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The EZ ratio method is one way to calculate the estimated anterior chamber depth. [2] To start, the patient looks at a target in the distance with one eye covered. The examiner takes a digital photograph of the open, examined eye, from the side, perpendicular to the visual axis (a profile photograph).
The central corneal power is the second important factor in the calculation formula. To simplify the calculation, the cornea is assumed to be a thin spherical lens with a fixed anterior to posterior corneal curvature ratio and an index of refraction of 1.3375. Central corneal power can be measured by keratometry or corneal topography.
The Van Herick's technique has become the most commonly used qualitative method of assessing the size of the anterior chamber angle (ACA). Whereby, it involves comparing the depth of the peripheral anterior chamber to the thickness of the cornea, when a narrow beam is shone within the limbus at a 60°angle. [4]
An anterior chamber IOL (ACIOL) Posterior chamber IOL (PCIOL). This is by far the most common type of implanted lens after cataract surgery, as this is the natural and optimum position for a lens. [citation needed] Anterior chamber IOL (ACIOL). A less-common type of intraocular lens, which is sometimes used if a PCIOL is not an option for a ...
A-scan ultrasound biometry, commonly referred to as an A-scan (short for Amplitude scan), uses an ultrasound instrument for diagnostic testing. [1] A-scan biometry measures the axial length (AL) of the eye prior to cataract surgery in order to assess the refractive power of the intraocular lens that will be implanted.
The anterior chamber angle is a part of the eye located between the cornea and iris which contains the trabecular meshwork. The size of this angle is an important determinant of the rate aqueous humour flows out of the eye, and thus, the intraocular pressure. The anterior chamber angle is the structure which determines the anterior chamber depth.
The depth of the anterior chamber and position of the posterior capsule may be maintained during surgery by OVDs or an anterior chamber maintainer, which is an auxiliary cannula providing a sufficient flow of buffered saline solution (BSS) to maintain stability of the shape of the chamber and internal pressure.
Anterior chamber depth (ACD, i.e. the distance between the crystalline lens and cornea including the corneal thickness) is required before the surgery and measured with the use of ultrasound. Iris-fixated IOLs are fixated to iris therefore they have the advantage of being one size (8.5 mm).