The document discusses the anatomy and surgical applications of the limbus. It defines the limbus as the transitional zone between the cornea and sclera, containing the pathways for aqueous humor outflow. Histologically, it describes how the layers of the cornea and conjunctiva become continuous at the limbus. Surgically, it notes the anterior limbal border, blue limbal zone, mid-limbal line, posterior limbal border, and white limbal zone. The best site for cataract incisions is the mid-limbal line, while anterior or posterior incisions risk damage to underlying structures. The limbus contains stem cells that renew the corneal epithelium.

1. The Limbus
Anatomy and Surgical application
Dr.Mohammad Dmour- PGY1
Supervised by : Dr.Mohammad Bilal khalil
Ophthalmology Department
Islamic Hospital

3. LIMBUS, INC., a shadowy employment agency
that operates at the edge of the normal world.

5. • Eye (2007) Developmental Biology Unit, University College London Institute of
Child Health and Great Ormond Street Hospital for Children NHS Trust,
London, UK

7. Histology

8. Histology

13. Anatomical Limbus
• Anatomically, the limbus refers to a circumcorneal
transitional zone of the conjunctivocorneal and
the corneoscleral junction.

14. Anatomical Limbus
• Conjunctivocorneal junction:
1. At this point, the bulbar conjunctiva is firmly
adherent to the underlying structures.
2. The Substantia propria of the conjunctiva stops here
but its epithelium continues with that of the cornea.
3. At the transition zone, the epithelium becomes
several layers thick (10-12) and arranged irregularly
at the limbus.
• Sclerocorneal junction:
At this point, Transparent corneal lamellae become
continuous With the oblique, circular and opaque
fibres of sclera.

18. At Limbus…….
1. Corneal epithelium becomes bulbar
conjunctival epithelium
2. Bowman's membrane becomes continuous with
the lamina propria of the conjunctiva and
tenon's capsule.
3. Stroma becomes sclera
4. Descemet's membrane becomes schwalbe's line.
5. Endothelium lines the trabecular meshwork
and becomes continuous with the anterior
surface of the epithelium

24. Surgical Limbus
• Is a 2mm wide circumcorneal transitional
zone between clear cornea on one side and
the opaque sclera on the other side.

26. Surgical Limbus
• Anterior limbal border:
1. It is the ant boundary of surgical limbus seen
from exterior.
2. Marked by prominent ridge created by insertion
of the conjunctiva and tenons capsule into the
cornea.
3. It overlies the termination of the bowman’s
membranes.

27. Surgical Limbus
• Blue limbal zone:
1. is bluish translucent zone seen post to ant
limbal border.
2. Post to this bluish zone is the white sclera
3. Extent of blue limbal zone varies in different
quadrants(due to variable insertion of conj
&tenon’s capsule into the cornea)- 1mm in
supquad, 0.8mm in inf quad, 0.4mm in nasal
&temp quad.

28. Surgical Limbus
• Mid limbal line:
1. junction of blue zone with white area.
2. Overlies termination of DM(schwalbe’s line)
3. It is the most useful external landmark.

29. Surgical Limbus
• Posterior Limbal Border:
1. Lies 1mm post to mid-limbal line
2. Overlies scleral spur
3. Seen with sclerotic scatter illumination
4. Forms post border of surgical limbus

30. Surgical Limbus
• White limbal zone:
1. 1mm wide whitish area which lies b/w mid-
limbal line and the post limbal border
2. overlies the trabecular meshwork

31. Surgical Limbus
• Ant border….. overlies the termination of the
bowman’s membranes.
• Midlimbal ….. Overlies termination of
DM(schwalbe’s line)
• Post border….. Overlies scleral spur
• White zone……overlies the trabecular meshwork.

36. The cataract incision & the surgical limbus
• Scleral incision: located post to post limbal border.
Main disadvantage is excessive bleeding & Hyphema
• Posterior limbal incision: Is located at the white
limbal zone b/w the midlimbal line & post limbal
border. The underlying trabecular meshwork may be
injured in this incision
• Mid-limbal incision: Located at mid-limbal line
externally which corresponds to the schwalbe’s line
internally. It is the preferred site of incision for entry
into the eye

37. The cataract incision & the surgical limbus
• Anterior limbal incision: is located in blue
limbal zone and transverses the descemet’s
membrane & may cause stripping
• Clear corneal incision:
Located in front of the ant limbal border & is
associated with a high induced astigmatism
Greater chances of descemet’s stripping

42. Take Home Massage….
• The limbus forms the border between the
transparent cornea and opaque sclera, contains
the pathways of aqueous humour outflow, and is
the site of surgical incisions for cataract and
glaucoma.
• Limbal epithelium is thought to contain the
source of the stem cells (SC) that serve as the
source of corneal epithelial cell renewal.