1. Topographically-guided photo-refractive keratectomy (TG-PRK) for complications of refractive surgery
David TC Lin, MD, FRCSC
Simon Holland, MD, FRCSC, FRCS(Eng), MRCP, FRC Oph
Pacific Laser Eye Centre
UBC Dept of Ophthalmology
ASCRS, San Diego 2011
No financial interests

2. Aim Management of complicated laser refractive surgery challenging
Patients often intolerant or reluctant to use specialty contact lenses
Surgical options - limited as often unable to capture wavefront analysis if severely aberrated cornea
Evaluate topographically guided photo-refractive keratectomy (TG PRK) for symptomatic patients with decentered ablations (DA) and radial keratotomy
(RK)

3. Methods
Custom neutralizing technique (TNT) for aberrated corneas with decentered ablation (DA) zones after laser refractive surgery and radial keratotomy (RK)
Allegretto Wavelight topographically-guided (TG) laser
Retrospective case series, 94 eyes DA and 49 eyes with irregular astigmatism following RK
Previous LASIK or PRK
LASIK Flap lift; PRK Trans-epithelial,
PTK with mitomycin C

4. Topographical Neutralisation Treatment
Method of compensating for induced refraction change by surface regularization
Plano TG: i.e. hyperopic effect in increasing optical zone after RK
Correction of astigmatism induced by plano TG
Correction of sphere induced by 1 and 2
Manifest refraction added =
final treatment 4

5. Methods : TG PRK for DA , RK
Patient evaluation:
- symptom score - blurred vision, doubling , glare , haloes, starbursts
- pre and post UVA, BSCVA, refraction, topography, change in centration relative to pupil center, predictability, safety

6. TG PRK for DA 14 months LASIK 3 months post-op
UCVA : 20/ UCVA : 20/20-
Pre-op: x / RX: /20

8. TG PRK for RK 20 years RK, LASIK 6 months post-op
BSCVA: 20/ UCVA: 20/60-
Pre-op: x Rx: /40

10. TG PRK for RK 20 years RK, LASIK 6 months post-op
UCVA: 20/ UCVA: 20/200
Pre-op: x150 20/25 Rx: /25

12. TG PRK for RK 20 years RK, LASIK 4 months post-op
UCVA: 20/ UCVA: 20/20
Pre-op: x /25 Rx: /20

14. Summary of Results - Decentered Ablations
UCVA >= 20/40 77% . >= 20/ %
24% gained ≥1 lines, 71% no change, No loss >2 line
Mean centration: from pupil center improved from 0.92mm to 0.30mm (p<0.01)
All had improved astigmatism, 1.25D-6.75D
All symptomatic prior to surgery , 19% still had symptoms following, rated >3 on 4 point scale as moderate/severe

15. Summary of Results: RK UVA >=20/40 62% >= 20/25 18%
Lost and gain >= 2 lines – 7%
Symptoms - improved in 72% .

16. Discussion
TG laser treatment for DA more predictable , better UCVA and less loss of lines than when performed for irregular astigmatism after RK
Tendency to overcorrect post-RK due to hyperopic effect of TG –expect to regress
Persisting diurnal fluctuation
Alleviated more severe symptoms in
most patients in both groups

17. Conclusion: TG laser for aberrated corneas after previous refractive surgery
Valuable option for highly symptomatic patients with Decenterd Ablations and after RK
Refractive predictability is better with neutralization (Custom TNT) but still needs improvement

18. Palmyra, Syria