Relationship between central corneal thickness and intraocular pressure in the Egyptian population

Abstract

With the fast development of refractive surgery, CCT has very important in choosing the type of surgery and assessing prognosis. Moreover, as we demonstrated before, CCT affects the measurement of IOP. In other words, when CCT increases, IOP increases also. This is of great help in the diagnosis and follow up of glaucoma. Various studies demonstrated that there are ethnic differences in CCT, but we don’t have a reference of the average CCT among Egyptians. This is why we performed this retrospective study in order to gather data about CCT and IOP in Egyptians. We included in this study normal subjects not known to be glaucomatous. 324 Egyptians were included, 107 men (33.03%) and 217 women (66.97%) with a ratio of 1:2.Their age ranged from 20 to 40 years with an average of 29.37±5.33 years. The average IOP was 16.71 ± 2.119 mmHg in the right eye, 16.92 ± 2.235 mmHg in the left eye and 16.82 ± 2.014 mmHg in both eyes.The average CCT was 543.50 ± 9.299 µm in the right eye, 542.87 ± 8.804 µm in the left eye and 543.188 ± 8.2436 µm in both eyes. The CCT of nonglaucomatous Egyptian subjects is comparable with that found in other Caucasians (on ultrasound pachymetry, the average CCT was found to be 544 ± 34 μm). Several studies have revealed a significant correlation between CCT and gender, reporting that CCT is slightly higher in men compared with women, whereas other investigators did not notice a difference between men and women.In our study, the mean CCT in both eyes was 543.079 μm among men and 543.242 μm among women with no significant difference. In the same way, the mean IOP in both eyes was 16.79 mmHg among men and 16.83 mmHg among women with no significant difference. Moreover, no significant correlation was found between age and CCT or between age and IOP. However, we found a statistically important positive relationship between CCT and IOP, thus when CCT increases IOP increases.The mean increase in IOP for every 10 microns increase in CCT is 0.29 ±0.14 mmHg. Through our study, we noticed that it’s very rare to find a subject with IOP<13 mmHg and CCT ≥ 527 µm. In other words, most of subjects with IOP<13 mmHg have thin corneas. This should be further investigated. Our data may be of value during daily clinic practice especially when dealing with refractive surgery and glaucoma suspects. We are so familiar now with pentacam reports that made it easy to know CCT and consequently we can adjust IOP. We hope that this study will be a good reference for the profile of CCT and IOP in the Egyptian population and for adjusting IOP.