3. SLIT LAMP BIOMICROSCOPY
LENSES
Quick Review
Slit lamp biomicroscopy is used to illuminate and examine
under magnification the anterior segment of the eye.
There are many different attachments of the slit-lamp:
1.Video attachment .
2.Goldman tonometer .
3.Gold 3-mirror lens .
4.Volk double aspheric lens.
(60D-78D-90D)
5.Direct contact goniolenses.
4. VOLK DOUBLE ASPHERIC LENS
History
-In 1956, aspheric ophthalmic lenses for subnormal vision
were developed by Dr. David Volk. He found that an aspheric
surface corrected the aberrations present in more common
spherical lenses.
-Several developments occurred through the years, leading
up to 1982 when all Volk lenses for indirect ophthalmoscopy
were redesigned with both surfaces aspheric, providing a
substantial improvement in image quality.
5. VOLK DOUBLE ASPHERIC LENS
Introduction
Volk's 60D,78D and 90D fundus lenses have
establishes slit lamp indirect ophthalmoscopy as
a standard diagnostic procedure for
comprehensive fundus evaluation.
Examination of the retina by Slit lamp and Volk
double aspheric lenses is called a Bio-
microscopic Indirect Ophthalmoscope BIO.
6. VOLK DOUBLE ASPHERIC LENS
60D
Primary Application :–
• High Magnification Views of the Posterior Pole.
• High magnification lens for detailed optic disc and macula
imaging.
• Ideal diameter for use in the orbital area.
( Its 31mm diameter allows a wide field of view and facilitates
easy handling within the orbital area.)
• Working distance from the cornea is 11mm.
7. VOLK DOUBLE ASPHERIC LENS
78D
Primary application:-
The Double Aspheric 78D is an excellent general
diagnosis .
Ideal balance of magnification and field of view.
Working distance from the cornea is 7mm.
8. VOLK DOUBLE ASPHERIC LENS
90D
Primary application:
General diagnosis and small pupil examinations.
The original Volk 90D lens started the slit lamp
examination.
It features a small 26mm diameter ring is ideal for dynamic
fundoscopy.
The Volk 90D has very good small pupil capabilities,
making it ideal for a quick look at the posterior pole.
Working distance from the cornea is 6.5mm.
9. VOLK DOUBLE ASPHERIC LENS
Color of 90D volk lens and it’s case:-
There are many of 90D VOLK’s colors , like green ,red,
silver, blue, gold and violet.
10. +60D , +78D , +90D.
For emmetropic eye, +60D lens with M(slit lamp)=X10 :
D.P(eye)=60D.
- Magnification = M.(retina) *M.(slit lamp).
= 6060 * 10 =X10.
For myopic eye by -8,+78D lens with M(slit lamp)= X10:
D.P(eye)= 68.
- Magnification = M.(retina) *M.(slit lamp).
= 6878 * 10 =X8.7.
For hyperopic eye by +10,+90D lens with M(slit lamp)=X16:
D.P(eye)=50.
- Magnification = M.(retina) *M.(slit lamp).
= 5090 *10 =X5.5 .
11. BIOMICROSCOPIC INDIRECT
OPHTHALMOSCOPE
The patient’s pupil may be dilated and background lights
dimmed as for direct ophthalmoscopy.
Once the patient is positioned comfortably at the slit
lamp.
The slit lamp viewing piece and the light column are kept
at an angle of 90 degrees.
The intensity of the beam is kept to the minimum possible and
the magnification preferably set at 10× initially.
The slit beam is set around 1.5–2.5 mm wide and 5–10
mm long.
The beam is focused onto the patient’s pupil and the
condensing lens aligned at around 1 cm from the patient’s
eye.
12. BIOMICROSCOPIC INDIRECT
OPHTHALMOSCOPE
The slit lamp is then pulled backwards gradually towards
the examiner until it comes into focus with the aerial
image of the fundus between the condensing lens and the
slit lamp.
Alternatively, the slit lamp could be drawn back
completely towards the examiner and then gradually
moved forwards until the image comes into focus
As with indirect ophthalmoscopy, the image from a non-
contact Volk Lens slit lamp biomicroscopic examination
is inverted and laterally reversed.
13.
14. VOLK DOUBLE ASPHERIC LENS
Characteristics of volk lenses:-
1.Stereoscopic ,3 dimensional view of the retina:
_Binocular viewing through the slit lamp.
2.Better image achieved when viewing through media
opacities:
_Cataract.
3.Allows for manipulation of image:
_Slit lamp magnification& filters.
4.Image size less affected by patient refractive error.
15. GOLDMANN THREE MIRROR
Primary Application:-
Viewing and treatment of the Anterior Chamber and
Central and Peripheral Fundus.
Because the curvature of the contact surface of the lens
is steeper than that of the cornea, a viscous coupling
substance with the same refractive index as the cornea is
required to bridge the gap between the cornea and the
goniolens.
16. GOLDMANN THREE MIRROR
It is important to be familiar with each part of the lens as
follows: C-PEG
1. The central part provides a 30° upright view of the
posterior pole.
2. The equatorial mirror (largest and oblong-shaped) enables
visualization from 30° to the equator.
3. The peripheral mirror (intermediate in size and square-
shaped) enables visualization between the equator and the
ora serrata.
4. The gonioscopy mirror (smallest and dome-shaped) may
be used for visualizing the extreme retinal periphery and pars
plana.
19. GOLDMANN THREE MIRROR
Characteristics:-
3- dimensional view obtained.
Used both on undilated and dilated pupil.
Mirror images can be confusing.
Inadvertent pressure on cornea can
lead to wide angle in AC.
20. INDIRECT OPHTHALMOSCOPE
LENSES
Introduction:-
BIO condensing lenses (Hand held lenses ) are biconvex,
aspheric designs with one surface more curved than the
other.
Less curved surface toward patient’s eye (silver).
21. INDIRECT OPHTHALMOSCOPE
LENSES
The hand-held lens acts both as:-
1. A condensing lens for the illuminating system.
2. A lens for forming an inverted image of the retina in space.
22. INDIRECT OPHTHALMOSCOPE
LENSES
The technique is called Indirect because the fundus is
seen through a condensing lens.
The image is formed close to the principle focus of the
lens, between the lens and the observer.
23. INDIRECT OPHTHALMOSCOPE
LENSES
The condensing lens is a powerful convex lens
(the usual power used is +14, + 20,and + 33 D )
The power of the condensing lens
determines:-
Retinal Magnification
Field of view
Stereopsis.
26. 1- magnification of a lens = dioptric power/ 4.
2- magnification of the retina =
D.P. of the eye /D.P of the lens.
3- Stereopsis = magnification / 4 .
4- Field of view = (D.P. of the lens x 2 ).
27. The high dioptric power lens (30D) has the highest
magnification :-
It yields the least magnification of the retina, 60/30 = 2.
Stereopsis is half that of the normal, 2/4= 1/2
Field of view is generally the largest =
(60 degrees, 30 x 2 ).
28. 30D lens is used to obtain a panoramic view
when detail and stereopsis are not as
important , and used with small pupil.
29. The middle dioptric power lens of (20D).
A- The retinal magnification = 60/20 = X3
B- The stereopsis is 3/4 that of the normal.
C- The field of view is 40 degrees (20x2 ).
30. 20D lens most widely used, since it
provides an adequate field of view,
stereopsis and magnification.
31. The low dioptric power lens of 14 or 15D.
A- The retinal magnification = 60/15 = X4.
B- The stereopsis is full ( 4/4 ).
C- The field of view is 30 degrees (15x2 ).
32. 15D lens, is most useful for detailed view of
the macula or optic disc or for determining
elevation of the retina in shallow retinal
detachment.
