Distribution of corneal spherical aberration in a Tanzanian population.

PURPOSE: To investigate the distribution of corneal spherical aberration (SA) in Tanzanian people of African descent, and to examine the correlation between corneal SA and ocular parameters. DESIGN: Cross-sectional population-based study. METHODS: Residents aged 40 years and older in three villages in the Mkuranga district in Tanzania were enlisted as study participants. Corneal higher-order aberrations (HOAs) for the right eye were measured with a wavefront analyzer (KR-1W, Topcon) and calculated for the central 6.0-mm zone. Corneal curvature radius (CR), corneal astigmatism, and axial length (AL) were also measured and their correlation with corneal SA was assessed. RESULTS: The right eyes of 657 participants (336 male, 321 female) were analyzed. The mean age of the subjects was 57.2 ± 10.3 years (mean ± SD). The mean corneal SA (Zernike spherical aberration coefficient C40) was 0.188 ± 0.095 µm (-0.242 to 0.613). The SAs in about three-quarters of all subjects were between 0.10 and 0.30 µm. The root mean squares of total corneal HOAs and the third- and fourth-order aberrations were 0.629 ± 0.250 µm, 0.539 ± 0.236 µm, and 0.269 ± 0.110 µm, respectively. Corneal SA showed weak significant correlations with CR (Spearman's rank correlation coefficient, r = -0.177, p < 0.001), corneal astigmatism (r = -0.142, p < 0.001), AL (r = -0.168, p < 0.001), and age (r = -0.085, p < 0.05). CONCLUSIONS: This finding may be beneficial for selecting aspheric intraocular lens in this population.

Clinical evaluation of posterior capsule opacification in eyes with different small-incision intraocular lenses.

BACKGROUND AND OBJECTIVE: To present a new method to quantify posterior capsular opacity with an anterior eye segment image analyzer (EAS 1000, NIDEK). PATIENTS AND METHODS: This study was comprised of patients who underwent phacoemulsification intraocular lens (IOL) implantation. Three types of IOLS, acrylic, silicone, and polymethylmethacrylate (PMMA) were allocated to 30 eyes and clinically evaluated. Patients were observed for 3 years postoperatively using an anterior eye segment image analyzer (EAS1000). Opacity was determined by calculating the area of opacity from a retroillumination image. In the retroillumination mode of analysis, the measurement was limited to a 4-mm-diameter region of the pupillary zone to eliminate the influence of anterior capsular opacity. For color map analysis, the threshold level was expressed as the color tone of 0-255 CCT (computer compatible tape). The glare disability was measured to evaluate the three types of IOLs. RESULTS: The color map analysis revealed a time-related increase in the opacity level of patients receiving the PMMA IOL implant. Three years after surgery, the levels were significantly higher in the PMMA group (P < 0.01) compared to the acryl and silicone groups: acryl (17.5 +/- 3.8), silicone (18.0 +/- 6.2%), and PMMA 36.5 +/- 32.9%. CONCLUSION: Quantitative evaluation using an anterior eye segment image analyzer is effective for observing the degree of posterior capsule opacification. The color map analysis using an anterior eye segment image correlated with the visual function revealed that the time-related increase in the opacity level was significant during the third year in patients receiving PMMA IOL implantation.