Applanation Ultrasound versus Optical Biometry in the measurement of Axial Length in a Normal Eye

Article Information

Title: Applanation Ultrasound versus Optical Biometry in the measurement of Axial Length in a Normal Eye

Authors: Arsh Zahoor, M. Azam Khan, Irfan Aslam Khattak, Ayisha Shakeel, Maria Saleem, Shaista Haider

Journal: Journal of Islamabad Medical and Dental College (JIMDC)

HEC Recognition History

Category	From	To
Y	2024-10-01	2025-12-31
Y	2023-07-01	2024-09-30
Y	2022-07-01	2023-06-30
Y	2021-07-01	2022-06-30
Y	2020-07-01	2021-06-30

Publisher: Healers Educational Society

Country: Pakistan

Year: 2024

Volume: 13

Issue: 2

Language: English

DOI: 10.35787/jimdc.v13i2.1164

Abstract

Objectives
Accurate measurement of the axial length (AL) of the eye is important to make sure that the patient is emmetropic postoperatively. Multiple studies conducted around the globe compare AL using optical and ultrasound biometry. However, results are still inconclusive, as some studies stated that there is no difference in both modalities, whereas other studies considered optical biometry to be more superior. We aim to compare AL measurements using applanation ultrasound and optical biometry AL Scan, in Islamabad, in order to find out which modality is more superior.
Methods
This was a prospective cross-sectional study that was conducted at the department of Ophthalmology, PAF Hospital, E9 Islamabad. The study was conducted over a period of eight months, from April to November 2023. Participants were enrolled using non-probability, consecutive sampling. The axial length of each eye was measured by both optical and ultrasound biometer.
Results
There were 80 eyes of 40 participants including both males (77.5%) and females (22.5%) aged between 16-58 years. The axial length using the optical biometer showed a greater value ranging from 22.01 to 30.18mm with a mean value of 23.89 ± 1.31mm whereas the axial length measured using applanation ultrasound was 21.62 to 30.00mm with a mean of 23.53 ± 1.29mm. The mean difference between both was 0.36 ± 0.21mm which was statistically significant (P &lt;0.005).
Conclusion
There is a statistically significant difference between the mean readings of the AL measured by the IOL master and ultrasound biometer, so both the devices cannot be used interchangeably.

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Research Objective

To compare axial length (AL) measurements using applanation ultrasound and optical biometry (AL Scan) in Islamabad to determine which modality is more superior.

Methodology

Prospective cross-sectional study conducted at the Department of Ophthalmology, PAF Hospital, Islamabad, from April to November 2023. Healthy participants with normal anterior and posterior segments were enrolled using non-probability, consecutive sampling. AL was measured using both optical biometry (NIDEK Optical Biometer AL Scan) and applanation ultrasound (Hi-Scan ultrasound 2000 by Optikon). Data was analyzed using SPSS version 26.0, with paired sample t-test for mean AL comparison and Pearson correlation.

Methodology Flowchart

                        graph TD
    A["Study Initiation & Ethical Approval"] --> B["Participant Recruitment"];
    B --> C["Enrollment Criteria Check"];
    C -- Meets Criteria --> D["Measure AL with Optical Biometer"];
    D --> E["Measure AL with Ultrasound Biometer"];
    E --> F["Data Recording"];
    F --> G["Data Entry & Analysis SPSS"];
    G --> H["Statistical Comparison"t-test, Correlation""];
    H --> I["Interpretation & Conclusion"];

Discussion

The study found a statistically significant difference in AL measurements between optical and applanation ultrasound biometry, suggesting they cannot be used interchangeably. This difference may be attributed to the use of contact ultrasound in this study compared to immersion ultrasound in some other studies. The findings align with some studies showing significant differences and preference for optical biometry, while contrasting with others that found no significant difference or considered the devices interchangeable.

Key Findings

The axial length measured by the optical biometer ranged from 22.01 to 30.18mm (mean 23.89 ± 1.31mm), while ultrasound biometry yielded values from 21.62 to 30.00mm (mean 23.53 ± 1.29mm). The mean difference between the two modalities was 0.36 ± 0.21mm, which was statistically significant (P <0.005). A strong positive correlation (0.988) was found between both methods.

Conclusion

There is a statistically significant difference between the mean readings of AL measured by optical biometry and applanation ultrasound biometry, indicating that these devices cannot be used interchangeably. Optical biometry is suggested to be preferred over ultrasound biometry for axial length estimation.

Fact Check

1. Study Period: The study was conducted over eight months, from April to November 2023. (Confirmed in Methodology)
2. Participant Count: 80 eyes of 40 participants were included in the study. (Confirmed in Results)
3. Mean Difference: The mean difference in AL between optical and ultrasound biometry was 0.36 ± 0.21mm. (Confirmed in Results)

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