12 August 2020
The Pentacam AXL Wave is the latest addition to Innovative Eye Care’s arsenal of advanced imaging technology. It functions as a:
The Pentacam AXL Wave is on the cutting edge of tomography, advancing beyond reflection-based systems. It’s able to directly measure the elevation of both the front and back surfaces of the cornea (the clear structure at the front of the eye that bends light) with Scheimpflug imaging. It also measures corneal thickness and volume, anterior chamber conformation and volume, and anterior lens topography and density. This is many steps beyond what most topographers use (Placido disc imaging) which maps only the front corneal surface. Its accuracy as a non-contact alternative independent of tear film quality has been proven in countless clinical trials. For this reason, it’s much better for mapping irregular cornea, and dry eyes. The data from the shape of the eye can be used to design and simulate various custom-made contact lenses including orthokeratology, corneal RGP and scleral lenses.
Figure 1: Tomographic scan of the structures at the front of the eye, including the cornea, sclera, anterior chamber, iris and lens.
The Pentacam AXL Wave can very accurately objectively measure your refraction, without needing to say whether you prefer ‘1’ or ‘2’. This makes determining your prescription quicker and easier, and allows more time for refining your spectacles.
The ability of the Pentacam AXL Wave to measure the way light passes through the eye’s multiple structures is known as wavefront aberrometry. Lower-order aberrations including defocus (myopia, hyperopia) and astigmatism can easily be corrected with spectacles and contact lenses. However, the Pentacam AXL Wave also quantifies higher-order aberrations, and can even isolate whether these aberrations are being induced by the cornea or by internal structures. Higher-order aberrations are present in specific diseases like keratoconus and pterygium, and are more difficult to manage by conventional means. It’s why patients with these conditions often have unclear vision even with optical correction. In future, we will be able to correct higher-order aberrations using custom-made scleral contact lenses.
Figure 2: Visual performance of an eye based on the presence of lower- and higher-order aberrations found on wavefront aberrometry.
Biometry measures the axial thickness of the eyes optical structures; cornea, anterior chamber, lens, and vitreous chamber. The measurement is contactless, noninvasive, and provides an extremely precise objective assessment. Quantifying the length of the eye is important for monitoring its growth in children, particularly in regards to myopia, hyperopia and amblyopia. Pathological myopia is defined as an axial length of over 26mm, and children are at risk of secondary conditions causing vision impairment if their eye growth is not controlled (see Myopia Management Software below).1 Corneal thickness is intrinsic to management of keratoconus and other thinning conditions (ectasia). The Pentacam AXL Wave provides both an anterior and posterior elevation map, which are crucial in identifying and monitoring early ectasia where standard corneal topography cannot.2 Biometry of the cornea, lens and axial length can also be applied to cataract surgery, where your Ophthalmologist considers these aspects when deciding on an intraocular lens (IOL). With biometric readings, assessment of the anterior chamber depth can determine whether you are at risk of angle-closure glaucoma.
Figure 3: A short-sighted patient with an above average axial length.
A built-in database can determine your child’s risk of myopia development and progression based on high quality peer-reviewed evidence from the Brien Holden Vision Institute. It uses external information including time spent outdoors, time spent reading and parental optical prescription, as well as actual measurements of the eye including axial length in optical biometry and refraction. It compares these against a database and can identify children with axial lengths outside the normal range. With repeat visits, it’s able to monitor growth of the eye and project the trajectory of that growth. This information helps determine the best course of action for implementing myopia control to slow the growth of the eye. Ultimately, controlling the eye’s growth process reduces the risk of vision impairment including retinal detachment.1
Almost everyone over the age of 55 has some degree of cataract.3 The Pentacam AXL Wave assesses the crystalline lens inside the eye where the cataracts form with retroillumination (back-lighting). We can monitor how the cataract progresses and take preoperative measurements for IOL selection in collaboration with your Ophthalmologist. If you have had cataract surgery before, this equipment also checks that your new lens is positioned exactly where it needs to be.
Figure 4: A small, spoke-like lenticular opacity seen with retroillumination.
Due to its extensive abilities, the Pentacam AXL Wave is a comprehensive screening tool for possible disease and abnormalities. It has many abilities relating to pinpoint accuracy of glasses and contact lens prescription and design, myopia control, cataract and corneal thinning disease. Evaluation of the cornea, anterior chamber and lens provides us with important information about your eyes that we can use in obtaining an accurate optical prescription, monitoring for myopia progression and managing disease.