Immediate changes in pupil size following Laser in situ keratomileusis (LASIK): Pupillometry study (2024)

Abstract

Keywords: LASIK, Suction ring, Pupillometry, Dilation

1. Introduction

The importance of pupil size measurement is becoming more extensively familiar in different areas of current ophthalmology. Assessment of the size and motility of the pupil is vital in cataract and refractive surgery outcome (Narváez et al., 2010; Lee et al., 2008). The pupil is affected by numerous factors, including pupillary hippus, emotional status, and systemic and topical ophthalmic medications. However, even slight changes in pupil size can correlate with considerable differences in contrast sensitivity and visual acuity (Novitskaya et al., 2009).

Pupillometry has long been used in research settings to study the autonomic nervous system, drug metabolism, pain responses, psychology, fatigue and sleep disorders (Kadoi, 2000; Tryon, 1975; Deijen et al., 1995; McLaren et al., 2002; Murillo et al., 2004).

LASIK surgery is the most popular form of laser eye surgery, in which an ophthalmic surgeon reshapes the cornea of the eye using an excimer laser, thereby corrects or enhances eyesight (Maldonado et al., 2008; Shaival et al., 2007). During LASIK, a microkeratome is affixed to the eye with suction, this suction greatly increases the IOP of the eye for a short time that transiently affects the pupil size and may negatively affect a patient with glaucoma or someone susceptible to glaucoma (Bashford et al., 2005; Montezuma et al., 2008).

In this study we measure the pupil size before and immediate after LASIK in mesopic condition using pupillmeter.

2. Patients and methods

This prospective study was held at the refractive eye centre, Riyadh, Saudi Arabia between January and June 2009 on 70 eyes of 35 patients using a hand-held pupillometer (colvard pupillometer, oasis Co.). All patients underwent pupil size measurement before and immediately after LASIK in mesopic condition in laser room. Other data were collected as; age, sex, central corneal thickness and refractive errors. Their refractive errors include; 14 (20%) eyes with simple myopia, 50 (71.4%) eyes with myopic astigmatism and 6 (8.6%) eyes with simple Hyperopia. Patient with glaucoma or pupil abnormalities were excluded.

3. Results

Eighty-two eyes of 41 patients were collected in our study, 12 eyes of 6 patients were excluded due to missing, or incomplete data. Seventy eyes of 35 patients were included. Nineteen patients (54.3%) were females and 16 (45.7%) males. Twenty-four patients (68.6%) where at the age of <30years and 11 (31.4%) where of ⩾30years of age. All data were collected and expressed in mean and standard deviation. The mean (±SD) of age was 27.5 (±5.9), ranging from 20 to 39. The mean spherical equivalent was −3.37 (±2.57), Sphere −2.79 (±2.5), Cylinder 1.16 (±0.68), and Axis 106 (±60.01), while the mean CCT was 531.13 (±32.36).

Mean pupil size before LASIK was 4.10±0.74 and immediate after LASIK was 4.74±0, p value <0.0100.

We looked for variables affecting our result such as age, sex, sphere, cylinder correction and corneal thickness: none of these variables was statistically significant that can be associated. However, there is a trend towards a sex to be a significant factor (P=0.057).

4. Discussion

In this prospective study, we compare the size of pupil before and immediate after LASIK in mesopic condition using colvard pupillometer.

Postulations were suggested to elucidate the reasons that explain the mild dilation of pupil size after the procedure, like, effect of the suction ring, steroid drops post-operatively, emotional stress, pain and dark room.

Suction ring is well known to be a major factor for spontaneous pupil dilatation which can be seen by LASIK surgeons on the microscope during operation. When a suction ring is applied to the eye during LASIK, IOP rises over 65mm Hg for 15–60s (Ozdamar et al., 2004). This change in pupil size may stay shortly after the procedure.

There are few data on the possible effect of steroids on pupil size. Armaly (1964) applied topical dexamethasone-21-phosphate and administered subconjunctival methylprednisolone acetate in monkeys, but did not demonstrate a change in pupil diameter. However, pupillary dilatation following topical application of corticosteroids was observed in some patients after 2weeks of therapy, and was reversible by stopping the medication. Newsome et al. (1971) investigated pupil size and interpalpebral fissure following the use of dexamethasone with vehicle and dexamethasone in normal saline, in monkeys. The results showed that dexamethasone with vehicle, and vehicle alone, produced relative pupillarydilatation and ptosis, but dexamethasone in saline did not. The authors suggested the mydriasis and ptosis appeared to be caused by a myopathic effect of the vehicle.

Moreover, anxiety and ocular pain during LASIK can dilate the pupil in response to extreme emotional situations such as fear, or to contact of a sensory nerve (Harrison et al., 2007). Also, the pupil is well known to have dilation in dark atmosphere which is a normal bio-physiological process occur to control the amount of light entering the retina to enhance good quality of vision in decreased light circ*mstances.

We reported a case of bilateral acute angle closure glaucoma after hyperopic LASIK correction in 49year old lady (Osman et al., 2009). In this case some additional factors such as hyperopia and age might be contributing to occurrence of bilateral angle closure glaucoma.

A Similar study published by Paciuc et al. (2000), Who reported a case of acute angle closure glaucoma 1year after hyperopic (LASIK), which cannot be explained by the direct LASIK procedure effect because it occurred one year after LASIK procedure.

In conclusion, there is change in pupil size immediate after LASIK. Pupillometry study might help to explain the mechanism of angle closure glaucoma after LASIK correction.

5. Disclaimer

The authors hold no financial or proprietary interest in any aspect of this study.

References