- Types of Poisoning.

• Deliberate متعمد
  
  • Overdose as self-harm or suicide attempt.إنتحار
  • Child abuse .
    
  • Munchhausen's syndrome :Factitious disorder, Hospital addiction syndrome(e.g psychic patient).
  • Third party (attempted homicide, terrorist, warfare).
  
  
• Accidental عن غير قصد
  • Most episodes of paediatric poisoning.
  • Dosage error.
  • Iatrogenic
  • Patient error
  • Recreational use.
  
  
• Environmental:
  • Plants
  • Food
  • Venomous stings/bites.
  
  
• Industrial exposures.

- cornea.

cornea

* Definition :

It is a colorless (transparent) structure

covering the anterior 1/6 of the eye ball.


*Development of the cornea:

• Surface ectoderm forms the epithelium of the cornea.
• Mesoderm gives rise to the corneal stroma.
• Neural crest cells gives rise to the corneal Endothelium.

**Characters of the cornea :-

- colorless (transparent) structure and has a smooth surface.

- A vascular structure.

- Highly innervated by non-myelinated trigeminal nerve fibers.

-The most powerful refractive media of the eye

( 42+ diopters ).

- Diameter :-

• Horizontal = 12mm 
• vertical = 11mm Why…?

Due to scleral overlapping on upper

& lower sides of the cornea.

- It is not uniformly curved How…?

>>the central or optical zone having a smaller radius of

curvature than the peripheral parts,and the

posterior surface is more strongly curved than the anterior.

>> Ant radius of curvature = 7.7 mm 

>> Post radius of curvature = 6.6 mm

>>Thus the cornea is thinner (0.6 mm) at its

center than near its margin (1 mm).

see you,

Dr Ibrahim

- 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.