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Toric IOL axis marking after anaesthesia: accuracy of a technique using landmark references

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Session Details

Session Title: Presented Poster Session: IOL Power Calculation/Paediatric

Venue: Poster Village: Pod 1

First Author: : B.LaHood AUSTRALIA

Co Author(s): :    M. Goggin   K. Ullrich           

Abstract Details

Purpose:

Toric intraocular lens (IOL) implantation is an effective method to manage corneal astigmatism with cataract surgery. Accurate alignment of toric IOLs is critical to achieving excellent results. Various marking techniques for toric IOL alignment exist including ink-marking, image-guidance-systems and intra-operative-aberrometry. Unfortunately, there are times when pre-operative marking is unsatisfactory or newer technologies fail. Our study aimed to assess the accuracy of using ocular landmarks to locate the vertical meridian in anaesthetised eyes of supine patients compared to a verified pre-operative marking technique in the same eyes. If accurate, this technique could be employed in eyes where conventional marking has failed.

Setting:

The Ophthalmology Department of the Queen Elizabeth Hospital in Adelaide, Australia.

Methods:

Thirty eyes underwent phacoemulsification surgery and toric IOL implantation. Pre-anaethetic, the inferior vertical meridian of the cornea was marked using a verified technique. All patients received peribulbar anaesthesia. While lying supine, a still photograph was taken from the operating microscope and the mark was electronically masked. An experienced surgeon and a senior trainee independently placed new marks on the image to indicate the vertical meridian using the reference points of the midlines of superior pannus and the widest points of the cornea. The angle of difference between pre-operative and secondary marks were compared to give a rotational angle of error.

Results:

For the experienced surgeon, the mean ± standard deviation (SD) error between the pre-operative mark and secondary mark was 2.24⁰ ± 1.20⁰. For the senior trainee, the mean ± standard deviation (SD) error between the pre-operative mark and secondary mark was 3.63⁰ ± 2.33⁰. Secondary marks were evenly distributed either side of the primary pre-operative mark for both the experienced surgeon and senior trainee. The maximum angle of error for all secondary marks, irrespective of surgeon level, was less than 10⁰. This included challenging cases with chemosis, subconjunctival haemorrhage and minimal pannus.

Conclusions:

Marking a reference point using ocular landmarks in a supine patient after peri-bulbar anaesthesia appears accurate. In all cases, the secondary mark was less than 10⁰ from the pre-operative mark, which is the commonly described threshold of visual significance of a misaligned toric IOL. In situations where a patient has received periocular anaethetic and has either no marking, suboptimal marking or failure of intra-operative guidance systems, it appears to be reasonable to proceed with implantation of a toric IOL after cataract surgery. This finding was consistent for both levels of experience, indicating that it is a safe and practical technique.

Financial Disclosure:

NONE

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