- What is Hypermetropia?
- Mechanism of Vision
- Does Age Affect Hypermetropia?
- Causes of Hypermetropia (Etiology)
- Axial Hypermetropia
- Curvatural Hypermetropia
- Index Hypermetropia
- Positional Hypermetropia
- Consecutive Hypermetropia
- Signs And Symptoms Of Hypermetropia
- Diagnosis of Hypermetropia
- Examination Procedures & Equipment
- Clinical Classification Of Hypermetropia
- 1. Physiological Hypermetropia
- 2. Non-Physiological Hypermetropia
- 3. Functional Hypermetropia
- Grading of Hypermetropia
- Components of Hypermetropia
- Management of Hypermetropia
- Patient Education
What is Hypermetropia?
Hypermetropia is a common vision error, where one can see far placed objects but have difficulty in focusing objects that are closer, exquisitely. Hypermetropia is also known as Hyperopia or Long Farsightedness.
People with Hypermetropia can see distant objects very well (Eg- Billboards) but have difficulty focusing on objects that are up close (Newspaper), hence this eye disorder is also known as longsightedness or farsightedness.
In a hypermetropic condition, an eye acts similar to a camera -with,
- Light focusing object
- Aperture system
- Light sensitive object
|Shutter and aperture of a camera||Iris and pupil of an eye|
|Refract and focus the light||Cornea and lens|
|Light sensitive medium||Retina of an eye|
Mechanism of Vision
The two main structures responsible for focus are cornea (the outer clear front surface) and lens (changes its shape according to the objects focussed),
These work together to refract the light entering the eye and focus it onto the retina, which receives visual information and sends it to the optic nerve that carries this information to the brain.
An eye in which a clear image focussed-falls onto the sensitive part of the retina by a perfect curved lens and cornea is known as an emmetropic eye.
Any change in these factors may result in defectiveness in focussing.
In the case of an abnormal deviation of an emmetropic eye, where the image focussed-falls behind the retina is known as hypermetropia.
Does Age Affect Hypermetropia?
At birth, the eyeball is relatively short, having a +2D to +3D hypermetropia, which is gradually reduced as one ages.
By the age of 5-7 years, the eye is emmetropic and remains so till the age of 50.
After 50 yrs of age, there is a tendency to develop hypermetropia again, which gradually increases until the extreme of life, by which the eye has the same, +2D to +3D hypermetropia, with which the life started.This senile hypermetropia is due to changes in crystalline lens.
Causes of Hypermetropia (Etiology)
Axial hypermetropia is caused due to shortening of the eyeball, generally by 1mm shortening in Anteroposterior diameter results in 3D of hypermetropia.
This is seen in conditions such as microphthalmos and nanophthalmos.
Curvatural hypermetropia is due to flattening of cornea or lens, generally by 1mm increase in radius of curvature resulting in 6D of hypermetropia.
This is seen in conditions such as cornea plana and keratoconus apart from hypermetropia.
Index hypermetropia is caused due to decrease in the refractive index of lens, prominently seen in old age group
It is also seen in conditions such as cortical sclerosis.
Positional hypermetropia is due to variations in the position of lens, posteriorly placed.
Consecutive hypermetropia is seen in
- Surgical cases of overcorrected myopia following LASIK and implantable contact lens.
- Intraocular Lens (IOL) implantation in cases of cataract surgery
- Refractive lens exchange
Signs And Symptoms Of Hypermetropia
Generally younger patients with mild hypermetropia may not show symptom
Usually people with hypermetropia have following complaints which they find interfering with day to day activities,
- Blurred vision
- Watery eyes
- Asthenopia (Eye strain)
Diagnosis of Hypermetropia
Hypermetropic patients are recommended to visit an opthamologist after noticing symptoms as they interfere in their daily activities.
During initial examination an Optometrist (not certified physician but they are healthcare professionals who provide primary vision care) or ophthalmologist (certified physician who also performs surgery) will perform a basic examination on the patient’s eye.
Examination Procedures & Equipment
A Snellen Chart is a paperback chart or a digital chart, consisting of variable texts of different sizes arranged in descending sizes, which is used to measure visual acuity of the patients by determining the level of visual detail generally by the ease of readability.
Snellen Chart was developed by Herman Snellen in 1862, a Dutch Ophthalmologist and Snellen Charts are adopted by medical professionals in many countries who have been using it for more than 100 years.
A phoropter is an instrument in which lenses are inserted for aiding visual discrimination of the patient according pateint’s eye sight.
While examining, the patients are asked to wear a phoropter and read the text on the Snellen Chart which is placed at an optimal distance and the lenses are placed in the phoropter according to the vision capability of the patient, helping in measuring any refractive error and prescribing glasses.
During this part of the examination, proper communication between patient and the healthcare professional is critical.
Slit Lamp Examination
A Slit Lamp is an equipment used to examine structures of the eye such as cornea, lens (front of an eye) and retina (back of an eye) using a light source.
Other than these aforementioned equipments, many advanced equipments are also used in investigating any further disorders, some of those are mentioned below,
An Indirect Ophthalmoscope is used to examine the posterior structure of an eye mainly retina.
A Tonometer is used to measure pressure in an eye, this is useful to diagnose glaucoma.
A Keratometer is used to measure the shape of cornea and helps in the diagnosis of certain conditions, such as corneal opacity, astigmatism, keratoconus.
An Autor Refractor is used to measure refractive error of the eye which is based on the basic refraction of image that projects on the retina.
A Direct Ophthalmoscope works similar to that of an indirect ophthalmoscope and direct ophthalmoscope is used to find evidence of many eye problems. (like glaucoma, high blood pressure damage, retinal detachment, diabetes, eye tumors, etc.,)
A Retinoscope is used for objective refraction testing. Retinoscopes illuminate the internal eye and aids in observing and measuring the rays of light as they are reflected by the retina.
Complete history of the patient is necessary before deriving the diagnosis to avoid misinterpretation of the patient’s condition which includes drug history, allergic history, surgical history and also family history.
Clinical Classification Of Hypermetropia
Clinically Hypermetropia is classified into (03), Physiological Hypermetropia, Non-Physiological Hypermetropia & Functional Hypermetropia.
1. Physiological Hypermetropia
Physiological Hypermetropia is also known as Simple or Developmental Hypermetropia. It is one of the most common types of hypermetropia.
Physiological Hypermetropia is caused due to developmental variations, this includes-
- Developmental axial hypermetropia
- Developmental curvatural hypermetropia
2. Non-Physiological Hypermetropia
Non-Physiological Hypermetropia includes other than developmental variations which may be either congenital or acquired,
Congenital Hypermetropia is seen in conditions like microphthalmos, nanophthalmos, microcornea, congenital posterior subluxation of lens and congenital aphakia.
Acquired Hypermetropia includes the following,
- Senile Hypermetropia- Old age, axial hypermetropia and curvatural hypermetropia
- Positional Hypermetropia- Seen in Posterior subluxation of lens
- Aphakia – Absence of lens
- Consecutive Hypermetropia- Seen in surgically overcorrected myopia
- Acquired axial Hypermetropia- Forward displacement of lens, seen in Conditions like retinal detachment,central serous retinopathy and orbital tumours
- Acquired curvatural Hypermetropia- Seen in conditions such asPost traumatic or post inflammatory corneal flattening
- Pseudophakic Hypermetropia- Seen in implantable intraocular lens
3. Functional Hypermetropia
Functional Hypermetropia is due to paralysis of accommodation of the eye.
This is seen in conditions like third nerve paralysis and internal ophthalmoplegia.
Grading of Hypermetropia
American Optometric Association (AOA) has defined three grades of hypermetropia as below, (depending upon the intensity)
|Moderate||+2 to +5D|
Components of Hypermetropia
Latent Hypermetropia refers to 1D of hypermetropia that is normally corrected by inherent tone of ciliary muscle, this is seen when refraction is carried after abolishing ciliary tone with atropine.
The degree of latent hypermetropia is usually high in children and gradually increases with age.
Manifest Hypermetropia refers to the part of hypermetropia that can not be corrected by inherent tone of ciliary muscle.
This consists of two components based on the patient’s accommodative efforts.
Facultative Hypermetropia can be corrected by patient’s accommodative efforts
Absolute Hypermetropia can not be corrected by patients’ accommodative efforts.
In severe cases, if Hypermetropia is left untreated it can lead to following complications,
In retinal detachment, the retinal membrane distances from the underneath layers at the back of the eye making it an emergency condition to be treated.
Symptoms of retinal detachment include partial loss of vision, floaters (the debris from detached retina floats around giving a false appearance in vision) etc,.
Cataract is defined as clouding of a clear lens which develops slowly over time or due to an eye injury.
Symptoms of cataract include blurry vision, faded image viewing and inability to see in dim lights.
Glaucoma is a disorder of the optic nerve that plays an essential role in transmitting signals to the brain from the eye. Glaucoma is characterised by increased intraocular pressure.
Choroidal Neovascularization is the growth of new blood vessels from the choroid layer of an eye.
Symptoms of choroidal neovascularization include distorted vision or loss of vision without pain and metamorphopsia (straight lines appear bent).
Strabismus is simply known as crossed eye. In this condition both eyes can’t align in the same direction while looking at the same object.
Strabismus may be caused by improper functioning of muscles that coordinate eye movements or maybe by a nerve injury.
Amblyopia is diminished vision (partial loss of eyesight) in one or both eyes. This is usually associated with strabismus.
Amblyopia may be seen in children with uncorrected bilateral high hypermetropia.
Management of Hypermetropia
Generally Hypermetropia is managed by the following measures, which aids in visual discrimination.
Glasses or Contact Lens
The correction of hypermetropia is through the convex lens (converging lens) which has a positive refractive power which increases with the severity of hypermetropia.
Use of contact lens benefits in cases of unilateral high hypermetropia and the patient’s who resist the use of glasses.
Hypermetropia can also be cured by refractive surgery.Refractive surgery will eliminate the need for glasses or lenses.
Here are few most routinely performed surgeries
LASIK (laser in-situ keratomileusis) is the most common refractive surgery performed. It is used to correct mild to moderate hypermetropia (+1 to +4D). In this surgery, some part of the cornea tissue is removed by the laser after placing a thin flap on it, making it more curved so that light rays are focussed further forward on the retina.
Phakic means having a lens- IOL (Intraocular lens ). During Phakic IOL, an intraocular lens is surgically introduced into the posterior chamber of the eye with an already existing lens untouched.
Phakic IOL is used to correct higher degrees of hypermetropia (+4 to +10D)
Hypometric patients are suggested to follow the below mentioned measures, to avoid further complications and to maintain good optic hygiene.
- Avoid eye strain.
- Work in good light.
- Avoid long hours of short distant vision.
- Maintain a proper diet, rich in Vitamin A (carotenoids) like carrot.
- Regular follow up for every 3-6 months.
- Consult the doctor when other symptoms are noticed
Hypermetropia is a common vision error. It is also known as hyperopia or long-sightedness (farsightedness).
Hypermetropia is affected by the age of a person, in the correlation between the size of the eyeball, right from the birth to death of a person.
Symptoms of Hypermetropia may include blurred vision, watery eyes, asthenopia and headache. Hypermetropia can be treated by clinical examination & surgeries if necessary or can be managed by using a few vision aids such as prescribed eyewear.