Journal of the Egyptian Ophthalmological Society

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 112  |  Issue : 1  |  Page : 30--33

Correlation between axial length and anterior chamber depth in short eyes, normal eyes, and long eyes


Rafik M.F El-Ghazawy, Amr I El-Awamry, Rania G Zaki, Joseph H.F Aziz 
 Department of Ophthalmology, Faculty of Medicine, Ain Shams University, Cairo, Egypt

Correspondence Address:
Joseph H.F Aziz
14 Al-Bakly Street, Heliopolis, Cairo, 1351
Egypt

Abstract

Context Accurate intraocular lens (IOL) power calculation is mandatory to achieve satisfactory refractive outcomes. Axial length, keratometric readings, anterior chamber depth, and other measurements are utilized to estimate postoperative effective lens position. Selecting the formula of IOL calculation depends mainly on axial length (AL) and anterior chamber depth (ACD). Aims To study the correlation between AL and ACD in short, normal, and long eyes. Settings and design The study was conducted at Ain Shams University Hospitals after the approval of the research ethics committee in the Faculty of Medicine, Ain Shams University. Study period: 6 months. Patients and methods The study included 90 eyes of patients presented for IOL or phakic lens implantation. They were divided into three groups according to the AL. Group A included 30 patients with short AL of less than or equal to 22 mm. Group B included 30 patients with normal AL of more than 22 mm and less than 24.50 mm. Group C included 30 patients with long AL of more than or equal to 24.50 mm. The AL and ACD of each patient were measured using The ZEISS IOL Master 500. Statistical analysis used The Statistical Package for the Social Sciences, version 24. 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. Conclusion The AL and ACD are inversely related in short eyes with an AL of less than or equal to 22 mm, while no correlation exists in normal and long eyes with an AL of more than 22 mm.



How to cite this article:
El-Ghazawy RM, El-Awamry AI, Zaki RG, Aziz JH. Correlation between axial length and anterior chamber depth in short eyes, normal eyes, and long eyes.J Egypt Ophthalmol Soc 2019;112:30-33


How to cite this URL:
El-Ghazawy RM, El-Awamry AI, Zaki RG, Aziz JH. Correlation between axial length and anterior chamber depth in short eyes, normal eyes, and long eyes. J Egypt Ophthalmol Soc [serial online] 2019 [cited 2020 Feb 21 ];112:30-33
Available from: http://www.jeos.eg.net/text.asp?2019/112/1/30/257214


Full Text

 Introduction



Axial length, keratometric readings, anterior chamber depth, and other measurements are utilized to estimate postoperative effective lens position. Selecting the formula of intraocular lens (IOL) calculation depends mainly on axial length (AL) and anterior chamber depth (ACD) [1],[2].

Applanation ultrasound biometry used to be the most widely used method for AL measurement. Later on, optical devices have become the standard method [3].

Optical method of AL measurement is more accurate than the conventional ultrasound biometry. Moreover, it can be used in different circumstances where the ultrasound biometry give markedly erroneous calculations as in silicone-filled eyes and the presence of posterior staphyloma in high axial myopic eyes [4].

Historically, a positive relationship between AL and ACD has been established [3]. Other recent studies confirm this result but only in normal to long eyes [5],[6],[7].

It was Hosny et al. [8] who first reported that there was no relationship between AL and ACD when AL was beyond 27 mm.

Hoffmann and Hutz [5] later agreed with the previous study by Hosny and colleagues with a larger population size.

Accordingly, they reached to a conclusion that IOL formulas need updating due to the difference between long eyes and normal to long eyes.

It has been reported that every 1.0 mm incorrect measurements of corneal radius, ACD and AL can result in 5.7, 2.7, and 1.5 D of refractive error, respectively. Olsen [9] showed that ACD, AL, and corneal power contribute to the postoperative refractive error by 42, 36, and 22%, respectively.

 Patients and methods



Type of study

Observational cross-sectional study. Study setting: the study was conducted at Ain Shams University Hospitals after the approval of the research ethics committee in the Faculty of Medicine, Ain Shams University. Study period: 6 months (from July 2018 to January 2019). Study population: patients presented for IOL or phakic lens implantation.

Inclusion criteria

Age between 21 and 70 years.

Exclusion criteria

History of glaucoma, ocular surgery, uveitis, ocular trauma, corneal ulcer, or the presence of posterior staphyloma.

Sampling method

Random samples of patients presented for IOL or phakic lens implantation.

Sample size

The study comprised 90 eyes of patients presented for IOL or phakic lens implantation.

Ethical considerations

All participants were consented to participate in the study. The participants were neither charged nor paid for being part of the study. Patients’ personal data were dealt with complete confidentiality.

Study tools

The ZEISS IOL Master 500 (Carl Zeiss, Germany) was used for measuring the AL and ACD.

Study procedures

The patients were divided into three groups according to the AL. group A: 30 patients with short AL of less than or equal to 22 mm. Group B: 30 patients with normal AL of more than 22 mm and less than 24.50 mm. Group C: 30 patients with long AL of more than or equal to 24.50 mm. The AL and ACD of each patient were measured using the ZEISS IOL Master 500.

Data management and analysis

The collected data were reviewed, coded, arranged, and introduced to a PC using the Statistical Package for the Social Sciences (SPSS, version 24). Data were presented and suitable analysis was done according to the type of data obtained for each parameter.

Descriptive statistics

Mean±SD, and range for parametric numerical data, while median and interquartile range for nonparametric numerical data. Frequency and percentage of non-numerical data.

Analytical statistics

One sample t test was utilized to test whether the mean of a single variable differs from a specified constant. Analysis of variance test was utilized to assess the statistical significance of the difference between more than two study group means. Pearson’s correlation coefficient was utilized to estimate the linear correlation between two variables.

Ninety eyes of patients presenting for IOL or phakic lens implantation were included in our observational cross-sectional study conducted in Ain Shams University Hospitals.

 Results



[Table 1],[Table 2],[Table 3],[Table 4],[Table 5],[Table 6] show that only the correlation between the axial length and the anterior chamber depth among short eyes is statistically significant and that both variables are inversely related according to Pearson’s correlation coefficient ([Figure 1]).{Table 1}{Table 2}{Table 3}{Table 4}{Table 5}{Table 6}{Figure 1}

 Discussion



The accuracy of IOL formulas differ according to the ACD even if the AL and K readings are identical [10].

In a study done in Germany by Hoffmann and Hutz [5] published in 2010 during a 6 year period including 15 448 patients, it was found that the mean AL and ACD were 23.43±1.51 and 3.11±0.43 mm, respectively.

Hoffer [11] assessed 7500 patients with cataracts, and found that the average AL and ACD were 23.65±1.35 and 3.24±0.44 mm.

In the study by Holladay, among 1000 eyes, 82% had average AL and only 0.9% of patients had short axial lengths. The relation between AL and ACD was the chief objective of this study. Holladay found that among patients with high AL, 90% of the patients have normal ACD (2.45–3.31 mm), 10% have high ACD (>3.31 mm), and none of them have short ACD (<2.45 mm). While in those with average AL, they found that 90% of patients had normal ACD, none of them had low ACD and 10% had high ACD. On the other hand, in patients with low AL they found that 20% have low ACD, 80% have average ACD, and none of them have high ACD [12].Hosny et al. [8] examined 211 patients in Spain and they reached a conclusion that that ACD has a positive correlation with AL and the corneal diameter.

Sedaghat et al. [13] found that positive relationship was only documented in patients with average AL and not in short and long eyes.

Chang and Lau [14] have concluded in their study that there was no statistically significant relationship between AL and ACD in eyes with an AL of 27.5 mm or more while positive statistically significant relationship existed in eyes of less than 27.5 mm.

Our study included 90 eyes of patients presenting for IOL or phakic lens implantation in Ain Shams University Hospitals. The patients were divided into three groups according to the AL; the short, normal, and long eyes with an AL less than or equal to 22 mm, more than 22 mm, and less than 24.50 mm and more than or equal to 24.50 mm, respectively. AL and ACD of each patient were measured using The ZEISS IOL Master 500.

In the normal eyes group, the mean age was 64.00±9.09, the mean AL was 23.21±0.48, and the mean ACD was 3.13±0.36. In the short eyes group, the mean age was 61.47±15.95, the mean AL was 21.18±0.77,and the mean ACD was 2.72±0.46. In the long eyes group, the mean age was 60.37±13.91, the mean AL was 27.15±2.60, and the mean ACD was 3.39±0.38. 52.2% of the study population were men and 47.8% were women.

The results show 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=0.011), while no statistically significant correlation exists between AL and ACD in normal and long eyes, that is, when AL is more than 22 mm.

This absence of correlation might affect the ELP calculations in third-generation formulas, which do not consider the preoperative ACD.

Our study results agree with most of the previous studies regarding long eyes of more than 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 and colleagues who showed positive correlation between AL and ACD in short eyes, although the latter study used contact ultrasound biometry which is not as accurate as the optical method we used in our study.

Our study results disagree 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.

The cause of this difference in the normal eyes group could be attributed to the fact that most of the previous studies did not classify separate short and normal groups, but studied long eyes separately and short with normal eyes together in one group giving different results than our study where normal eyes were studied separately in one group and short eyes in another group.

Our study was not without limitation. First, it was retrospective in nature, which did not allow an assessment of other factors which may have affected AL and ACD, including lens thickness and corneal diameter. The sample size was also smaller than in other studies.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Aristodemou P, Cartwright KN, Sparrow JM, Johnston RL. Formula choice: Hoffer Q, Holladay 1, or SRK/T and refractive outcomes in 8108 eyes after cataract surgery with biometry by partial coherence interferometry. J Cataract Refract Surg 2011; 37:63–71.
2Hoffer KJ. The Hoffer Q formula: a comparison of theoretic and regression formulas. J Cataract Refract Surg 1993; 19:700–712.
3Raymonds FI, Santamaria L. Comparing ultrasound biometry with partial coherence interferometry for intraocular lens power calculations. Invest Ophthalmol Vis Sci 2009; 50:2547–2552.
4Tehrani M, Krummenauer F, Blom E, Dick HB. Evaluation of the practicality of optical biometry and applanation ultrasound in 253 eyes. J Cataract Refract Surg 2003; 29:741–746.
5Hoffmann PC, Hutz WW. Analysis of biometry and prevalence data for corneal astigmatism in 23,239 eyes. J Cataract Refract Surg 2010; 36:1479–1485.
6Leung CK, Palmiero PM, Weinreb RN, Li H, Sbeity Z, Dorairaj S et al. Comparisons of anterior segment biometry between Chinese and white using anterior segment optical coherence tomography. Br J Ophthalmol 2010; 94:1184–1189.
7Park SH, Park KH, Kim JM, Choi CY. Relation between axial length and ocular parameters. Ophthalmologica 2010; 224:188–193.
8Hosny M, Alio JL, Claramonte P, Attia WH, Perez-Santonja JJ. Relationship between anterior chamber depth, refractive state, corneal diameter, and axial length. J Refract Surg 2000; 16:336–340.
9Olsen T. Calculation of intraocular lens power: a review. Acta Ophthalmol Scand 2007; 85:472–485.
10Yang S, Whang W-J, Joo C-K. Effect of anterior chamber depth on the choice of intraocular lens calculation formula: PLoS ONE 2017; 12:e0189868.
11Hoffer KJ. Clinical results using the Holladay 2 intraocular lens power formula. J Cataract Refract Surg 2000; 26:1233–1237.
12Holladay JT. Quality of vision: essential optics for the cataract and refractive surgeon: SLACK Incorporated. 2007; 5:48–68.
13Sedaghat MR, Azimi A, Arasteh P, Tehranian N, Bamdad S. The relationship between anterior chamber depth, axial length and intraocular lens power among candidates for cataract surgery. Electron Physician 2016; 8:3127–3131.
14Chang J, Lau S. Correlation between axial length and anterior chamber depth in normal eyes, long eyes, and extremely long eyes. Asia-Pacific J Ophthalmol 2012; 1:213–215.