Posterior segment of eye.pdf

This is a class based presentation presented on Lecture of Shaalakya Tantra guided by Dr. Sadhana Parajuli Mam, H.O.D, Ayurveda Campus & Teaching Hospital, Kirtipur, I.O.M, T.U

1. Posterior segment of eye
SarojPanthi
3
rd
Prof
Roll no. 4

2. Components :
•Choroid
•Vitreous humor
•Retina
•Optic disc

3. Choroid
•Posterior part of the vascular coat of the eyeball.
•It is brown, thin, and highly vascular membranelining the inner surface of the
sclera.
•Anteriorly, connected to the iris by the ciliary body and
•Posteriorly, pierced by the optic nerve
•Arteries: Derived from short ciliary arteries, which pierce the sclera around the
optic nerve.
•Veins: They are arranged in the form of whorls, which converge to form the 4 or 5
venae vorticosae, which pierce the sclera just behind the equator to open into
the ophthalmic veins.
**** The inner surface of the choroid is firmly attached to the retina and nourishes
the rods and cones of the retina by diffusion.

5. Choroid
•Structure : It consists of four layers (from outside inwards), viz.
1.Suprachoroidlamina(laminafusca):Itconsistsofloosenetworkof
elasticandcollagenfibresandistraversedbylongposteriorciliary
vesselsandnerves.
2.Vascularlamina:Itconsistsoflooseareolartissueandpigment
cells.Itcontainsbranchesofshortposteriorciliaryarteriesand
veins,whichconvergeinwhorlstoform4or5venaevorticosae,
whichpiercethescleraanddrainintoophthalmicveins.

6. Choroid
3. Capillary lamina (capillary layer of choroid): It consists of fine
network of capillaries, which nourish photoreceptors of the retina (rods
and cones) by diffusion.
4. Basal lamina (membrane of Bruch):It is a thin transparent
membrane, which is firmly attached to the pigment cell layer of the
retina. The last three layers form the choroid proper, which is
separated from sclera by suprachoroidlamina.
****In some animals such as cat, tiger, lion, etc. the specialized cells of
choroid form a reflecting media called tapetum, which produces
greenish glare in the eyes of these animals in the night.

7. Choroid
Choroiditis

8. Vitreous humor
•It is a transparent, gelatinous substance. This can’t be replacedunlike
aqueous humor.
•The vitreous body is 99% water but, vitally, also contains collagen
fibrils and hyaluronic acid, which impart cohesion and a gel-like
consistency.
•The vitreous is adherent to the retina at certain points, particularly at
the optic disc and at the oraserrata.

9. Vitreous humor
•The vitreous body can be divided into two parts: the cortex and the medulla or nucleus
(the main vitreous body)
1.Cortical vitreous:It lies adjacent to the retina posteriorlyand ciliary body, zonulesand
lens anteriorly. The density of collagen fibrils is greater in this peripheral part. The
condensation of these fibrils form a false anatomic membrane which is called as
anterior hyaloid membrane anterior to oraserrataandposterior hyaloid membrane
posterior to ora. The attachment of the anterior hyaloid membrane to the posterior
lens surface is firm in young and weak in elders, whereas, posterior hyaloid membrane
remains loosely attached to the internal limiting membrane of the retina throughout
life.
2.Vitreous body (medulla or nucleus): It has a less dense fibrillarstructure and is a true
biological gel. It is here where liquefactions of the vitreous gel start first.
Microscopically, the vitreous body is homogenous, but exhibits wavy lines as of
watered silk in the slit-lamp beams. Running down the centreof the vitreous body
from the optic disc to the posterior pole of the lens is the hyaloid canal (Cloquet’s
canal) of doubtful existence in adults. Down this canal ran the hyaloid artery of the
foetus.

11. Vitreous humor
•Attachments :The part of the vitreous about 4 mm across the ora
serratais called as vitreous base, where the attachment of the
vitreous is strongest. The other firm attachments are around the
margins of the optic disc, fovealregion and back of the crystalline lens
by hyaloidocapsularligament of Wieger.

12. Vitreous humor
Functions of vitreous
•Screen out UV and IR light.
•Provide a clear media for optical transmission.

13. D/s of Vitreous humor
Vitreous liquefaction
Vitreous detachments
Inflammatory vitreous opacities
Vitreous haemorrhage

15. Retina
The retina is the innermost coat of the eyeball. It consists of two layers,
viz.
1.An outer pigment layer.
2. An inner sensory layer. The space between the two layers contains a
gummy substance that glues the two layers.
The retina is present between the choroid and the hyaloid membrane
of the vitreous. The retina diminishes in thickness from behind
forwards. Anteriorly, it presents an irregular edge called oraserrata.

17. Retina
•Structure :
1.The outer layer of the retina is insensitive to light and made up of
pigmented cuboidal epithelium.
2.The inner sensory layer of the retina is sensitive to light and is made up
of photoreceptors cells called rods and cones; as well as numerous relay
neurons, viz. bipolar neurons and ganglion cells. The very thin non-
cellular continuation of the retina in front of the oraserratacovers the
ciliary body and iris. Thus,photosensitive part of the retina lines the
inner surface of the eyeball posterior to the ciliary body. The nerve fibres
arising from its ganglion cells covers inner surface and collect in the
inferomedialregion, where they pierce the outer two coats of eyeball
and emerge as the optic nerve.

18. Retina
•Histologically, the retina is composed of following 10 layers:
1.Outer pigmented layer
2.Layer of rods and cones (photoreceptor cells)
3.External limiting membrane
4.Outer nuclear layer (Cell bodies of rods and cones)
5.Outer plexiform layer
6.Inner nuclear layer (Cell bodies of bipolar neurons)
7.Inner plexiform layer
8.Ganglion cell layer
9.Nerve fibrelayer
10.Internal limiting membrane

19. Retina
•Macula lutea-Lateral to optic disc a small area with a hint of
yellowish coloration
•Fovea centralis–central depression in Macula lutea
•Thinnest yet most visual sensitive area

21. Retina
•Blood Supply : The deeper part of the retina, i.e., up to the bipolar
neurons is supplied by the central artery of the retina (a branch of the
ophthalmic artery), while the superficial part of the retina up to the
rods and cones is nourished by diffusionfrom the capillaries of the
choroid.
•Venous Drainage: It is by central vein of the retina, which drains into
the cavernous sinus.

22. D/s of Retina
Retinitis
Eale’sd/s
Retinal artery occlusions
Hypertensive retinopathy

23. Optic disc
•Optic disc is where the optic nerve leaves the retina. It is lighter than
surrounding retina and branches of the central retinal artery spread
from this point outward to supply the retina.
•Blind spot in the retina because no photosensitive receptors are in
the optic disc.

24. D/s of Optic disc
Coloboma
Drusen
Hypoplasia

25. Arterial Supply of Eyeball
•The eyeball is supplied by the following arteries:
1.Central artery of the retina
2.Long and short posterior ciliary arteries
3.Anterior ciliary arteries
In the region of ciliary body, a major arterial circle is formed by the
anastomosis between long posterior ciliary artery and anterior ciliary
artery. From major arterial circle the vessel passes centripetally and
anastomoses close to the pupillary margin to form the minor arterial
circle.

28. Reference
•Snell Clinical Anatomy
•Gray’s Anatomy
•Textbook of Human anatomy VishramSingh
•Comprehensive ophthalmology A.K Khurana

29. सर्वे जन ाः सुखिनोभर्वतु
Thank You