It is a mixture of 70% blue (488 nm) and 30% green (514 nm) light.
They are most commonly employed for retinal photocoagulation & for trabeculoplasty
Photocoagulation aims to treat the outer retina and spare the inner retina to avoid damaging the nerve fiber layer.
Argon green (blue screened out) photocoagulation of the macula does not cause direct retinal damage. It is well absorbed by melanin and haemoglobin , but Xanthophyll ( in the inner layer of the macula) absorbs blue light (but not green) and thus the use of blue light at the macula is contraindicated in order to avoid, direct damage to the retina in this region.
It emit an infrared (wavelength of 810 nm) in continuous wave mode. It is absorbed only by melanin i.e why most commonly used for retinal photocoagulation ;
low scattering of this wavelength ensures good penetration of the ocular media and of oedematous retina. It also penetrates the sclera. Thus if retina is obscured from view through the pupil, coagulation may still be performed by placing the probe on the sclera.
Although refractive errors are most commonly corrected by spectacles or contact lenses, laser surgical correction is gaining popularity.
The excimer laser precisely removes part of the superficial stromal tissue from the cornea to modify its shape. Myopia is corrected by flattening the cornea and hypermetropia by steepening it.
In photorefractive keratectomy (PRK),the laser is applied to the corneal surface. In laser assisted in situ keratomileusis (LASIK), a hinged partial thickness corneal stromal flap is first created with a rapidly moving automated blade, the flap is lifted and the laser applied onto the stromal bed.
Schematic representation of the pattern of corneal ablation necessary to correct hyperopia with the excimer laser. The greatest amount of tissue is removed from the periphery of the ablation zone with a gradual transition toward the anterior corneal surface.
The goals in retinal photocoagulation vary with the clinical entity being treated. For example, in pan photocoagulation for diabetic retinopathy the aim is the elimination of abnormal retinal blood vessels through direct treatment to the blood vessels or destruction of the ischemic areas of the retina .