Changes in IOL Positioning and Refraction after

Neodymium:Yag Laser Posterior Capsulotomy

Adriana S. Forseto1, MD

Walton Nosé1,2, MD

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

1Eye Clinic Day Hospital 2Federal University of São Paulo - UNIFESP

São Paulo - Brazil

Introduction Intraocular lens (IOL) positioning alteration is a possible

complication of Neodymium:YAG laser posterior capsulotomy (Nd:YAG).

Some studies have already been proposed to quantify IOL positioning changes after Nd:YAG by measuring the anterior chamber depth (ACD) pre and after the treatment. Using the Scheimpflug’s principle we can determine not only the ACD changes but also the actual value of IOL decentration and tilt.

PurposeThe purpose of this study is to evaluate the effect of

Neodymium:YAG laser posterior capsulotomy

(Nd:YAG) on intraocular lens (IOL) positioning and

refraction

Methods Prospective study: 25 eyes (20 patients)

Inclusion criteria Presence of posterior capsule opacification (PCO)

Minimum post cataract surgery follow-up: 3 months

The anterior chamber depth (ACD) and the IOL positioning changes (tilt and decentration) were measured using a Scheimpflug camera (EAS-1000; NIDEK): 4 measurements were obtained from each eye within 15 days prior to Nd:YAG and 30 days post

treatment to assess the method’s reproducibility

Changes in refraction and best corrected visual acuity (BCVA) were analyzed

Statistical analysis: parametric and nonparametric testing (significant level: p < 0.05)

Example of decentration and tilt analysis of a posterior chamber IOL pre Nd:YAG using the Scheimpflug camera

Two images of the anterior segment of the eye were obtained with the rotating CCD camera at the 45º and 135º angles The images were transferred to the computer for storage and analysisMeasurements of the extension and direction of decentration (mm) and the degree of tilt (°) of the implanted IOL, were calculated through the IOL image modes of the apparatus

Results The mean time between cataract surgery and Nd:YAG:

24 ± 20 months (range, 3 to 60 months)

IOL type:

3-piece IOL: 12 eyes

1-piece IOL: 12 eyes

unknown: 1 eye (impossible to evaluate: insufficient mydriasis)

Nd:YAG energy power for 4.00mm capsulotomy opening:

1.7 0.3 mJ (range, 1.0 to 2.2 mJ)

Complications: Retinal detachment (n = 1)

Excluded because of poor post Nd:YAG eye fixation for evaluation

Results

No statistically significant changes were observed comparing the mean pre and post Nd:Yag ACD (p=0.327) :Pre Nd:YAG: 4.14 0.39 mm Post Nd:YAG: 4.11 0.46 mm

ACD pre Nd:YAG = 3.87mm ACD post Nd:YAG = 3.84mm

Results

Pre-Nd:YAG Decentration

(mm)

Post-Nd:YAG Decentration

(mm)

Pre-Nd:YAGTilt(o)

Post-Nd:YAGTilt(o)

Measurements

Mean S.D.

Mean S.D.

Mean S.D.

Mean S.D.

1 0.340.31

0.380.26

3.402.39

3.271.73

2 0.320.28

0.330.20

2.982.21

2.791.71

3 0.340.17

0.330.20

3.362.92

2.531.52

4 0.360.35

0.320.20

3.493.07

2.531.65

Comparison 2 r = 0.41p= 0.937

2 r = 1.39p= 0.709

2 r = 4.85p= 0.183

2 r = 6.45p= 0.092

Reproducibility test of the Scheimpflug camera for IOL decentration and tilt

The four IOL positioning measurements taken from each eye were similar

Results

Exam Decentration(mm)

Tilt(o)

Pre Nd:YAG 0.34 0.25 3.30 2.55

Post Nd:YAG 0.34 1.18 2.78 1.44

z= 0.24 p= 0.808

z= 1.14 p=0.235

Posterior chamber IOL decentration and tilt pre and post Nd:YAG

There were no statistically significant differences between pre and post laser measurements

Results

Variation Number of laser shoots

Power of laser shoots(mJ)

Tilt rs= 0.08p= 0.736

rs= 0.11p= 0.651

Decentration rs= -0.01p= 0.980

rs= 0.31p= 0.166

Correlation between the number and the power of laser shoots used and the post Nd:YAG IOL positioning percent variation

No statistically significant correlation was observed between the number and power of laser shoots used and the IOL positioning

percent variation

Results

IOL Decentration Tilt

1-piece 17.76 105.15 31.77 113.17

3-piece 14.67 43.00 13.35 75.27

U= 50.0 p=0.347

U=58.0 p= 0.651

Association between the IOL type and its post Nd:YAG positioning percent variation (mean standard deviation)

No association was demonstrated between the type of the IOL and its positioning change post laser

Results

No statistically significant changes were observed comparing the mean pre and post Nd:YAG mean Sph Eq refraction (p=0.362):Pre Nd:YAG: –0.65 1.47 D (range, -3.90 to +2.00D)

Post Nd:YAG: –0.59 1.44D (range, -3.80 to +2.40D)

The BCVA remained unchanged in 8 eyes and improved in 14 eyes. Only the case with retinal detachment lost lines of BCVA

Conclusions

No statistically significant changes of the IOL

positioning and refraction were induced by the Nd:YAG laser posterior capsulotomy