Analysis of Intraocular Pressure in the Ablation and Nonablation Zones Before and After PRK
Purpose
To compare the intra-ocular pressure on the pre-operative and post-operative photorefractive keratectomy (PRK), on the ablation zone and non ablation zone with three different methods.
Methods
Twenty two eyes of 11 patients were analyzed along one year with three different methods of IOP analysis, being three male and eight female, from 22 thru 51 years old, May thru July of 2012(first measurement) and, May thru July of 2013(second measurement). These patients had myopia from -0,75 thru -5,75 and, 0,25 thru 2,25 of astigmatism. There were evaluated keratometries that ranged from 40,1 thru 47,4 and central corneal thickness from 456 thru 608 micras and periphery corneal thickness from 500 thru 682 micras. They measured by Orbscan(Bausch & Lomb™). There were also measured on the pre and post-operative central and peripheral IOP with two different methods: Tonopen(Reichert™) and tonometry of Goldmann(Haag-Streit™). All 22 eyes underwent to photorrefrective keratectomy(PRK) with Allegreto Wavelight™.
Results
Comparing the data of the variables there was a reduction of all on the post-operative.Evaluating the IOP by tonometry of Goldman, there was a reduction of 1,65mmHg on the general average. By the pneumotonometry there was a reduction of 2,66mmHg on the general average and, by the Tonopen on the periphery, there was a reduction of 1,65mmHg on the general average. There was also a reduction of 0,96 micras on the ablation zone.
Conclusion
There was reduction on measured IOP value on ablation zone and periphery.The whole cornea structure was modified,despite total extension not having undergone ablation,masking real IOP value.Despite the different measurement zones,both underestimated,still we could conclude the method is valid,and IOP value on periphery was closer to real value.While does not exist an instrument able of correlating cornea biodynamic and IOP,the evaluated method showed itself being alternative with great cust-benefit for IOP follow-up in patients underwent PRK