Scotopic measurement of normal pupil size with the Colvard pupillometer and the Nidek auto-refractor

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Abstract

Purpose:

To compare prospectively, pupil size with the Nidek AR700A auto-refractor and the Colvard pupillometer.

Methods:

Pupil diameter was measured in 46 eyes at 2 min intervals in a low mesopic and under photopic light conditions.

Results:

The mean pupil diameter was 4.8 ± 1.0 mm with the Colvard pupillometer and 4.8 ± 0.9 mm with the Nidek auto-refractor in low mesopic light conditions. The mean photopic pupil diameter was 3.3 ± 0.8 mm with the Colvard pupillometer and 3.9 ± 0.8 mm with the Nidek auto-refractor.

Conclusion:

The pupil sizes are very similar with both instruments.

Introduction

The measurement of pupil size has become increasingly important as the pupil diameter is recognised as one of the limiting factors for visual outcome in cataract and refractive surgery, particularly in scotopic conditions. Optical phenomena, such as starbursts and glare, occur in eyes with small optical zones relative to pupil size after excimer laser refractive surgery or edge effects after intraocular lens implantation in patients with large scotopic pupils [1], [2].

Pupil size can be evaluated by various methods, of which the infrared technique has been shown to be a very reliable method of measuring scotopic pupil diameter [3], [4].

The purpose of this study was to compare pupil measurements by two infrared instruments: the Colvard pupillometer, which was designed specifically for this purpose, with the Nidek auto-refractor, which can be used to measure pupil diameter as well as its primary use an auto-refractor.

Section snippets

Methods

Healthy volunteers were recruited from the staff and relatives of patients attending a general ophthalmology clinic in Birmingham, UK.

Volunteers were excluded if they were on topical medication, had a history of eye disease, eye surgery and eye trauma. They were also excluded if they were diabetic, had a history of autonomic neuropathy, were on systemic drugs or had a history of alcohol abuse. All volunteers underwent a full ocular examination which included examination of the iris looking for

Results

Forty-six volunteers (46 eyes) were recruited for this study, 22 males and 24 females. The age range was 24–40, with a mean of 33.3 ± S.D. 3.5 years. The mean pupil diameter was 4.8 ± 0.9 mm S.D. (range 3.0–7.0 mm) with the Colvard pupillometer and 4.8 ± 0.9 mm S.D. (range 3.0–6.5 mm) with the Nidek auto-refractor at the commencement of the study in low mesopic conditions.

The mean photopic pupil diameter was 3.2 ± 0.7 mm (range 2.0–5.5 mm) with the Colvard pupillometer and 3.9 ± 0.8 mm (range 2.0–5.5 mm) with

Discussion

Galileo was probably the first to document measurement of pupil diameter and 300 years later, the significance of this in refractive surgery has been realised [7].

In refractive surgery, pupil diameter may directly influence visual performance and quality of life. When the pupil diameter is greater than the ablation zone in Excimer laser surgery, myopic blur may be expected, which reduces visual function [8] following photorefractive surgery.

If the ablation zone is smaller than pupil diameter,

References (13)

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Presented in part at NIDEK International Excimer Laser User Meeting, Monte Carlo, December 2001; British Society for Refractive Surgery, Birmingham, March 2002; International Congress for Ophthalmology, Sydney, April 2002.

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