INTRA OPERATIVE ONLINE PACHY METRY –A SAFETY TOOL

Dr. KUMAR J DOCTORDOCTOR EYE INSTITUTE MUMBAI INDIA NO FINANCIAL INTEREST

On line pachymetry

Is a high resolution non contact method

which enables the corneal thickness changes to be measured intra operatively during all steps of the surgery.

It adds new safety dimensions to Lasik.

Importance OF OCP

Is in patients with Thin corneas High refractive errors Who need enhancement and

retreatments Fear of keratectasia

Online OCP Optical Coherence Pachymeter

AMARIS SCHWIND LASER

mirror

beamsplitter

light source

detector

eye

s(t)

OCP-signal from Michelson Interferometer

The direct integration of Online Pachymetry into

the AMARISIt comes with fiberglass coupling and through Automatedmeasurements of changes in Corneal thickness, allowscontinuous and real time values with 10 measurements persecond, without havingto interrupt thetreatment.

LASIKLASIK--CutCutPre-cut

540 µm394 µm

0 µm

t

Post-cut

The reproducibility of current System is 1 to 2 microns.

OCPRECORDING DURING SURGERY

Purpose:

To investigate Intraoperative Optical Coherence Pachymetry during various steps of Laser in Situ Keratomileusis (LASIK)

Method: With the Integrated Online Pachymetry 50

patients with Myopia were studied. LASIK was performed with 90 micron head for

all eyes using Carriazo Pendular Microkeratome. Online pachymetry measures the corneal

thickness before and after lifting the flap AUTOMATICALLY .

This reading was subtracted from the one before flap creation to get accurate flap thickness.

Post-op 1 month OCT for Flap thickness was done for every eye.

Observation Mean spherical equivalent refraction was – 5.0 D, +/-

4.0 D . Mean stromal depth of 100 +/- 18 µ was ablated. Mean flap thickness was 90 µ, +/-9 µ. Residual corneal stromal bed of more than 300

microns was preserved in all cases.

The immediate post op showed swelling of the cornea.

ResultsThe flap thickness measured by OCP

and OCT post I month.

Mean Thickness of Flap by OCP Mean Thickness of flap by OCT85

86

87

88

89

90

91

92

93

90 90

Thic

knes

s in

Mic

rons

Discussion Efficiency and safety of lasik procedure has

increased with the integrated OCP. Further horizons are widened for treatment of

thin corneas , to prevent keratectasia This has proved extremely beneficial in cases

that require retreatment or enhancement . OCP is a great link with the Excimer Laser

Conclusion:The real time online pachymetry being

non contact takes measurement through all steps of the surgery .

This is an important safety feature for monitoring flap thickness with each cut and to check residual stromal thickness.

Prevents itrogenic corneal ectasia in patient with thin corneas.

Increases the efficiency, predictability and safety of the procedure .