Eye Department

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

CHANGES IN CORNEAL VOLUME AFTER MYOPIC PHOTOREFRACTIVE KERATECTOMY

Michele Lanza, Maria Borrelli, Maddalena De Bernardo, Marco De Luca, Antimo Flagiello, Nicola Rosa.

Purpose of our study was to evaluate the changes in central corneal

thickness (CCT) and corneal volume (CV) in eyes that underwent

myopic PRK.

PURPOSE

Myopic photorefractive keratectomy (PRK) is a reliable method to

correct refractive errors.

With this method a slice of corneal tissue is ablated, thus giving a

flattening and a thinning of the central cornea.

METHODS

CCT and CV obtained with an Oculus Pentacam

Before, 1, 3 and 6 months after PRK

were analyzed in 118 eyes of 64 patients (38 male, 26 female)

The changes were compared with the amount of refractive

treatment.

The mean preoperative refraction was -5.04 ± 2.23 D

(range: -1 D to -14.5 D)

CV has been measured at 10 mm, as default setting of the device

METHODS

RESULTS

Corneal parameters before and after surgery

BEFORE1 MONTH POST OP

3 MONTHS POST OP

6 MONTHS POST OP

CCT500 – 645 µ

(560.17 ± 30.45 µ)340 – 581µ

(477.14 ± 46.43 µ)324 – 582 µ

(478.01 ± 44.14 µ) 385 – 591 µ

(485.28 ± 39.07 µ)

CV53.2 - 69.8 mm3

(61.88 ± 3.40 mm3)47.3- 66.8 mm3

(59.3 ± 3.53 mm3)47.5 – 67.2 mm3

(59.57 ± 3.49 mm3)53.2 – 69.1 mm3

(60.38 ± 3.59 mm3)

RESULTS

1 month after PRK

CCT and CV mean differences were 82.39 ± 34.56 microns

(p<0.001) and 2.47 ± 1.76 mm3 (p< 0.001) respectively.

3 months after PRK

CCT and CV mean differences were 79.2 ± 33.48 microns

(p<0.001) and 1.98 ± 1.59 mm3 (p<0.001) respectively.

6 months after PRK

CCT and CV mean differences were 74.48 ± 28.96 microns

(p<0.001) and 1.65 ± 1.37 mm3 (p<0.001) respectively.

RESULTS

RESULTS

RESULTS

Our results showed a decrease in both CCT and CV after treatment

with a good correlation between CCT changes and treatment

(one month after PRK R2=0.48; three months after PRK R2=0.52;

six months after PRK R2=0.61)

No correlation could be found between CV changes and treatment

(one month after PRK R2= 0.05; three months after PRK R2=0.09;

six months after PRK R2=0.06).

CONCLUSIONS

CONCLUSIONS

2) After myopic PRK when a series of corneal lamellae are severed centrally the remaining peripheral segments relax.

CONCLUSIONSWith the reduction of tension in the lamellae the squeezing force on the matrix is

reduced and the distance between lamellae expands. This allows the periphery of

the cornea to thicken and the peripheral increase in corneal thickness will

compensate for the ablated corneal tissue leading to a change in CV.