Medical information gathered by Dr. Marco Abbondanza on experience with ocular surgery
(Myopia, Hyperopia, Myopic Astigmatism, Hyperopic Astigmatism)
Myopia
The most common worldwide visual impairment is myopia. 25-30% of the Italian population is affected by this problem.
Myopia means eyesight is difficult from afar and good from near. Myopia is measured in diopters. A low level of myopia measures up to four diopters, medium from seven to eight, while anything more than that is considered to be a high level. Myopia is usually due to an eye's excessively long shape. This is the reason that images are in front of the retina and not on it when the cornea and crystal put them into focus.
Astigmatism
Astigmatism is a visual impairment caused by an irregular curve of the cornea. The first and foremost lens of the eye is the cornea. Its shape is spherical meaning it should curve the same way on each axle. An astigmatic eye has curves which differ depending on the area. 5% of the Italian population is affected by astigmatism.
The astigmatic patient has difficulty seeing both far and near, depending on whether the problem is myopic astigmatism or hyperopic.
Hyperopia
 |
Hyperopia is a visual impairment which is the opposite of myopia. In hyperopia either the cornea is too flat or the eye is not long enough, so that images come into focus behind the retina and are therefore blurred.
10% of the Italian population is affected by hyperopia.
A person who is hyperopic has difficulty seeing things that are near and can only see well through an accommodation. This is a focusing mechanism caused by the movement of an internal eye muscle. This mechanism works only in youth and where the impairment is not high.
Presbyopia
Our eyes are capable of detailed vision at various distances, this capability is provided by a complicated and marvellous focus mechanism. This physiological system requires the continuous action of a small muscle that is located in our eyes, the ciliary muscle. The contraction of the ciliary muscle modifies the power of the main intraocular lens, and thus, modifies the total dioptric power of the eye allowing variable focus of our vision.
With advancing age, the efficiency of the ciliary muscle diminishes because of a progressive hardening of the crystalline lens, hence, reduction of lens flexibility combined with an actual weakening of the ciliary muscle reduces our capability of near vision. The process is gradual and starts in the fourth decade of life but a great individual variability exists.
The difficulty of near vision is initially greater for the smallest characters, for the nearest distances, and in dim lighted conditions, but sooner or later the necessity for an optical correction will arise.
Reading spectacles must be prescribed by the ophthalmologist after a thorough examination that aims to ascertain the complete health and well being of the visual apparatus.
In fact, certain ocular disease conditions can present initially with the same symptoms of presbyopia. Most often, ocular lens cataract or age related retinal diseases may considerably diminish near sight and create reading difficulties.
An important , but frequently overlooked problem is the customized , task oriented, prescription of near sight spectacles, a near spectacle allows good vision in a narrow distance range; this distance must be applied to the patients reading or work distance , and must also be ergonomically correct, not too near nor too far from the observed object
Patients that already wear prescription glasses may find bifocal or progressive focus glasses more convenient, as the use of two glasses, for near and far can be annoying and difficult. However, the patient must be informed that the adaptation to progressive spectacles is individually variable , and that the process may take considerable time and patience.
In presbyopia, the strength of the prescription must be increased over time to correct the gradual reduction of near sight that increases steadily and stops approximately at the age of 65. Furthermore, the difficulty of near vision may fluctuate during the day, depending on the lighting conditions, ocular fatigue, and physical conditions of the moment.
The age of onset is also variable, depending on the individuals ocular condition. For example, a hyperopic patient will develop presbyopia much sooner than a myopic patient. Patients with low degree myopia often notice increasing difficulty to read with their regular glasses and develop the habit of removing their glasses for reading. In these patients presbyopia, although present, is “hidden” by pre-existing myopia.
In conclusion, presbyopia consists in increasing difficulty for near vision and must be corrected by the use of prescription glasses, a careful ophthalmologic examination is always necessary to rule out other eye disorders that may cause similar difficulties of near vision.
Correcting visual impairments
Myopia, hyperopia and astigmatism can be permanently corrected through different surgical techniques. An important part of a surgeon's job is to select the best technique for each patient. Remember: THE FOREMOST ISSUE IS THE PATIENT'S WELL-BEING.
Eyeglasses
Eyeglasses are a valid solution when the impairment is not high. With medium or high impairments, the lenses are heavy and unattractive and often produce distorted images, making them an unsatisfactory solution.
Contact lenses
Practically all problems having to do with eyeglasses are overcome through use of contact lenses.
They've represented a giant step forward in correcting optical problems in visual impairments, especially in astigmatism or medium to high levels of myopia.
Not everyone tolerates them especially if worn all day. Many people become intolerant to contact lenses even after years and must quit using them.
Contact lenses also require great care to avoid risks of corneal infection which can weaken vision.
