Topography-Guided Photorefractive
Keratectomy (TG-PRK) for Keratoconus (KC)
With Simultaneous Collagen Cross-Linking
(CXL): Excimer Laser
Simon Holland
David TC Lin
ASCRS, Chicago, Illinois 2012
*No financial interests
Purpose
 To evaluate efficacy and safety of
simultaneous TG-PRK for KC with
simultaneous CXL
Methods
 127 keratoconus eyes underwent treatment with Allegretto
excimer laser
 Treatment targeted at -1.25 post-op, with minimal residual stromal
depth 300microns
 Epithelial removal by trans-epithelial laser
 Topography-guided PRK, T-CAT software, modified by TNT
(topographical neutralization)
 Riboflavin 0.1% in dextran, until aqueous staining
 UV irradiation with riboflavin (up to 20 minutes)
 UV 370 um, 3mW/cm2 - 5.4 J/m2
 Hypotonic dextran if <400 um
 Bandage contact lens, standard post PRK
management
TG-PRK CXL for KERATOCONUS
Pre-op: +1.75-4.00x060
BSCVA: 20/30-
6 months post-op
UCVA: 20/30
RX: +0.25-0.75x170 20/25
TG-PRK CXL for KERATOCONUS
Pre-operative
6 months post-op
UCVA 20/60
UCVA: 20/40+
MR: +2.25-2.00X120 20/40- MR: -0.50-0.50X60 20/30-
TG CXL PRK for KERATOCONUS
Pre-op: -2.75-2.25x010 12 months post-op
BSCVA: 20/20UCVA: 20/30RX: +0.50-0.50x020
20/30-
Results
 99 eyes completed 6 months follow-up
 53 (54%) had ≥20/40 or better uncorrected visual acuity
(UVA)
 92 (93%) had ≥20/40 or better best corrected visual acuity
(BCVA)
 51 (52%) had BCVA improved, 32 (32%) improved BCVA 2
lines or more, 33 (33%) no change, 4 (4%) lost 2 lines or more
 Mean astigmatism decreased -2.77D pre-op to
-1.14D
 4 had delay in epithelial healing with subsequent haze, 2
developed haze sufficient to reduce BCVA more than 2 lines,
1 had herpetic keratitis – 3 recovered pre-operative BCVA.
 Glare, halos, and difficulties with night driving decreased from
3.5 to 2.0 on a 4 point score (n=25)
Conclusions
 Simultaneous TG-PRK with CXL using customized
TNT technique shows promise to improve both
UCVA and BCVA in keratoconus patients with
reasonable efficacy and safety
 Longer term results are needed to establish value
and safety of combining attempted refractive
correction and topographical regularization with
collagen cross linking