The normal eye is a perfect sphere. This is called emmetropia. Clear vision is possible because the cornea, lens and retina work together perfectly. Light rays enter the eye through the cornea (clear, front surface of the eye), pass through the lens and are focused on the retina.
Myopia or nearsightedness occurs when light rays are focused in front of the retina instead of directly on the retina. This occurs when the cornea is too steep or the eye is too long. When light is not focused directly on the retina, images appear blurry. Glasses or contact lenses are needed to focus images clearly on the retina.
Hyperopia or farsightedness occurs when light rays focus behind the retina.
Most people who are farsighted are not aware of it when they are young. The innate accommodating (focusing) power of the eyes often compensates for farsightedness until adulthood or sometimes until the forties or fifties. Eventually glasses or contacts are needed to focus images clearly on the retina.
Astigmatism occurs when the light rays are focused at more than one point on the retina. With astigmatism, the curvature of the cornea is not the same in all directions. Like a football, the curves of the cornea may be steep in one direction and less steep in the other. Because of that, the vision is distorted and a person sees more clearly in one orientation than the other. For example a person with astigmatism sees the vertical part of the letter T clearer than the horizontal, or vice versa. A person also may have astigmatism along with Myopia or Hyperopia.
Presbyopia occurs when a person reaches a certain age, generally in the mid 40's. It is part of the natural aging process. Before the onset of presbyopia, the human lens has the ability to flex and change focus and to vary its optical power, permitting those with normal vision to view distant objects and refocus their eyes to see near objects sharply. This ability begins to decline after the age of 40 with the onset of presbyopia (which literally means "old eye") when the human lens starts to lose its flexibility.
Presbyopic individuals with previously normal vision require reading glasses to see for near, while nearsighted and farsighted patients require bifocals for clear viewing at both far and near distances. The most common way to treat presbyopia is with bifocal or multifocal/progressive glasses or contact lenses.
People who are nearsighted often notice that they can see well for near and read fine print comfortably without glasses or any corrective lenses well past the age of 40. Although nearsightedness patients still require corrective lenses for distance, they can take off their lenses to see for near. Since removing glasses or contact lenses every time you want to read is inconvenient, most nearsighted patients prefer to wear bifocal or progressive/multifocal glasses or contact lenses.
Bifocal lenses allow the user to view distant objects through the top portion of their lens, and to view near objects with additional magnification added to the bottom portion of their lenses. Multifocal or progressive lenses take the concept of many lenses (and many prescriptions) to the extreme and provide sharp vision at all distances by progressively adding magnification to the lens. Multifocal/progressive lenses do not have a line that separates the distance prescription from the near prescription, which many patients find cosmetically more pleasing than bifocal lenses with a line. There are many visual and functional advantages to multifocal/progressive and the opticians at sacramento Contact Lenses and Optometry will be happy to discuss your particular multifocal needs based on your prescription, lifestyle and occupational requirements.
Contact lens wearers have many options with regard to presbyopia including bifocal or multifocal contact lensesand something called monovision.
The term keratoconus is derived from two Greek words: "kerato", meaning cornea, and "konos", meaning cone. Keratoconus is a disease of the cornea in which the cornea looses its natural round shape and becomes distorted with cone-like bulging, progressive thinning, and associated reduction in vision quality. Keratoconus is a progressive disease that can range from very mild to very severe. The progression is generally slow and may stop at any stage. Keratoconus is one of a group of corneal degenerations that is characterized by corneal thinning. These conditions are termed "Ectasias" of the cornea.
Causes of Keratoconus
Although we have been aware of keratoconus for over two hundred years, we are still not certain about the cause of keratoconus. We are fairly certain that it is genetically programmed and family history is a risk factor. About 7% of patients with keratoconus have known relatives with the disease. Generally speaking, there is about a 1 in 10 chance of a patient with keratoconus having an offspring with the disease (unless there is evidence of keratoconus in successive generations, which increases the probability level). Additionally, there may be links to the endocrine (hormonal) system in that keratoconus tends to appear in its early stages at puberty. Associations with allergy ("atopy") are common as well. Currently there are a number of studies going on in terms of determining the underlying causes and associations of and with keratoconus.
The incidence of keratoconus is not well known, but an approximation is that about 1 in 2,000 persons in the general population have keratoconus. This is a relatively high number in terms of disease rates. Keratoconus is a relatively common eye disease. Because contact lenses are the primary treatment of keratoconus our doctors at Sacramento Contact Lenses and Optometry have successfully treated and followed for years hundreds of patients with keratoconus. Our expertise and experience in keratoconus has earned us referrals from other doctors across the United States and from abroad.
With new technologies that measure the shape and thickness of the cornea in exquisite detail, we are now able to detect the presence of keratoconus well before subjective symptoms develop. Corneal Topography has become the standard of care in diagnosing keratoconus. A computerized system images the shape of the cornea by taking tens of thousands of data points from the corneal surface. The results are instantly analyzed and a topography map is generated. The colors of the map correspond to the shape of the cornea. In keratoconus the cornea tends to be very steep in shape and quite irregular in shape. Quantitatively the topography values can be monitored for change over time to determine if the condition is progressive. Sacramento Contact Lenses and Optometry is proud to use the most advanced corneal topography system since 1994.
Most cataracts are part of the normal aging process. A cataract forms when the natural lens of the eye becomes clouded. The cause is usually unknown but can result from exposure to ultraviolet light, injury, heredity, disease and advancing age.
Opacification of the lens causes vision to become dimmer and fuzzier. As it occurs gradually patients are often unaware that the quality their vision is deteriorating. Your doctors at Sacramento Contact lenses and Optometry routinely examine your eyes for changes in the clarity of your lenses and presence of cataracts.
In the early stages of cataract development vision can usually be improved by changing your eyeglasses prescription. We recommend that patients with cataracts see their eye doctors every six to twelve months to monitor their vision and "fine tune" their prescription.
Eventually, changing the eyeglass prescription is no longer sufficient to maintain good vision. Surgical removal of the cataract may be indicated if blurring of the vision interferes with normal daily activities (reading, driving, etc.).
A cataract is removed using microsurgical techniques. A small (3.0 mm) incision is made into the eye. This incision is so small that, in most cases, it is self-sealing and sutures are not required. The most advanced technique for removing a cataract is called phakoemulsification. In this procedure an ultrasound probe is placed into the cataract. The probe vibrates at a very high speed (20,000 to 40,000 cycles-per-second), which breaks the cataract into many tiny pieces. The pieces are removed using aspiration through a small tube.
Once the cataract (clouded lens) has been removed it is replaced with a new, clear lens. This lens is called an intraocular lens implant (IOL). The implant (with a diameter of approximately 6 mm) is folded in half and then inserted into the eye through the original (3 mm) incision. The implant enables patients to see well without having to wear thick, heavy eyeglasses.
The cataract procedure is most frequently performed under local anesthesia in an outpatient surgery facility. It does not require a stay in the hospital. Sedation is given to most patients to help them relax. The procedure is performed in about 30 to 45 minutes. Thanks to the anesthetic, patients do not feel or see the surgery.
After the procedure patients are instructed to spend a day relaxing at home. Most patients return to normal activities the day following the surgery.
The Results of Cataract Surgery
Cataract removal with insertion of an intraocular lens implant is performed over one million times each year in the United States. It is one of the safest surgical procedures known to modern medicine. As with any type of medical procedure there is always the possibility of complications. The rate of complications is extremely low.