Influence of corneal thickness on tonometric indexes

Poster Details

First Author: Y.Novak RUSSIA

Co Author(s):    L. Balashevich              

Abstract Details

Purpose:

To define the influence of corneal thickness in its central area before and after the surgical interference (LASIK) on tonometric indexes of intraocular pressure, and analysis of the achieved results.

Setting:

St.-Petersburg Branch IR&TC " Eye microsurgery" named after academisian S. Fyodorov, St.-Petersburg, Russia

Methods:

LASIK operations became an acceptable method of refraction anomaly correction. Recent studies demonstrated that it is a safe, efficient and predictable procedure for correction of myopia and astigmatism. Clinical study included 250 somatic healthy patients from 18 to 46 years old with myopia of different degree and with no other ophthalmic pathology. For statistic processing of data were considered values of corneal thickness in central optical area as a parameter that can be easily standardized. A comparative study was made for applanation (Maklakov applanation tonometry) and noncontact tonometry results. Period of observation was 3 years. All kerato-refractive interferences were performed on laser system MEL 80 with thinning of corneal stroma proportionally to its ablation. Diameter of interference made 6 mm. Visometry, refractometry, biometry, keratometry, ultrasound pahimetria, keratotopometry, Maklakov applanation tonometry and pneumotonometry were performed in all patients in 1,3,6, 12 months after operation. Changes in the indexes of thickness in central corneal area and changes in the level of tonometric intraocular pressure were valued.

Results:

Obviously the results of tonometry depend directly on the changes of central corneal thickness, especially it is true for pneumotonometry. Cornea with different thickness in its central area has its own level of pneumotonometric pressure and of pressure measured by Maklakov applanation tonometry. Indexes of intraocular pressure statistically increase and decrease along with increase or decrease of corneal thickness (p <0.001) which is confirmed by correlation analysis. It should be mentioned that the speed of growth of intraocular pressure indexes achieved by pneumotonometer is significantly higher than the speed of growth of indexes achieved by Maklakov tonometer. It is very important to consider the indexes of corneal thickness not only in refractive surgery, but also if there are ophthalmotonus pathologies.

Conclusions:

It is proved that results of tonometric intraocular pressure measurements before and after intrastromal interference LASIK for myopia correction differ from each other and show that it is lower because of the thinning of cornea in its central area. FINANCIAL DISCLOSURE?: No