Myopia, commonly known as nearsightedness, and astigmatism are two common vision conditions that affect a significant number of people worldwide. Both of these conditions can impact the clarity of vision, but they are different in nature, causes, and treatment options. In this comprehensive guide, we will discuss the differences between myopia and astigmatism, including their definitions, causes, symptoms, diagnosis, and treatment options.
Defining Myopia:
Myopia, also referred to as nearsightedness, is a refractive error that affects the ability to see distant objects clearly. People with myopia typically experience clear vision when looking at close objects, such as reading a book or using a smartphone, but have difficulty focusing on distant objects like road signs or the chalkboard in a classroom. This condition occurs when the eyeball is slightly longer than normal or when the cornea (the clear front surface of the eye) is overly curved, causing light rays entering the eye to focus in front of the retina instead of directly on it.
Understanding Astigmatism:
Astigmatism, on the other hand, is a refractive error that affects the overall curvature of the eye. It occurs when the cornea or lens of the eye has an irregular shape, leading to a blurred or distorted vision at any distance. The cornea usually has a spherical shape like a basketball, but in astigmatism, it resembles more of a football shape, with different curves in different meridians. This difference in curvature causes light to be focused on multiple points instead of a single point on the retina, resulting in blurred vision.
Causes of Myopia:
The exact causes of myopia are not fully understood, but several factors contribute to its development. Genetics plays a significant role, as children with one or both parents having myopia are more likely to develop the condition. Environmental factors, such as spending excessive time on near work activities like reading or using electronic devices, can also contribute to the onset and progression of myopia. Additionally, certain medical conditions, such as diabetes or cataracts, may increase the risk of developing myopia.
Causes of Astigmatism:
Astigmatism can either be present from birth (congenital) or develop later in life due to various factors. Congenital astigmatism is usually caused an irregularity in the shape of the cornea or lens during the development of the fetus. This irregularity can occur due to genetic factors or prenatal conditions that affect the eye’s growth. Acquired astigmatism, on the other hand, can result from eye injuries, certain eye surgeries, or progressive changes in the cornea shape over time.
Symptoms of Myopia:
The primary symptom of myopia is difficulty focusing on distant objects. People with myopia often complain of blurry vision when looking at signs, movie screens, or objects in the distance. Squinting or straining the eyes to see clearly, frequent headaches, eye fatigue, or excessive rubbing of the eyes may also be experienced. In some cases, myopia progression may occur rapidly during childhood and teenage years, leading to a stronger lens prescription.
Symptoms of Astigmatism:
Astigmatism can cause a variety of symptoms that can affect both distance and near vision. Blurred or distorted vision at all distances is a common complaint among individuals with astigmatism. Squinting, eyestrain, eye discomfort, and headaches after extended periods of visual tasks may also occur. Some individuals may find it challenging to read small print or notice that vertical lines may appear tilted or slanted.
Diagnosing Myopia:
To diagnose myopia, a comprehensive eye examination an optometrist or ophthalmologist is necessary. The eye doctor will perform a series of tests, including a visual acuity test using an eye chart to measure the sharpness of your vision. A refraction test will also be conducted to determine the precise lens prescription needed to correct myopia. This test involves looking through a device called a phoropter and providing feedback on which lens choices provide the clearest vision.
Diagnosing Astigmatism:
Similarly, diagnosing astigmatism involves a comprehensive eye examination. The eye doctor will perform a series of tests, including a visual acuity test, where you will be asked to read letters or numbers from an eye chart. The doctor may also use a keratometer or corneal topographer to measure the curvature of your cornea, determining the degree and axis of astigmatism. In some cases, additional tests like a corneal mapping or a retinoscopy may be performed for a more accurate diagnosis.
Treating Myopia:
Myopia can be managed through several treatment options, each tailored to the individual’s needs and the severity of their condition. The most common treatment involves the use of corrective lenses, such as glasses or contact lenses, with a prescription specifically designed to correct nearsightedness. Glasses or contact lenses help focus light directly onto the retina, allowing for clear vision. Another option for myopia management is orthokeratology, a non-invasive procedure that involves wearing specialized gas permeable contact lenses overnight to temporarily reshape the cornea. This allows for improved vision during the day without the need for glasses or lenses. In some cases, refractive surgery, such as LASIK or PRK, may be considered, providing a more permanent solution reshaping the cornea using laser technology.
Treating Astigmatism:
Like myopia, astigmatism can be corrected with glasses or contact lenses that have a special cylindrical power to compensate for the irregular shape of the cornea or lens. These corrective lenses, known as toric lenses, can improve vision clarity refocusing light in a more precise manner. Depending on the severity and type of astigmatism, rigid gas permeable (RGP) contact lenses may also be recommended to provide better visual acuity. For individuals seeking a more permanent solution, refractive surgery options like LASIK, LASEK, or PRK can be considered to reshape the cornea and correct the irregularities causing astigmatism.
Although myopia and astigmatism both affect vision, they have distinct differences in their nature, causes, and treatment options. Myopia refers to difficulties in seeing distant objects clearly, caused an elongated eyeball or overly curved cornea. Astigmatism, on the other hand, involves blurry or distorted vision caused an irregular shape of the cornea or lens. Proper diagnosis and treatment an eye care professional are crucial for managing these conditions effectively. Whether it is through corrective lenses, orthokeratology, or refractive surgeries, advancements in optometry have provided options to improve the visual clarity and quality of life for individuals with myopia and astigmatism.