Central corneal thickness in full-term newborns
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A C T A O P H T H A L M O L O G I C A 67 (1989) 719-720
S H 0 RT CO M M U N I CAT1 0 N
Central corneal thickness in full-term newborns
T. Autzen and L. Bjplrnstrplm
Department of Ophthalmology (Head: K. Work), Odense University Hospital, Odense, Denmark
Abstract. The central corneal thickness (CCT) was measured in 30 full-tern newborns in the first week post partum using ultrasonic pachometry. The mean CCT in the right eyes was 0.581k0.047 111111. In 19 babies the CCT was measured twice. The mean CCT in the second read- ing was 0.584k0.042 mm. This difference was not statisti- cally significant. There was no correlation between gesta- tional age, birth weight and length, and CCT. The small difference between girls and boys was not statistically sig- nificant. The values in the left eyes were similar to the data for the right eyes. These results confirm the results in the only previous study on CCT in newborns, that is, that CCT is significantly larger than the CCT in adults.
Key words: ultrasonic pachometry - central corneal thickness - birth weight and length.
Previously the central corneal thickness (CCT) in children has only been subject to one study show- ing decreasing thickness after birth, but no corre- lation between CCT and birth weight (Ehlers et al. 1976). The CCT was measured optically with a slit- lamp. This method is less convenient for measur- ing CCT in premature babies and inter-observer variability might reduce the possibility of compar- ing CCT measurements on rare congenital eye dis- eases from different departments.
Applanation tonometry in adults is influenced by CCT. It is unknown if the same is true in new- borns, but CCT might be of great influence in the diagnosis of buphthalmia (Ehlers et al. 1975). The purpose of this study was to report CCT in the nor- mal full-term newborn using ultrasonic pacho- metry and to correlate CCT to gestational age, birth length and weight.
Material and Methods
We measured CCT in 30 consecutively born full- term babies in the first post-natal week. The mean age was 2.6 f 1.2 days at the measurement. There were 13 girls and 17 boys. CCT was measured twice in each eye in 19 babies. Informed consent was ob- tained.
The mean gestational age was 40.2 f 1.4 weeks. The mean birth weight and length were 3473.3 f 415.8 g and 52.4 f 2.2 cm, respectively. Topical an- aesthesia was obtained with one drop of 0.2% oxy- buprocain in each eye. The CCT was measured with a Storz Corneo-scan I1 CS 2000 AC ultrasonic pachometer. The sound velocity was set at 1630 mls, and the measurements were made with the babies in the supine position. The pachymeter re- ported each reading and calculated the standard deviation based on approximately 4000 sample measurements. If the standard deviation was above 0.005 mm the reading was rejected.
The resulting data were entered in a IBM com- patible AT personal computer. We used Medstat ver 2.1 with the included database for statistical analysis of the data (Wulf& Schlichting 1989). The mean and standard deviations were calculated and compared by unpaired t -tests. The correlation be- tween CCT and gestational age, birth weight and length were analysed with the Spearman test. The level of significance was chosen at P< 0.05.
The mean CCT for the first and second readings in the right eyes were 0.581 k 0.047 mm and 0.584 f
Table 1. Correlation between central corneal thickness (CCT) and birth weight (BW), birth length (BL) and gestational age
(GA) in the right eyes.
l N I R I P BW 30 -0.287 0.13 BL 30 -0.274 0.14 GA 30 -0.264 0.16
0.042 111111, and the mean CCT in the right eyes in boys and girls were 0.589 f 0.041 mm and 0.571 f 0.054 111111, respectively. These differences were not statistically significant.
The correlation between CCT, birth weight and length and gestational age are shown in Table 1. Although there was a tendency towards negative correlations between CCT and all three parame- ters, none of these reached sigrdcance. There was no correlation between CCT and the age of the babies. The data on the left eyes were similar to the right eyes.
The standard deviation of the single meas- urements in the present study was limited at 0.005 mm. A similar standard deviation may be obtained in optical pachometry in adults, but the inter-ob- server error in optical measurement may be ap- proximately four times larger than the intra-obser- ver error due to differences in the definition of the edges of the optical section in the cornea, slit- width and perception differences between the ob- servers (Olsen et al. 1980). However, previous studies showed good accordance between the mean CCT on optical and ultrasonic pachometry in adults. We found no significant inter-observer difference with ultrasonic measurements (Kremer et al. 1985; Autzen & Johansen, unpublished data), but these errors may account for the small dif- ference between the mean CCT in the first study on CCT in newborns and the present results (Ehlers et al. 1976).
The present analyses showed increased CCT in full-term newborns and no correlation between CCT and birth weight, length and gestational age. This is in agreement with previous studies (Ehlers et al. 1976; Ehlers & Hansen 1976).
Weinreb et al. (1987) found increased CCT in
pregnant women with no correlation with the week of gestation. The CCT returned to baseline levels within a few weeks post partum, suggesting that hormonal changes during pregnancy could be related to increased CCT during pregnancy in mother and child (Weinreb et al. 1987). This hypo- thesis would apply to the previous observation of CCT in premature babies, which was not signifi- cantly different from CCT in full-term babies.
We found ultrasonic pachometry easy to per- form, even in the newborn. The inter-observer error is low. This might permit future multicenter studies on CCT in rare congenital diseases such as buphthalmia and anterior chamber cleavage syn- drome, and studies on CCT in the premature new- born.
We thank the staff of the Department of Gynecology and Obstetrics, Odense sygehus for their generous assistance.
Ehlers N, Bramsen T & Sperling S (1975): Applanation tonometry and central corneal thickness. Acta Oph- thal (Copenh) 53: 34-43.
Ehlers N & Hansen F K (1976): Further data on biometric correlations of central corneal thickness. Acta Oph- thal (Copenh) 54: 774-778.
Ehlers N, Srarensen T, Bramsen T & Poulsen E H (1976): Central corneal thickness in the newborns and child- ren. Acta Ophthal (Copenh) 54: 285-290.
Kremer F B, Walton P & Gensheimer G (1985): Determi- nation of corneal thickness using ultrasonic pacho- metry. Ann Ophthalmol 17: 506-507.
Olsen T, Nielsen C B & Ehlers N (1980): On the optical measurement of corneal thickness. 11. The measuring conditions and sources of error. Acta Ophthal (Co- penh) 58: 975-984.
Weinreb R N, Lu A & Beeson C (1987): Maternal corneal thickness during pregnancy. Am J Ophthalmol 105: 258-260.
Wulff H R & Schlichting P (1989): Medstat ver 2.1. ASTRA gruppen A/S, Copenhagen, Denmark.
Received on June 14th, 1989.
Authors address: Torben Autzen, Department of Ophthalmology, Odense University Hospital, DK-5000 Odense C, Denmark.