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First Author: R.Perrott-Reynolds UK
Co Author(s): M. Muhtaseb J. Glasbey
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To report the decision-making process and outcome in a case of toric lens implantation in a subject with cataract, high corneal astigmatism and discordant pre-operative K readings from the topographer and biometer.
The Royal Glamorgan Hospital, UK
A 27 year old male with a history of keratoconus, penetrating keratoplasy (PKP), and an ocular hypertensive response to steroid treatment developed a dense posterior subcapsular cataract. He underwent phakoemulsification cataract extraction and implantation of a toric lens with a good visual outcome. We used a T-Flex lens from Rayner Intraocular Lenses Ltd (Sussex, United Kingdom) and employed their proprietary online calculation software (Raytrace) for the lens power calculations, aiming for -0.25D sphere post-operative refraction. Pre-operative topography and biometry yielded discordant keratometry readings, and each was entered into the Raytrace software separately. Widely variant lens recommendations resulted and we needed to decide which recommendation to utilise.
Pre-operative examination showed a high corneal astigmatism. Visual acuity was hand movements improving to only 6/60 with pinhole correction. Keratometry values were obtained from both the Orbscan II corneal topographer (Bausch & Lomb, Germany) and the IOL Master (Carl Zeiss, Germany). Orbscan II keratometry values were K1 = 43D x 72 degrees and K2 = 51.50D x 162 degrees with a recommended lens power of 11D sphere and 11D cylinder placed at 162?. The IOL Master gave values of K1 = 38.79D x 76 degrees and K2 = 47.87D x 166 degrees with a recommended lens power of 15.50D sphere and 11D cylinder placed at 166?. If IOL Master values were used and were incorrect the patient would be myopic, whereas he would be hyperopic if the Orbscan II values were chosen but turned out to be incorrect. At face value this scenario would encourage us to use the IOL Master values. However, we chose to utilise the Orbscan II values given that this is a dedicated topographer. Two days post-operatively the unaided acuity was 6/12 improving to 6/4 with pinhole. Refraction was +0.50/+2.75x13
Keratometry readings based on corneal topography give the most accurate toric lens calculations in the presence of previous corneal surgery and high corneal astigmatism. Furthermore, excellent visual outcomes may be achieved in eyes with a history of corneal surgery and high astigmatism.
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