Correlation between Ocular Axial Length and Body Mass Index in a Black Population

Abstract

Aim: To determine the correlation between Ocular axial length (AL) and body mass index (BMI) in a black population. Methods: This was a descriptive cross sectional study carried out in Port Harcourt City LGA, Nigeria. Subjects were selected using multistage random sampling with inclusion criteria of Visual Acuity > 6/18, age greater than 18 years with no history of past ocular surgeries or trauma. Socio demographic data was obtained through an interviewer based structured proforma. Data obtained included age, sex, tribe, occupation and level of education. Weight, height and Body Mass Index (BMI) were measured using a standard height and weight automated scale (SECA 769,220). Ocular examinations done included visual acuity, applanation tonometry and ophthalmoscopy. Axial length (AL) was measured using Amplitude (A) scan ultrasonography (SONOMED PACSCAN 300AP). Data obtained from one eye of the subjects were analyzed using SPSS (Version 17), and p value was set at ≤ 0.05. Results: Four hundred and sixty six (466) subjects participated in the study made up of two hundred and twelve (212) males (45.5%) and two hundred and fifty four (254) females (54.5%) with M: F ratio of 1:1.2. The age range was 18-92 years and mean age of the subjects studied 43.0±14.2 years. Findings revealed mean AL, Body Mass Index, Height and Weight to be (23.2±1.0 mm), (26.9±6.2 kg/m2), (162.5±9 cm) and (70.5±14.8 kg) respectively. The mean AL was greater in males than females. There was no statistically significant relationship between age and axial length. There was a statistically significant relationship between height and AL in both gender with AL increasing by 0.035 mm (p=0.001, r=0.261) with one centimeter change in height in males and 0.025 mm (p=0.001, r=0.2680) in females and between AL and level of education (p=0.001). There was also a statistically significant (0.009 mm) increase in AL per one kilogramme change in weight in females (p=0.0001, r=0.188). Males had longer AL than females in all the BMI groups with a statistically significant difference found between the different BMI classes. Conclusion: This study noted that although there is no statistically significant relationship between AL and BMI, there are significant relationships between AL and height and weight respectively. Estimated AL in mm= 16.91 + 0.039 (height in cm).