The human eye is an amazing organ comprised of fifteen parts, all working together so we can experience vision. Over time, our eyes start to age showing signs of lost efficiency of various functionalities. One of the main parts of the eye, the cornea, is a fascinating piece of tissue. It is comprised of five layers, all of which are designed to be optically transparent.
The cornea provides a surface for the tear film, the layer of moisture with multiple functions, to cling to. Light is bent by the greatest degree when passing through these structures so it can be focused on point with the retina. The crystalline lens accounts for the remaining third of refractive power.
Refractive issues appear when the power of these anatomical components – the cornea and crystalline lens is not well coordinated with the physical length of the eyeball. In hyperopia (long-sightedness), the eyeball is too short for its refractive power, and in myopia (short-sightedness), it is too long.
Common surgeries such as LASIK and PRK have addressed this imbalance of refractive power to eyeball length by reshaping the cornea. Thin corneas can be treated with refractive procedures, and treatment suitability is also subject to other eligibility criteria such as pre-existing corneal disease and even lifestyle factors. Therefore, it is important to choose the appropriate candidates for each type of procedure.
The minimum corneal thickness required for refractive surgery is dependent on the degree of refractive error that needs to be corrected. The higher the refractive error, the higher the prescription required, and usually, the more tissue that needs to be removed.
LASIK procedures require the creation of a flap of corneal tissue and, for those with thin corneas, make it challenging for reshaping. PRK surgery solves this issue by removing the very top layer, known as the epithelium, which leaves the rest of the corneal matter available for sculpting by laser. However, there are still requirements for patients considering PRK surgery, and sometimes other options must be considered that do not involve a laser to reshape the cornea.
Some options include intraocular contact lenses, or implantable contact lenses (ICL). These lenses are artificial and are made of biosynthetic material that goes between the iris and the crystalline lens. However, not everyone may benefit from these lenses, and LASIK or PRK treatments may be more suitable to those who could benefit from a more permanent solution.
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