IOLMaster® and Integration of the Holladay 2 Formula for Intraocular Lens Calculations
The results from this study led to the release of the Holladay 2 formula and an easy-to-use programme that allowed for data entry of the new variables and instant calculation of ELP and the appropriate IOL power selection. It also led to a new paradigm of evaluating eyes by both their axial length (short, normal and long) and their anterior segment size (small, normal and large). In essence, there are now nine eye types – not just three – that could be used to classify a given patient’s eye,4
as
shown in Figure 1. The WTW measurements demonstrate that normal axial length eyes (21–26 mm) had an equal distribution of eyes of either large (2 %) or small (2 %) anterior segment size. In short axial length eyes (<21 mm), 80 % would be considered normal and 20 % would be considered small in terms of anterior segment size. In eyes of long axial length (>27 mm), Dr Holladay commented that ‘effective lens position is much less a factor than obtaining an accurate axial length measurement in the first place, because the intraocular power is so low.’ Following this study, there are now 17 independent, peer-reviewed, published studies that show improved accuracy with the Holladay 2 formula.
Impact on Modern Cataract Surgery ‘For the first time we understood clearly why cataract surgeons were struggling to gain “refractive-like” outcomes on a more consistent basis,’ added Dr Holladay. ‘This study showed that the more you know about the anatomy, the better you can predict the outcome. But, you must automate your measurements to get the benefits of the precision of the formula.’
Holladay 2 has emerged as the ‘state-of-the art’ IOL calculation formula and today is the leading formula used by US surgeons.5
With over
11,000 IOLMaster devices in use worldwide, Carl Zeiss Meditec Inc. has now made it a priority to increase access to this formula by integrating it directly into the IOLMaster itself. Until now, using Holladay 2 required transfer to an external computer as well as purchase of a separate software package.
Through an exclusive agreement with Dr Holladay, IOLMaster users can now upgrade their IOLMaster and do calculations within the device, and so eliminate the need to transfer data to an external computer and to purchase a separate software package. While other systems still require data transfer to a PC to gain access to the Holladay 2 formula, Dr Holladay confirmed that ‘the IOLMaster 500 is the only instrument on the market that has the Holladay 2 formula inside the unit.’
Summary
Improvements in technology have allowed the accuracy of cataract surgery to double every 5–10 years.6
The IOLMaster device and the
1. Mahdavi S, The IOLMaster and its role in modern cataract surgery, November 2011. Available at:
http://sm2strategic.com/files/IOLMaster-Holladay_r6.pdf (accessed 24 November 2011).
2. Mahdavi S, IOLMaster 500: improving upon the gold standard in biometry for cataract surgery, 2010. Available at:
http://sm2strategic.com/files/2010-Nov-The-IOLMaster-500-for-
Table 1: Relative Importance of Variables Affecting Intraocular Lens Calculation
Rank 1
2 3 4 5 6 7
Variable
Axial length Average K
Horizontal WTW Refraction
Anterior chamber depth Lens thickness Age
Relative Significance 100
76 24 18 8 7 1
K = keratometry; WTW = white-to-white. Data from a worldwide study of 34,000 eyes. Source: Jack Holladay.
Figure 1: Categorisation of Eyes According to Axial Length and Anterior Segment Size
Large Megalocornea
+ axial hyperopia (0 %)
Normal Axial hyperopia (80 %)
Small Small eye
nanophthalmia (20 %)
Short
Megalocornea (2 %)
Large eye buphthalmos
megalocornea + axial myopia (10 %)
Normal (96 %)
Microcornea (2 %)
Normal Axial length Data from a worldwide study of 34,000 eyes. Source: Jack Holladay.
Holladay 2 formula are key contributors to this trend. Current surveys suggest that eight of 10 surgeons use the IOLMaster platform, yet only three of 10 surgeons use the Holladay 2 formula. The fact that Zeiss has now ‘married’ them into the same box will only help increase access to the Holladay 2 formula. ‘I’m gratified that a much larger population of surgeons and their patients will benefit from the improved accuracy of IOL power calculations by having direct access to the Holladay 2 formula,’ concluded Dr Holladay.
As more and more surgeons face increasing demands on their time and skills because of an ageing population (that often also has higher expectations of their cataract outcomes than in the past), the convenience offered by this upgrade will have a positive impact on clinic workflow and the overall reputation of the ophthalmic surgical practice. n
Cataract-Surgery-Carl-Zeiss.pdf (accessed 24 November 2011).
3. Tyson F, Choosing the proper formula for accurate IOL calculations, Ophthalmology Times, 2006. Available at:
www.ophmanagement.com/article.aspx?article=86640 (accessed 24 November 2011).
4. Holladay JT, Gills JP, Leidlein J, Cherchio M, Achieving emmetropia in extremely short eyes with two piggyback
posterior chamber intraocular lenses, Ophthalmology, 1996;103:1118–23.
5 2011 survey of American Society of Cataract Refractive Surgery (ASCRS) members. Available at:
www.analeyz.com (accessed 24 November 2011).
6. Hill W, Highly accurate IOL calculations, Cataract & Refractive Surgery Today, 2005;67–70.
Axial myopia (90 %)
Microcornea + axial opia (0 %)
Long
EUROPEAN OPHTHALMIC REVIEW
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Anterior segment size
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