Hypermetropia, also known as hyperopia, long-sightedness, or far-sightedness, is a prevalent refractive error. This condition means that the eye does not focus light directly on the retina, leading to blurred vision, especially for close objects.
In this article, we will delve deep into the intricacies of hypermetropia, shedding light on its symptoms, causes, diagnostic methods, management techniques, and potential complications. Hypermetropia is a condition where the eye focuses light behind the retina instead of directly on it.
This refractive error results in blurred vision, especially for close objects. The term “refractive error” refers to the eye’s inability to focus light correctly. The unit for measuring this error is the dioptre (D).
For a condition that affects the alignment of the eyes check this article.
Historical Perspective
Donders, in 1864, discussed hypermetropia in his historical review. He highlighted the confusion between the effects of presbyopia and hypermetropia on near vision.
Over time, understanding and management of this condition have evolved, offering better solutions to those affected. In hypermetropia, the cornea might be flatter, or the axial length of the eye might be too short.
This discrepancy means that by the time light rays reach the retina, they haven’t focused correctly. For clear vision, a hypermetropic eye must adjust its lens power, requiring the ciliary muscle to work harder. This constant adjustment means the eye is never truly at rest, especially when viewing near objects.
Symptoms of Hypermetropia
The symptoms of hypermetropia can vary based on the patient’s age and the severity of the refractive error. Some patients might not exhibit any symptoms, especially if the error is minor.
Common Symptoms
- Asthenopia (eyestrain): A common complaint, especially after prolonged work.
- Headaches: Often frontal or frontotemporal in nature.
- Watering of the eyes: Especially after reading or other close work.
- Mild aversion to light: Some patients might find bright lights uncomfortable.
Symptoms Based on Severity
- Low Hypermetropia: Patients might experience eyestrain and headaches, especially later in the day.
- Moderate Hypermetropia: Vision might be slightly blurred, especially for near objects.
- High Hypermetropia: Marked vision defects for both near and distant objects.
- Age-related Changes: As one age, the eye transitions from latent and facultative hypermetropia to more absolute hypermetropia, leading to progressively blurred vision.
Causes
Understanding the root causes of hypermetropia can help in its management and treatment.
Axial Hypermetropia
This is the most common type of hypermetropia. Here, the eye’s refractive power is normal, but the eyeball is shorter in its axial length. A 1 mm reduction in the anteroposterior length can result in about 3 Dioptres (D) of hypermetropia.
Curvature Hypermetropia
In this type, the curvature of the cornea or lens (or both) is flatter than normal. A 1 mm increase in the radius of curvature can lead to 6 D of hypermetropia.
Other Causes
- Index Hypermetropia: Changes in the lens’s refractive index with age.
- Positional Hypermetropia: Due to the lens being positioned more posteriorly.
- Absence of Crystalline Lens: This can be congenital or acquired, leading to aphakia and high hypermetropia.
Diagnosis
Diagnosing hypermetropia involves a combination of understanding the patient’s symptoms and conducting clinical examinations.
Clinical Signs
- Visual Acuity: This can vary based on the degree of hypermetropia and the power of accommodation.
- Cover Test: This test can reveal an accommodative convergent squint.
- Eyelids: Conditions like blepharitis, stye, or chalazion might be present.
- Eyeball: The size might be normal or smaller than average.
- Cornea: It might be slightly smaller in size or flatter.
- Anterior Chamber: It might be shallower in cases of high hypermetropia.
- Lens: The lens might be positioned more posteriorly.
- Fundus Examination: This can reveal a small optic disc, which might appear hyperaemic.
Advanced Diagnostic Methods
- Ultrasonography or Biometry: This can show a decreased anteroposterior length of the eyeball.
- Severity Classification: Based on the degree of hypermetropia, it can be classified as low, moderate, or high.
Management of Hypermetropia
Managing hypermetropia effectively is crucial for ensuring optimal vision and preventing complications. The approach to management can be broadly classified into medical optical therapy and surgical therapy.
Medical Optical Therapy
Assessment of Vision
The primary step in managing hypermetropia is assessing the visual acuity. This assessment determines the ability to read symbols of varying sizes at a standard testing distance, typically 6 meters.
A 6/6 letter on the standard eye chart devised by Snellen is considered normal visual acuity. Refractive errors may result in uncorrected visual acuities that fall below 6/6. In the absence of other diseases, hypermetropia can be corrected, restoring normal visual function using spectacles or contact lenses.
Prescribing Corrective Lenses
The basic principle of therapy is to converge and focus the light rays on the retina using convex (plus) glasses.
- Cycloplegia: Total hypermetropia is determined by performing refraction under complete cycloplegia.
- Spherical Power: The power is prescribed to the extent that it is suitably acceptable to the patient.
- Astigmatism: This should be fully corrected.
- Children’s Prescription: Younger children might accept full cycloplegic correction, while older children might require a gradual increase.
- Exophoria: If associated with exophoria, hypermetropia should be under-corrected by about 1-2 D.
- Accommodative Convergent Squint: Full cycloplegic correction should be given.
- Amblyopia: In the presence of amblyopia, full correction with occlusion therapy should be given.
Surgical Therapy
For those who do not wish to wear glasses or contact lenses, or for whom these are not suitable, surgical options are available.
- Non-contact Holmium:YAG Laser Thermokeratoplasty: Suitable for hypermetropia of about +1 D to +2.5 D.
- Hypermetropic Photorefractive Keratectomy (H-PRK): The cornea is sculpted to correct mild-to-moderate hypermetropia.
- Conductive Keratoplasty: A non-invasive procedure using radiofrequency to correct low hypermetropia.
- Hypermetropic LASIK: Used to correct mild-to-moderate hypermetropia.
- Phakic Intraocular Lens (IOL) Implants: Suitable for correcting higher degrees of hypermetropia.
- Refractive Lens Exchange: Involves the extraction of the clear lens and implantation of an IOL.
Prognosis
The prognosis for hypermetropia is generally good, especially when detected and managed early. Asymptomatic children with low to moderate hypermetropia usually do not require glasses. However, as they grow, their visual acuity might decrease due to the loss of accommodation.
It’s essential to understand that untreated hypermetropia can lead to complications, impacting the quality of life.
Complications
If left untreated, hypermetropia can lead to several complications:
- Accommodative Convergent Squint: Excessive use of accommodation can lead to this condition.
- Amblyopia: Different types of amblyopia can develop, including anisometropic, strabismic, and ametropic amblyopia.
- Lid Diseases: Conditions like blepharitis, stye, or chalazion might develop due to repeated rubbing of the eyes.
- Primary Narrow Angle Glaucoma: High hypermetropia can predispose individuals to this condition.
FAQ
Is hypermetropia the same as presbyopia?
No, while both conditions involve difficulty in focusing on near objects, they have different causes. Hypermetropia is a refractive error present from birth or early life, while presbyopia develops with age, usually after the age of 40, due to the lens’s reduced flexibility.
Can hypermetropia be prevented?
Hypermetropia is often hereditary and cannot be prevented. However, regular eye check-ups can help in early detection and management.
Is laser surgery safe for correcting hypermetropia?
Laser surgeries like LASIK have been used for years to correct refractive errors, including hypermetropia. While generally safe, all surgeries come with risks. It’s essential to discuss potential complications and benefits with an ophthalmologist.
Can hypermetropia lead to blindness?
While hypermetropia itself doesn’t lead to blindness, untreated hypermetropia can lead to complications like amblyopia (lazy eye) or glaucoma, which can impair vision.
Can children outgrow hypermetropia?
Some children with mild hypermetropia may outgrow the condition as their eyes grow and develop. However, regular eye exams are crucial to monitor the condition and ensure proper vision development.
Are contact lenses a good option for hypermetropia?
Yes, contact lenses can be an excellent option for those with hypermetropia, especially for those who do not wish to wear glasses. They can offer a more natural field of vision.
How often should I get my eyes checked if I have hypermetropia?
It’s recommended to have annual eye check-ups. However, if you notice any sudden changes in your vision or experience discomfort, you should consult an ophthalmologist immediately.
Final Words
Hypermetropia, while common, is a condition that requires understanding and timely intervention. With advancements in medical science, there are numerous ways to manage and treat this refractive error, ensuring that those affected can lead a life with clear vision.
Regular eye check-ups and being informed are the first steps towards eye health. Remember, your vision is a precious gift; take care of it.