Eye doctors will perform a wide range of exams during the glaucoma diagnosis process, however there is one exam that is critical to ensuring an accurate diagnosis
Pachymetry comes from the Greek word Pachys, which means ‘thick’. Corneal pachymetry is the measurement of the corneal thickness. There are several primary reasons why you would need to do this.
Why is the corneal thickness important in diagnosing glaucoma?
Glaucoma is a progressive optic neuropathy which can lead to blindness and one of its primary risk factors is high intra ocular pressure (IOP). There are numerous studies that show a link between thinner corneas and a higher risk of developing glaucoma.
Also, tonometry (the measurement of the IOP) relies on an assumption of the patient’s corneal centre thickness (CCT). If the patient’s CCT is a lot different to the assumed thickness, the tonometer might significantly over or underestimate the IOP. This could lead to false positive and false negatives and may mean some people ‘slip through the net’ of glaucoma screening until they’ve lost some level of vision unnecessarily. Measuring CCT and then correcting the IOP result has been shown to provide a better diagnostic result and improves patient outcomes.
What other conditions can a pachymeter help diagnose?
Another condition that can cause sight threatening damage is Keratoconus. This is a form of Ectasia (chronic thinning of the cornea). It typically develops in childhood and the teens and gradually there is central thinning of the cornea leading to misshaping and reduced vision (the cornea becomes ‘cone shaped’ – hence keratoconus). Screening for this is important and measuring CCT is a key tool.
There are conditions where the cornea is too thick, such as after excessive soft contact lens wear or from Fuch’s endothelial dystrophy. Again, screening for these problems requires pachymetry.
How do modern pachymeters work?
Modern pachymeters rely either on ultrasound devices which (handheld sometimes) contact the cornea and therefore require anaesthetic and risk cross infection or corneal abrasion – including potentially Covid, or they are large desktop-based devices using Scheimpflug cameras, OCT or other optical methods. These tend to be expensive and non-portable products.
Is there a non-contact pachymeter?
There is one device which is handheld and uses optical technology, thus removing the need for anaesthesia and avoids cross infection risk. It is small, portable, and considerably more affordable than the larger desktop-based products. There is no risk of cross infection or corneal abrasion most importantly.
The Pachymeter Development
The Pachymeter has come a long way since our first prototype device.
2019 - The first pachymeter prototype (December tested the scanning optics and data collection but linked to a separate PC to process the data and supply power.
Q1 2020 - The next prototype miniaturized the technology from the first device, added in a camera and rear screen and moved to a self-contained, battery-powered version complete with its own processing power.
Q3 2020 - The production prototype is close to the final device and contains enhancements to the second device with a better camera, screen, processing, and connectivity options. This device will undergo CE and FDA approval and will be used in the clinical trials in Q2 2021.