Purpose: To determine the mean angle kappa and its determinants in the population of Tehran, Iran. Methods: In a cross-sectional survey with random cluster sampling, a total of 442 participants aged >14 years were selected from 4 municipality districts of Tehran for Orbscan acquisitions. Exclusion criteria were history of eye surgery for refractive errors, cataract or glaucoma, and use of topical medication or any type of contact lens at the time of the study. Mean angle kappa in different age and gender groups and its association with other factors was assessed. Considering the high correlation between the right and left eyes, only results of the right eyes are presented. Results: After applying exclusion criteria, 800 eyes (399 right eyes and 401 left eyes) were examined. Mean participant age was 40.6±16.8 years (range: 14 to 81 years), and 38.8% of eyes were from men. Mean angle kappa was 5.46±1.33° in total; 5.41±1.32° in men and 5.49±1.34° in women ( P =.558). It decreased significantly with age; 0.015°/year ( P <.001). In individuals with myopia, emmetropia, and hypermetropia, the mean value was 5.13±1.50°, 5.72±1.10°, and 5.52±1.19°, respectively ( P =.025); the post-hoc test indicated this was due to the difference between emmetropes and myopes. Conclusions: According to our results, angle kappa reduces with age, and the inter-gender difference is not significant. Largest angle kappas were seen among individuals with emmetropia. Angle kappas were larger in the hypermetropic population compared to the myopic population.

To determine the agreement between scanning slit topography (Orbscan II, Bausch & Lomb) and Scheimpflug imaging (Pentacam, Oculus) in corneal elevation, corneal curvature, and anterior chamber depth (ACD) measurements before and after laser refractive surgery for myopia and to compare the postoperative changes seen with these devices. Noor Vision Correction Center, Tehran, Iran. In a prospective observational case-series study, 23 consecutive myopic patients having laser refractive surgery were examined with the Orbscan II and Pentacam preoperatively and 6 weeks postoperatively. Readings of ACD, anterior (A-) and posterior (P-) best-fit sphere (BFS) size, central elevation (CE), maximum elevation (ME), axial power in the 3.0 mm zone (AX3) and 5.0 mm zone (AX5), and tangential power in these zones (TG3 and TG5, respectively) were collected and used in the analyses. Statistically significant interdevice differences were found preoperatively for all parameters except P-TG3 (P = .014) and in operated eyes for ACD, anterior parameters of A-AX3 and A-AX5, and all posterior corneal parameters. In posterior corneal measurements, Orbscan II demonstrated significant postoperative changes in all parameters except P-AX5 (P = .004) and P-TG5 (P = .034), although none of the differences was statistically significant with the Pentacam. The devices measured similar postoperative changes in anterior curvature parameters and in P-AX5 and P-TG5; all other changes were significantly different. Compared to the Pentacam, the Orbscan II yielded larger posterior elevation values before and after surgery and significant postoperative changes in P-CE and P-ME. Further studies can determine which device gives more accurate images of the cornea and redefine screening criteria.

To determine the agreement in central corneal thickness (CCT) measurements between the gold standard method of ultrasound (US) pachymetry (UP-1000, Nidek) and 2 noncontact systems based on Scheimpflug imaging (Pentacam, Oculus) and scanning-slit topography (Orbscan II, Bausch & Lomb) in myopic eyes before and after laser refractive surgery. Noor Vision Correction Center, Tehran, Iran. In this prospective study, 30 consecutive patients having refractive surgery for myopia were enrolled. All 60 eyes were examined with the 3 devices preoperatively and 6 weeks after surgery; the US measurements were performed last. The Pentacam and Orbscan II CCT readings were compared with the US readings. Both the original and corrected Orbscan II readings were used in the analyses. The mean CCT readings with US, Pentacam, and Orbscan II were, respectively, 555 microm, 548 microm, and 580 microm before surgery and 478 microm, 468 microm, and 474 microm after surgery. Preoperatively, the 95% limits of agreement (LoA) with US were -31 microm and +19 microm for the Pentacam device and -5 microm and +57 microm for the Orbscan II device. Postoperatively, the LoA were -40 microm and +19 microm and -51 microm and +50 microm, respectively. Corrected Orbscan II measurements gave 95% LoA of -48 microm and +6 microm before surgery and -85 microm and +5 microm after surgery. Refractive surgery had a modest effect on the agreement between Pentacam readings and US measurements. With Orbscan II, the 95% LoA width nearly doubled after surgery. Although the Pentacam seems to show better agreement than Orbscan II, especially after refractive surgery, it is not advisable to use the 3 devices interchangeably in every clinical situation.

To determine the mean corneal diameter and its determinants in the population of Tehran. From the Tehran Eye Study participants who were sampled through a stratified cluster approach, those in the first 4 municipality districts of Tehran were selected, and after applying the inclusion and exclusion criteria, 399 right eyes and 401 left eyes of 410 people aged 14 years and older were examined with the Orbscan II. The corneal diameter was defined as the horizontal limbus-to-limbus distance. Linear regression was used to detect separate and multiple correlations. The design effect of cluster sampling was also considered and adjusted for. The studied participants were male in 38.80%, and their mean age was 40.68 +/- 16.80 years. The mean corneal diameter was 11.68 mm (95% confidence interval: 11.63-11.73). The 95% range (mean +/- 2 SDs) was 10.76-12.60 mm. The mean corneal diameter was 11.76 and 11.63 mm in males and females, respectively. The corneal diameter in the studied population had no significant correlation with age (P = 0.186) but showed an increase of 0.18 mm for each millimeter increase in the anterior chamber depth (P = 0.028). Although the mean corneal diameter in the present population was not different from that reported in other studies, the data suggest that slightly different cutoff values for the definition of macrocornea (>12.60 mm) and microcornea (<10.76 mm) can be used with this population.

To determine the distribution of corneal thickness at 6 different points in an Iranian population and find any possible relationship between the thickness values and some independent variables. As part of the "Tehran Eye Study," 410 people (800 eyes) aged 14 years and older, residing in the first 4 municipality areas of Tehran, were selected through a stratified random cluster sampling method. The participants were examined with Orbscan II to measure the corneal thickness at the central, thinnest, and 4 peripheral points of the cornea. In addition, the relationships between central corneal thickness (CCT) values and variables of age, sex, refractive error, pupil diameter, corneal diameter, anterior chamber depth (ACD), and body mass index were assessed. The design effect was also considered, and all estimates were standardized for age and sex. The reported results pertain to the right eyes only. The mean thickness (+/-SD) at the central and thinnest points was 555.6 +/- 39.9 and 550.7 +/- 40.6 microm, respectively. The minimum corneal thickness was below 500 microm in 9.6% of the participants. The superior area showed the largest thickness, and the thinnest point was most commonly in the inferotemporal quadrant. The mean "distance" and "thickness difference" between the central and thinnest points were 0.52 +/- 0.31 mm and 4.85 +/- 6.2 microm, respectively, and they showed a significant direct relationship (r = 0.708 and P < 0.001). Neither sex had a significant relationship with thickness values at different areas. Participants younger than 20 years, compared with those older than 20, had significantly thicker corneas (P = 0.001 for the central and thinnest points, P < 0.001 for peripheral areas). In the multiple regression model, age and ACD showed significant inverse correlations with CCT. The mean CCT in the present study was 555.6 microm, which is relatively higher in comparison with that in other ethnic groups. In the multiple regression model, age and ACD were correlated with the CCT, but refractive errors showed no correlation.