Evolution of retinal laser therapy: minimum intensity photocoagulation (MIP). Can the laser heal the retina without harming it?

Laser photocoagulation is a photo-thermal therapy validated by landmark studies and commonly accepted as the standard of care for various retinal diseases. Although its mechanism of action is still not completely understood, it is normally administered with visible endpoints, true intra-retinal burns that cause chorioretinal scars, which, with time, evolve into expanding areas of atrophy. New hypotheses on the mechanism of action of laser photocoagulation suggest that its therapeutic benefits derive from biologic activities that cannot be inducted within the "burned" area of photocoagulation necrosis, but that occur in the adjacent surrounding areas affected by a lower, sub-lethal, photo-thermal elevation. Thus, the iatrogenic chorioretinal damage caused by visible endpoint photocoagulation may be redundant and an equally effective laser therapy could be administered with minimum intensity photocoagulation (MIP) using laser protocols aiming to create only non-lethal photo-thermal elevations with no intraoperative visible endpoint. It is the purpose of this paper to review laser techniques and clinical protocols that have been utilized to administer retina-sparing MIP treatments that hold the promise of healing the retina while minimizing the iatrogenic harm.