Analysis of Factors Affecting the Change in Axial Length of Premature Infant's Eye

Dae Il Park; Sung Woo Ha; Seong Bae Park; Young Soo Yun

doi:10.3341/jkos.2010.51.1.81

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Park, Ha, Park, and Yun: Analysis of Factors Affecting the Change in Axial Length of Premature Infant's Eye

Original Article

J Korean Ophthalmol Soc 2010;51(1):81-87.

Published online: 7 September 2010

DOI: https://doi.org/10.3341/jkos.2010.51.1.81

Analysis of Factors Affecting the Change in Axial Length of Premature Infant's Eye

Dae Il Park, MD, Sung Woo Ha, MD, Seong Bae Park, MD, Young Soo Yun, MD

Department of Ophthalmology, CHA University, CHA Bundang Medical Center, Seongnam, Korea

Address reprint requests to Sung Woo Ha, MD Department of Ophthalmology, CHA University, CHA Bundang Medical Center #351 Yatap-dong, Bundang-gu, Sungnam 463-712, Korea Tel: 82-31-780-5330, Fax: 82-31-780-5333, E-mail: swha@chamc.co.kr

Received 25 May 2009 Accepted 13 October 2009

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To analyze the effect of presence with or absent of retinopathy of prematurity (ROP) and its stage, birth weight, conceptual age and associated diseases on the axial length of premature infants' eye.

Methods

A total of 102 eyes of 51 premature infants less than 36 weeks of conceptual age were evaluated in this study. Fundus examination for ROP and axial length measurement were conducted at 40, 52 and 64 weeks of postconceptual age. The medical records were reviewed retrospectively. Independent t-test analysis, simple regression analysis, and one-way ANOVA were performed to assess the influence of each factor on axial length.

Results

The mean axial length at 40, 52 and 64 weeks were 17.35, 18.80 and 19.78 mm, respectively. The mean axial length with and without ROP at 40 weeks were 17.10 mm and 17.54 mm, respectively, which were statistically significant (p=0.000). There was a significant decrease in axial length at 40 weeks in the higher ROP stage (p<0.05). Axial length and birth weight showed positive correlation with statistical significance at 40 weeks, while these parameters showed no significant correlation at 64 weeks. Axial length and conceptual age showed a positive correlation with statistical significance at 40 weeks (p=0.000), yet a negative correlation at 64 weeks with no statistical significance (p=0.306). A significant difference was not observed between sex and the associated diseases.

Conclusions

The factors that affect the axial length of an infants'eye at 40 weeks were ROP and its stage, birth weight, and conceptual age. Additionally, there was no significant relationship between sex and the associated diseases.

Keywords: Axial length, Birth weight, Conceptual age, Prematurity, Retinopathy of prematuriy

References

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Figure 1.

Changes in axial length for each stage of ROP with conceptual age.

Figure 2.

Changes in anterior chamber depth for each stage of ROP with conceptual age

Figure 3.

Relationship between birth weight and axial length. (AL: axial length)

Figure 4.

Relationship between conceptual age and axial length. (AL: axial length)

Figure 5.

Relationship between birth weight and axial length in ROP group. (AL: axial length)

Figure 6.

Relationship between conceptual age and axial length in ROP group. (AL: axial length)

Figure 7.

Relationship between birth weight and axial length in without ROP group. (AL: axial length)

Figure 8.

Relationship between conceptual age and axial length in without ROP group. (AL: axial length)

Table 1.

Patient data

	N^*	Mean ± SD^† (range)
Birth age (weeks)	102	30.59±2.8 (24.71–35.86)
Birth weight (gram)	102	1495.45±511.66 (680–3260)
Anterior chamber at 40week (mm)	102	2.23±0.19 (2.02–2.77)
Male	44	43.14%
Female	58	56.86%
With ROP^‡	54	52.94%
Without ROP	48	47.06%
Associated disease	31	61%
Respiratory distress syndrome	16	52%
Intraventricular hemorrhage	3	10%
Necrotizing enterocolitis	1	3%
Bronchopulmonary dysplasia	3	10%
More than 2 Diseases	8	26%

^* N=number

^† SD=standard deviation

^‡ ROP=retinopathy of prematurity.

Table 2.

Factors affecting axial length of premature infant's eye

	Factor	At 40 weeks		At 52 weeks		At 64 weeks
	Factor	N	Axial length (mm)	N	Axial length (mm)	N	Axial length (mm)
Sex	Male	58	17.38	24	18.84	20	19.85
	Female	44	17.31	18	18.74	14	19.62
	p-value		0.564		0.626		0.649
ROP^*	Absence	54	17.54	12	18.24	10	19.80
	Present	48	17.13	30	18.62	24	19.77
	p-value		0.000^*		0.006^*		0.913
Associated diseases	Absence	40	17.32	20	18.72	16	19.92
	Present	62	17.36	22	18.87	18	19.65
	p-value		0.725		0.496		0.220
Associated Diseases number	1 Disease	42	17.32	16	18.94	10	19.63
	More than 2 disease	22	17.37	8	18.56	8	19.68
	p-value		0.735		0.283		0.885
Respiratory disease	Absence	48	17.31	22	18.81	20	19.96
	Present	54	17.40	20	18.79	14	19.52
	p-value		0.455		0.937		0.243

Statistical significance was tested by independentt test. p<0.05

^* ROP=retinopathy of prematurity.

Table 3.

Mean anterior chamber depth and axial length

	N^*	Mean	SD^†	Min	Max
Anterior chamber at 40 weeks	102	2.23	±0.19	2.02	2.77
Anterior chamber at 52 weeks	42	2.58	±0.22	2.11	2.95
Anterior chamber at 64 weeks	34	2.81	±0.22	2.37	3.10
Axial length at 40 weeks	102	17.35	±0.61	16.12	18.97
Axial length at 52 weeks	42	18.80	±0.68	17.6	20.62
Axial length at 64 weeks	34	19.78	±0.63	18.78	21.18

^* N=number

^† SD=standard deviation.

Table 4.

Summary statistics, each time point, for stage of ROP

Parameter	Stage of Rop	n^*	40 weeks		52 weeks		64 weeks
Parameter	Stage of Rop	n^*	mean	SD^†	mean	SD	mean	SD
ACD^‡ (mm)	0	54	2.23	±0.21	2.63	±0.22	2.79	±0.22
	1	34	2.26	±0.19	2.51	±0.23	2.72	±0.20
	2	10	2.17	±0.08	2.62	±0.16	2.85	±0.18
	3	4	2.11	±0.06	2.52	±0.05	2.69	±0.02
AL^§ (mm)	0	54	17.54	±0.61	18.94	±0.84	19.8	±0.57
	1	34	17.22	±0.47	18.66	±0.56	19.75	±0.65
	2	10	17.08	±0.64	18.76	±0.23	19.91	±0.75
	3	4	16.48	±0.02	18.52	±0.07	19.27	±0.14

^* N=number

^† SD=standard deviation

^‡ ACD=anterior chamber depth

^§ AL=axial length.

Table 5.

Axial length in preterm infants who require ROP screening examination

			At 40 wks			At 52 wks			At 64 wks
			N	Axial length (mm)	SD^†	N	Axial length (mm)	SD	N	Axial length (mm)	SD
All	Birth weight	≥1500	48	17.63	±0.55	12	18.68	±0.49	10	20.13	±0.50
	(gram)	<1500	54	17.09	±0.54	31	18.76	±0.62	26	19.60	±0.61
		(p-value)		0.000^‡			0.673			0.021^‡	
	Conceptual	≥28	82	17.44	±0.61	25	18.71	±0.72	20	19.68	±0.60
	age(week)	<28	22	17.01	±0.48	18	18.77	±0.32	16	19.83	±0.66
		(p-value)		0.003^‡			0.736			0.465	
Without ROP	Birth weight	≥1500	36	17.63	±0.55	6	18.60	±0.10	6	20.15	±0.44
	(gram)	<1500	18	17.09	±0.54	5	19.35	±1.18	4	19.26	±0.12
		(p-value)		0.002^‡			0.226			0.003^‡	
	Conceptual age	≥28	52	17.56	±0.61	11	18.94	±0.84	10	19.80	±0.57
	(week)	<28	2	16.92	±0.00	0			0		
		(p-value)		0.143							
With ROP^§	Birth weight	≥1500	12	17.32	±0.62	6	18.75	±0.71	4	20.09	±0.66
	(gram)	<1500	36	17.06	±0.49	26	18.65	±0.40	22	19.66	±0.64
		(p-value)		0.143			0.625			0.236	
	Conceptual age	≥28	28	17.21	±0.54	14	18.53	±0.58	10	19.56	±0.64
	(week)	<28	20	17.01	±0.50	18	18.77	±0.32	16	19.83	±0.66
		(p-value)		0.217			0.139			0.309	

^* N=number

^† SD=standard deviation

^‡ Statistical significance was tested by independentt test. p<0.05

^§ ROP=retinopathy of prematurity.

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