1. The effect of corneal edema on intraocular pressure measurements after phacoemulsification surgery Ilker Eser M.D. 1 Arzu Taskiran-Comez M.D. 1 Baris Komur M.D. 1 None of the authors have proprietary interest in any product mentioned. 1 Canakkale Onsekiz Mart University, School of Medicine, Department of Ophthalmology, Canakkale, TURKEY

2. Purpose and Methods 1 Purpose To determine the impact of corneal edema on intraocular pressure (IOP) measurements after phacoemulsification surgery. Methods  20 eyes of 17 patients (mean age 64.9 ± 11 (range, 44 to 79) years  11 male, 6 female  Exclusion criteria: corneal disease or previous ocular surgery  Patients undergone phacoemulsification with the use of Infiniti (Alcon, Fort Worth, Texas, USA).

3. Purpose and Methods-2 Methods  IOP measurements were taken by Dynamic Contour Tonometer (DCT) (Swiss Microtechnology AG, Port, Switzerland) and then by Goldmann Applanation Tonometer (GAT) (Optilasa, Spain).  After IOP measurements central corneal thickness (CCT) measurements were taken by ultrasound pachymeter (US-4000, Nidek, Japan). All measurements were taken preoperatively and postoperative at day1, 7 and 30.  Statistical analysis: T tests and Pearson Correlation tests was used. P values less than 0.05 was considered statistically significant.

4. Results-1 Mean CCT increase postoperatively at day 1, 7, and 30 were 149.7 ± 139.1 (36-551) μ, 62.3 ± 59.7 (0-202) μ, 9.7 ± 23.3 (-23 – 69) μ, respectively. Mean IOP measurement differences (DCT minus GAT) preoperatively, postoperative day 1, 7 and 30 were 2.0 ± 2.3 mmHg, 0.6 ± 3.2 mmHg, 1.4 ± 2.1 mm Hg, 1.4 ± 2.0 mm Hg, respectively. Differences of IOP measurements with DCT and GAT were not correlated with CCT preoperatively (r= 0.297; p=0.21) and postoperative at day 1 (r= 0.297 ;p=0.22), day 7 (r= 0.139;p=0.57) and day 30 (r= 0.173;p=0.48).

5. Results-2 Graphic 1. Mean central corneal thicknesses preoperatively and at postoperative 1, 7 and 30 days. Table 1. Preoperative and Postoperative corneal thickness differences and preoperative and postoperative Goldmann and Dynamic contour tonometry measurement differences Difference from Preoperative CCT GAT and DCT DifferenceP Value* Preoperative02.0 ± 2.3 (-4.4-6.4)0.21 Postoperative Day 1149.7 ± 139.1 (36.0-551)0.6 ± 3.2 (-5.5-6.7)0.22 Postoperative Day 762.3 ± 59.7 (0.0-202.0)1.4 ± 2.1 (-1.2-6.3)0.57 Postoperative Day 309.7 ± 23.3 (-23.0-69.0)1.4 ± 2.0(-1.8-5.8)0.48 CCT=Central Corneal Thickness, DCT=Dynamic Contour Tonometry, GAT=Goldmann Applanation Tonometry, *=Pearson correlation of difference between GAT and PASCAL Tonometry and CCT

6. Conclusion-1 Measurement of IOP is a necessary part of post operative assesment after uncomplicated cataract surgery. 1 Surguries may induce significant corneal edema and endothelial changes. 2 Several studies have reported that IOP measurement with the DCT is not affected by CCT. 3,4 By contrast, GAT tonometry have been reported to paradoxically underestimate IOP in eyes with corneal edema and higher CCT values in studies. 5,6 1. Chong NH, Aggarwal RK, Shah P, Murray PI. Is measuring intraocular pressure necessary on the first post-operative day following uncomplicated cataract surgery? Eye (Lond). 1994;8:115-116. 2. Polack FM, Sugar A. The phacoemulsification procedure. II. Corneal endothelial changes. Invest Ophthalmol. 1976 Jun;15:458-469. 3. Schneider E, Grehn F. Intraocular pressure measurement comparison of dynamic contour tonometry and Goldmann applanation tonometry. J Glaucoma 2006;15:2–6. 4. Ku JY, Danesh-Meyer HV, Craig JP, Gamble GD, McGhee CN. Comparison of intraocular pressure measured by Pascal dynamic contour tonometry and Goldmann applanation tonometry. Eye (Lond). 2006;20:191-198. 5. Simon G, Small RH, Ren Q, Parel JM. Effect of corneal hydration on Goldmann applanation tonometry and corneal topography. Refract Corneal Surg. 1993;9:110-117. 6. Kohlhaas M, Boehm AG, Spoerl E, Pürsten A, Grein HJ, Pillunat LE. Effect of central corneal thickness, corneal curvature, and axial length on applanation tonometry. Arch Ophthalmol. 2006 ;124:471-4766.

7. Conclusion-2 In our study we found that postoperatively CCT can increase to 1049 μ. This can lead to errous reading on IOP shown in previus studies 3,4,5,6. Altough no statistically difference found between DCT and GAT measurements according to CCT, we found that the difference can be high as up to 7 mm Hg postoperatively. The influence of corneal edema on IOP measurements should be addressed in further studies. 3. Schneider E, Grehn F. Intraocular pressure measurement comparison of dynamic contour tonometry and Goldmann applanation tonometry. J Glaucoma 2006;15:2–6. 4. Ku JY, Danesh-Meyer HV, Craig JP, Gamble GD, McGhee CN. Comparison of intraocular pressure measured by Pascal dynamic contour tonometry and Goldmann applanation tonometry. Eye (Lond). 2006;20:191-198. 5. Simon G, Small RH, Ren Q, Parel JM. Effect of corneal hydration on Goldmann applanation tonometry and corneal topography. Refract Corneal Surg. 1993;9:110-117. 6. Kohlhaas M, Boehm AG, Spoerl E, Pürsten A, Grein HJ, Pillunat LE. Effect of central corneal thickness, corneal curvature, and axial length on applanation tonometry. Arch Ophthalmol. 2006 ;124:471-4766.

8. Authors Ilker Eser MD, was born in Gaziantep, Turkey and was graduated from Ankara University School of Medicine in 1997. Dr. Eser did his residency in Istanbul University Microbiology department for two years. Dr. Eser then completed Ophthalmology residency at Beyoglu Eye Education and Research Hospital, Istanbul in 2005. During his residency he was a visiting physician for three months in Wilmer Eye Institute Cornea Department, Baltimore, USA. Dr. Eser did his refractive surgery fellowship with Dr. Daniel Durrie in Durrie Vision, KS, USA. He is interested in refractive surgery and ocular infections and is currently the head of Canakkale Onsekiz Mart University School of Medicine, Dept. of Ophthalmology. Arzu Taşkıran-Çömez MD, was born in Istanbul, Turkey and was graduated from Dokuz Eylul University, School of Medicine in 1998. She completed her residency in Istanbul Dr.Lutfi Kirdar Kartal Training and Research Hospital. She is interested in oculoplastics surgery, cataract surgery and pediatric ophthalmology. She is currently working in Canakkale Onsekiz Mart University School of Medicine, Dept. of Ophthalmology. Barış Kömür MD, was born in Izmir, Turkey and was graduated from Ege University School of Medicine in 2006. He has been doing his residency in Canakkale Onsekiz Mart University School of Medicine, Dept. of Ophthalmology since 2009.