Comparative Analysis of Contact and Immersion Technique in Ultrasonographic Biometry

Jay Won Rhim; Su Yeon Kang; Hyo Myoung Kim

doi:10.3341/jkos.2009.50.12.1795

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Rhim, Kang, and Kim: Comparative Analysis of Contact and Immersion Technique in Ultrasonographic Biometry

Original Article

J Korean Ophthalmol Soc 2009;50(12):1795-1799.

Published online: 7 September 2009

DOI: https://doi.org/10.3341/jkos.2009.50.12.1795

Comparative Analysis of Contact and Immersion Technique in Ultrasonographic Biometry

Jay Won Rhim, MD, Su Yeon Kang, MD, Hyo Myoung Kim, MD, PhD

Department of Ophthalmology, College of Medicine, Korea University, Seoul, Korea

Address reprint requests to Hyo myoung Kim, MD, Department of Ophthalmology, Anam Hospital, Korea University College of Medicine #126-1 Anam-dong 5-ga, Seongbuk-gu, Seoul 136-705, Korea Tel: 82-2-920-5521, Fax: 82-2-924-6820, E-mail: hyomkim@hanmail.net

Received 8 December 2008 Accepted 25 August 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 establish the accuracy of the newly released biometer Ocuscan RxP^® (Alcon, USA) by comparison with the established Ultrasonic Biometer Model 820^® (Allergan Humphrey, USA), and to compare the accuracy of contact and immersion biometries.

Methods

This is a prospective study involving 27 patients (40 eyes) who were scheduled for cataract surgery and had axial lengths measured with an Ocuscan RxP^® biometer using both contact (Method 1) and immersion (Method 2) techniques. As a reference, a contact type Ultrasonic biometer 820^® (Method 3) was also used. IOL(Intraocular Lens) power for the cataract surgery was calculated

using this result. An axial length which would have caused no post-operative refractive error was reversely calculated from the difference of target diopter and post-operative refractive error. This length was compared with the axial lengths obtained via Methods 1, 2 and 3.

Results

The means and standard deviations for the measurement sets were compared. Methods 1 and 2 showed no significant difference (23.22±0.68, 23.24±0.69 mm, p=0.55). The axial length measured by Method 3 was 23.32±0.67 mm. The difference between the target refraction and post-operative refractive error was 0.29±0.60D. The axial length was reversely calculated from the difference (23.07±0.84 mm). The differences between the reversely calculated axial lengths and those of Methods 1, 2 and 3 were 0.15± 0.31, 0.17±0.31 and 0.24±0.28 mm, respectively.

Conclusions

Biometric results from Methods 1 and 2 caused less refractive error than did Method 3. The contact and immersion methods are both accurate for IOL power calculation if performed by a well-skilled examiner.

Keywords: Alcon Ocuscan, Axial length, Contact, Immersion, Ultrasonic biometry

References

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Figure 1.

Reverse calculation of axial length from the post-op refractive error.

Figure 2.

Comparison of axial length of each method and reversely calculated axial length.

Figure 3.

Comparison of method 1 (contact) and method 2 (immersion) with reversely calculated axial length.

Table 1.

Patient demographics

	Male	Female
Patient number	13	14
Mean age	67	73
Age range	44∼82	55∼85

Table 2.

Mean axial length and difference with the reversely calculated axial length

	Mean± SD	Difference with the reversely calculated axial length
Method 1 (Contact)	23.22±0.68	0.15±0.31
Method 2 (Immersion)	23.24±0.69	0.17±0.31
Method 3 (Reference)	23.32±0.67	0.24±0.28

Table 3.

Average IOL power calculated based on axial lengths by each method

	Average IOL power	Difference with the error-free IOL
Method 1 (Contact)	20.87±1.54	0.39±0.76
Method 2 (Immersion)	20.84±1.56	0.42±0.78
Method 3 (Reference)	20.65±1.48	0.60±0.70

Table 4.

Number of cases which would have been the most correct method

	Correct	moderate	Most different
Method 1 (Contact)	23	8	9
Method 2 (Immersion)	10	20	10
Method 3 (Reference)	7	12	21

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