- gonioscopy.

In the name of Allah

to know the principle of goniolens we

must know some important information.....

- There is an angle called critical angle which need  rays come from media of high refractive index to media of low refractive index at this angle no refraction occur.

- When rays come from the angle between cornea and  iris outward to air as it has total internal reflection as there is critical angle so don't released to air .

- Total internal reflection as rays fall with angle is more than critical angle.
- corneal R.I = 1.38
- Air R.I = 1.00

- Goniolens eliminates the total internal reflection by replacing the cornea-air interface  by a new geniolens-air interface that has  higher R.I (n=1.50) than
that of the cornea and the tear.



-uses :-
used for viewing the anterior chamber angle of the eye for evaluation, management and classification of  normal and abnormal angle structures which is important in glaucoma management and evaluation.

- Contraindications for gonioscopy:-

• Hyphaema.
• Compromised cornea (e.g corneal ulcer).
• Lacerated or perforated globe.

Thanks alot

Dr Ibrahim

- Anatomy and histology of eye lids.

- Eye lid :

• It is movable muco-cutaneous fold covering anterior surface of eye globe.
• Upper eye lid is more movable than lower eye lid as it have levator palpebrae superioris muscle and Muller's muscle .
• The upper eyelid skin crease (superior palpebral furrow) is approximately 8-11 mm superior to the eyelid margin and is formed by the attachment of the superficial insertion of  levator aponeurotic fibers  (8-9 mm in men and 9-11 mm in women).

-The palpebral fissure is that empty space between the upper and  lower eyelid margins when the eyelids are open (that is, the space between the eyelids that allows you to see  your eyeball and your eyeball to see the world).

- Development of eye lids.

Development of eye lids

Time :

Begins during 6th week.

process:

1- Eye lids develop from two folds of skins over the

cornea during 6th week.

2- Eye lids adhere to each other by the beginning of 10th week

& remain adhered till 26th to 28th weeks.

Congenital anomalies:

usually congenital anomalies appear together

to give a syndrome.

1-congenital ptosis:-

cause: failure of development of levator palpebrea

superioris muscle.

- It may be simple( alone).

- It may be associated eith other lid deformities or

congenital opthalmoplegia.

- it is usually bilateral & hereditary.

2- Epicanthus:

- is a semilunar skin fold at the side of the nose

covering the medial canthus & the caruncle leading

to false convergent squint.


3- Telecanthus:

increased distance () two medial canthi.

4-Blepharo-phimosis:

-Diminution of the horizontal width of the palpebral

fissure from 25-30 mm (normal) to 18-22mm without

pathologic changes in the eyelids.

- It is rare & usually asscociated in

Blepharo-phimosis syndrome.

5-Blepharo-phimosis syndrome:

presence of congenital ptosis,Epicanthus,

elecanthus & Blepharo-phimosis with each other.

6- Congenital trichiasis ( distichiasis)

- rare condition.

- In which abnormal extra raw of lashes replacing white line.

7- Congenital entropion:

- rare with micropthalmos.


8- Congenital ectropion:

- rare with Blepharo-phimosis syndrome.


9- coloboma of the eye lids:

- It is triangular , quadrilateral or

irregular shaped defect of the lid margin.


10- Epiblepharon:

-horizontal redundant medial fold of skin of the

eye lid inducing vertical orientation of the cilia.

-Epiblepharon may co exist with entropion.

-It usually imrpoves by age as the eyelid skin stretches.

- Vision.

- Vision: - is a complex sense composed of many elements including:-

Perception of image on retina.-

-Conduction of the image as nerve impulse to brain.

- Interpretation & recognition of the image by brain.

- Organ of Vision: - is the eye.

- Eye is formed of: -

-Eyeball which located inside the orbit.

-Extra ocular structures surrounding it

(eyelids – Conjunctiva - lacrimal apparatus - Extra ocular muscles)

N.B… nerve of vision is :-

optic nerve which is the second (2nd) cranial nerve.

N.B… Ocular muscles 2:-

1- Extra ocular muscles:-

-Levator Palpebrae Superioris.

-Four recti :-

• Lat. Rectus
• Med. Rectus.
• Sup. Rectus.
• Inf. Rectus.

- Inf. Oblique.

- Sup. Oblique

2- Intra ocular muscles:-

- ciliary muscle.

- Sphincter pupillae muscle.

- Dilator pupillae muscle.

- what is ophthalmology?

The medicine and surgery of the eye and
its surrounding structures and its connections
to the brain, in order to maintain clear
, pain-free and useful vision
with an aesthetic attractive appearance.

- Cranial nerves.

**There are 12 cranial nerves...

1. I      Olfactory nerve (purely sensory).
2. II     Optic nerve  (purely sensory).
3. III    Occulomotor nerve  ( Purely motor).
4. IV    Trochlear  nerve  ( Purely motor).
5. V     Trigeminal nerve ( Mixed ).
6. VI    Abducent. ( Purely motor).
7. VII   Facial  ( Mixed ).
8. VIII  Auditory nerve  (Vestibulocochlear) (purely sensory).
9. IX    Glossopharyngeal  ( Mixed ).
10. X     Vagus  ( Mixed ).
11. XI    Spinal Accessory.( Mixed ).
12. XII   Hypoglossal .( Mixed ).

** Important notes:-

- The largest cranial nerve .... CN V (Trigeminal).
- Cranial nerves responsible for eye movements are

•    III (Oculomotor)
•    IV (Trochlear)
•    VI (Abducens)

- The longest cranial nerve ....CN X (Vagus) which reaches from the medulla to the digestive and urinary organs.


- CN I and II are  attached to Cerebrum.

See you ,

Ibrahim

- Histology of the cornea.

Histological structure :- is Composed of 5 Layers:-

1- Epithelium:-

• Active mitosis → regeneration within 6- 24 hrs.
• Continue with conjunctiva.

2-Bowman's membrane:-

• Acellular Clear membrane lie under the epithelium.
• Ends abruptly at the limbus. (i.e. end in folded manner)
• Is considered as modified lamella of stroma.
• If destroyed cannot regenerate.

3-Stroma:-

• Represent 90% of corneal thickness .
• Formed of collagen fibrils (Type 1) which has special arrangement which run parallel to each other and parallel to the surface of the cornea making the cornea transparent, unlike sclera in which arrangement is not done in specific way so appear opaque.
• Collagen fibrils lie in mucoid matrix Scattered keratocytes lie between lamellae and are stellate in shape.

4-Descemet's membrane:-

• An elastic membrane which lie ( ) Endothelium and stroma.
• It is resistant to pathology and regenerate easily. 
• This layer is continuous with material of the pectinate ligament or trabecular meshwork of the iris.

5-Endothelium:-
Single layer of flat hexagonal cells with No mitosis.

- Pumps water out → prevent corneal edema → prevent corneal opacification.

(By light microscope)

So Cornea formed of :-

• Epithelium resting on B.M
• Endothelium resting on D.M
• stroma in between