OPTHALMOLOGY ANATOMY OF THE EYEBALL, IOPOCULO CARDIAC REFLEX

1. OPTHALMOLOGY ANATOMY
OF THE EYEBALL, IOP
OCULO CARDIAC REFLEX
Dr. Smita Joshi (Professor)
Dr Soumya Nath Maiti

2. INTRODUCTION
 Eyeball is a cystic structure, Although
referred as a globe it is ablate
spheroid in shape.
 It has two pole anterior and posterior.
 Antero-posterior diameter of the eye
is 24mm

3. Layers of the Eyeball
It has three concentric layers.
 Outer fibrous layer – Cornea, Sclera,
imbus.
 Middle vascular layer [uveal tract] – Iris,
Ciliary body and Choroid.
 Inner neural layer – Retina
Containing Rods and cones
photoreceptors concerned
with visual function.

4. SEGMENTS
ANTERIOR SEGMENT:
 Cornea to the lens.
 It as two chambers.
 Anterior chamber- from
endothelium of cornea to
endothelium of iris.
 Diameter is 2.5 mm and
contains aqueous humour
 Posterior chamber- Iris
epithelium to anterior surface
of the lens.

5. SEGMENTS
 POSTERIOR SEGMENT : Posterior
to lens which includes vitreous,
choroid, retina, and optic disc.

6. TEAR FILM
 It has three layers.
 Outer lipid layer, middle aqueous
layer, inner mucin layer.
 It forms the coat over the cornea and
conjunctiva and protects it.

7. CONJUNCTIVA
 Derived from surface ectoderm.
 Translucent mucous membrane which
lines the anterior aspect of the eye ball
and posterior surface of the eyelid.
 Can be divided into three parts:
◦ Palpebral conjunctiva
◦ Bulbar conjunctiva
◦ Conjunctival fornix.

8. CORNEA
 It is transparent, avascular, elliptical in
shape , being 12mm X 11mm in size.
 Innervated by ophthalmic division of
trigeminal nerve.
It has five layers
 Corneal epithelium, derived from surface
ectoderm
 Bowman’s membrane
 Stroma }
 Descemet’s membrane} Mesoderm
 Endothelium }

9. SCLERA
 Dense opaque tough fibrous envelope
and covers the posterior 5/6th of the
eyeball.
 It has three layers
Episclera
Sclera proper
Lamina fusca
 Blood supply – episcleral and choroidal
vessels
 Nerve supply – Short ciliary and long
ciliary nerves.

10. UVEA
 The pigmented layer of the eye, lying
beneath the sclera and cornea, and
comprising
 Iris,
 Ciliary body
 choroid.

11. IRIS
 A free circular diaphragm with central opening
called Pupil.
 Colour – brown , Pattern – Collarette.
 It has two muscles viz
 Sphincter pupillae (Circular muscle) –causes
pupillary constriction.
 Dilator pupillae ( Radial muscle) – causes
pupillary dilatation.

12. CILIARY BODY:
 Middle portion of uvea
 Pars plicata – about 70 plication, has
ciliary process responsible for production of
aqueous
 Pars plana – posterior smooth part, safe
and avascular zone for pars plana
lensectomy and vitrectomy procedures.

13. CHOROID
 It is posterior part of uvea.
 This is a vascular sheet which
separates sclera from retina.

14. CRYSTALLINE LENS
 It is transparent biconvex structure derived from
surface ectoderm.
 Dioptric power : 16 – 20mm.
 9mm in diameter, 4mm in thickness
suspended by suspensory ligament called zonules.
Structure of Lens:
 Anterior lens capsule
 Anterior lens epithelium
 Lens Nucleus – consists of
elongated lens fibres
 64% water, 35% Protein (crystallin),
 1% Lipids (Cholesterol,
sphingomyelin, lipoproteins)

15. VITREOUS CAVITY
 Contain vitreous humour which is
transparent gel like structure.
 Composed of collagen fibers and
hyaluronic acid.
 Mainly serves the optical medium.
 In addition, it mechanically stabilizes
the volume of the globe and is a
pathway
for nutrients to reach the lens
and retina.

16. RETINA
 Membranous light sensitive layer of the
eyeball.
 Layered structure with several layers
of neurons. The only neurons that are
directly sensitive to light are
the photoreceptor cells,
 Two types: the rods and cones

17. NORMAL FUNDUS PHOTOGRAPH
 Optic disc. Pink coloured, well-defined circular Area.
 All the retinal layers terminate except the nerve fibres,
which pass through the lamina cribrosa to run into the
optic nerve
 Macula. Deeper red than
the surrounding fundus
 Situated at the posterior
pole temporal to the
optic disc.
 Fovea centralis is the central
depressed part of the macula
1.5 mm in diameter and
is the most sensitive
part of the retina.

18. Intraocular pressure (IOP)
• Range 10 - 20 mmHg
• Increases with age
• Direct correlation with axial length
• Main determinant is aqueous humour
• Increased IOP impairs blood flow to
the retina leading to loss of vision .
18

19. Circulation of Aqueous
HumourProduced by
ciliary body in
posterior
Chamber
Enters the
anterior chamber
through pupil
Absorbed by the
trabecular
meshwork into
the scleral
venous sinus

20. Events that Decrease
IOP
• IV anaesthetics
• Volatile anaesthetics
• Mannitol
• Timolol
• Betaxolol
• NDMR
• Hyperventilation
• Hypothermia
20
Events that Increase IOP
• Succinylcholine
• Direct laryngoscopy
• Hypoventilation
• Arterial hypoxaemia
• Increased venous pressure

21. Oculocardiac reflex
Incidence ---- 30% to 90%
 The oculocardiac reflex is most
commonly encountered in pediatric
patients undergoing strabismus
surgery, although it can be evoked in
all age groups and during a variety of
ocular procedures,
 This reflex consists of a trigeminal
(V1) afferent and a vagal (X) efferent
pathway.

22. Oculocardiac reflex -Causes
 Reflex triggered by
• Pressure on globe
• Traction on the extraocular muscle (Esp
medial rectus ) as in strabismus surgery.
• Ocular trauma
• Severe pain
• Orbital compression due to haematoma
or edema
• Procedures under tropical anesthesia
• Orbital injections
• Hypercapnia or hypoxemia

23. Oculocardiac reflex
 Bradycardia
 Bigeminy
 Ectopic
 Atrioventicular block
 Cardiac arrest

24. Pathway
Stretch receptors--- present in
Extraocular Muscle
Afferent through short & long ciliary nerves.
The ciliary nerves will merge with ophthalmic division of the
Trigeminal nerve at the ciliary ganglion.
Gasserian ganglion.
Nucleus of Trigeminal & vagus
Efferent vagal fibres
↑Para symp tone & Bradycardia

25. Treatment-
Inform surgeon, Stop stimulation.
Verify adequate ventilation &
oxygenation
Atropine (20 µg/kg) or glycopyrolate
(10-20 µg/kg)
In recalcitrant episodes, infiltration of
the rectus muscles with local
anesthetic. The reflex eventually
fatigues with repeated tractionon the
extraocular muscles.

26. Oculo-respiratory reflex
 Causes shallow breathing, reduced
respiratory rate and even full
respiratory arrest.
 Pathways are similar to occulo-cardiac
reflex. Due to connection between
trigeminal nucleus and pneumotactic
centre
 Atropine is ineffective.
 Adequate ventilation.