Common Eye Problems
A bent concave lens is used to bring the focus on the retina to restore clear distance vision.
However, the myopic eye can still see near objects clearly without any correction depending on the distance of the near objects in relation to the degree of myopia.
In adults, this condition will cause deterioration of distance vision and near visual problem due to the gradual loss of focusing ability of the eye. A bent convex lens is used to bring the focus back onto the retina.
In children, distance vision is often not affected because of the active and strong focusing mechanism, the eyes have ability to bring the focus back onto the retina. However, for higher degrees of hypermetropia, it may cause blurred vision, headache, and even converging squints. These problems will be aggravated when doing near works which required greater focusing power.
It's important to detect
and correct the medium to high degrees of hypermetropia for children under
6 years old. If uncorrected, it can lead to Amblyopia.
Astigmatism is a refractive error where distant object comes into two focal lines perpendicular to one another. These lines may lie in any orientation and any position in relation to the retina. This is primarily due to the aspherical (toroidal) corneal shape.
A bent lens with a toric surface is used to correct this condition.
Astigmatism may occur by itself or may occur with one of the refractive errors but in most cases are less than 2.50 dioptres. Although for a similar degree of defect, astigmatic eyes suffer less blurness than the other refractive errors, uncorrected astigmatism often leads to eyestrain and headache due to the focal lines formed in the eye cause the eye's focusing mechanism under strain as it constantly exert effort for best possible focus.
on young children can also lead to Amblyopia.
Presbyopia is the condition where one reaches early forties, his crystalline lens starts to lose its elasticity and gradually hardening hence its focusing power diminishes, the eye finds focusing on near objects difficult.
If the presbyope has good distance vision, he will naturally hold the reading material progressively further away for clear vision. Correction is with the convex lenses of usually less than +3.00 dioptres, in the form of single vision "reading glasses" or progressive power lenses. Reading glasses is only used for reading or near visual tasks.
If he is medium or low myopic, he will remove his spectacle in order to see near objects clearly.
power lenses, which enable distance, intermediate and near vision with
the same spectacle, is the most convenience for people who find switching
spectacle from distance vision to reading a nuisance.
A child's visual development continues till he reaches the age of about 6 years old. If there is a lack of proper stimulation to any eye during this critical period from the conditions of refractive errors, squints or cataract, the visual development of that eye will be retarded, and he will also not be able to develop stereoscopic vision.
Early detection and treatment
is important to prevent amblyopia. Once amblyopia is established after
the critical period, sub-normal vision cannot be corrected.
Strabismus (Heterotropia, Squint or Crossed eyes) is a condition of any abnormal alignment of the two eyes and is most commonly horizontal - when one eye is looking at an object, the other eye turning horizontally to another direction.
This condition can occur at any age.
The intact co-ordination of the neural pathway from the brain to the external eye muscles provides us the normal binocularity and stereoscopic vision. When this neural pathway or the external eye muscles are disrupted, strabismus results and the sufferer sees double images.
In children, the brain
will learn to suppress the more deviated image thus eliminate the double
vision, although the squint remains. This will lead to amblyopia of the
deviating eye due to disuse, as a result of the continuing mental suppression.