Test 27

1. Hruby's lens 

a. is a contact lens

b. gives a minified view of the retina

c. forms a real inverted image. 

d. used with concave surface towards patient 

e. works by neutralizing the refractive power of the eye
 

Answer

a.F   b.T   c.F   d.T   e.T
Hruby lens has a power of -58.6D. It works by neutralizing the refractive power of the eye. 
The resultant image is formed behind the lens. 
The image formed is erect, virtual and minified. 
As other lenses can give a better field of view 
and bigger image, the Hruby lens is losing its popularity.

2. Jackson cross cylinder:

a. is composed of equal-power, perpendicular plus and 
    minus cylinders

b.  has a handle 45⁰ to the axes.

c. spherical equivalent is 0 

d. the interval of Sturm is unchanged with either positions 
    of the cross cylinder

e. does not affect the spherical equivalent when placed 
    before an ametropic eye

 
Answer
a. T   b.T   c.T   d.T   e.T

3. Alternate cover test 

a. should always be performed before cover-uncover test

b. if both eyes move in on uncovering the patient has 
    esophoria 

c. putting neutral density filter in front of one eye will 
    affect the result 

d. detects both phoria and tropia

e. is not useful in detecting cyclophoria
 

Answer
a.F   b.F   c.T   d.T    e.F
Cover and uncover test detects the presence of tropia whereas alternate cover test detects both tropia and phoria. The cover uncover test should be performed first to detect any abnormalities before the alternate cover test. The alternate cover test detects esophoria, exophoria and also cyclophoria. In the eye moves in on uncovering the patient has exophoria.

4. If -10.0D myope change from spectacles to contact lenses 

  a. visual field increases 

  b. peri-aberrations reduces 

  c. symptoms of presbyopia more prominent 

  d. image size is reduced 

  e. patient with exophoria may become symptomatic

Answer
a. T  b.T   c.T   d.F   e.T
The image size is increased when contact lens is worn compared with spectacles. Minus lenses can act as base in prism and in patient with exophoria, the symptoms are reduced with glasses.

5. In sac syringing:

a. a hard stop indicates common canalicular block 

b. while doing syringing through the lower canaliculi, 
    fluid can regurgitate through upper canaliculi in 
    presence of patent drainage system 

c. punctum and position of lower lid should be examined 
    in upright position 

d. if punctum is absent always indicates past inflammation 
    or injury

e. if fluid can be felt in the throat, diseases of nasolacrimal 
    duct are excluded as a cause of epiphora

Answer
a.F   b.T   c.T   d.F   e.F
A soft stop indicates common canalicular block. Absent punctum may be congenital. During syringing, fluid is forced down the nasolacrimal duct with great pressure. In cases of partial obstruction, fluid may be forced through the stenosis.

 

 

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