Safety and Efficacy of Advanced Surface

Ablation for Extreme Prescriptions

Emil W. Chynn, MDSze H. WongDorina Jaubelli

The authors have no financial interest in the subject matter of this poster.

LASEK or Epi-LASEK to treat extreme refractive errors is not FDA-approved.

IntroductionLASIK is not recommended for high prescriptions because of compromised visual outcomes1

Stromal bed thickness >250 microns to avoid iatrogenic keratectasia2

PRK is prone to scarring for extreme prescriptions3

Advanced Surface Ablation (LASEK/Epi-LASEK) is an excellent alternative that maximizes stromal thickness

Purpose

To determine whether extreme prescriptions may be safely and effectively treated with Advanced Surface Ablation (ASA)

Method

Adjunctive treatment to prevent scarring:• Mitomycin C (MMC) 0.01% intraop• Oral steroids: 1-3 wks postop• Topical steroids: 2-6 mo postop • Vitamin C: 2-6 mo postop• UV protection: 3-12 mo postop

Patient Characteristics

n = 105 Patients (187 Eyes)

Male 51%

Female 49 %

Age (mean ± SD [range]) 32 ± 9 [19 – 66]

Eyes With Extreme Myopia (SE ≥ -9) 78 %

Eyes With Extreme Hyperopia (SE ≥ +6)

7 %

Eyes With Extreme Astigmatism (cyl ≥ -3)

29 %

LASEK Eyes 83 %

Epi-LASEK Eyes 17 %

WaveFront Eyes 55 %

Rx Range (SE) -22.63 to +7.50

Preop Corneal Thickness (mean ± SD)

554 ± 38 µm

Ablation Thickness (mean ± SD) 126 ± 36 µm

Postop Corneal Thickness (mean ± SD)

428 ± 53 µm

Results:Uncorrected Visual Acuity (UCVA)

UCVALine

Number

0 1 2 3 4 5 6 7 8 9 10 11 120

1

2

3

4error bar = standard error

20/20 =

20/32 =

Mo. Postop

20/40 =

20/50 =

20/25 =

n = 152

n = 134n = 143 n = 94

n = 70

1 line = 0.1 logMAR 4

Postop UCVA vs. Preop UCVA

Postop 1 Mo.(n = 152)

2 Mo.(n = 134)

3 Mo.(n = 143)

6 Mo.(n = 94)

12 Mo.(n = 70)

Lines Gained ± Standard

Error

19.21 ± 0.78

19.64 ± 0.87

19.83± 0.84

19.49 ± 1.01

18.55 ± 1.19

% Eyes Postop UCVA ≥ Preop UCVA

98 97 97 95 97

% Eyes Postop UCVA

>Preop UCVA

97 96 97 95 94

% Eyes Postop UCVA

=Preop UCVA

1 1 0 0 3

1 line = 0.1 logMARCF = 20/2000, HM = 20/20,000 4

Postop UCVA vs. Preop Best Corrected Visual Acuity

(BCVA)

Postop UCVAMinus

Preop BCVA(line difference)

0 1 2 3 4 5 6 7 8 9 10 11 12

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

Mo. Postop

error bar = standard error

n = 152

n = 134

n = 143 n = 94n = 70

Postop UCVA vs. Preop BCVA

Postop 1 Mo.(n = 152)

2 Mo.(n = 134)

3 Mo.(n = 143)

6 Mo.(n = 94)

12 Mo.(n = 70)

% Eyes Postop UCVA ≥ Preop BCVA

40 58 72 65 69

% Eyes Postop UCVA

>Preop BCVA

18 28 34 33 35

% Eyes Postop UCVA

=Preop BCVA

22 30 38 32 34

Preop BCVA to Postop UCVA Line Difference Comparisons

Postop 1 Mo. 2 Mo. 3 Mo. 6 Mo. 12 Mo.

Male vs. Female 0.414 0.612 0.431 0.849 0.314

Age < 40 vs. ≥ 40

0.664 0.149 0.647 0.909 0.400

Extreme Myopia vs. Extreme Hyperopia

*0.047 0.076 0.067 0.408 0.400

Extreme Astigmatism vs. Without

0.801 0.526 0.999 0.057 0.864

Amblyopia vs. Without

0.216 0.424 0.718 0.114 0.568

Null hypothesis tested with unpaired, two-tailed, unequal variance t-test. P values listed below:

Extremely hyperopic eyes had significantly worse line gain than extreme myopic eyes 1 mo. postop

Ablation Depth vs. Preop BCVA to

6 Mo. Postop UCVA Line Difference

Postop UCVA minus

Preop BCVA

Ablation

Depth (micro

ns)

Correlation coefficient = 0.02

20 40 60 80 100 120 140 160 180 200

-8

-6

-4

-2

0

2

4

6

8

Pulses vs. Preop BCVA to 6 Mo. Postop UCVA Line

Difference

Postop UCVA minus

Preop BCVA

Number of

Pulses

Correlation coefficient = -0.04

0 200 400 600 800 1,000 1,200

-8

-6

-4

-2

0

2

4

6

8

Treatment Time vs. Preop BCVA to

6 Mo. Postop UCVA Line Difference

Postop UCVA minus

Preop BCVA

Treatment

Time (s)

Correlation coefficient = -0.02

0 50 100150200250300350400450500

-8

-6

-4

-2

0

2

4

6

8

Complications

Of 187 eyes:

8 (4 %) postop haze (tr to 2+)1 (0.5%) corneal edema3 (1.5%) scarring2 (1%) iatrogenic keratoconus

ConclusionExtreme prescriptions may be safely and effectively treated with advanced surface ablation when combined with adjunctive treatments to prevent scarring

72% eyes: 3-mo. postop UCVA ≥ preop BCVA (maintained for at least one year)

Further studies are needed to determine whether extremely hyperopic eyes are at risk for loss of BCVA and how to avoid this loss

References1. Knorz MC, Wiesinger B, Liermann A, Seiberth V, Liesenhoff H.

Laser in situ keratomileusis for moderate and high myopia and myopic astigmatism. Ophthalmology. 1998;105:932-940.

2. Seiler T, Koufal K, Richter G. Iatrogenic keratectasia after laser in situ keratomileusis. J Refract Surg. 1998;14:312-317.

3. Kremer I, Kaplan A, Novikov I, Blumenthal M. Patterns of late corneal scarring after photorefractive keratectomy in high and severe myopia. Ophthalmology. 1999;106:467-473.

4. Holladay JT. Proper method for calculating average visual acuity. J Refract Surg. 1997;13:388-391.