FP1082 : Normative Biometric Data in Pediatric Eyes from Birth To 2 Years of Age

Dr.Viraj Abhayakumar Vasavada, V11115, Dr.Sajani Kalpit Shah, Dr. Shail, Dr. Samaresh

Authors : Dr. Sajani Shah, Dr. Viraj Vasavada , Dr. Shail Vasavada , Dr. Samaresh Srivastava

Iladevi Cataract & IOL Research Center, Raghudeep Eye Clinic, Gurukul Road, Memnagar, Ahmedabad, India.

Address :

Raghudeep Eye Hospital,

Gurukul Road, Memnagar,

Ahmedabad – 380052. India.

E-mail: info@raghudeepeyeclinic.com

 Normative Biometric Data in Pediatric Eyes from Birth to 2 Years of Age

INTRODUCTION.

The human eye undergoes extensive growth in the postnatal period¹. The earlier in life, the greater the absolute and relative increase; about two thirds of the postnatal ocular axial length increase takes place within the first24-30 months of life; after that age growth further decelerates. The time for attaining final eye size is still under debate², which requires approximately 10 to 15 diopter undercorrection to maintain emmetropic eye. The first extensive cross-sectional study examining the refractive components of the eye, which include axial length, keratometric power, and lens power, was performed by Sorsbyet al³. Their subjects ranged in age from 3-year-old children to young adults. No Biometric Data available in normal eyes from recent studies, particularly in Indian eyes, which has so many clinical implication for IOL Power Calculation, and also for microphthalmos.

In this paper, we have reported the ocular biometric parameters such as keratometry(K), axial length(AL), central corneal thickness(CCT), anterior chamber depth(ACD), lens thickness(LT), horizontal corneal diameter(HKD) and intraocular pressure(IOP) at different ages in normal eyes of Indian children from birth upto 2 years of age.

Material and method:

The Institutional Review Board approved this study. The methodology used adhered to the tenets of Helsinski. The Ethics committee of Iladevi Cataract and IOL Research Centre approved the study.  The examination was undertaken after obtaining written informed consent from the parents.

This is observational, Cross-sectional study of 204 eyes of 408 children from birth (both term and preterm) to 2 years with no ocular abnormalities.Children were examined   in neonatal nurseries (Preterm and neonates) under topical anaesthesia and    Children undergoing surgeries under general anaesthesia for non-ophthalmic disease (e.g. hernia repair, surgery for pyloric stenosis, urinary tract stenosis etc) were examined. Ocular abnormality diagnosed previously or during examination was excluded from the study.

All examinations were performed    by a single, trained ophthalmologist.    A topical anaesthetic agent Proparacaine hydrochloride (U.S.P. 0.5%.) (Paracain, Sunways India Pvt. Ltd. Mumbai, India)) was instilled once. A fluorescein paper strip was applied on the eye and IOP measurements were done using a calibrated hand-held Perkin’s applanation tonometer. (Haag Streit, USA)  The tonometer was calibrated every morning by the staff technician. The corneal curvature was noted using a hand-held keratometer (Nidek Co., LTD. ). An average of 3 readings was taken for the purpose of analysis. The horizontal corneal diameter was measured using calipers. (Eye Castroviejo Caliper, Duckworth & Kent).  Corneal thickness was assessed by ultrasonic pachymetry (Ocuscan, Alcon lab., Forthworth USA). After topical anaesthesia, the ultrasound probe was placed perpendicular to the central cornea without undue pressure being applied on the cornea.  An average of 3 values with an error less than 0.001 was taken into account. The ultrasonic pachymetry was calibrated periodically. The same instrument was used for all measurements. The axial length (AL) was measured with an ultrasound A-Scan using the immersion or contact techniques (Ocuscan, Alcon lab., Forthworth USA). The velocity was set to 1555 mil/sec.  The fundus was examined using a direct and indirect ophthalmoscope.

Statistical analysis

All data were analyzed using SPSS statistical software. The patients were divided into subgroup according to age. Only right eye finding were taken.

• 0 months – Preterm (born before 37 weeks of gestation)
• 0-3 months – Term (37 weeks) to 3 months from birth,
• 3-6 months ,
• 6-9 months,
• 9-12 months,
• 12-24 months.

The ocular variables IOP, horizontal corneal diameter, average corneal curvature, average corneal thickness, central anterior chamber depth (ACD), lens thickness and axial length were compared.

RESULT :

The total numbers of 204 eyes under 2 years were analyzed. The values of various measurements were subdivided into groups based on age.

The mean aggregate K was 46.58±6.09 (range 34.81-63.62) diopters, mean IOP 11.93±2.50 (range 7.9-22.2)mm Hg, mean AL 20.49±2.76(range 12.54-25.07)mm,mean CCT 540.76±51.17(range 438.0-673.0)µm, mean ACD 3.31±0.67(range 1.34-4.80)mm, mean LT 3.97±0.60 (range 2.70-5.50)mm and mean HKD 10.62±1.34 (range 7.3-12.8) mm.The biometric data of all age group is described in table 1.Axial  length of right eye and left eye is described in table 2,while table 3 shows interocular axial length.Table 4 shows biometric data of all age group with reference to gender.

In the present study we further analyzed the multiple regression and found that with increase in age by one month, the axial length increased by 0.709 mm attaining statistical significance (P<0.001). On the other hand if the child is female, then the axial length decreased by -0.204 mm attaining statistical significance (P<0.001).

The multiple regression found that with increase in age by one month, the mean CCT decreased by -0.175mm attaining statistical significance (P<0.001). On the other hand if the child is female, then the mean CCT decreased by -0.017 which is statistically not significant.

The multiple regression found that with increase in age by one month, the average keratometry decreased by -0.294 attaining statistical significance (P<0.001). On the other hand if the child is female, then the average keratometry increased by 0.230, but the increase is not statically significantly different than that of male children..

Discussion:

In this study we have reported the ocular biometric parameters such as keratometry(K), axial length(AL), central corneal thickness(CCT), anterior chamber depth(ACD), lens thickness(LT), horizontal corneal diameter(HKD) and intraocular pressure(IOP) at different ages in normal eyes of Indian children from birth upto 2 years of age has reported.

We found  mean K was 46.58±6.09 (range 34.81-63.62) diopters, mean IOP 11.93±2.50 (range 7.9-22.2)mm Hg, mean AL 20.49±2.76(range 12.54-25.07)mm,mean CCT 540.76±51.17(range 438.0-673.0)µm, mean ACD 3.31±0.67(range 1.34-4.80)mm, mean LT 3.97±0.60 (range 2.70-5.50)mm and mean HKD 10.62±1.34 (range 7.3-12.8) mm.

Dahan et al  has investigated a complete refractive investigation was performedon 148 normal eyes of 79 patients ranging from premature new-borns to36-year-  old adults.Cycloplegic refraction,keratometry,and  axial length measurements were performed.From these Data they then calculated  the refractive power of the lens.With  cross sectional analysis they found mean axial length in full term was 16.8mm, a mean keratometric power of 51.2 diopters¹.

Fledelius et al has reported   early eye growth in preterm and full term infants,where axial length was reported 17.02 mm at full term with growth rate in mm per week².

In 1992-3 supplementary material was published by Tucker et al⁴ and by Denis et al⁵.’Examining the newborn preterm infant in the incubator on day 0-9 Tucker et al declared the aim of establishing normative values for corneal diameter, axial eye length, and intraocular pressure. Valid axial eye length measurements were obtained from 23 subjects aged 25-29 weeks, from 16 aged 30-33 weeks, and

from 31 infants in the 34-37 weeks age group. The mathematical examination used linear regression for the full sample, without attempting a breakdown according to age. The overall axial length increase was 1 mm/23 days, or 0.3 mm/week. Extrapolating to 40 weeks ‘gestation, the authors found fair agreement with established newborn ultrasound term figures.

We found that with increase in age by one month, the axial length increased by 0.709 mm, which is different than above study. With regard to axial length to axial length is consistent at pre term while slightly higher in all other group.

The limitation of our study is small sample size in 3 to 6 months of age group, but practically it is also not possible as major pediatric surgeries are performed either after birth as of emergency or after 6 to 12 months if not life threatening.

The information is reported first time in Indian population, which would help in refractive management of pediatric patients requiring cataract surgery,congenital glaucoma or assessing other developmental anomalies.

References:

1. Robert A. Gordon, MD, Paul B. Donzis, MDRefractive Development of the Human Eye.Arch Ophthalmol 1985;103:785-789
2. Hans C Fledelius, Anders C Christensen. Reappraisal of the human ocular growth curve in fetal life, infancy, and early childhood. BrJ Ophthalmol 1996;80:918-921
3. Sorsby A, Benjamin B, Sheridan M: Refraction and its components during growth of the eye from the age of 3. London, Medical Research Council Special Report Series, No. 301, 1961
4. Denis D, Righini M, Scheiner C, Volot F, Boubli L, DezardX, et al. Ocular growth in the fetus. 1. Comparative study of axial length and other biometric parameters in the fetus.Ophthalmologica 1993;207:117-24.
5. Tucker SM, Enzenauer RW, Levin AV, Morin JD, Hellman Corneal diameter, axial length and intraocularpressure in premature infants.  Ophthalmology 1992;99: 1297-300.

Table 1 : Descriptive of Intraocular pressure,axial length central corneal thickness, anterior chamber depth, lens thickness,corneal diameter, and keratometry of all age groups

	IOP (mmHg)	Axial Length (mm)	Central Corneal Thickness (µm)	Anterior Chamber Depth (mm)	Lens Thickness (mm)	H.Corneal Diameter (mm)	K1(D)	K2(D)	Aggregate Keratometry (D)
N	200	204	200	204	200	198	199	199	199
Mean	11.93±2.50	20.49±2.76	540.76±51.17	3.31±0.67	3.97±0.60	10.62±1.34	43.68±2.93	45.26±3.64	46.58±6.09
Median	11.25	21.12	533.00	3.31	3.91	10.70	43.25	44.30	45.34
Minimum	7.99	12.54	438.00	1.34	2.70	7.30	40.00	39.62	34.81
Maximum	22.20	25.07	673.00	4.80	5.50	12.80	55.25	59.50	63.62

Table 2  :  Evaluating for all age groups a comparisonof axial length between the two eyes

to prove to be similarof each patient

	Axial Length
Months in Age	OD	OS	N (patients)
less than 0	15.47±1.39	15.53±1.58	32
0 to 3 months	19.48±1.44	19.7±1.53	36
3 to 6 months	20±0.55	19.88±0.55	4
6 to 9 months	21.23±1.45	21.5±1.37	44
9 to 12 months	21.94±1.18	22±1.21	36
12 to 24 months	22.69±1.29	22.76±1.28	52

Table 3  :  Comparison of axial length between the two eyes according to age group.

		Mean	95% Confidence Interval		P value
			Lower	Upper
less than 0	OD-OS	-0.05±0.89	-0.38	0.26	0.720
0 to 3 months	OD-OS	-0.21±1.08	-0.58	0.14	0.236
3 to 6 months	OD-OS	0.12±0.90	-1.31	1.56	0.800
6 to 9 months	OD-OS	-0.26±1.12	-0.60	0.07	0.124
9 to 12 months	OD-OS	-0.06±1.53	-0.58	0.45	0.800
12 to 24 months	OD-OS	-0.07±1.36	0-.45	0.30	0.685

 

	IOP(mm Hg)	AXL(mm)	CCT(µm)	ACD(mm)	LT(mm)	HKD(mm)	K1(D)	K2(D)	Agg.K
MALE
N	64	100	96	100	64	68	69	69	72
Mean	11.66±2.14	21.11±2.16	541.46±53.12	3.35±0.69	3.96±0.66	10.81±1.17	42.92±1.54	44.42±2.24	44.83±5.32
Median	11.25	21.44	542.5	3.39	3.91	10.8	43	44.3	44.08
Minimum	7.99	13.58	438	1.34	2.7	7.8	40	39.62	34.81
Maximum	16.5	25	665	4.7	5.5	12.8	46.75	53.75	59
FEMALE
N	36	104	104	104	56	60	70	70	72
Mean	12.39±3.01	19.94±3.13	540.12±49.55	3.27±0.64	3.99±0.53	10.41±1.49	44.43±3.72	46.12±4.49	48.35±6.34
Median	11.4	20.8	524.5	3.28	3.91	10.3	43.47	44.67	47
Minimum	9.5	12.54	459	1.87	3	7.3	40	40.5	37.4
Maximum	22.2	25.07	673	4.8	5.2	12.8	55.25	59.5	63.62

Table 4 : Descriptive of Intraocular pressure,axial length central corneal thickness, anterior chamber depth, lens thickness,corneal diameter, and keratometry of all age groups with reference to gender

Table 5 : Comparison of Intraocular pressure,axial length central corneal thickness, anterior chamber depth, lens thickness,corneal diameter, and keratometry of all age groups with reference to gender

	F	P Value*	95% Confidence Interval
			Lower	Upper
Central Corneal Thickness	.771	0.381	-12.97	15.65
Anterior Chamber Depth	.164	0.686	-0.10	0.26
Lens Thickness	2.778	0.098	-0.25	0.18
Horizontal Corneal Diameter	5.232	0.024	-0.06	0.86
K1	19.467	0.000	-2.46	-0.56
K2	21.507	0.000	-2.88	-0.50

* P Value: Independent Sample T Test 

Table 6 :  Comparison of Intraocular pressure,axial length central corneal thickness, anterior chamber depth, lens thickness,corneal diameter, and keratometry of all age groups with reference to gender 

	P Value
Axial Length	0.01
IOP	0.54
Aggregate K	0.001

 P Value:Mann-Whitney U test