Journal of Clinical Ophthalmology and Research

ORIGINAL ARTICLE
Year
: 2015  |  Volume : 3  |  Issue : 1  |  Page : 15--18

Is intraocular pressure same at same time on different days in normotensives?


Nisheeta S Agarwala, Moushmi Chaudhari, Barun Kumar Nayak 
 P. D. Hinduja Hospital and Medical Research Center, Mumbai, Maharashtra, India

Correspondence Address:
Barun Kumar Nayak
P. D. Hinduja Hospital, Veer Sawarkar Marg, Mahim, Mumbai - 400 016, Maharashtra
India

Abstract

Purpose: To determine the variation in the intraocular pressure (IOP) at the same time on different days using Goldmann applanation tonometer in normal eyes. Materials and Methods: Two hundred eyes of hundred included subjects underwent detailed eye examination including vision assessment, slit lamp examination, baseline IOP measurement, and fundus examination. The IOP was measured on 4 days with the Goldmann applanation tonometer. The measurements were taken on consecutive days or separated by no more than one day between daily testing sessions. A difference of 1 hour on either side from the first day«SQ»s IOP reading was considered. The readings taken on 4 days were compared to find if there was any statistical difference between them. Results: There was no significant difference between the IOP«SQ»s measured at the same time on four different days in both eyes. The IOP measured in the right eye on days 1, 2, 3, 4 when compared were not statistically significant (median 12.5, 12.0, 12.0, 12.0, respectively and P-value 0.201). The IOP measured in the left eye on days 1, 2, 3, 4 when compared were also not statistically significant (median 13.0, 13.0, 12.0, 12.5, respectively and P-value 0.062). Conclusion: In normal eyes, the IOP measured using Goldmann applanation tonometer at the same time on different days within a week was not significantly different.



How to cite this article:
Agarwala NS, Chaudhari M, Nayak BK. Is intraocular pressure same at same time on different days in normotensives?.J Clin Ophthalmol Res 2015;3:15-18


How to cite this URL:
Agarwala NS, Chaudhari M, Nayak BK. Is intraocular pressure same at same time on different days in normotensives?. J Clin Ophthalmol Res [serial online] 2015 [cited 2022 May 25 ];3:15-18
Available from: https://www.jcor.in/text.asp?2015/3/1/15/149344


Full Text

A large diurnal variation in the intraocular pressure (IOP) is suggested as an independent risk factor for the glaucoma progression. [1],[2] Ideally 24 hour IOP monitoring is required to detect large IOP fluctuations in a day. But such measurements are practically not possible manually and also due to the unavailability of a 24 hour IOP monitoring device. Hence, a diurnal curve can be obtained by assessing the IOP at various different times on the same day. This evaluation may be avoided by the physician and also rejected by the patients due to the cost and the inconvenience to spend the entire day at the clinic to perform a diurnal curve. Therefore, to obtain maximum patient compliance patients are called at different times on their different follow up visits to draw a diurnal curve. [3] But in order to follow this system of IOP measurement, it has to be proved that the IOP at the same time on different days is the same. The aim of this study was to find out if there was any significant difference in the IOP at the same time on different days which can act as a baseline study to support the actual clinical system of obtaining a diurnal curve by measuring the IOP at different times on different days.

 Materials and Methods



The study design was conceived and planned in the Department of Ophthalmology at India, a comprehensive eye care center which acts as a tertiary eye care unit. The Ethics Committee approval was obtained and a complete patient information sheet was prepared with the details of the study. A written consent was obtained after the patient agreed for the study. Two hundred eyes of hundred patients were included in the study as per the statistician's advice.

Inclusion criteria were age between 18 years and 70 years, normal eyes, i.e., eyes without any intraocular pathology including all acute eye conditions and chronic eye conditions like uveitis, hypermature cataract, or any type of glaucoma.

Exclusion criteria were as follows: history of diabetes mellitus or hypertension, any previous eye trauma, any intraocular surgery in the past 6 months, subjects undergoing medical therapy for glaucoma, corneal scarring, recent use of glucocorticoids and beta-blockers through any route of administration, and pregnancy.

After the eligibility was established, detailed history was taken and clinical examination was done in all patients as per the study proforma. Patients' history included age, sex, history of acute or chronic ocular disease, ocular surgery in the past 6 months, history of previous eye trauma, history of undergoing any medical therapy for glaucoma, history of consumption of corticosteroids or beta-blockers through any route of administration, history of any systemic illness like diabetes mellitus or hypertension.

Distance (unaided, best corrected, pinhole) and near visual acuity was recorded on Snellens' optotype charts. Detailed adnexal (lids and lashes) and anterior segment (conjunctiva, cornea, sclera, anterior chamber, pupil, iris, lens) examination was carried out. IOP was measured with Goldmanns' applanation tonometer. Dilated fundus examination was carried out by binocular indirect ophthalmoscopy and fundus biomicroscopy using + 78 diopter (D) lens.

The IOP was measured on four days with the Goldmann applanation tonometer and the measurements were taken on consecutive days or separated by no more than 1 day between daily testing sessions to obtain maximum patient compliance. The time at which the IOP was measured on the first day was taken as the baseline time and an hour difference on either side from the first day's time was allowed while considering the consecutive 3-day measurements.

Technique for applanation tonometry: It was ensured that the tonometer was disinfected with isopropyl alcohol 70% (methylated spirit) or sodium hypochlorite 1%. The disinfectant was allowed to act for 1 min and then wiped dry with a clean swab. The graduation marked "0" on the measuring prism was aligned with the white marker point on the tonometer head. The calibrated dial of the tonometer was set at 10 mmHg. It was ensured that the patient was sitting comfortably on the slit lamp: At the right height, with chin on the rest and forehead against the headband. The magnification of the slit lamp was set at 10×.

Method: Local anesthetic drops were instilled in the patient's eyes following which fluorescein was instilled. The slit beam of the slit lamp was aligned to shine into the tonometer head. The filters were arranged such that the cobalt blue filter was used to produce a blue beam. The beam of light was as wide as possible, and the light bright enough which helped visualise the fluorescein rings easier (with the slit diaphragm fully open).The patient was asked to look straight ahead, open both eyes wide, fix his or her gaze, and keep perfectly still. If the patient had difficulty in opening the eye, then only the upper eyelid was gently held to keep it open taking care not to put any pressure on the eye. The blue light from the slit lamp was directed onto the prism head. The tonometer head was made perpendicular to the eye.

The tonometer was moved forward slowly until the prism rested gently on the centrr of the patient's cornea. With the other hand, the calibrated dial on the tonometer was turned clockwise or anticlockwise until the two fluorescein semi-circles in the prism head were seen to meet. (Note: The correct end point is when the inner edges of the two fluorescein semi-circle images just touch). The reading on the dial was recorded. The prism was withdrawn from the corneal surface. The procedure was repeated for the other eye.

The data were recorded as per proforma in the master chart. Statistical analysis was done by standard methods accepted internationally and all the data storage, calculation and analysis was carried out in computers. The statistical software Statistical Package for the Social Sciences (SPSS) version13 was used for data analysis. A sex distribution chart was made. All the statistical variables were tabulated. Friedman Repeated Measures Analysis of Variance on Ranks was applied for calculating the difference in the IOP on different days in both eyes as data failed Shaprio-Wilk Normality test. P values < 0.05 were considered statistically significant.

 Results



Present study included 200 eyes of 100 normal subjects who underwent IOP measurements on four different days at the same time at P.D. Hinduja National Hospital and Medical Research Centre.

It was observed that among the subjects 61% were females and 39% were males.

[Table 1] shows the statistics of various variables among the cases.{Table 1}

[Table 2] shows the repeated measures analysis of variance (ANOVA) for IOP at various intervals in the right eye among cases.{Table 2}

[Table 3] shows the repeated measures ANOVA for IOP at various intervals in the left eye among the cases.{Table 3}

 Discussion



It has been observed that the patients are called on different days at different times of the day to draw a diurnal curve, [3] to obtain maximum patient compliance. This system of IOP measurement can be considered only if the IOP at the same time on different days is same. This study was done to find out if there was any significant difference in the IOP at the same time on different days and it was found that it was not statistically significant.

Normal eyes were included in the study. Eyes with any intraocular pathology including acute eye conditions and chronic eye conditions like hypermature cataracts, uveitis, or any type of glaucoma were excluded since most of these conditions are associated with variation in the IOP. Patients with diabetes mellitus were excluded from the study. The IOP was found higher in diabetics than in the general population except in patients with proliferative diabetic retinopathy. The mean IOP in maturity onset diabetes was found to be 19.26 mm which was higher than the normal mean IOP reported in the general population, i.e., 16.1mm of Hg (Becker-Shaffer). [4] A direct correlation has been found between systemic blood pressure and IOP. Therefore, hypertensives were excluded from the study. Any previous ocular trauma, any intraocular surgery in the past six months were excluded from the study since these conditions could be associated with either increase or decrease in the IOP. Eyes with corneal edema or corneal scarring which affect the corneal thickness were excluded since Goldmann applanation tonometer gives misleading results in these corneas. [5] Pregnant women were also excluded from the study since it has been studied that in pregnancy, the IOP was found to be lower than seen in normal subjects. [6],[7] Strengths of this study are that this study was prospective study with strict criteria of inclusion and exclusion, making the study a homogenous one. The IOP measurements were taken by a single observer on a single instrument, therefore interobserver variation factor was negated. Subjects had to follow up for the subsequent three IOP measurements within seven days from the initial baseline measurement therefore attrition rates were minimum. A single gold standard instrument (Goldmann applanation tonometer) which was calibrated daily was used for all the subjects; therefore chances of errors were minimum. This was a cost effective study. Limitation was that a single measurement was taken at a time by the observer therefore chance of observer error between measurements on different days was a possibility. Mean of multiple measurements at a single time if taken would be more accurate to compare IOP on different days.

 Conclusion



This study had proven the fact that the IOP at the same time on different days is same hence, the practice of calling appears to be justified. This study will be useful to the patient as well as the ophthalmologists where percentage of compliance from both the sides would increase leading to a faster and more promising management of glaucoma. We had compared only normal patients as per our inclusion and exclusion criteria where it was found that here was no significant difference in the IOP at the same time on different days. A separate study needs to be conducted in order to find out the difference in the IOP in patients with glaucoma or those with significant diurnal variation.

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