Topography-Guided Photorefractive Keratectomy

for Irregular Astigmatism following

Penetrating Keratoplasty Johnson Tan, MBBS MRCSEd (Ophth) FRCSEd (Ophth) FAMS1,2

Simon Holland, MD FRCSC1,3

David TC Lin, MD FRCSC3

1University of British Columbia, Vancouver, Canada2National Healthcare Group Eye Institute, Singapore

3Pacific Laser Eye Centre, Vancouver, Canada

WCC, San Diego 2015

Financial InterestHolland, Simon:

Alcon Laboratories Inc: Research SupportAllergan and Bausch & Lomb: Travel Support

The other authors have no financial interests in the materials mentioned

PurposeTo evaluate the efficacy and safety of the

custom Topographic Neutralization Technique (TNT) in Topography-Guided Photorefractive Keratectomy (TG PRK) in irregular astigmatism following Penetrating Keratoplasty (PK)

MethodsRetrospective, non-randomized, consecutive, case

series

49 eyes with irregular astigmatism after PK

Topography-Guided Customized Ablation Treatment (T-CAT) planning software with ALLEGRETTO WAVE® (AW) Eye-Q Excimer laser platform (Alcon Laboratories Inc, Ft Worth, Texas)

Custom Topography Neutralization Technique (TNT) adjust for the induced refractive change of surface

regularization from topography-guided treatments

ProcedureTrans-epithelial PTK, followed by TG PRK

with T-CAT software and TNT

Mitomycin-C 0.02% for 60-75 seconds

Bandage contact lens fitted and remained in place until full re-epithelialization

Fluoromethalone 0.12% eyedrops were given for 3 months, with a tapered dosing

Data AnalysisAt 3, 6 and 12 months

Uncorrected Visual Acuity (UCVA)Best Corrected Visual Acuity

(BCVA)Manifest Refraction (MR)Topographic Keratometry

Results49 eyes had treatment; 23 eyes had follow

up of at least 12 months

UVA:35% (8/23) achieved UVA ≥ 20/40None had UVA ≥ 20/40 preoperatively

BCVA:48% (11/23) had improved BCVA35% (8/23) gained 2 or more lines17% (4/23) lost 1 line4% (1/23) lost 2 or more lines

0%

10%

20%

30%

40%

GAIN 2LINES OR

MORE

GAIN 1LINE

NOCHANGE

LOSS 1LINE

LOSS 2LINES OR

MORE

Change in BCVA at 12 Months Post Op

ResultsManifest Cylinder:

Pre-operative: 0.75D to 8.00DPost-operative: 0.00D to 6.00DAverage improvement: 2.97D

Average Spherical Equivalent improved by 1.45D, from -2.32D to -0.87D

Topographic Cylinder:Pre-operative: 1.79D to 13.74DAverage improvement: 2.89D of cylinder

ResultsRetreatment rate: 8.7%

No cases of delayed epithelial healing

No significant haze (<2)

TG-PRK for PK

Pre-op 13 Months Post-op

UVA: 20/300 UVA: 20/50-2

MR: +4.00-6.00 x 005 20/80-1 MR: pl-4.00 x 175 20/40+1

Topo Cyl: -13.74 x 007

Tx: +1.01-5.73 x 007

Pre Op Post Op

Difference Map

TG-PRK Retreatment for PK43 years old male 18 months post-op

PK x 2yrs, PRK x 8 months

UVA: 20/100 UVA: 20/40-1

MR: pl-5.75 x 122 20/40 MR: +0.50-1.25 x 180 20/40

Tx: -1.25-5.88 x 130

CT: 485µm CT: 409µm

Final Post Op

1o Tx Pre Op

1o Tx Post Op

1o Tx PreOp MR:-1.50-8.00 x 122 20/60-

1

Topo Cyl: 9.40 x 113Total Tx Cyl: 11.88D

Final PostOp MR:UVA: 20/40-1 MR: +0.50-1.25 x 180 20/40

Difference Map

DiscussionPost-keratoplasty astigmatism is highly

irregular, may be extreme

Challenging, often not correctable with contact lenses or glasses

TG-PRK aims to regularize the uneven corneal front surface to achieve the desired refractive outcome Any corneal topographic change will lead to an

accompanying change in refraction Often not possible to acquire a wavefront map

DiscussionRemoves less tissue

Even if VA is not improved, we believe there is an improvement in the quality of vision from smoothening the corneal surface

PRK preferredLASIK flap may be difficult along graft-host

junction and suture linesHaze is an issue

LimitationsQuality of vision

HOAContrast sensitivity

Vector analysis

ConclusionsEarly results of TG-PRK with TNT shows potential

to improve both UVA and BCVA with good efficacy

and safety

35% UVA improved to 20/40 or better, none

preoperatively

More than one third of the patients gained 2 lines

or more of BCVA

Thank You