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ORIGINAL ARTICLE
Year : 2021  |  Volume : 3  |  Issue : 1  |  Page : 1

Correlation between axial length, anterior chamber depth, and other biometric measurements with iol master 700 in normal eyes, short eyes, long eyes, and extremely long eyes in latin american population


1 Hospitales Puerta de Hierro, Instituto Tecnológico de Estudios Superiores de Monterrey, Zapopan, Jalisco, Mexico
2 Centro Medico Puerta de Hierro, Zapopan, Jalisco, Mexico
3 Universidad Autonoma De Guadalajara, Zapopan, Jalisco, Mexico

Date of Submission18-Aug-2020
Date of Acceptance30-Nov-2020
Date of Web Publication13-Jan-2021

Correspondence Address:
Carlos Emiliano Rodriguez Lopez
Av Universidad 185, Zapopan, Jalisco, Postal Code 45066
Mexico
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/pajo.pajo_42_20

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  Abstract 


Background: Several studies have shown the correlation between ocular biometry with refractive errors. Since these parameters can be influenced by race, ethnicity, and genetics, their differences between different populations can probably explain the differences in refractive errors. We present the biometric values measured in 431 eyes with normal, short, long, and extremely long axial length (AL) from the Latin American population.
Patients and Methods: All eye measurements were performed using optical biometry with IOL Master and stratified according to AL and anterior chamber depth (ACD) and evaluated in relation to each other. Symmetry between right eye (RE) and left eye (LE) was also analyzed.
Setting: The study was conducted at Private practice, Guadalajara, Jalisco, Mexico.
Results: ACD, white-to-white (WTW), and average keratometries (K) increase as AL increases in normal, short, and long eyes, but this correlation is not maintained in extremely long eyes. Most of the short eyes and eyes with normal AL have a normal ACD, but most of the long and extremely long eyes have an ACD >2.5 mm. In normal and short eyes, the AL and WTW are symmetric in both eyes, but in long and extremely long eyes, there are significant differences between RE and LE. ACD is symmetric in RE and LE regardless of AL.
Conclusions: The importance of the ocular biometry in Latin American eyes relies on clarifying the assumptions of biometric measurements commonly used in various areas of ophthalmology including intraocular lens calculation formulas.

Keywords: Anterior chamber depth, aqueous depth, axial length, hypermetropia, myopia, white-to-white


How to cite this article:
Rodriguez Lopez CE, Mora Gonzalez GF, Felix JR, Perez Garcia SY, Ibanez Hernandez MA, Munoz AR. Correlation between axial length, anterior chamber depth, and other biometric measurements with iol master 700 in normal eyes, short eyes, long eyes, and extremely long eyes in latin american population. Pan Am J Ophthalmol 2021;3:1

How to cite this URL:
Rodriguez Lopez CE, Mora Gonzalez GF, Felix JR, Perez Garcia SY, Ibanez Hernandez MA, Munoz AR. Correlation between axial length, anterior chamber depth, and other biometric measurements with iol master 700 in normal eyes, short eyes, long eyes, and extremely long eyes in latin american population. Pan Am J Ophthalmol [serial online] 2021 [cited 2021 Apr 21];3:1. Available from: https://www.thepajo.org/text.asp?2021/3/1/1/306945




  Introduction Top


Recent studies and the World Health Organization (WHO) reports indicate that refractive errors are the first cause of visual impairment and the second cause of visual loss worldwide, as 43% of visual impairments are attributed to refractive errors. Africa and America have the highest prevalence of hyperopia. In adults, the prevalence of myopia ranged from 4% to 51%. Myopia and high myopia will show a significant increase in global prevalence, affecting nearly 5 billion and 1 billion people, respectively, by 2050.[1],[2]

Ultrasound measurement has historically been the standard for ocular biometry; however, optical biometers, especially the IOL Master 700 (Carl Zeiss Meditech AG, Jena, Germany), have become the gold standard and have similar or better results than ultrasound, particularly in patients with a long or short axial length (AL). It also has excellent reproducibility in its results, which makes it the ideal tool to carry out this study.[3]

IOL Master 700 uses swept-source optical coherence tomography (SS-OCT) technology to obtain all axial measurements including AL, anterior chamber depth (ACD), central corneal thickness, and lens thickness (LT). SS-OCT performs sequentially scans through a series of wavelengths to enhance the interference pattern, which is then decoded with Fourier transformation into an A-scan trace. Multiple adjacent A-scans can be combined to form a B-scan image. The advantages of SS-OCT include a deeper range of imaging into the eye, less sensitivity reduction with depth, and faster scanning speeds.[4]

Several studies have shown the correlation between ocular biometry, specially AL, with refractive errors. Since these parameters can be influenced by race, ethnicity, and genetics, their differences between different populations can probably explain the differences in refractive errors, and it would be useful to determine the distribution of biometric indices in each area of the world.[5] Based on this need and because there is little information in the Latin American population, our group presents the biometric values measured with IOL Master 700 in normal, short, long, and extremely long eyes from the Latin American population.


  Patients and Methods Top


This is a descriptive, observational, and retrospective study. The sample was collected for convenience from base data of 2000 eyes and corresponds to 431 eyes of 274 Mexican patients of both sexes, which underwent the biometry scan between 2019 and 2020 in private ophthalmic consultation at Centro Médico Puerta de Hierro in Guadalajara, Jalisco, Mexico. Exclusion criteria were previous corneal or intraocular surgery and any other corneal disease that could generate important changes in the ocular architecture. Patients with laser-assisted in situ keratomileusis (LASIK) were included but excluded when keratometries were analyzed. All patients underwent the measurements with IOL Master 700. The patients' pupil was not dilated for the measurements. Only measurements with all automatic quality indicators were accepted. All measurements were made by expert ophthalmologists. According to the evidence, a cutoff value of AL >25 mm was used to define long eyes, extremely long eyes were defined as AL >27.5, and short eyes were defined when AL was <22 mm. On the other hand, to stratify the ACD, a narrow ACD was considered when it was <2.49 mm, normal ACD when 2.5 mm to 3.5 mm, and finally wide ACD when it was >3.51 mm. Statistical analysis was performed with specialized computerized system recommended by the WHO Epi Info.[6]


  Results Top


Our sample was made up of 274 patients, 104 of them were male (38%) and 170 female (62%). In total, 431 eyes were included, of which 206 were right eyes (REs) and 225 were left eyes (LEs). The mean age of the population was 54 years with a standard deviation of ±18 years. Participants were in a range from 21 to 96 years. [Table 1] and [Table 2] summarize the results of the optical biometrics taken with the IOL Master 700. The relationship between the ACD and the average keratometries (K) was also analyzed [Table 3]. The mean K average of the eyes with Narrow ACD is more curved than the average K of the eyes with the eyes with bigger ACD (45.26 D in ACD <2.5 mm vs. 42.26 D in ACD >3.5 mm).
Table 1: Presents the distribution of eyes in the different AL categories in relation to the size of the ACD obtain with optical biometry by IOL Master 700

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Tabla 2: Shows results of optical biometry with IOL master 700 stratified according to AL

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Table 3: shows the correlation between the ACD and the average keratometry in 362 eyes (eyes with previous LASIK were excluded)

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Symmetry between right and left eyes

Out of the patients in which both eyes (362 eyes) were analyzed, the symmetry of the AL between RE and LE was analyzed, finding that, in eyes of normal or short AL, there was no significant difference in AL (P >0.05/confidence Interval [CI]: 95%). However, in long and extremely long eyes, there was a significant difference between both eyes (P <0.05/CI: 95%). ACD symmetry was compared between the four groups of AL, and there were no significant differences between LE and RE (P > 0.05/CI: 95%).

It was found that, in long and extremely long eyes, there are significant differences between the white-to-white (WTW) of RE and LE (P < 0.05/CI: 95%), while eyes with normal and short AL have no significant differences between eyes (P > 0.05/CI: 95%). For the average keratometry (K) analysis, patients with previous LASIK surgery were excluded, leaving 332 eyes, and finding that both eyes are statistically different in extremely long, long, and normal AL (P < 0.05/CI: 95%). Only in the short AL group, both eyes were symmetric (P >.05/CI: 95%).

Normal eyes (22–25 mm)

The biometry of 119 eyes with normal AL was analyzed. The mean age was 62 years (±16.59). In this group, most of the analyzed eyes presented a normal ACD (2.5–3.5 mm), leaving 16% of the eyes with wide ACD (>3.5 mm) and a minimum of eyes with narrow ACD (<2.5 mm). It was unusual to find eyes with narrow ACD in the sampled eyes (<18%). Mean measurements were AL: 23.3 mm (±0.74), ACD: 3.12 mm (±0.39), and WTW: 11.95 (±0.41). A positive correlation was found between ACD and AL in normal eyes (Pearson's r = 0.59). On the other hand, no correlation was found between AL and WTW (Pearson's r = 0.32). For the analysis of average K (where LASIK patients were excluded), 110 eyes were analyzed, finding a mean K of 43.67 D (±3.18). No correlation was found between AL and average K (Pearson's r = 0.14).

Short eyes (<22 mm)

The biometry of 93 short eyes with a mean age of 59 years (±19 years) was analyzed [Table 1]. The narrowest ACDs were found in this group. However, this finding represented <13% of the group. The majority of the short eyes (86%) had a normal ACD, and one isolated case in which the ACD was wide was found. Mean measurements were AL: 21.54 mm (±0.43), ACD: 2.8 mm (±0.35), and WTW: 11.7 (±0.46).

No correlation was found between ACD and AL in short eyes (Pearson's r = 0.20); however, ACD was significantly smaller in short eyes than in eyes with normal, long, and extremely long AL (P <.05/CI: 95%). No correlation was found between AL and WTW (Pearson's r = 0.17), but WTW was significantly lower than eyes with normal, long, and extremely long AL (P < 0.05/CI: 95%). For the analysis of average K (where LASIK patients were excluded), 76 short eyes were analyzed, finding a mean K of 45.12 D (±4.02). Average K in this group was significantly higher than eyes with normal, long, and extremely long AL (P < 0.05/CI: 95%). No correlation was found between AL and average K (Pearson's r = 0.089).

Long eyes (25–27.5 mm)

The biometry of 148 long eyes with a mean age of 47 years (±17 years) was analyzed. Most of the eyes in this group presented a normal or wide ACD, finding narrow ACDs on 2% of the cases. The following means were obtained: AL: 25.9 mm (±0.67), ACD: 3.48 mm, (±0.39) and WTW 12.15 mm (±0.42). No correlation was found between ACD and AL in long eyes (Pearson's r = 0.15); however, ACD in long eyes was not significantly different than in extremely long eyes (P > 0.05/CI: 95%), but it was significantly higher than in normal eyes (P <.05/CI: 95%).

On the other hand, no correlation was found between ACD and WTW (Pearson's r = 0.02). The WTW in long eyes was not significantly different than in extremely long eyes (P > 0.05/CI: 95%), but it was significantly greater than in normal eyes (P < 0.05/CI: 95%). For the analysis of average K (where LASIK patients were excluded), 119 long eyes were analyzed, finding a mean of 41.73 D (±3.62). The average K in this group was significantly lower than in eyes with normal and short AL (P < 0.05/CI: 95%) but was not different from those in the extremely long eyes group (P > 0.05 CI: 95%). No correlation was found between AL and average K (Pearson's r = 0.013).

Extremely long eyes (>27.5 mm)

A total of 71 extremely long eyes with a mean age of 49.4 years (±15 years) were analyzed. The behavior of this group was similar to the long eyes group, having a normal or large ACD only. The following means were obtained: AL: 29.8 mm (±0.15), ACD: 3.5 mm (±0.33), and WTW 12.15 mm (±0.43). For the analysis of average K (where LASIK patients were excluded), 57 extremely long eyes were analyzed, finding a mean of 42.06 D (±5.39). No correlation was found between AL and ACD (Pearson's r = 0.33) and WTW (Pearson's r = 0.24), or average K (Pearson's r = 0.017).


  Discussion Top


For all IOL power calculations, it is a necessity to know the actual measurements of different eye variables such as AL, corneal power, ACD, LT, age, WTW, corneal diameter, and preoperative refractive data. Some of them are used in 4th-generation formulas such as Haigis and Holladay II[7],[8] Some formulas (like Hoffer Q) include (1) a factor that increases ACD with increased LA, (2) a factor that increases ACD with greater corneal curvature, (3) a factor that moderates the change in ACD for extremely long and short eyes, and (4) a constant added to ACD?.[9],[10],[11] Even new generation formulas (such as Barrett Universal II) use a theoretical model eye involving the previous ACD, AL, and K. In other toric formulas (such as the Barrett Toric), the posterior corneal curvature is calculated (based in a nomogram) and makes adjustments for WTR and ATR astigmatism, as opposed to the Barrett TK formulas (such as the Barrett TK Universal II for nontoric IOLs, and the Barrett TK Toric for toric IOLs), when the posterior corneal surface is measured.[12] To optimize the IOL power calculations with the IOL Master 700 (firmware 1.80), it is important to quantify and analyze whether or not there is a correlation between these variables and other biometric measurements in our population.

Little has been written about ocular biometry in Latin American eyes. A 2019 study by Barlatey et al. analyzed some of the variables measured in this study in 430 eyes of the Mexican population using the Ocuscan RxP (Alcon®, Fort Worth, TX, USA) ultrasonic biometer, finding the following results: mean AL: 23.44 ± 1.71 mm, mean ACD: 3.12 ± 0.46 mm, mean LT: 4.47 ± 0.57 mm, mean vitreous chamber depth: 15.81 ± 1.63 mm, and mean age: 70.03 ± 10.50 years (median: 70 years and range: 40–96). There was no significant difference between these results and those obtained by this study, even when the instruments used to measure were different (P > 0.05/CI: 95%).[13]

The Los Angeles Latino Eye Study conducted in 2005 included 5588 Latinos over 40 years of age and reported an AL: 23.38 ± 1.01, being similar to what was found in the studied sample for normal eyes (P > 0.05/CI: 95%). The study reported an ACD: 3.41 ± 0.35, being significantly higher than in the studied sample in normal eyes (P < 0.05/CI: 95%), and when comparing the vitreous body length (VBL), it was significantly lower to the VBL found in our sample: 15.05 ± 1.06 (P < 0.05/CI: 95%). These differences may be due because of the A-scan ultrasound (A-Scan pachymeter, Ultrasonic, Exton, PA) used in this study (a less reliable biometry measurement method than the optical biometry, generating different results).[14]

In Korea, Chunga and Park performed a biometric analysis using spectral-domain OCT (SD-OCT) in 412 eyes of young and myopic patients. The study found that the ACD increased proportionally with the AL (Pearson's r = 0.346, P < 0.01). However, in the high myopic group, ACD was not correlated with AL (Pearson's r = 0.065, P = 0.383). Something similar happened the studied sample, where long eyes have wider ACD than normal eyes, but not different than extremely long eyes, indicating that the tendency of the ACD to increase along with the ACD is lost by a certain AL size.[11] This trend was also found in a study of 750 eyes in the USA, concluding that there was a positive correlation between AL and ACD and an inverse correlation between AL and LT.[15]

A study carried out in Hong Kong to investigate the correlation between AL and ACD in 1184 normal, long, and extremely long eyes using the IOL Master found a statistically significant positive correlation between AL and ACD in normal and long eyes but not in extremely long eyes, coinciding with Chunga and Park, and also with the presented study. They also highlight the importance of these data for new generation IOL formulas (such as Haigis and Holladay II) which take into account the ACD.[10]

A study with IOL Master in China included 74 normal eyes, 74 long eyes, and 78 short eyes. It found the following results for normal eyes: AL: 23.09 ± 0.72 and ACD: 2.84 ± 0.46; for long eyes, AL 28.27 ± 2.57 and ACD: 3.54 ± 0.37; and for short eyes, AL: 21.44 ± 0.50 and ACD: 2.42 ± 0.34. Although all the measures are smaller compared to the same groups in our study, this is somewhat expected due to the racial difference between the two groups. However, both studies found that the ACD increased as the AL grew, except in the extremely long eyes group.[16]

Hashemia et al. analyzed 4787 Iranian patients with the LENSTAR/BioGraph (Haag-Streit, Köniz, Switzerland) to determine the relationship between the biometric values and WTW. The mean WTW was 11.80 mm, and it was concluded that there is a positive correlation between AL and WTW. Our study also showed that the higher the biometrics values, the higher the WTW, except in the extremely long group of eyes. Coinciding with this paper, it was also found that increasing AL also increased WTW except in the extremely long eyes group.[17]


  Conclusions Top


In Latin American eyes, ACD, WTW, and average K increase as AL increases in normal, short, and long eyes, but this correlation is not maintained in extremely long eyes. Eyes with a narrow ACD (<2.5 mm) are rare, as most of the short eyes and with normal AL have normal ACD. On the other hand, most of the long and extremely long eyes are distributed in normal and large ACDs. In normal and short eyes, the AL and WTW are symmetric in both eyes, but in long and extremely long eyes, there are significant differences between RE and LE. ACDs are symmetric in RE and LE regardless of AL. Average K is not symmetric in both eyes, excepting short eyes, where there is no significant difference in the average K of RE and LE. There is little information on the biometrics of Latin American eyes made with optical biometers such as the IOL Master 700. The importance of this information relies in stop making assumptions of biometric measurements commonly used in various areas of ophthalmology including intraocular lens calculation formulas.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Shufelt C, Fraser-Bell S, Ying-Lai M, Torres M, Varma R. Los Angeles Latino Eye Study Group. Refractive error, ocular biometry, and lens opalescence in an adult population: The Los Angeles Latino Eye Study. Invest Ophthalmol Vis Sci 2005;46:4450-60.  Back to cited text no. 14
    
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JDong J, Zhang Y, Zhang H, Jia Z, Zhang S, et al. Comparison of axial length, anterior chamber depth and intraocular lens power between IOL Master and ultrasound in normal, long and short eyes. PLOS One 2018;13:e0194273.  Back to cited text no. 16
    
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Hashemia H, Khabazkhooba M, Emamianb M, Shariatic M, Yektad A. White-to-white corneal diameter distribution in an adult population. J Curr Ophthalmol 2015;27:21-4.  Back to cited text no. 17
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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