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Year : 2020  |  Volume : 8  |  Issue : 1  |  Page : 38-39

The Warren Hill calculator: A simplified online guide for surgically induced astigmatism calculation


Department of Ophthalmology, Shri Sathya Sai Medical College and Research Institute, Ammapettai, Tamil Nadu, India

Date of Submission14-Mar-2019
Date of Decision19-Dec-2019
Date of Acceptance19-Dec-2019
Date of Web Publication6-Mar-2020

Correspondence Address:
Venkatesh Suganthraj
H. No: Old No. 21, New No. 3, Navarathna Gardens, Near PNB ATM, Ekkaduthangal, Chennai - 600 032, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcor.jcor_15_19

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  Abstract 


Surgically induced astigmatism (SIA) ranks as one of the principle factors resulting in compromised post- operative visual acuity. There are several factors contributing to the post -operative SIA, namely type and site of wound construction, the age of the patient and the surgical expertise of the surgeon. The first and foremost step in this process is for the surgeon to be aware of the magnitude and the vector of the SIA induced by his/her hands. The SIA online calculator software for orthogonal astigmatism has opened newer vistas in the field of cataract surgery. This software has been developed by Dr Warren Hill and can be downloaded from the online site. To simplify matters, the same data is made available in the form of a mobile APP- the SIA calculator App. This is a rapid and comfortable way to obtain the results.

Keywords: Orthogonal astigmatism, surgically induced astigmatism, vector analysis


How to cite this article:
Suganthraj V, Sekharreddy MR, Hegde SP. The Warren Hill calculator: A simplified online guide for surgically induced astigmatism calculation. J Clin Ophthalmol Res 2020;8:38-9

How to cite this URL:
Suganthraj V, Sekharreddy MR, Hegde SP. The Warren Hill calculator: A simplified online guide for surgically induced astigmatism calculation. J Clin Ophthalmol Res [serial online] 2020 [cited 2020 Mar 29];8:38-9. Available from: http://www.jcor.in/text.asp?2020/8/1/38/280208



Surgically induced astigmatism (SIA) ranks as one of the principle factors resulting in compromised postoperative visual acuity. There are several factors contributing to the postoperative SIA, namely the type and site of wound construction, the age of the patient, and the surgical expertise of the surgeon. It is important to know the magnitude of SIA to be able to plan the surgical outcomes.

The SIA could be used to minimize preexisting corneal astigmatism by placing on-axis incisions. The first and foremost step in this process is for the surgeon to be aware of the magnitude and the vector of the SIA induced by his/her hands. The calculation of the SIA in the past had either been by educated guesswork or by the surgeon simply subtracting meridian wise the pre- and postoperative cylindrical powers of the cornea. This often leads to decreased accuracy as the vector shift is not taken into due consideration in such calculations.[1]

The SIA online calculator software for orthogonal astigmatism has opened newer vistas in the field of cataract surgery. This software has been developed by Dr. Warren Hill and can be downloaded from the online site (www.doctor-hill.com). It has an inbuilt excel sheet where one can enter the Flat K and steep K as well as the axis of astigmatism, which can be obtained from either the manual or autokeratometer. The basic working principle is by vector analysis.[2] The software has got cells to enter the flat K and steep K values and the flat and steep meridia. It has also got cells in place to enter the size and axis of incision. The SIA is calculated automatically and displayed.

To simplify matters, the same data are made available in the form of a mobile APP – the SIA Calculator App that can be downloaded from the “Google Play” and “iTunes” and can be easily operated on the mobile. Currently, version 1.0 is being adopted. The data entered are similar to that perceived in the online software. This is a rapid and comfortable way to obtain the results.[3] The results obtained will display both the magnitude and vector of the SIA.

On a personal note, we have been employing this software in a recently completed research project that compares the SIA between a superotemporal and temporally placed incision in manual small incision cataract surgery. We have found the SIA calculator to be user-friendly, besides exhibiting accuracy in results.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Cravy TV. Calculation of the change in corneal astigmatism following cataract extraction. Ophthalmic Surg 1979;10:38-49.  Back to cited text no. 1
    
2.
Jaffe NS, Jaffe MS, Jaffe GF. Cataract Surgery and its Complication. 6th ed., Ch. 6. St. Louis: Mosby; 1997. p. 134-8.  Back to cited text no. 2
    
3.
Sánchez-Tabernero S. SIA-formula: An easy way to calculate surgically induced astigmatism. Eye (Lond) 2018;32:659-60.  Back to cited text no. 3
    




 

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