eOphtha

Menu

 

Negative Lenses:

Principle: Placing a negative lens in front of the eye creates an optical system analogues to a Galilean telescope. These lenses produce an upright, virtual image, with somewhat limited field of view.

Hruby Lens:

Goldmann 3 mirror contact lens
       

 

Goldmann
3 mirrors
Lens (64D)

Smallest mirror
(Has an inclination of 590)

used to view
AC angle
+
Occasionally periphery of the fundus.

Medium sized mirror
(has an inclination of 670)

used to view
retinal periphery  ant to the equator

Largest mirror
(Has an inclination of 730)

used to view
area with in the equatorial

post equatorial region of fundus

Positive lense:                           

El Biyadi lens:

Panfundoscopic Lens:

Mainster Lens:

+78D, +90D lens:

Lens/Examination Technique

Magnification

Field of view

Direct ophthalmoscopy (Erect image) 

14X

78 D indirect slit-lamp biomicroscopy      

10X

30°

90 D indirect slit-lamp biomicroscopy      

7.5X

40°

Hruby lens biomicroscopy (Erect image)  

12X

10°

Goldmann fundus contact lens biomicroscopy (Erect image)                

10X

20°

Fundus camera (Erect image)                  

2.5X

30°

14 D indirect ophthalmoscopy

4X

40°

20 D indirect ophthalmoscopy                  

3X

45°

30 D indirect ophthalmoscopy                  

2X

50°

40 D indirect ophthalmoscopy                  

1.5X

65°

 

                                           

                                           Total diopteric power of eye (+60D)
Magnification by a lens = ----------------------------------------------------
                                                      Power of the lens