Patient Learning Center
The eye is the organ that senses light and so is the basis of the sense of sight. Its role is basically to transform light energy into electrical signals that are sent to the brain via the optic nerve.
The human eye has a crystalline lens that is adjustable by distance; a diaphragm, whose diameter is called the pupil, covered by the iris, and the retina, a light -sensitive tissue.
Light enters through the pupil, goes through the crystalline lens and is projected on the retina, where photo receptor cells transform it into nerve impulses which are then transferred to the brain through the optic nerve.
Every part of the eye must work properly in order to have perfect vision; otherwise, eye diseases and refractive errors can cause vision defects.
It is advisable to have an annual comprehensive eye exam to detect the early signs of malfunction of the eyes. When detected early, it is easier to treat, correct and overcome any disease. It is also recommended that you read through the following information regarding your eyes that will help you to recognize the signs of possible diseases and so you can make an immediate visit to OCUCENTRO if necessary.
Structure and function of the eye
Structure of the eye:
- Cornea: is the clear and transparent front layer of the eye which refracts light rays as they pass through the pupil.
- Sclera: is the white external portion of the eye which, together with the cornea, forms the external covering of the eyeball.
- Iris: is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupil and, thus, the amount of light reaching the retina. It can be green, blue, grey or brown.
- Crystalline lens: is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract the light so it is focused on the retina.
- Pupil: is the opening in the center of the iris that allow light to strike the retina.
- Retina: is a light-sensitive layer of tissue, lining the inner surface of the eye. Light striking the retina initiates a cascade of chemical and electrical events that ultimately triggers nerve impulses. These are sent to various visual centres of the brain through the fibers of the optic nerve.
- Macula: oval-shaped pigmented area near the center of the retina of the human eye which allows detailed vision.
- Optic Nerve: is a paired nerve that transmits visual information from the retina to the occipital lobe of the brain, turning electric impulses into images.
In first place, the light enters the eye through the cornea, the outer portion of the eye. Due to the curvature of the cornea, the light rays deviate and this allows the light to pass through the pupil into the crystalline lens.
The iris (the colored part of the eye) and the ciliary muscles regulate the amount of light entering the eye. These movements make the pupil constrict when exposed to excessive light or dilate when there is less light.
When light strikes the curved surface of the lens it refracts and focuses on the retina. Then, the retina converts the light into electrical energy. This energy passes through the optic nerve to the brainstem and, finally, to the occipital lobe, where it becomes an image.
Some eye problems are minor and transient. Others may cause permanent vision loss.
Common eye problems include:
- Corneal Opacity
- Retina pathologies
- Refractive defects
- Deseases related to the eyelids.
This is the darkening or clouding of the natural lens of the eye (the crystalline). This opacity results in a distortion of the light rays passing through the lens, making objects appear blurry
Most cataracts are the result of the normal aging process of the individual and they progress gradually.
Cataract correction is relatively simple and could have extraordinary outcomes. The only treatment for cataracts is the surgical extraction of the cloudy crystalline. Cataract surgery depends on how much it affects your vision; you must not remove it just because it is there, just if it interferes in your activities.
Frequently asked questions:
What’s the best time to remove cataracts?
Most people think that the cataracts must be “mature” in order to be removed. This is no longer true, cataract surgery is a routine procedure that can be performed as soon as you notice that blurry vision is interfering with your quality of life.
What happens if cataracts are not treated?
Over time, the cloudy crystalline areas may increase in size and become more dense causing deterioration of sight. This can take several months to many years. The crystalline could become totally cloudy and cause blindness.
How do I know which is the best lens for me?
There is no such thing as the best lens for everybody. Only your ophthalmologist can say which is the most appropriate lens for you. Patients who have opted for an intraocular multifocal lens instead of a monofocal lens have expressed a higher satisfaction level and a better quality of life.
Can cataracts reoccur?
Once a cataract is removed, it can’t grow back. Nonetheless, over time, patients can complain about cloudy sight again. This condition is known as a secondary cataract. It can be easily and quickly treated by means of a simple procedure performed in the office.
Who can perform cataract surgery?
Only an ophthalmologist with a specialization in cataract surgery is able to carry out such surgery.
This is a fibro vascular tissue growth of the conjunctiva that is wedge-shaped and which slowly and progressively invades the surface of the cornea, manifesting as a “membrane” that is high and congestive in many cases. The rapidity with which the enlarging occurs varies and its growth can cause changes in vision.
Its cause is controversial. Exposure to sunlight (UV radiation) is accepted as being a causal factor. Others are: dust, wind, irritating chemicals and extreme temperatures.
Symptomatic treatment can be done with eye drops or ointment. If it is large enough to threaten sight or to cause persistent discomfort it must be surgically removed. Even after surgical removal, the pterygium may recur. Some factors that increase the risk of recurrence are being of black ethnic origin, and temporary location of the pterygium.
The cornea is a transparent tissue of the eye that transmits light, allowing us to see clearly. Light passes through the crystalline lens to the cornea in the same way as it does through a window.
When the cornea becomes cloudy, like a fogged glass, the light does not pass through the eye and the result is poor vision.
The only way to restore vision is to replace the cornea with healthy tissue from a healthy cornea. (Trasplante de córnea http://www.geteyesmart.org/eyesmart/diseases-es/opciones-de-trasplante-de-cornea.cfm).
This is a disease in which the optic nerve is damaged, altering the visual field. The most important risk factor is high eye pressure.
It is chronic, but vision can be saved with an appropriate treatment, although the lost visual field cannot be recovered. There are several types of glaucoma: open-angle; narrow-angle; closed-angle; normal tension; ocular trauma, neovascular; pigmentary; congenital or developmental. Control of glaucoma by medication can be effective only if the treatment plan prescribed by the doctor is followed fully. Treatment with Argon and Yag lasers is needed almost immediately in cases that cannot be controlled with medication. The success of the surgery depends on factors such as the type and extent of the glaucoma and the presence of other conditions.
If laser treatment does not work, surgery may be used under a microscope to create a new drain line.
The most common of these is diabetic retinopathy, a complication of diabetes caused by deterioration of the blood vessels that supply the eye. The retina is a nerve layer at the back of the eye whose function is to sense light and help send images to the brain. Damage to the blood vessels of the retina may result in leakage of fluid or blood, and the formation of irregular and fragile conduits and fibrous tissue. This may cause the images that the retina sends to the brain to become blurry or distorted.
In many cases, treatment is not necessary, but the patient will require periodic eye exams. In other cases, treatment will be recommended to stop the spread of lesions caused by diabetic retinopathy and, if possible, to improve the quality of sight.
For the eye to be able to produce a completely clear picture, the light rays entering through the pupil and cornea, and from there to the lens, should be focused precisely on the retina. When these light rays do not focus directly on the retina but elsewhere this is known as a refractive error. To correct or eliminate such errors it is necessary to perform a surgical procedure using a technique called “Lasik”.
MYOPIA is a refractive error in which the rays of light focus in front of the retina, resulting in a blurred image. Myopia can be produced by a curved cornea or an eye that is too long. The most common symptoms are poor long distance vision but good short distance vision.
FARSIGHTEDNESS is a refractive error in which the rays of light focus behind the retina, also producing a blurred image. It is usually produced by a very flat cornea or by the patient having a short eye. Its most common symptom is poor short distance vision.
ASTIGMATISM is a refractive defect in which there are several points either in front or behind the retina. It may be accompanied by myopia or farsightedness. It is generally produced because the cornea has an oval shape, which generates image distortion.
PRESBYOPIA literally means “aging eye”. It is an eye condition related to age which hinders the ability to see things up close. When you are young, the crystalline is soft and flexible. It changes its shape easily, allowing you to focus on near and far objects. After the age of 40, the crystalline becomes stiffer. Because the lens cannot change shape as easily as before, there may be difficulty in activities such as reading or seeing things at close range.
This is the inflammation of the conjunctiva layer, the mucous membrane that covers the eyelids and extends to the front of the eyeball.
According to its cause, the conjunctivitis might be:
- Bacterial: In bacterial conjunctivitis pink eye symptoms are usually associated with tears greenish or yellowish color. They are characterized by abundant and yellowish discharge, and formation of buds on the palpebral conjunctiva. It is very contagious, can be cured between 7 and 10 days after onset of symptoms.
- Viral: are the most common, usually produced by adenovirus, with less crusts but with possible painful corneal involvement. They are produced by transmission through the hands, towels or even sneezing.
- Allergic: typically seasonal, are distinguished by having a significant itching, watery crusting and having frequent association with sinusitis.
- Foreign body. The misuse of contact lenses, or not having them properly disinfected, facilitates the introduction of microbes causing conjunctivitis.
- Traumatic. Hits and scratches make it easy to develop conjunctival infections
Deseases related to the eyelids:
The eyelids are responsible not only for protecting the eyes, but also to help in expressing emotions that are reflected on our face.
It has always been said that the eyes are the mirror of the soul, but as the years pass, the eyelid skin becomes flaccid, starts falling and the eyelid muscle weakens.
Along with this sagging, on many occasions fat bags start showing. Sagging skin and muscle give a tired, sad and aged appearance to the face.
Blepharoplasty is surgery to remove or reposition fat pockets and dry unwanted skin on the eyelids, to rejuvenate the eyes.
Its purpose is to mitigate the effects of age on our looks and to extend the visual field. This procedure can usually be performed under local anesthesia assisted by intravenous sedation and, thus, it may be carried out on an outpatient basis. The approximate surgery time is 50 minutes for partial surgery (upper or lower) and 90 minutes for the complete (upper and lower).
When to see your Ophthalmologist:
The eyes are a part of thebody which requires special attention. Through its controlled examination you can not only prevent and correct diseases of the eyes, but also other diseases that are evidenced by gaps and changes in vision.
The best defense is to have regular eye checkups, because eye diseases do not always have symptoms.
Early detection and early treatment can prevent blindness.
If you experience sudden changes in vision, blurred vision or see flashes of light, seek immediate help from a professional eye care specialist.
Everyone should visit an ophthalmologist at least once a year to review their eye health holistically, more so if they meet any of the following characteristics:
- Baby born before 36 weeks of pregnancy
- Child under 5 years, more so if referring some visual difficulty
- Anyone over 40 years of age
- Suffer frequent headaches or migraines
- High cholesterol
- Family history of glaucoma
“Through the eye we perceive the world; we see our dear ones, appreciate beauty and get to know everything that surrounds us. 50 % of the information we receive about the environment comes through our eyes.”