representative cases : topography-guided photorefractive keratectomy for irregular astigmatism...
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Representative Cases:
Topography-guided Photorefractive Keratectomy for Irregular Astigmatism following Penetrating Keratoplasty
Purpose: Evaluation of efficacy and safety of topography-guided photorefractive keratectomy (TG PRK) for irregular astigmatism following penetrating keratoplasty (PK). Post-keratoplasty astigmatism often high and irregular. Previously variable results with PRK – haze, regression with poor quality of vision. Potential advantages with topography guided techniques to reduce irregular astigmatism and vision of quality.
Methods:Retrospective case series. 87 cases with post keratoplasty astigmatism underwent TG PRK with Allegretto Wavelight (AW) laser Custom Topography Neutralization Technique (TNT) Trans-epithelial TG-PRK using TCAT. Application of mitomycin C 0.02% and standard post-PRK management. Data evaluated: 3, 6 and 12 months on: Uncorrected visual acuity (UCVA), Best spectacle corrected visual acuity (BSCVA), Manifest refraction (MR), Topography and Keratometry.
Results:87 eyes had treatment; 49 eyes had follow up of 12 months or more. UCVA:
• 35% (17) achieved UCVA ≥ 20/40, while none preoperatively
BSCVA:• 49% (24) had improved BCVA• 35% (17) gained ≥ 2 lines• 4% (2) lost ≥ 2 lines
Refractive Cylinder:• Pre-operative: 0.75D to 8.00D• Post-operative: 0.00D to 6.00D• Average improvement: 2.24D
Topographic Cylinder:• Pre-operative: 1.79D to 13.74D• Average improvement: 2.92D
Average Spherical Equivalent:• improved by 1.70D, from -3.13D to -1.43D
Retreatment rate: 15%. No cases of delayed epithelial healing. None with clinically significant haze (> +2)
Conclusion:Early results of TG-PRK with TNT shows potential to improve both UCVA and BSCVA with good efficacy and safety. 35% UCVA improved to 20/40 or better, none preoperatively. High re-treatment rate: 15%. Almost half of the cases had improved BSCVA, more than one third gained ≥2 lines.
References:1. Ohno K., Customized photorefractive keratectomy for the correction of regular and irregular astigmatism after penetrating keratoplasty. Cornea. 2011 Oct;30 Suppl 1:S41-4. doi: 10.1097/ICO.0b013e318228174b2. Knorz MC, Jendritza B. Topographically-guided laser in situ keratomileusis to treat corneal irregularities. Ophthalmology. 2000 Jun;107(6):1138-43.3. Pedrotti E, Sbabo A, Marchini G. Customized transepithelial photorefractive keratectomy for iatrogenic ametropia after penetrating or deep lamellar keratoplasty. J Cataract Refract Surg. 2006 Aug;32(8):1288-91.4. Alessio G, Boscia F, La Tegola MG, Sborgia C. Corneal interactive programmed topographic ablation customized photorefractive keratectomy for correction of postkeratoplasty astigmatism. Ophthalmology. 2001 Nov;108(11):2029-37.5. Rajan MS, O'Brart DP, Patel P, Falcon MG, Marshall J. Topography-guided customized laser-assisted subepithelial keratectomy for the treatment of postkeratoplasty astigmatism. J Cataract Refract Surg. 2006 Jun;32(6):949-57.6. Mularoni A, Laffi GL, Bassein L, Tassinari G. Two-step LASIK with topography-guided ablation to correct astigmatism after penetrating keratoplasty. J Refract Surg. 2006 Jan-Feb;22(1):67-74.
Pacific Laser Eye Centre tel: (604)736-2625
CASE 1 – 39 y.o. male, PK x5yrsPreop: 22 months postopUCVA 20/400 UCVA :20/30Rx: -1.75-4.50x048 20/25 Rx : -0.50-1.25x030 20/20-1 CT: 521µm CT: 447µm
Pre-Op Pos-Op Pos - Pre
Simon P. Holland MB, FRCSC, FRCS, MRCP; David T.C. Lin MD FRCSC; Umi K. Noh MB BCh BAO, Ms(Ophth)
Pre-OpPre-Op
CASE 2 – TG PRK for post PK with retreatmentPreop Final PosopBSCVA: 20/60-1 UCVA: 20/40MR: -1.50-8.00x122 MR: +0.50-1.25x180 20/40
Topo Cyl: 9.40x113Total Tx Cyl: 11.88D
Pos - Pre
Pre-Op of 1o tx Pos-Op of 1o tx Pos-Op of 2o tx (Final)
Final Pos-Op – Pre-Op
4.1%8.2%
38.8%
14.3%
34.7%
0%
10%
20%
30%
40%
GAIN 2LINES OR
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GAIN 1LINE
NOCHANGE
LOSS 1LINE
LOSS 2LINES OR
MORE
Change in BCVA at 12 Months Post Op