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Astigmatism “NO TOUCH” PROCEDURE
TransPRK (Transepithelial Photorefractive Keratectomy) For the Treatment of Low to Moderate Myopia with Astigmatism “NO TOUCH” PROCEDURE Presenting author Dr K V Satyamurthy, Dr Jaysheel V Nazare M.M.Joshi eye institte Hubli, India Authors have no financial or proprietary interest in any material or methods
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Introduction Transepithelial PRK
Most commonly indicated in eyes which cannot undergo LASIK procedure due to inadequate corneal thickness (estimated residual stromal thickness beneath the flap after the ablation would have been less than 250 µm) No corneal flap created Both epithelium and stroma are ablated in single procedure, decreasing overall treatment time and minimizing risk of corneal dehydration. PURPOSE OF STUDY To evaluate efficacy of transepithelial Photorefractive keratectomy (transPRK) for the treatment of low to moderate myopia with astigmatism, using the Amaris 500 Hz laser platform.
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METHODS Inclusion Criteria
Phakic patients with low to moderate myopia (-1.0 to -6.0 D of myopia with -1.0D to -4.0D astigmatism) Spherical equivalent from -3.5 to -8D. Healthy myopic patients 18 years or older. Vision correctable to at least 20/20 bilaterally. written informed consent form signed by patient. Refractive status to be stable for at least 1 year. Corneal pachymetry greater than 480µm. The estimated residual Stromal thickness after ablation would have been µm Prior to preoperative evaluation, hard (PMMA) contact lens discontinued for at least 3 weeks and soft lens discontinued for at least 3 days. Pupil diameter of equal or less than 7mm under scotopic conditions.
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Complete Ophthalmologic Examination
- Uncorrected (UDVA) and corrected (CDVA) distance visual acuities - Manifest and cycloplegic refractions - slitlamp evaluation of the anterior segment and the fundus - Applanation tonometry and tear-film assessment Preoperative refractive workup included - Combined Placido-Scheimpflug Imaging Based Topography System (SIRIUS) - Ultrasonic Pachymetry Total of 29 subjects, were enrolled instudy. Preoperatively, - 0.25/0.5 mg of oral alprazolam. - Topical drops of Proparacaine (0.5%) instilled in the eye to be treated During procedure, epithelium and stroma were ablated in a single step using transepithelial PRK nomogram of Amaris laser's ORK-CAM software.
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After ablation 0.02% Mitomycin-C solution applied 30
seconds. - Cold BSS irrigation. - High-O2 Content (59%) soft contact lens placed. Ofloxacin (0.3%) and fluorometholone (0.1%) drops. Post-operative Care and Follow-up - Preservative-free artificial tears. - Epithelial healing assessment on day 1and 3. - CL removed once epithelium healed completely - Fluorometholone drops tapered over 2-3 months. At each follow-up visit (at1 week, at 1 month, and at 3 months) the UDVA, CDVA, and Corneal evaluation was done. Haze grading using the Fantes et.al system 0 = no haze; +0.5 = trace haze on oblique illumination; +1.0 = corneal cloudiness not interfering with the visibility of fine iris details; +2.0 = mild effacement of fine iris details; +3, +4 = details of the lens and iris not discernible.
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RESULTS Parameters Values No of Patients 29 Age(yrs) Mean 24 Gender
- Male - Female 13 16 Number of eyes - Right - Left 15 14
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RESULTS Parameters Preop Post op 1month (p value) Post op 3month
Mean UDVA (logMAR) 1.08 0.11(0.000) - Mean Spherical Equivalent
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RESULTS Parameters Preop Postop 1month Postop 3month
Mean CCT (microns) 506 421(o.ooo) 424.9(0.000) Mean SimK1 (D) 43.95 40.34(0.000) 40.43(0.000) Mean SimK2 (D) 45.11 41.08(0.000) 41.16(0.0000 Mean Pupil (mm) 3.45 3.50(0.000) 3.67(0.007)
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RESULTS Parameters Preop Postop 1month (p value) Postop 3month
Mean Thinnest pachy 503.5 418.7(0.000) 425(0.000) Mean Thickness At Apex 529.8 590.7(0.000) 602.7(0.000) Mean Cornea Volume 55.89 54.65(0.000) 54.76(0.000) Mean LSA 1.02 2.26(0.000) 1.12(0.000) Mean MPP 44.18 39.73(0.000) 39.52(0.000) Parameters Preop Postop 1month (p value) Postop 3month Mean SIF 0.10 0.15(0.000) 0.24(0.000) Mean SIB -0.03 -0.02(0.000) -0.03(0.000) Mean KVF 3.75 8.96(0.000) 9.17(0.000) Mean KVB 12.79 16.75(0.000) 17.34(0.000)
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RESULTS Parameters Preop Postop 1month (p value) Postop 3month
Mean BCVF 0.16 0.13(0.000) 0.24(0.000) Mean BCVB 0.06 0.09 (0.000) 0.09(0.000) Mean BCVT 0.1 0.11(0.000) 0.10(0.000) Parameters Mean Optical Zone(mm) 6.41 Mean Treatment Time (ablation) 42.58 s
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RESULTS POST-OPERATIVE CORNEAL HAZE GRADES Total o 0.5 1 2 3-4 1 Month
24(82.75%) 5(17.24%) 29 3 Month 22(75.86 %) 7(24.13%)
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CONCLUSION Safety, predictability and efficacy of the Schwind Amaris advanced surface ablation nomogram(TransPRK) for the treatment of mild to moderate myopia with astigmatism in eyes with thinner corneas not suitable for LASIK procedure was found to be better than the existing alcohol assisted PRK technique.
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