Central corneal thickness in premature babies
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A C T A 0 P H T H A L M 0 L O G I C A 69 (1991) 251-252
S H 0 RT CO M M U N I CAT1 0 N
Central corneal thickness in premature babies
T. Autzen and L. Bjprrnstr~m
Department of Ophthalmology (Head: K. Work), Odense University Hospital, Odense, Denmark
Abstract. Central corneal thickness was measured in 13 premature babies with a gestational age below 33 weeks. No difference was found between the thickness in the first and third post-natal week. At the age of 3 months the thickness had decreased significantly to the same level previously reported in full-term newborns. There was no correlation between gestational age, birth length and weight and central corneal thickness.
Key words: ultrasonic pachometry - central corneal thick- ness - premature babies - birth weight and length.
Studies using both optical and ultrasonic pacho- metry have shown that the central cornea in full- term newborns is signifkantly thicker than in adults, but no difference in central corneal thick- ness (CCT) between premature and full-term babies could be demonstrated using optical pacho- metry (Ehlers et al. 1976; Weinreb et al. 1987; Aut- Zen & Bjarnstrom 1989).
Measurement of CCT in premature babies using optical pachometry is dXicult, and impossible without removing the babies from the incubator. We have found no previous reports on CCT in pre- mature babies using ultrasonic pachometry. The aim of this study was to estimate CCT in premature babies.
The CCT was measured 3 times, as described previously, using a Storz Corneo-scan I1 CS 2000 AC ultrasonic pachometer (Autzen & Bj~rnstrram 1989). The median age at the measurements was 5 days (range 0-8), 20.2 days (range 18-26) and 109.8 days (range 103-142). Prematures placed in incuba- tors were measured inside the incubator.
The mean CCT values were compared by paired t-tests. The correlation between CCT and gesta- tional age birth weight and length was analyzed using the non-parametric Spearman test. The level of siwicance was chosen at P < 0.05.
Table 2 presents the 3 readings and means of CCT in the right eyes. The data on the left eyes were similar. The mean difference between the CCT in the first and second reading was -0.012 SE 0.009 mm (P> 0.05). Excluding patients lost on follow- up the mean CCT decreased with 0.078 SE 0.016 mm from the first to the third reading (p = 0.001). The correlation between CCT, gestational age, birth length and weight are shown in Table 3.
In the only previous study on CCT in premature babies no difference compared to full-term new- borns could be demonstrated. The CCT was measured using optical pachometry (Ehlers et al. 1976). In this study CCT in prematures decreased
Material and Methods
The CCT was measured consecutively in 6 girls and 7 boys. Prematures with a gestational age > 32 weeks were excluded. Table 1 shows the median gestational age, birth weight and length.
GA (weeks) 31.4 26-32 BL (cm) 41.5 35-47 BW (9 1400 936-2088
Table 2. Central corneal thickness (mm) in right eyes of 13 prema-
ture babies at 3 readings (9999 =lost on follow up).
Median age (days)
Authors address: P
1 0.702 0.673 0.608 2 0.798 0.793 0.605 3 0.785 0.771 0.699 4 0.686 0.666 0.582
significantly with 12% in the first few months to 5 0.652 9999 0.570 0.566 mm. The slightly higher CCT of 0.581 mm 6 0.573 0.625 0.568
7 0.527 0.567 0.493 8 0.633 0.669 0.585 previously reported in full-term newborns in the
9 0.511 0.523 0.463 first postnatal week was not statistically significant
10 0.570 0.588 0.536 (Autzen & Bj~rnstrcam 1989). Several concurrent
factors may explain the decrease in CCT, such as 11 0.642 0.667 0.517 change in the sound velocity with gestational age, increase in evaporation, hormonal influence and improved hydration control (Ehlers et al. 1976; Weinreb et al. 1987). However, no difference be- tween the first and second readings was demon- strated.
No correlation could be demonstrated between CCT and gestational age, birth weight and length, but the reduction in CCT in the first 3 months may explain the tendency of negative correlation be- tween CCT and all 3 parameters previously re- ported (Autzen & Bj0rnstrplm 1989).
We thank the staff at the Department of Pediatrics, Odense Hospital for their generous assistance.
12 0.836 9999 9999 13 0.608 9999 9999
Mean 0.656 0.654 0.566 SD 0.103 0.084 0.064
Autzen T & Bjmnstrorn L (1989): Central corneal thick- ness in full-term newborns. Acta Ophthalmol (Co- penh) 67 719-720.
Ehlers N, S~rensen T, Bramsen T, Poulsen E H (1976): Central corneal thickness in newborns and children. Acta Ophthalmol (Copenh) 54: 285-290.
Weinreb R N, Lu A, Beeson C (1987): Maternal corneal thickness during pregnancy. Am J Ophthalmol 105: 258-260.
Table 3. Correlation between central corneal thickness (CCT) and gestational age (GA), birth length (BL) and birth weight
(BW) in the right eyes. Received on November llth, 1990.