Abstract
Purpose: :
To evaluate the occupational exposure to UV radiation during photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with the ALLEGRETTO WAVE Eye-Q 400 MHz excimer laser system.
Methods: :
Intraoperative UV scatter measurements were made with the Ophir Nova Power/Energy Meter (LaserStar Model PD-10 with silicon detector) during PRK and LASIK treatments performed with the Wavelight ALLEGRETO WAVE excimer laser. 12 PRK patients had corneal epithelial removal using the Amoils epithelial scrubber [BRUSH PRK]; 12 PRK patients had epithelial removal with 20% ethanol [ETOH PRK]; 12 LASIK patients had a superiorly-hinged flap created with the Intralase FS femtosecond laser. The maximal measured pulse energy for each treatment was recorded during ablation of the left eye at a distance of 25.4 cm from the corneal surface. These measurements were averaged and evaluated using a worst-case scenario for exposure to operating room personnel. Results were compared to the occupational exposure limit of 3mJ/cm2 set by the International Commission on Non-Ionizing Radiation Protection (ICNRP).
Results: :
The average maximum pulse measured during BRUSH PRK was 137.16 +/-23.96nJ (range 60.0 - 248.06nJ); the average maximum pulse during ETOH PRK was 70.66 +/-14.15nJ (range 10.92 - 254.04nJ); and the average maximum pulse during LASIK was 27.99 +/-4.10nJ (range 11.16 - 62.76nJ). Total exposure during surgery at close range (80 cm from the treated eye) was calculated using an average treatment time of 12.61 seconds. BRUSH PRK, ETOH PRK and LASIK averaged a maximum exposure of 0.089mJ/cm2, 0.046mJ/cm2 and 0.018mJ/cm2 per eye, respectively. If all procedures during a heavy workday of 20 patients (40 eyes) were BRUSH PRK, the total maximum exposure would be 3.55mJ/cm2. A full day of ETOH PRK procedures would result in a maximum exposure of 1.83mJ/cm2, while a full workday of LASIK procedures would result in a maximum exposure of 0.019mJ/cm2.
Conclusions: :
The ALLEGRETTO WAVE Eye-Q laser has the potential for greater UV exposure than previously studied systems. PRK consistently resulted in higher scatter than LASIK. BRUSH PRK in particular resulted in higher readings than either ETOH PRK or LASIK and by our worst-case calculations would exceed the occupational UV exposure limit of 3mJ/cm2. The reason for this finding is unclear but may be due to variations in regularity/reflectivity of the stromal bed/Bowman’s layer. For the protection of providers, manufacturers should warn of the risks of exposure to laser emissions and eye protection should be available, particularly during rotary BRUSH PRK procedures.
Keywords: laser • refractive surgery