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Impact of preoperative astigmatism on corneal biomechanics and accurate IOP measurement after micro-incision phacoemulsification

Poster Details

First Author: Z.Pniakowska POLAND

Co Author(s):    P. Jurowski                    

Abstract Details


The aim of the study was to identify whether preoperative corneal astigmatism can influence corneal biomechanics and therefore the assessment of intraocular pressure (IOP) following coaxial micro-incision phacoemulsification with IOL implantation.


Department of Ophthalmology and Visual Rehabilitation, The University Clinical Hospital of Military Medical Academy-The Veterans Central Hospital, Lodz


39 patients diagnosed with cataracts were enrolled in the study. Patients were divided into two groups based on their range of astigmatism. Group 1 included those with corneas with astigmatism values of K1-K2<1.0 Dcyl, and group 2 with values of K1-K2 >1.0 Dcyl and <2.25 Dcyl. Coaxial micro-incision phacoemulsification of a corneal opening of 2.0 mm was performed followed by implantation of IOL. Corneal hysteresis (CH), corneal resistance factor (CRF), Goldman-correlated IOP (IOPg), corneal compensated IOP (IOPcc) and waveform score (WS) were measured preoperatively as well as one day, one week and one month postoperatively using an Ocular Response Analyzer.


Group 1 consisted of 23 patients with a mean corneal astigmatism value of 0.5�Â�± 0.5 Dcyl. Group 2 included 16 patients with astigmatism of 1.38 �Â�± 0.44 Dcyl. In group 1, preoperative values of IOPg, IOPcc, CH and CRF did not differ from their corresponding values obtained one week and one month postoperatively. By contrast, in group 2 we observed a significant decrease in IOPg (t=2.29, p<0.05), IOPcc (t=2.36, p< 0.05) and CRF (t= 2.39, p<0.05) one month after phacoemulsification, when compared to preoperative values. CH did not differ significantly when assessed before, and 1 month after cataract surgery (p>0.05).


In long-term follow up, preoperative corneal astigmatism higher than 1.0 Dcyl affects corneal biomechanics, described by reduced CRF, IOPcc, and IOPg in eyes after micro-incision cataract surgery. CH remained the stable factor, uninfluenced by preoperative corneal astigmatism. Hence, postoperative bias in IOP measurement in patients with preoperative corneal astigmatism above 1.0 Dcyl may cause false underestimation of the actual IOP. Further studies are required to define the objective cause of lowered or unchanged postoperative IOPcc or IOPg in eyes that have undergone micro-incision cataract surgery.

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