- 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