Specular Microscopy Test - Explained in Hindi

Specular microscopy is a noninvasive photographic technique that allows you to visualize and analyze the corneal endothelium. Using computer-assisted morphometry, modern specular microscopes analyze the size, shape and population of the endothelial cells.
The instrument projects light onto the cornea and captures the image that is reflected from the optical interface between the corneal endothelium and the aqueous humor. The reflected image is analyzed by the instrument and displayed as a specular photomicrograph. In clinical practice, specular microscopy is the most accurate way to examine the corneal endothelium.
𝐓𝐡𝐞 𝐂𝐨𝐫𝐧𝐞𝐚𝐥 𝐄𝐧𝐝𝐨𝐭𝐡𝐞𝐥𝐢𝐮𝐦
============================
The corneal endothelium is a monolayer of 350,000 to 500,000 specialized cells that cover the posterior surface of the cornea. One of the endotheliums physiological functions is to secrete a collagen matrix that forms Descemets membrane.1 But, the primary physiological function of the corneal endothelium is to maintain the health and transparency of the corneal stroma. Because the cornea is avascular, the supply of nutrients occurs via diffusion of glucose and other solutes from the anterior chamber across the cornea endothelium. To facilitate diffusion, intraocular pressure constantly forces aqueous into the stroma from the anterior chamber. Although the influx of aqueous into the stroma is necessary to maintain corneal health, the level of corneal hydration must be controlled to prevent edema.
𝐒𝐩𝐞𝐜𝐮𝐥𝐚𝐫 𝐌𝐢𝐜𝐫𝐨𝐬𝐜𝐨𝐩𝐲 𝐈𝐧𝐝𝐢𝐜𝐞𝐬 𝐃𝐞𝐟𝐢𝐧𝐞𝐝
==============================
Below is a quick summary on the various quantitative indices generated with specular microscopy.
Cell density (CD): The number of endothelial cells per mm2. Cell density decreases with age and disease. When evaluating the cell density, it is important to consider age-expected values, as anything below the age-expected average value may be an indicator of underlying disease. Patients with a cell density less than 1,000 cells/mm2 are at higher risk for developing pseudophakic bullous keratopathy.4 To maintain proper hydration of the cornea, 300 to 600 cells/mm2 are necessary.2 When cell density falls below this critical number, the balance of stromal hydration is tilted toward corneal edema and loss of corneal transparency.
Coefficient of variation (CV): Represents the amount of variation in cell size. The coefficient of variation is a measure of polymegethism, which occurs during corneal endothelial repair. A coefficient of variation less than 33 is considered normal. An elevated coefficient of variation is often considered an early sign of endothelial disease, as this is a marker of endothelial cell remodeling.
HEX or 6A: Represents the number of cells that have a hexagonal shape. Pleomorphism is the decrease of hexagonal cells within the corneal endothelium. As pleomorphism increases, the barrier function of the corneal endothelium decreases. A HEX or 6A less than 50% is considered abnormal.
Central corneal thickness (CCT): The central corneal thickness measured during image acquisition. A thickened central cornea may denote corneal edema and reduced endothelial function.
Number of cells counted (NUM): The number of cells counted in the analysis. Visualization of imaging of endothelial cells in diseased corneas may be difficult, so it is important that an adequate number of cells are included in the quantitative analysis.
Average cell area (AVG): Measurement of the average cell area. This number increases with age as polymegathism increases.
Standard deviation of mean cell area (SD): The standard deviation of mean cell area within the analysis.