Posters

Comparison of pupil centration on Schiempflug tomographer versus operating microscope: a prospective image analysis study

Poster Details

First Author: H.Naveed UK

Co Author(s):    Z. Ashena   M. Nanavaty                 

Abstract Details

Purpose:

Intraoperative centration of intraocular lenses and intracorneal ring segments are often planned on the basis of pupil centration measurements from tomography/topography devices. We designed a prospective, comparative, image analysis study that aimed to compare and quantify the degree of pupil centre shift between the Scheimpflug tomographer (Pentacam HR®, Oculus) in undilated mesopic conditions versus intraoperatively when the same patient with a dilated pupil is asked to look at various light sources at the bottom of the operating microscope.

Setting:

Sussex Eye Hospital, Brighton and Sussex University Hospitals NHS Trust, UK

Methods:

Routine cataract surgery patients through temporal approach underwent Scheimpflug tomography with undilated pupil. Intraoperatively these same patients, with dilated pupils, were asked to look under the microscope (Zeiss OPMI Lumera T) at its 3 light sources and their centre. Photographs were acquired in these four positions, namely superior, inferior, co-axial and central. The iris image from the Pentacam-HR® was used to calibrate pictures from the operating microscope and determine reference co-ordinates using the horizontal white-to-white (WTW). Pupil centre measurements, provided in x and y co-ordinates, were derived using image analysis on WebPlotDigitizer and Plotly softwares. Statistical t-tests were used.

Results:

The initial results show that mean of x vs. y coordinates for pupil centre for Pentcam, superior, inferior, co-axial and central were 0.00±0.31mm vs. -0.01±0.31mm; 0.14±0.12mm vs. 0.07±0.17mm; 0.11±0.10mm vs. -0.03 ±0.21mm; 0.10±0.15mm vs. 0.08± 0.15mm; and 0.07 ± 0.10mm vs. 0.02 ± 0.20mm respectively. There was no significant difference between left and right eyes for x and y co-ordinates for all groups (p>0.05). For right eye comparing Pentacam co-ordinates versus microscope photographs showed a significant difference in x co-ordinates (p=0.05) of superior and y coordinates (p=0.02) of inferior light groups only. For the left eyes there was no significant difference comparing Pentacam versus all microscopic light group co-ordinates (p>0.05).

Conclusions:

The centre of the pupil is significantly different in the dilated right eyes intraoperatively when the patient is asked to look at superior or inferior light of the microscope during temporal clear corneal surgery in comparison to pupil centre obtained from the Pentacam in an undilated eye during the clinic appointment. This may have implication with regards to centration planning for multifocal and toric capsule fixed intraocular lenses and for intracorneal ring implantation procedures. NOTE: Prospective study aimed to recruit 30 patients, but due to coronavirus pandemic the study had to be stopped for safety. Initial results will be presented.

Financial Disclosure:

None