Home About us Editorial board Ahead of print Current issue Search Archives Submit article Instructions Subscribe Contacts Login 
  • Users Online: 4328
  • Home
  • Print this page
  • Email this page

   Table of Contents      
BRIEF COMMUNICATION
Year : 2014  |  Volume : 62  |  Issue : 7  |  Page : 826-828

A study regarding efficacy of various intraocular lens power calculation formulas in a subset of Indian myopic population


Sadguru Netra Chikitsalaya, Chitrakoot, Madhya Pradesh, India

Date of Submission25-Dec-2013
Date of Acceptance13-May-2014
Date of Web Publication13-Aug-2014

Correspondence Address:
Ashish Mitra
Sadguru Netra Chikitsalaya, Jankikund, Chitrakoot - 210 204, Madhya Pradesh
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0301-4738.138634

Rights and Permissions
  Abstract 

Efficacy of intraocular lens power calculation formulas in a subset of Indian myopic population. Retrospectively reviewed 43 patients who underwent phacoemulsification with high axial length (AL) (>24.5 mm, range 24.75-32.35 mm). The power of the implanted intraocular lens (IOL) was used to calculate the predicted post-operative refractive error by four formulas: Sanders-Retzlaff-Kraff (SRK II), SRK/T, Holladay 1, and Hoffer Q. The predictive accuracy of the formulas was analyzed by comparing the difference between the "actual" and "predicted" postoperative refractive errors. Repeated measures analysis of variance (ANOVA) tests were done to have pair-wise comparisons between the formulas and P < 0.05 was considered significant. A subcategory of axial length 24.5-26.5 mm was also tested. Holladay 1, Hoffer Q and SRK/T formulas showed a slight tendency toward resultant hyperopia, with mean error of +0.24 diopters (D), +0.58 D, and +0.92 D, respectively. The Holladay 1 formula provided the best predictive result overall.

Keywords: High myopia, intraocular lens power calculation, long axial length


How to cite this article:
Mitra A, Jain E, Sen A, Tripathi S. A study regarding efficacy of various intraocular lens power calculation formulas in a subset of Indian myopic population. Indian J Ophthalmol 2014;62:826-8

How to cite this URL:
Mitra A, Jain E, Sen A, Tripathi S. A study regarding efficacy of various intraocular lens power calculation formulas in a subset of Indian myopic population. Indian J Ophthalmol [serial online] 2014 [cited 2020 Mar 29];62:826-8. Available from: http://www.ijo.in/text.asp?2014/62/7/826/138634

This is an era where refinement of cataract surgery in terms of various techniques is occurring at a fast pace. Cataract surgery being a single stage procedure, one needs to be cautious while determining intraocular lens (IOL) power in patients with high myopia to avoid refractive surprises. Prevalence of myopia as shown in Andhra Pradesh Eye Disease Study is much higher in adult Indian population than similarly aged white population (34.6% vs 17.5%) but there is no study which has been done to check for the efficacy of different IOL power calculation formulas in Indian myopic population. [1] Choice of IOL power in such patients is based on references from Western, Chinese and Japanese population and the optimal formula for the Indian myopic population is inconclusive.


  Aim Top


To determine the accuracy of the Holladay 1, Hoffer Q, Sanders-Retzlaff-Kraff (SRK)/T, and SRK II IOL power calculation formulas in patients with high myopia in a subset of Indian population.


  Materials and Methods Top


Design: Retrospective study

This study was conducted at Sadguru Netra Chikitsalaya, Chitrakoot, Madhya Pradesh, India.

Inclusion criteria

All consecutive patients attending our out patient department (OPD) for phacoemusification with axial length (AL) more than 24.5 mm (range 24.75-32.35 mm) between May 2009-October 2009 (In all patients hydrophilic acrylic foldable within the bag IOL was implanted).

Exclusion criteria

  • Pre-existing astigmatism >3.0 diopters (D)
  • Corneal scar
  • Keratoconus
  • Complications significantly affecting the refractive status (vitreous loss with IOL implanted in sulcus or anterior chamber, high wound induced astigmatism).


In our study, keratometry measurements were retrieved from records and A scan applanation ultrasonography was done on Echorule2 and analyzed. The implanted IOL power was used to calculate the predicted postoperative refractive error by four commercially available IOL formulas: SRK II, SRK-T, Holladay 1, and Hoffer Q. With each formula, the mean error (ME) was calculated from the difference between the formula predicted refractive error and actual postoperative refractive error. The spherical equivalent was measured by a single trained optometrist using an autorefractor and subjective retinoscopy 1-2 months after cataract surgery. The smallest ME indicated the formula with the best predictive accuracy. Repeated measures ANOVA tests were done after making bonferroni corrections to have pair-wise comparisons between the formulas and P < 0.05 was considered as significant. Subcategoryof long AL (24.5-26.5 mm) was also tested. All surgeries were done by three experienced surgeons.


  Results Top


Forty three eyes of 43 patients with axial length more than 24.5 mm in our set-up were retrospectively studied. The keratometry in most of the patients (81%) was within the normal range of 42.0-46.0 D.

Overall performance of all the formulas in AL more than 24.5 mm showed a tendency to cause a hyperopic refractive error post-operatively [Table 1].
Table 1: Overall performance of formulas in eye with AL>24.5 mm


Click here to view


Holladay 1 caused the smallest ME, +0.24 D. Fifty three percent of patients had mean absolute error less than 1.00 D. The Hoffer Q and SRK-T caused a little larger hyperopic shift with MEs of +0.58D and +0.92 D. SRK II caused the largest hyperopic error +1.23 D. [Table 1].

Pair-wise comparisons between different formulas shows that P value between different formulas is significant (P < 0.05) implicating that Holladay 1 with least ME is significantly different from other formulas and have better performance in patients with AL more than 24.5 mm when compared to SRK-T, SRK II, Hoffer Q [Table 2].
Table 2: Pair-wise comparisons measure: ME (mean error)


Click here to view


The performance of each formula in AL subcategory in eyes with AL between 24.5-26.5 mm also found Holladay 1 as the best formula [Table 3].
Table 3: Performance of formulas in eye with axial length 24.5-26.5 mm


Click here to view


Pair-wise comparisons between different formulas in a subset of patients with a AL 24.5-26.5 mm shows that Holladay 1 (ME = +0.4320 D) and Hoffer Q (ME = +0.4695 D) are comparable, P value not being significant [Table 4].
Table 4: Pair-wise comparisons measure: ME (mean error)


Click here to view



  Discussion Top


Our preliminary results showed that in our patients with axial myopia with ALs longer than 24.50 mm, the Holladay 1 provided the best predictive result and the Hoffer Q was comparable to Holladay 1 for AL 24.5-26.5 mm for IOL power calculation. The SRK II was the least accurate. This agrees with the results in several studies in which better performances were found in cases with long eyes with the Holladay 1 formula than the SRK II formula. Olsen and co-authors reported that the Holladay formula is more accurate than the SRK II. [2] In a study conducted by Stopyra, in which a study of patients with AL 24.51-26.72 mm and found Holladay 1 formula was the most accurate with 88.5% of the patients achieving full Visual acuity (1.0 on Snellen) after cataract surgery. [3] Stopyra also found SRK/T formula satisfactory with 63.9% of the patients achieving full visual acuity on Snellen but only 36.1% of the patients achieved full visual acuity using Hoffer Q. Kijima et al., report the best results using the Holladay and SRK/T in the midrange AL (24.5-26.9 mm) group and the SRK/T or L-SRK in the long AL (longer than 27.0 mm) group. [4] Tsang CS and co-authors also reported best results in patients with AL 25.0 mm using Hoffer Q and Holladay 1 and SRK-T were comparable with SRK II being least accurate and in patients with AL > 28.0 mm they found Holladay 1 and SRK/T more accurate than Hoffer Q. [5] Narvaez and co-authors also reported better performance of these formulas when compared with SRK-II. [6] In studies by Bang and co-authors on AL > 27.0 mm and Wang and co-authors on AL >25.0 mm using IOL Master reported that Haigis formula is the best. [7],[8] Ghanem and El-Sayed reported that in patients with high axial myopia, the performance of SRK-T, Hoffer-Q, Holladay-2, and Haigis formulas are comparable in low plus - powered IOL implantation and Haigis formula is the best formula when minus power IOL is implanted. [9] However, we did not find performance of SRK-T formula better in Indian myopic population. Our recommendation is to avoid using the SRK II and SRK/T formula for IOL power calculation in eyes with axial myopia in Indian population with AL longer than 24.50 mm. In our study, all four formulas had a tendency to cause a postoperative hyperopic refraction. This finding has been reported earlier. [5] Our study had some limitations: (a) It was a single center retrospective study and (b) Surgeons, and time of the postoperative refraction were not standardized. To conclude, the results of our study provide useful information to aid the choice of IOL power in patients with high axial myopia in Indian population during our daily practice with Holladay 1 being the most accurate and SRK II and SRK/T to be avoided.

 
  References Top

1.
Krishnaiah S, Srinivas M, Khanna RC, Rao GN. Prevalence and risk factors for refractive errors in the South Indian adult population: The Andhra Pradesh Eye disease study. Clin Ophthalmol. 2009;3:17-27.  Back to cited text no. 1
    
2.
Olsen T, Thim K, Corydon L. Accuracy of the newer generation intraocular lens power calculation formulae in long and short eyes. J Cataract Refract Surg 1991;17:187-93.  Back to cited text no. 2
    
3.
Stopyra W. The accuracy of IOL power calculation formulas for eyes of axial length exceeding 24.5 mm. Klin Oczna. 2013;115:93-5.  Back to cited text no. 3
    
4.
Kijima T, Kozawa T, Kora Y, Yaguchi S, Inatomi M, Koide R, et al. Accuracy of intraocular lens power calculation formulas. Nihon Ganka Gakkai Zasshi 1999;103:470-6.  Back to cited text no. 4
    
5.
Tsang CS, Chong GS, Yiu EP, Ho CK. Intraocular lens power calculation formulas in Chinese eyes with high axial myopia. J Cataract Refract Surg 2003;29:1358-64.  Back to cited text no. 5
    
6.
Narváez J, Zimmerman G, Stulting RD, Chang DH. Accuracy of intraocular lens power prediction using the Hoffer Q, Holladay 1, Holladay 2, and SRK/T formulas. J Cataract Refract Surg. 2006;32:2050-3.  Back to cited text no. 6
    
7.
Bang S, Edell E, Yu Q, Pratzer K, Stark W. Accuracy of intraocular lens calculations using the IOL Master in eyes with long axial length and a comparison of various formulas. Ophthalmology. 2011;118:503-6.  Back to cited text no. 7
    
8.
Wang JK, Hu CY, Chang SW. Intraocular lens power calculation using the IOLMaster and various formulas in eyes with long axial length. J Cataract Refract Surg. 2008;34:262-7.  Back to cited text no. 8
    
9.
Ghanem AA, El-Sayed HM. Accuracy of intraocular lens power calculation in high myopia. Oman J Ophthalmol. 2010;3:126-30.  Back to cited text no. 9
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

Top
 
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

 
  In this article
Abstract
Aim
Materials and Me...
Results
Discussion
References
Article Tables

 Article Access Statistics
    Viewed2018    
    Printed19    
    Emailed1    
    PDF Downloaded255    
    Comments [Add]    

Recommend this journal