a. T    b.T   c.F    d.T   e.F
The picture shows corneal blood staining.
The condition usually arises from traumatic hyphaema and is commoner with secondary total hyphaema and in the presence of high intraocular pressure.
Histology shows haemosiderin and the breakdownof red blood cells.
The opacity usually clears from the periphery towards the centre and from the posterior to the anterior.
Vision is affected. The staining may take up to two years to clear and in cases which fail to clear penetrating keratoplasty may be needed.

3. With regard to the following condition:
 

a. the Bowman's layer is seldom involved.
b. there are three components (ie. a head, cap and body) to this tissue.
c. the whole abnormal structure is adherent to the corneal surface.
d. it is commoner in white than black population.
e. the following corneal topography may be taken from a patient with this
    condition.

Answer
a.F     b.T    c.T    d.F    e.T
The picture shows pterygium.
The tissue is firmly adherent to the underlying cornea.
The Bowman's layer always shows fragmentation.
The condition is related to ultraviolet light damage of the conjunctiva and cornea.
The corneal topography shows flattening of the right cornea at 3 O'clock which is seen in pterygium.

4. The following corneal topography is taken from a patient with bilateral poor vision:
 

a. there is inferior thinning of the cornea
b. against the rule astigmatism is common 
c. iron deposition on the cornea is rare 
d. corneal neovascularization is a common complication.
e. acute hydrop secondary to Descemet's membrane break can occur

Answer
a.T   b.T   c.T   d.F   e.T
The corneal topography is typical of pellucid marginal degeneration.
The corneal thinning is situated inferiorly.
Unlike keratoconus, Fleischer's ring is rare
Corneal neovascularization is rare.
Acute hydrop resembling that in keratoconus can occur.

 5. True statements about the following corneal appearance include:
 

a. endothelial count is reduced
b. topical steroid is contraindicated in this condition
c. associated with sudden onset hearing loss
d. can occur after tick bite
e. corneal biopsy is useful for diagnosis

Answer
a.T    b.F   c.T   d.T   e.F
The picture shows interstitial keratitis with ghost vessels.
The endothelium is often damaged by the stromal damage and may require corneal graft at a later date.
Topical steroid is useful for reducing the inflammation.
Association with sudden onset visual loss and cardiovascular diseases such as aortic insufficiency is seen in Cogan's syndrome.
It occurs in Lyme's disease.
Corneal biopsy is not useful because the corneal changes (whether in syphilis, TB, Lyme's disease or herpes simple) are thought to be an immune response and not caused by direct infection.