Test 27  (Medical retina)

1. Differentiating classic and occult neovascular membranes is 
    possible using:

a. Amsler grid

b. indocyanine green

c. fundus fluorescein angiography 

d. optical coherence tomography

e. B-scan ultrasound
 

Answer
a.F   b.T   c.T   d.F   e.F
Only FFA and ICG can be used to differentiate between classic and occult neovascular membrane.
ICG can also detect classic neovascular membrane which appears to be occult on FFA. Classic 
neovascular membrane has well-defined pattern of fluorescence whereas occult is poorly defined and has stippled appearance.

2. The following are true about choroidal neovascular membranes
    (CNV):

a. subfoveal CNV is best treated with direct focal argon 
    laser 

b. juxtafoveal CNV is 0-200um from the foveal avascular 
   zone

c. extrafoveal CNV is more than 200um from foveal 
    avascular zone

d. optic nerve pit is a cause of CNV

e. optic disc drusen is a cause of CNV
 

Answer
a.F   b.T   c.T  d.F  e.T
PDT is useful for subfoveal CNV. Argon laser will reduce the central vision immediately. Optic nerve pit is a cause of central serous retinopathy.

3. The following statements are true regarding dry age-related macular 
    degeneration (AMD):

a. it will typically have a visual acuity of 6/60 or worse 
   within 2 years

b. the optimal management is with low visual aids

c. the contralateral eye will be simultaneously affected in 
    all cases 

d. the patient should be promptly referred for fluorescein 
    angiography

e. dry AMD can be treated with photodynamic therapy 
    without verteporfin
 

Answera.F  b.T  c.F  d.F  e.F
In dry AMD, the progression is slower than wet or neovascular AMD, causing moderate and sometimes severe vision loss over one or two decades. 

4. Photodynamic therapy (PDT) is useful for the following conditions 
    resulting from age-related macular degeneration :

a. retinal pigment epithelium detachment

b. disciform macular degeneration

c. geographic atrophy

d. occult subfoveal neovascular membrane

e. classic subfoveal neovascular membrane

Answer
a.F   b.F  c.F g  d.T  e.T
Subfoveal neovascular membrane is best treated with PDT. The TAP Study Group (1999 and 2001) showed classic subfoveal neovascular membrane responded best to PDT compared with occult subfoveal neovascular membrane. The VIP Study Group (2001) showed that verteporfin therapy was also effective in AMD patients composed of occult CMV with no classic CNV.

 

5. The following are true about verteporfin used in photodynamic therapy
    (PDT):

a. verteporfin is activated by green laser light

b. verteporfin is a derivative of prophyrin

c. it generates free radicals which causes blood clotting 
    local to the lesion

d. it destroys the new vessels through heat 

e. it is contraindicated in pseudophakia
 

Answer
a.F   b.T  c.T   d.F  e.F
Verteporfin is a liposomal benzoporphyrin derivative. 
It is activated by a non-thermal, red (689nm) laser light targeted specifically at the area where the CMV is located. The energy of the laser is absorbed by verteporfin, causing photochemical reactions and the generation of free radicals and singlet oxygen. These in turn causes localized cellular and tissue damage, resulting in the formation of a platelet thrombus and hence vascular occlusion of the choroidal neovascular membrane.

 

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