Studies indicating unacknowledged dangers of laser eye surgery

Shockwaves from the excimer laser:

Peter J. McDonnell, Complications of Excimer Laser Refractive Surgery, in Peter Hersh, ed., Refractive Surgery, ch. 24, p.364, 1997.

(note:  although this excerpt refers to PRK, the referred-to mechanical damage produced by laser ablation is identical to that which can result from Lasik)

    "During PRK, mechanical damage to the deeper layers of the cornea may originate from two potential mechanisms:  (1) manual or laser debridement of the epithelium and (2) shockwaves produced during the ablation process.  Whereas potential damage from the abrasion should be localized to the outer cornea, pressure waves can travel through the eye and may affect deeper ocular structures, such as endothelium, lens, iris, and retina. 

    Kermani and Lubatschowski found pressure waves with an amplitude of 80 bar at a distance of 3 mm behind the cornea when an excimer laser beam with a diameter of 4 mm and a fluence of 200 mJ/cm² was applied to the corneal surface.  These waves travel with sonic velocity through the eye and, in contrast to the shockwaves generated by Nd:YAG photodisruption, the amplitude falls slowly with distance.  In freshly enucleated porcine eyes treated with a clinical (Apogee, Summit Technology, Waltham, MA) excimer laser, Gobbi et al reported positive (compressive) pressure pulses lasting 100 nsec in time and ranging from 90 bars in the anterior chamber down to 20 bars close to the retina.  They also observed rarefaction pulses with negative pressures as high as -40 bar.  These authors concluded that high pressure rarefaction pulses could induce direct damage to ocular tissues and can also trigger the formation of cavitation bubbles in both anterior and posterior chambers.  They assert that these photoacoustic phenomena could represent a particular threat to the corneal endothelium, iris, and retina."

    "Whether the incidence of subretinal hemorrhage is increased after PRK or whether any such hemorrhages have occurred immediately after PRK is not known;  however, during PRK, mechanical shockwaves with an amplitude of up to 100 bar travel through the eye and potentially might irritate or disrupt the fragile subretinal vessels."

http://latimes.com/features/health/la-011402lasik.story