Purpose
To study the distribution of ocular biometric parameters using a swept-source optical coherence tomography (SS-OCT) biometer in adult candidates for cataract surgery.
Design
A retrospective cross-sectional study.
Methods
This is a single-center analysis of consecutive eyes measured with the IOLMaster 700 SS-OCT biometer at a large tertiary medical center between February 2018 and June 2020.
Results
Three thousand eight hundred thirty-six eyes of 3836 patients were included in the study. The mean ± SD age was 72.3 ± 12.8 years and 53% were female. The mean biometric values were as follows: total corneal power (44.17 ± 1.70 diopters [D]), total corneal astigmatism (TCA; 1.11 ± 0.87 D), mean posterior keratometry (−5.87 ± 0.26 D), posterior corneal astigmatism (−0.26 ± 0.15 D), axial length (AL; 23.95 ± 1.66 mm), anterior chamber depth (ACD; 3.18 ± 0.42 mm), lens thickness (LT; 4.49 ± 0.47 mm), white-to-white distance (WTW; 11.92 ± 0.44 mm), central corneal thickness (CCT; 0.54 ± 0.04 mm), angle alpha (0.49 ± 0.17 mm), and angle kappa (0.34 ± 0.17 mm). There were sex-related differences in all biometric parameters save for LT ( P = .440), angle kappa ( P = .216), and corneal astigmatism ( P = .103). Biometric parameters demonstrated correlations between AL, WTW distance, ACD, and LT ( P < .001). Age correlated with all parameters ( P < .001) except CCT and posterior keratometry. Angle alpha and angle kappa magnitudes also correlated ( P < .001). The prevalence of patients with TCA ≥0.75 D, 1.0 D, and 1.5 D were 59.1%, 43.4%, and 22.6%, respectively.
Conclusions
Age significantly correlated with most of the biometric parameters and significant differences between sexes were noted. In addition, the high prevalence of TCA and relatively large angle alpha and angle kappa magnitudes were noted among subjects. These data can be relevant in planning local and national health economics.
C ataract surgery is the most prevalent elective procedure performed worldwide, and the demand for cataract surgery continues to increase as the size of the elderly population increases. Advances in biometric device accuracy, intraocular lens (IOL) development, and modern IOL calculations have led to increased precision in postoperative refractive outcome and spectacle-free vision. Accurate biometry measurements are fundamental requirements for predicting refractive outcomes. The ocular biometric parameters of axial length (AL), anterior chamber depth (ACD), and corneal power differ between populations and vary according to age, sex, and ethnicity. , Studies describing mean parameters had initially been performed in European populations, with Asian and African populations having received attention only recently. , Population- and country-based data are needed in order to achieve optimal refractive outcomes. Few population-specific ocular biometric studies have been performed in the Middle East. In addition, previous countrywide demographic studies have not included biometric measurements provided by later-generation ocular biometers, including posterior keratometry, total keratometry (TK), angle kappa, and angle alpha. The swept-source optical coherence tomography (SS-OCT) device provides measurements with increased accuracy, repeatability, and reproducibility when compared with biometers used in earlier studies, thus enabling cataract surgeons to select optimal IOLs for the individual patient. , The objective of this study was to evaluate the distribution of biometric parameters using a swept-source optical biometer in individuals planned for cataract surgery in a large tertiary medical center.
PATIENTS AND METHODS
This is a retrospective single-center cross-sectional analysis of consecutive eyes for which ocular biometric parameters were measured with a SS-OCT device at the Department of Ophthalmology of Shaare Zedek Medical Center in Jerusalem, between February 2018 and June 2020. Inclusion criteria were age ≥18 years, eyes with no previous cataract or refractive surgery, and biometric measurements with complete, good quality data, as defined by successful repeat measurements of each parameter. One eye was randomly selected in subjects in whom both eyes met the inclusion criteria. In subjects with >1 successful measurement, a single measurement was randomly chosen. This study conformed to the Declaration of Helsinki and was approved by the Shaare Zedek Medical Center Institutional Review Board.
The IOLMaster 700 (software version 1.80.6.60340; Carl Zeiss Meditec, Jena, Germany) device was used to measure ocular biometric parameters, including AL, ACD, anterior and posterior corneal radii of curvature (R anterior and R posterior , respectively), lens thickness (LT), central corneal thickness (CCT), white-to-white (WTW) distance, standard keratometric astigmatism (KA), angle alpha, and angle kappa. Standard corneal power (K) was calculated by 1000 × (1.3375 − 1)/R anterior . Mean keratometry was defined by (K steep + K flat )/2. Posterior corneal power (PK) was calculated by 1000 × (−0.04)/R posterior . KA was calculated as K steep − K flat . Total corneal astigmatism (TCA) was calculated as TK steep − TK flat . Posterior corneal astigmatism (PCA) was calculated as posterior K steep − posterior K flat. Horizontal and vertical components of angle kappa and angle alpha were also measured by the device, and their magnitudes were calculated by the square root of the sum of the squares of their respective horizontal and vertical components.
The normality of the data was assessed using the Shapiro–Wilk test, and homoscedasticity was assessed using Levene’s test. All variables showed statistically significant deviations in ≥1 of these parameters with the exception of the WTW distance. A 2-sample t test was applied to compare WTW distances, and a Mann-Whitney U test was used for comparing the remainder of the variables. Correlations between all variables were examined by means of Spearman correlation coefficients. Data were entered into an electronic spreadsheet (Excel; Microsoft, Redmond, Washington, USA), and statistical analyses were conducted with R software (version 4.0.3). Results were expressed as the mean ± standard deviation (SD) and the critical α was .05.
RESULTS
BIOMETRIC PARAMETERS AND DEMOGRAPHIC DATA
The analysis included 3836 eyes of 3836 consecutive patients with a mean age of 72.3 ± 12.8 years and of whom 2040 were female (53%). Of these, 2044 were right eyes and 1792 were left eyes. There was no significant difference between the number of eyes per side between sexes ( P = .795). Table 1 describes the biometric parameters of the study population. Figure 1 displays sex-dependent comparisons of the biometric parameters, demonstrating that the male patients were significantly younger than the female patients ( P < .001, Figure 1 ), and no significant sex-related differences were demonstrated in LT ( P = .440), angle kappa ( P = .216), or KA ( P = .103). In all other biometric parameters, sex demonstrated a statistically significant difference ( Table 1 ). Figure 2 presents the distribution of the AL and Figure 3 presents the distribution of TCA in the study population.
| Biometric Parameters | Total Mean ± SD (Range) | Male Mean ± SD (Range) | Female Mean ± SD (Range) | P Value |
|---|---|---|---|---|
| Axial length (mm) | 23.95 ± 1.66 (19.25-35.59) | 24.39 ± 1.71 (19.25-35.59) | 23.56 ± 1.5 (20.01-34.76) | <.001 |
| Anterior R flat (mm) | 7.76 ± 0.30 (6.33-10.40) | 7.83 ± 0.31 (6.34-10.40) | 7.69 ± 0.28 (6.60-8.65) | <.001 |
| Anterior R steep (mm) | 7.58 ± 0.30 (5.41-9.93) | 7.64 ± 0.31 (5.41-9.93) | 7.52 ± 0.29 (6.27-8.49) | <.001 |
| Mean anterior R (mm) | 7.67 ± 0.29 (5.87-10.17) | 7.73 ± 0.30 (5.87-10.17) | 7.61 ± 0.28 (6.44-8.57) | <.001 |
| K flat (D) | 43.58 ± 1.69 (32.44-53.27) | 43.18 ± 1.68 (32.44-53.27) | 43.93 ± 1.62 (39.02-51.15) | <.001 |
| K steep (D) | 44.63 ± 1.80 (33.98-62.40) | 44.25 ± 1.82 (33.98-62.40) | 44.96 ± 1.72 (39.77-53.82) | <.001 |
| Mean K (D) | 44.11 ± 1.69 (33.21-57.84) | 43.72 ± 1.70 (33.21-57.84) | 44.45 ± 1.61 (39.40-52.48) | <.001 |
| Keratometric astigmatism (D) | 1.05 ± 0.85 (0.00-10.43) | 1.07 ± 0.85 (0.00-9.13) | 1.03 ± 0.86 (0.00-10.43) | .103 |
| TK flat (D) | 43.62 ± 1.70 (31.76-52.53) | 43.20 ± 1.69 (31.76-52.53) | 43.99 ± 1.63 (38.96-51.19) | <.001 |
| TK steep (D) | 44.73 ± 1.80 (33.02-61.84) | 44.36 ± 1.82 (33.02-61.84) | 45.05 ± 1.72 (39.79-53.89) | <.001 |
| Mean TK (D) | 44.17 ± 1.70 (32.39-57.18) | 43.78 ± 1.70 (32.39-57.18) | 44.51 ± 1.62 (39.39-52.54) | <.001 |
| Total corneal astigmatism (D) | 1.11 ± 0.87 (0.00-10.40) | 1.16 ± 0.88 (0.00-9.31) | 1.06 ± 0.87 (0.00-10.40) | <.001 |
| Posterior R flat (mm) | 6.99 ± 0.31 (5.06-8.43) | 7.05 ± 0.32 (5.062-8.434) | 6.93 ± 0.29 (5.80-7.87) | <.001 |
| Posterior R steep (mm) | 6.69 ± 0.31 (4.45-7.96) | 6.75 ± 0.33 (4.45-7.96) | 6.63 ± 0.29 (5.30-7.59) | <.001 |
| Posterior mean R (mm) | 6.84 ± 0.30 (4.76-8.20) | 6.90 ± 0.31 (4.76-8.20) | 6.78 ± 0.28 (5.65-7.73) | <.001 |
| Posterior K flat (D) | −5.74 ± 0.26 (−7.90 to −4.74) | −5.69 ± 0.26 (−7.90 to −4.74) | −5.78 ± 0.25 (−6.90 to −5.09) | <.001 |
| Posterior K steep (D) | −6.00 ± 0.29 (-8.99 to −5.02) | −5.94 ± 0.29 (−8.99 to −5.02) | −6.04 ± 0.27 (−7.54 to −5.27) | <.001 |
| Posterior mean K (D) | −5.87 ± 0.26 (-8.45 to −4.88) | −5.81 ± 0.27 (−8.45 to −4.88) | −5.91 ± 0.25 (−7.09 to −5.18) | <.001 |
| Posterior corneal astigmatism (D) | −0.26 ± 0.15 (−1.47 to 0) | −0.25 ± 0.15 (−1.09 to 0) | -0.26 ± 0.15 (-1.47-0) | <.02 |
| Anterior chamber depth (mm) a | 3.18 ± 0.42 (1.78-4.76) | 3.25 ± 0.42 (1.89-4.76) | 3.11 ± 0.41 (1.78-4.44) | <.001 |
| Lens thickness (mm) | 4.49 ± 0.47 (2.52-6.56) | 4.50 ± 0.48 (2.83-6.56) | 4.47 ± 0.46 (2.52-5.89) | .44 |
| Central corneal thickness (mm) a | 0.54 ± 0.04 (0.40-0.65) | 0.54 ± 0.04 (0.40-0.65) | 0.54 ± 0.04 (0.41-0.65) | .001 |
| White-to-white (mm) b | 11.92 ± 0.44 (10.20-13.56) | 12.02 ± 0.44 (10.20-13.29) | 11.83 ± 0.42 (10.42-13.56) | <.001 |
| Angle alpha (mm) | 0.49 ± 0.17 (0.04-1.87) | 0.47 ± 0.18 (0.04-1.87) | 0.50 ± 0.16 (0.06-1.52) | <.001 |
| Angle kappa (mm) | 0.34 ± 0.17 (0.01-1.56) | 0.33 ± 0.18 (0.01-1.48) | 0.34 ± 0.17 (0.01-1.56) | .216 |
a Variables had equal variance and normally distributed residuals (t-test).
b Variables had unequal variance and normally distributed residuals (Welch’s t test). Noe: Remaining, otherwise unmarked variables were assessed using a Mann-Whitney U test. P values represent comparisons of parameter measures between the sexes.
