Evaulation of Pupillometry in patients with pseudoexfoliation and healthy individuals - A comparative study.

INTRODUCTION               Pseudoexfoliation syndrome is an age-related systemic disorder of extracellular matrix which is characterized by the progressive accumulation of an abnormal whitish, fibrillar material in many ocular tissues such as ciliary body, iris, iridocorneal angle, lens capsule, zonules and corneal endothelium.1

The abnormal deposition of Pseudoexfoliative material causes a wide array of ocular manifestations in anterior segments such as Pseudoexfoliation syndrome, increased intraocular pressure , phacodonesis, and blood aqueous barrier dysfunction.

Additionally, cataract surgery in eyes with Pseudoexfoliation syndrome has higher incidence of intraoperative and post-operative complications, associated with poor mydriasis, posterior synechiae, lens subluxation, and vitreous loss. 2

76% of patients with Pseudoexfoliation syndrome are initially diagnosed as having unilateral Pseudoexfoliation syndrome . The presence of Pseudoexfoliative material is frequently asymmetric and clinically Pseudoexfoliation syndrome may be seen only unilaterally.3

Automated quantitative pupillometry is an objective, non-invasive method for quantitative assessment of pupillomotor function. By static pupillometry, pupil diameter is assessed in different light conditions and dynamic pupillometry studies different parameters of the constriction and dilatation phase of pupillary reflex. 4

Hence in this study we aim to evaluate pupillary function in Pseudoexfoliation syndrome patients using static and dynamic pupillometry. We will also measure retinal nerve fibre layer thickness, macular ganglion cell layer (mGCC) thickness and iris thickness, and look for any association with pupillary parameters.

LACUNAE IN EXISTING KNOWLEDGE

There is a paucity of literature evaluating static and dynamic pupillometry in patients with Pseudoexfoliation syndrome in the Indian population.

REVIEW OF LITERATURE

Pseudoexfoliation syndrome is an age-related micro-fibrillopathy characterized by accumulation of amyloid-like material in ocular tissues. Pseudoexfoliation syndrome is diagnosed in the presence of dandruff-like deposition, often target shaped, on the lens capsule and other ocular structures such as pupil, cornea, or conjunctiva. Pseudoexfoliative material may cause mechanical blockage of trabecular meshwork and functional disturbances and impairment of aqueous outflow and progressive optic nerve damage. Glaucoma associated with Pseudoexfoliation syndrome is known as Pseudoexfoliation Glaucoma (PXG) and is the most common identifiable reason for secondary open-angle glaucoma.

The prevalence of Pseudoexfoliation syndrome increases with increasing age and can vary from region to region. The Andhra Pradesh Eye Disease Study reported a prevalence of 3.01% in patients over 40 years of age and 6.28% in those older than 60 years of age.5 The Aravind Comprehensive Eye Survey reported the prevalence of Pseudoexfoliation syndrome in Southern India to be 6.0%.6 Pseudoexfoliation syndrome prevalence was found to be 1.49% in a rural Central Indian population aged 30+ years.7 Pseudoexfoliation syndrome may be present unilaterally or bilaterally. More than half of unilateral cases may become bilateral over 20 years. 3

Eyes with Pseudoexfoliation syndrome often have pupil abnormalities that are likely due to the progressive accumulation of Pseudoexfoliation syndrome material in and on the iris. Additionally, eyes with Pseudoexfoliation syndrome usually show weak pupil dilation mainly because of the rigidity and fibrosis caused by involvement of iris sphincter muscle. 4 While most commonly seen on the anterior lens capsule, exfoliation material is also prominent at the pupillary border. The accumulation of Pseudoexfoliation syndrome material between the iris and the lens may result in posterior synechiae formation, which may further limit iris mobility. 8 Pseudoexfoliation syndrome material has also been observed histologically in iris dilator muscle cells. 9

A poorly dilating pupil may be a gauge of the severity of intraocular infiltration of Pseudoexfoliation syndrome

material. Zonular fragility and weakness are invariable features of severe Pseudoexfoliation syndrome, and occur due to the infiltration of the Pseudoexfoliation syndrome material at its origin, insertion, and length. 10,11 Incidence of complications during or after cataract surgery is much higher in patients with Pseudoexfoliation syndrome.2

Since zonules cannot be directly visualized to assess their integrity or quantity of PXF deposits on them Nath et al., have proposed a new clinical classification for predicting the zonular strength based on the maximum pupillary dilatation.12

Pupillary reflexes are under the control of the autonomic nervous system and allow evaluation of the parasympathetic and sympathetic system responses. The parasympathetic nervous system acts on the iris sphincter muscle leads miosis, while the sympathetic system controls the iris dilator muscle.13 Measurement of pupillary response via infrared pupillography was introduced by Lowenstein and Loewenfeld, and recent developments in automated pupillometry devices have permitted quantitative, objective, non-invasive, and repeatable measurements of pupil diameter along with the pupillary kinetics. 4 However, for correct evaluation of pathological findings, a functional iris mechanism is required.

1.Tekin et al, compared automated pupillometry between patients of Pseudoexfoliation syndrome, Pseudoexfoliation glaucoma and age matched healthy controls.4 They showed that accumulation of pseudoexfoliative material cause alterations in static and dynamic pupillary characteristics and progression from Pseudoexfoliation syndrome to Pseudoexfoliation glaucoma may be associated with reduced amplitude of pupil contraction values. In another study by the same authors, even patients with clinically unilateral Pseudoexfoliation syndrome showed altered static and dynamic pupillary parameters in both eyes when compared to healthy subjects. 14

2.Biçer et al., found that static and dynamic pupillary parameters and pupil dilation speed of eyes with clinically unilateral Pseudoexfoliation material were reduced when compared to healthy individuals. Although Pseudoexfoliation syndrome is a systemic syndrome, the emergence of iris dysfunction findings correlated with the clinically visible Pseudoexfoliation material.13

In addition, studies have shown that primary open-angle glaucoma (POAG) is associated with impairments in pupillary responses as evidenced by automated pupillometry measurements.15 Spectral domain optical coherence tomography (SD-OCT) provides objective, quantitative structural measurements of the optic disc, circumpapillary retinal nerve fiber layer (RNFL), and macular thickness.

3. Sarezky et al., assessed the relationship between the relative afferent pupillary response by automated pupillography and average RNFL thickness by SD-OCT. They found that the asymmetry in afferent pupillary responses was proportional to structural and functional asymmetry as measured by SD-OCT (RNFL thickness).

4.Pradhan et al. reported that glaucomatous damage as estimated by RNFL and mGCC were best predicted by the latency parameters of pupillography. 16

5.Rao HL et al. found that inter-eye asymmetry in RNFL and mGCC measurements in glaucoma was best predicted by inter-eye difference in amplitude change percent on automated pupillography.17

6. Chang et al reported significant correlations between the magnitude of pupillary light response and visual field and RNFL loss in patients with glaucoma. 18

7. Yoo et al., found correlation between mGCC and pupillometry parameters in patients with ethambutol-induced optic neuropathy, compared to normal controls. 19

Anterior segment optical coherence tomography (ASOCT), allows in vivo visualization as well as quantification of anterior segment structures. Abnormal pupillary dilatation, zones of stromal hypoplasia, and pigment loss imply possible changes in iris function and differences in iris thickness or morphology correlate with different stages of exfoliation. 20 The stromal thickness at 1 mm and 2 mm from the pupillary edge may be used to evaluate the pupillary sphincter and dilator pupillae responses, respectively. 21

8. Chen et al found that patients with POAG had a lower iris thickness compared to healthy individuals. 21

AIM AND OBJECTIVES

AIM

To assess pupillometry function in patients with Pseudoexfoliation syndrome .

OBJECTIVES

To study difference in pupillometry parameters from healthy individuals

To assess parameters contributing to pupillary function.

MATERIALS AND METHODS

Study design: Comparative observational study.

Study population:

The study population will consist of patients with Pseudoexfoliation syndrome attending OPD of Guru Nanak Eye Centre, Maulana Azad Medical College. Written and informed consent will be taken from the patients before inclusion in study.

Place of study: Guru Nanak Eye Centre

Time period: 1 year

The study will be commenced after approval from the Protocol Review Committee and Institutional Ethics Committee.

Inclusion Criteria(patients)

1. Patients with unilateral or bilateral Pseudoexfoliation syndrome .

2. Age group between 40 to 75 years.

Inclusion Criteria(healthy individuals)

1. Age group between 40 to 75 years.

Exclusion criteria(patients) :

1. Any retinal disease or optic nerve disease other than Pseudoexfoliation syndrome glaucoma (treatment naïve)

2. Diabetics.

3. Any iris or pupillary abnormalities.

4. History of head or ocular trauma or uveitis.

5. Corneal opacification, retinal vein occlusions

6. Patients on topical mydriatic and miotic agents and systemic medication like anticholinergics.

7. Patients taking narcotics like opioids.

8. Patients with hazy media which refuse good quality imaging.

Exclusion criteria(healthy individuals)

1. Any retinal disease or optic nerve disease,Pseudoexfoliation syndrome or glaucoma .

2. Diabetics.

3. Any iris or pupillary abnormalities.

4. History of head or ocular trauma or uveitis

.5. Corneal opacification, retinal vein occlusions

Study groups

1. Patients with Pseudoexfoliation syndrome .

2. Age and sex matched healthy subjects.

Outcome Parameters

Primary outcome:

1.To study pupillary indices in patients with Pseudoexfoliation syndrome by static and dynamic pupillometry.

Secondary outcome:

1. To compare pupillary indices of patients with Pseudoexfoliation syndrome with those of healthy individuals .

2. To correlate retinal nerve fiber layer thickness and macular GCC with pupillary parameters.

3. To correlate iris thickness with pupillary parameters.

4. To correlate maximum pupillary dilatation with pupillometry parameters.

SAMPLE SIZE CALCULATION

The sample size for the study was based on Tekin et al (2020) velocity of pupil constriction values and the sample size required in each arm of the study was calculated according to the formula

Sample size =[ Z1-α/2+ Z1-β ]2 *(σ1+σ 2)2 /(d )2

Where:

σ1(SD of control)=1.29,σ2(SD of pseudoexfoliation syndrome cases)=1.48

d (Difference of Means) = 0.89

z – value for 5% level of significance = 1.96

z – value for 80% power = 0.84

Based on the formula given above, using the mentioned values, assuming 80% Power and 95% Confidence interval, the minimum sample size required is 75.94≈ 76 in each group (total 152).

For convenience sample size of 40 is taken in each group(total 80)

Sampling methodology- Since Pseudoexfoliation syndrome is an uncommon condition (0.95-3.8%), all patients diagnosed as Pseudoexfoliation syndrome in GNEC shall be included in the study, subject to patient consent and criteria for exclusion.

Methods

History – Detailed history will be taken regarding duration of disease and treatment

Examination- All patients will undergo general physical examination and ocular examination including

Blood pressure

Best corrected visual acuity BCVA using Snellen chart.

Slit lamp examination.

Intraocular pressure measurement using Goldmann applanation tonometry( GAT).

Fundus examination using indirect ophthalmoscope, Fundus Photography

OCT RNFL, mGCC

Anterior segment OCT for iris thickness

Investigations

Pupillometry

After taking informed consent selected subjects will undergo static and dynamic pupillometry using (name and detail). Pupillometry will be performed on MonPack One, Vision Monitor System (Metrovision, Pérenchies, France). An average of three readings will be taken.Study will be done during the same period of the day between 11 am to 3 pm to minimize the effect of circadian variation on iris mechanics. Pupillometry will be done at least 3 days after dilated fundus examination. The stimulus is white light obtained from a full field back light and the system is equipped with a near infrared high resolution camera which allows measurement to be taken from both pupils simultaneously. Both static and dynamic pupillometry can be measured by this system. Three consecutive measurements shall be taken from each participant and average shall be taken. The automatic-release mode of the device is used to minimize examiner-induced errors. During the pupil recording, participants are required to fixate on a target in the center of the test field to control fixation stability. Pupil contours of participants are outlined on the image to ensure the accuracy of measurements. Static pupillometry will help us to measure pupillary diameter in different light conditions and Dynamic pupillometry measurements will be obtained for the duration of 90 seconds after 5 mins of dark adaptation. The patients will be examined using white light flashes on time 200ms and off time 3300ms. Wave form contaminated with blinks will be rejected.

Static parameters:

1. high photopic 100 cd/m2

2. low photopic 10cd/m2

3. mesopic 1cd/m2

4.scotopic 0 cd/m2

Dynamic parameters:

1. amplitude of contraction

2. duration of contraction

3. latency of contraction

4. Velocity of contraction

5. latency of dilatation

6. Velocity of dilatation

7. Duration of dilatation

OCT

RNFL and GC-IPL thickness will be measured using high resolution SD-OCT (Copernicus, Optopol Technology S.A., Zawiercie, Poland), in both eyes.

ASOCT

The anterior chamber angle and lens scan protocols of CASIA 2 (Tomey Corporation, Nagoya, Japan) will be used to obtain a volume scan with a length and depth of 16 mm and 13 mm, respectively. Images are acquired during the 5 s while the patient was fixing on an internal

target. Images with motion or lid artifacts were excluded. Iris thickness at 1 mm and 2 mm from the pupillary margin will be calculated in the nasal and temporal scans.

Statistical analysis

Data will be coded and recorded in MS Excel spreadsheet program. SPSS v25 (IBM Corp.) will be used for data analysis.

Descriptive statistics will be elaborated in the form of means/standard deviations and medians/IQRs for continuous variables, and frequencies and percentages for categorical variables. Data will be presented in a graphical manner wherever appropriate for data visualization using histograms/box-and-whisker plots/column charts for continuous data and bar charts/pie charts for categorical data.

Group comparisons for continuously distributed data will be made using independent sample ‘t’ test when comparing two groups. If data will be found to be non-normally distributed, appropriate non-parametric tests in the form of Wilcoxon Test/Kruskal Wallis test will be used for these comparisons.

Chi-squared test will be used for group comparisons for categorical data. In case the expected frequency in the contingency tables will be found to be <5 for >25% of the cells, Fisher’s Exact test will be used instead.

Linear correlation between two continuous variables will be explored using Pearson’s correlation (if the data will be normally distributed) and Spearman’s correlation (for non-normally distributed data).

Statistical significance will be kept at p < 0.05

ETHICAL CONSIDERATIONS

The confidentiality of the subjects will be maintained throughout the study.

Informed consent will be taken from the study subjects.

Study subjects will be given an open choice to leave the study whenever they want to leave the study.