Correlation between Axial Length and Anterior Chamber Depth in Eyes with High, Low and Average Axial Length
Authors: Aziz J H F , Elghazawy R M F , Elawamry A I , Zaki R G 
Published: May 2020

Abstract

Background
To achieve optimal refractive outcomes after cataract surgeries, accurate IOL power calculation is mandatory. IOL power is calculated using preoperative biometric measurements such as AL, corneal power, ACD and an estimation of postoperative effective lens position. Choosing the formula of IOL calculation depends mainly on AL and ACD.

Objective
The objective of this study is to investigate the correlation between AL and ACD in short eyes, normal eyes and long eyes.

Patients and Methods
The study was conducted at Ain Shams University Hospitals after the approval of the research ethical committee in the Faculty of Medicine, Ain Shams University. Study Period: 6 months (from July 2018 to January 2019).

Results
The results of our study showed that the correlation between the axial length and the anterior chamber depth among short eyes was statistically significant and they were negatively correlated, while no statistically significant correlation existed between AL and ACD in normal and long eyes.

Discussion
IOL power is calculated using preoperative biometric measurements such as AL, corneal power, ACD and an estimation of postoperative effective lens position. In the study by Holladay, 82% had normal AL and only 0.9% of patients had short eyes. Holladay et al. found that among patients with long eyes, 90% have normal ACD, 10% have high ACD and none of them have short ACD. In the group of patients with normal AL, they found that 90% of patients had normal ACD, none of them had low ACD and 10% had high ACD. In patients with short eyes they found that 20% have low ACD, 80% have normal ACD and none of them have high ACD. Sedaghat et al. documented that linear relationship was only seen in patients with normal AL and not in short and long sighted patients. Chang and Lau have concluded in their study that there was no statistically significant correlation between AL and ACD in eyes with AL of 27.5 mm or greater while positive statistically significant correlation existed in eyes shorter than 27.5 mm. Our study included ninety eyes of patients presenting for IOL or phakic lens implantation in Ain Shams University Hospitals. Patients were divided into three groups according to the AL; the short, normal and long eyes with AL ≤ 22 mm, &gt; 22 mm and &lt;24.50 mm and ≥24.50 mm, respectively. AL and ACD of each patient were measured using The ZEISS IOL Master 500. The results shows that the correlation between the axial length and the anterior chamber depth among short eyes is statistically significant and they are negatively correlated (r = -0.458. P value 0.011), while no statistically significant correlation exists between AL and ACD in normal and long eyes, i.e.: when AL &gt; 22 mm. This lack of correlation might influence the ELP predictions in third generation formulas, which do not consider the preoperative ACD. Our study results agree with most of the previous studies regarding long eyes &gt;27.5 mm that there is no statistically significant correlation between AL and ACD. While in short eyes it disagrees with Chang and Lau who concluded that there was no statistically significant correlation in short eyes and Sedaghat et al. who showed positive correlation between AL and ACD in short eyes. Our study results disagrees with most of the previous studies regarding normal eyes showing that there is no statistically significant correlation between AL and ACD in normal eyes, while previous studies concluded that a positive linear correlation exists.

Conclusion
The AL and ACD are inversely related in short eyes with AL ≤ 22 mm while no correlation exists in normal and long eyes with AL &gt; 22 mm.