Refractive Status at Birth: Its Relation to Newborn Physical Parameters at Birth and Gestational Age

Refractive status at birth is related to gestational age. Preterm babies have myopia which decreases as gestational age increases and term babies are known to be hypermetropic. This study looked at the correlation of refractive status with birth weight in term and preterm babies, and with physical indicators of intra-uterine growth such as the head circumference and length of the baby at birth.All babies delivered at St. Stephens Hospital and admitted in the nursery were eligible for the study. Refraction was performed within the first week of life. 0.8% tropicamide with 0.5% phenylephrine was used to achieve cycloplegia and paralysis of accommodation. 599 newborn babies participated in the study. Data pertaining to the right eye is utilized for all the analyses except that for anisometropia where the two eyes were compared. Growth parameters were measured soon after birth. Simple linear regression analysis was performed to see the association of refractive status, (mean spherical equivalent (MSE), astigmatism and anisometropia) with each of the study variables, namely gestation, length, weight and head circumference. Subsequently, multiple linear regression was carried out to identify the independent predictors for each of the outcome parameters.Simple linear regression showed a significant relation between all 4 study variables and refractive error but in multiple regression only gestational age and weight were related to refractive error. The partial correlation of weight with MSE adjusted for gestation was 0.28 and that of gestation with MSE adjusted for weight was 0.10. Birth weight had a higher correlation to MSE than gestational age.This is the first study to look at refractive error against all these growth parameters, in preterm and term babies at birth. It would appear from this study that birth weight rather than gestation should be used as criteria for screening for refractive error, especially in developing countries where the incidence of intrauterine malnutrition is higher

Association between MSE and Head Circumference (Right Eye).

<p>Association between MSE and Head Circumference (Right Eye).</p

MSE (Right eye, N = 559) for various Gestation (in weeks) - Birth weight (g) groups with partial correlation and Pearson correlation of weight and gestation.

<p>Values are mean MSE in each combination group of gestation and birth weight.</p><p>Pearson Correlation of MSE with weight 0.48 (p<0.001) and with gestation 0.41 (p<0.001).</p><p>Partial Correlation of MSE with weight 0.28 (p<0.001) and with gestation 0.10 (p = 0.02).</p

Association between MSE and Weight (Right Eye).

<p>Association between MSE and Weight (Right Eye).</p

Refractive status (MSE, astigmatism and anisometropia) against growth parameters (weight, length and head circumference) and gestational age – Right Eye.

<p>SD Standard deviation.</p><p>IQR Inter Quartile Range.</p

Correlation matrix for the 4 variables gestation, weight, length and head circumference at birth (N = 559 babies).

*<p>signifies p<0.001.</p

Association between MSE and Length (Right Eye).

<p>Association between MSE and Length (Right Eye).</p

Prevalence of astigmatism (1.00D or more) among term and preterm babies (Right Eye).

<p>Fisher's Exact p between Term and Preterm = 0.26.</p