1. Laser in ophthalmology laser: Abbreviation of Light Amplification by Stimulated Emission of Radiation .
Criteria of laser:
Collimated: Parallel light rays.
Coherent: all waves at the same phase (constructive interphase).
Monochromatic: all rays with the same wave length

3. Emission of laser: In a laser chamber (resonator area) we have tow reflecting mirrors, in between them there is a laser medium, which could be; solid, liquid, or gas around this chamber there is a pumping source (electrical, optical, or, chemical) to stimulate laser production. On simulation of the laser material the atoms will be at a higher energy levels, while on emission, these atoms will return back to a low energy level.

4. Laser Tissue Interactions:
The effect of the laser on the tissues:
1.Photo-Coaglation.
2. Photo-disruption.
3. Photo-ablation.

5. Types of laser used in Photocoagulation:
Argon lasers (gas laser medium) which is of tow types:
Blue light (480nm).
Green light (514.5nm)
Frequency doubled YAG lasers (solid laser medium) its wave length is 532nm.
Diode laser infrared light of nm.
Krypton laser red light.

6. Uses of laser Photocoagulation:
1.Treatment of diabetic retinopathy:
- PRP (pan retinal photocoagulation) in prolipherative stage .
-Grid or focal laser therapy in exudative or edematous state of maculopathy , not in ischemic type.
2- Prophylaxis of peripheral retinal degenerations e.g. in high myopia or any other cases retinal breaks (hole or tear).
3-Argon laser trabeculoplasty; shrinkage of the burned areas leads to traction on surrounding area and opening the trabecular meshwork.
4-Cyclodestructive (ciliary body) procedures in cases of glaucoma.

7. Uses of laser photodisruptions:
Peiphral iridectomy e.g.in cases of angle closure glaucoma.
Posterior capsulotomy in cases of thickening of posterior capsule after cataract surgery.
Disruption of any inflammatory membrane on the implanted lens.
Cutting of any vitreous bands e.g.post operative or after ocular trauma.
C yclodestraction in cases of glucomas.

8. Uses of photoabilation:
PRK: photorefractive keratectomy to reshape the
Cornea in cases of myopia, hypermetropia, and astigmatism.
LASIK: laser intrastromal keratomeleusis. To reshape the Cornea in cases of myopia, hypermetropia, and astigmatism.
PTK: phototherapeutic keratoctomy to remove abnormal corneal surface tissue.