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June 2012 myopia for trans-PRK is shown in Figure 5. For example, the number of op- erated eyes with an initial corrected visual acuity less than 0.5 with the value of initial myopia over 12 D (Figure 6) exceeds 50%. Criterion Action sequence To correctly and vividly deter- mine efficiency (productivity), we can compare post-op uncorrected distance visual acuity (UDVA) against pre-op corrected distance vi- sual acuity (CDVA) as their mathe- matical ratio of efficiency coefficient Classic PRK –local anesthesia –de-epithelization (mechanical, laser, or other) –refractive stage: laser treats the stroma (flying spot scanning or ray profiling as geometric figures) –placement of scleral lens (not always) Post-op pain The patient feels strongly marked discomfort for 3-4 days Keff.7 Figure 7 shows the efficiency of trans-PRK on a general basis of operation (depending on initial my- opia) at Ost-Optic K Co. Ltd. at 1 year post-op. To correctly evaluate trans-PRK results based on a safety criterion,8 Trans-PRK on Profile 500 –local anesthesia –transepithelial treatment by a wide laser ray (radial Gaussian distribution of energy density over the whole zone of operation) Pain on the day of the operation goes away in 30% of patients toward the evening. The next day, they feel only photophobia and eye watering. Two days later, 91.5% of patients have no discomfort Blepharospasm Time to put in drops after op- eration 3-4 days For 4-6 months, eye drops must be used according to a special regimen depending on the complexity of the patient's pre-op refraction Drop composition Steroid load; an increase in the IOP may be observed in about 5% of patients. This effect is neutralized by medicines reducing the IOP, or a whole regimen of post-surgical treatment should be applied, which is a non-standard situation Vision recovery Within 3-4 days 1-2 days post-op 1-2 months maximum irrespective of initial myopia EWInternational 55 we excluded the following types of patients from the analysis: • where the operation was planned to be performed in two stages but the second stage was not per- formed for various reasons • undercorrection was planned according to age; • post-surgical follow-up was less than 2 months; and • maximum visual acuity with correction before surgery was less than 0.5. In view of the above we see the following observations as shown in Table 2. A corresponding graph is shown in Figure 8. The main features and differ- ences of trans-PRK on the Profile 500 versus classic PRK are listed in Table 3. Conclusion The basic advantages of the trans- PRK with the use of the Profile 500 in comparison with classic PRK are vividly demonstrated. The large number of surgeries performed (more than 6,000) show the effi- ciency and safety of trans-PRK. These results also demonstrate the efficiency of laser correction for high and super high myopia. EW An IOP increase is more unusual due to therapy; medicines reducing IOP are prescribed only if its increase affects the visual acuity In the evening of post-op day 1, the patient can see about 30%; photophobia is possible Sports and driving Computer and TV Occurrence of high-order aberrations Range of initial myopia Procedure of correction Received optical profile Within a month Within a month Frequently occur during twilight and night vision Up to –6 to –8 D One eye first followed by the second eye a week later Monofocal Table 3. Characteristics of classic PRK and trans-PRK on the Profile 500 Source (all): Alexander I. Myagkikh, Ph.D., Eugene V. Makurin, Eugene A. Subbotin Within 7-10 days Within 5-7 days Do not occur Not limited (single-step correction up to 17 D) Both eyes at the same time Multifocal. Pseudoaccommodation may reach 3 D References 1. Fyodorov SN, Semyonov AD, Kornilovsky IM, Kachalina GF. Laser refractive surgery. The Report Theses VII Russian Ophthalmology Congress. 2000;221-225. 2. Kachalina GF. Surgical Ttechnology of transepithelial PRK for myopia with the "Pro- file-500" eximer laser. Abstract of MD Disser- tation. 2000;25. 3. Semyonov AD, Doga AV, Kachalina GF, et al. Photoastigmatic refractive keratectomy with the "Profile-500" for correction of compound myopic astigmatism. Ophthalmosurgery. 2000;4:3-8. 4. Semyonov AD, Doga AV, Kachalina GF, et al. Specific features of clinical course in pho- toastigmatic refractive keratectomy with the "Profile-500" at different terms postopera- tively. Ophthalmosurgery. 2001;1:3-7. 5. Arba-Mosquera S, Hollerbach T. Ablation resolution in laser corneal refractive surgery: The dual fluence concept of the AMARIS Plat- form. . Advances in Optical Technologies. 2010;1. 6. Kodo O, Kachalina G, et al. Superficial PRK. The Report Theses VIII Russian Ophthalmology Congress. 2005;262-263. 7. Myagkikh AI. Method of determination of re- fractive operations efficacy. . Fyodorov's col- lected science articles. 2002;246-248. 8. Standardized graphs and terms for fefrac- tive surgery results. JRS. 2011;27(1). Editors' note: The authors have no financial interests related to this article. Contact information Myagkikh: ostoptik@mail.ru