IOP Device Comparison Study

Intraocular pressure measurement (IOP) is part of a routine eye examination. High and low eye pressure may be linked to certain eye conditions such as glaucoma. The current gold standard for IOP measurement is a technique called Goldmann Applanation Tonometry (GAT). GAT requires the use of a Goldmann applanation tonometer mounted on a slit lamp. Apart from GAT, there are many other devices that can be used to measure IOP, including the iCare tonometers. In this prospective study, investigators will be measuring participant's IOP with GAT, Icare PRO, and Icare ic200 tonometers to see if there is an agreement in IOP between the different devices. Investigator will also look if there is a concordance between different tonometers in low, moderate and high IOP range. Given the postural requirements for performing GAT, patients with higher body mass index (BMI) tend to have difficulties with proper positioning at the slit lamp that may lead to inaccurate GAT measurements. To this end, investigators will analyze the effect of BMI on IOP measurements with different devices. Additionally, comfort level of the patients with different tonometry devices will be recorded using a visual analog scale.

Intraocular pressure measurement (IOP) is a vital part of the routine eye examination. High and low eye pressure may be associated with various ocular pathologies, including glaucoma. The current gold standard for IOP measurement is Goldmann Applanation Tonometry (GAT). To perform measurements with GAT, topical anaesthetic and fluorescein eye drops are applied to the eye. The Goldmann tonometer tip directly contacts the cornea and measures the intraocular pressure by the Imbert-Fick principle. IOP measurement is generally performed by a trained and experienced ophthalmologist or ophthalmic technician on patients in an upright position. There may be minor discomfort associated with the use of topical anaesthetic in this technique.

Icare tonometers are a new class of rebound tonometers used for IOP measurements. A disposable tip of the Icare tonometer is propelled towards the cornea and the deceleration of the tip is measured to calculate the IOP. The Icare series of devices are hand-held tonometers, which are easy to operate and do not require topical anaesthesia for IOP measurements.

Despite being the most reliable and clinically validated method to measure IOP, GAT has several limitations. First, it requires extensive training and experience to accurately measure IOP. Moreover, IOP measurement with GAT may be associated with minor discomfort due to the need for topical anaesthesia. Apart from that, GAT is not a portable device and the patient needs to be seated upright, making it difficult to perform in certain populations, such as pediatric, elderly and those with high BMI. Several hand-held tonometers are available, including the Icare series. These tonometers allow for quick, portable, and arguably easier IOP measurements. These tonometers do not require as rigorous training to use. However, there is an inconsistency in the data to verify if the IOP measurements by Icare is in concordance with GAT measurements. Recent Meta-analysis by Rödter and colleagues neither confirm nor deny the agreement between Icare and GAT tonometers.

The purpose of the current study is to prospectively evaluate and determine the relationship of the IOP measurements obtained by Icare PRO, Icare ic200, and GAT. The study will evaluate IOP measurements in different IOP ranges (low: 7-15mmHg, Moderate: 16- 22mmHg, High: 23-60 mmHg) as well as the effects of central corneal thickness and BMI on IOP measurements. Patient comfort during tonometry will be measured using a visual analogue scale. To date, this will be the first study in Canada to compare IOP measurements between Icare PRO, Icare ic200, and GAT in different IOP ranges. Additionally, as the Icare ic200 is a new device, this will be the first study to perform a comparative functional analysis of the Icare ic200 versus GAT.

Eligibility Criteria:
Inclusion Criteria:

* Age greater than 18 years
* Willingness to participate in all study procedures, along with signed written consent

Exclusion Criteria:

* Age younger than 18 years
* Participants with corneal defects (edema, scarring, cicatrix, opacity)
* Participants with epithelial lesions, prior refractive surgery and keratoplasty surgery
* Participants having corneal astigmatism ≥ 3D
* Participants who wear contact lenses
* Participants with proliferative diabetic retinopathy, Uveitis
* Participants who are unable to have IOP measured by Goldmann Tonometry
* Inability to provide informed consent
* Participants with proliferative diabetic retinopathy, Uveitis
* Participation in a clinical trial with investigational products