mm 10mm % 4,000 CGCC VISION AUG

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谱淑郁
7 years ago
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2 mm 10mm % 4,000 CGCC VISION AUG

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4 Modern Cataract Treatment A common eye disease, cataract can affect a patient s vision in its early stage, and can result in loss of sight in serious cases. Thanks to advancement in medical technology, cataract can now be removed with surgical implantation of artificial lens, which can correct refraction together

5 What is cataract? Dr Arthur Cheng, Specialist in Ophthalmology at Hong Kong Sanatorium & Hospital and Member of the Cataract Concern Alliance, explained, Under normal circumstances, the crystalline lens in our eyes can focus light onto our retinas to form clear images. If the lens turns cloudy, light passing through the eyes cannot focus precisely and a cataract is said to have developed. At its later stage, the lens will appear white or pale yellow. The vision of a cataract patient is foggy and fuzzy. The commonest cause for cataract is natural ageing of the lens. Cataract can also be caused by hereditary or other congenital causes. Diabetes, prolonged intake of steroids, over exposure to ultraviolet lights, eye injury, etc. can accelerate cataract. A study by the Chinese University of Hong Kong has revealed that people with high myopia are four times more likely to develop cataract than people with normal vision. Early Treatment Called For Patients with cataract have blurry vision, but such a symptom is an indication that the disease has entered its final stage. Dr Cheng stressed that when cataract starts to form, there are some subtle changes in vision that should not be overlooked. Examples are: (1) dimmed color vision (similar to discoloring of clothes), (2) blurry vision with black spots, (3) sudden progression of myopia, (4) glare or dazzle from light sources such as street lights and headlights at night, (5) double vision, and (6) fear of light. Table 1: Different Choices of IOLs Suit Patients Needs Types of IOLs Monofocal Astigmatism correction monofocal Multifocal Astigmatism correction multifocal Relevant Vision Problems Cataract and myopia Cataract, myopia and astigmatism Cataract, myopia and presbyopia Cataract, myopia, hyperopia, astigmatism and presbyopia Features Design: A single focus at the middle of the lens for focusing; various myopic diopter options available; two extrusions on the sides to prevent the lens from slipping. Post-surgery vision: Clear distant vision, glasses required for seeing near distance objects; astigmatism correction needed in glasses. Design: Two different levels of diopters to mitigate myopia and astigmatism; axis marking dots on the lens for gauging during implantation to offset the astigmatism. Post-surgery vision: Clear distant vision; glasses needed for those with presbyopia. Design: Spherical aberration on the center of lens provide different correction levels; dividing light into two parts (one for distant vision, the other for focusing on near objects) to correct presbyopia. Post-surgery vision: Clear distant and near vision; glasses not needed in most cases, except that glasses or light adjustment needed in case of inadequate lighting. Patient might see halos of light in the dark after surgery, which takes some time to adjust to. Design: Both axis marking and spherical aberrations included. Post-surgery vision: Glasses not required in 80-85% of the cases; a very few people need them in dim light conditions. Fully developed cataract can either be a completely white or a completely black lens. The former can be treated by surgery, whereas the latter can be quite surgically challenging. In the past, surgical intervention of cataract requires complete removal of the patient s lens. This can only be done after the cataract has fully developed. Now that minimally invasive procedures have become available, surgical removal of cataract can be done as soon as it begins to impair vision. The later the surgery, the higher the difficulty and the risk. Fully developed cataract can lead to acute glaucoma, inflammation, or even blindness. Those having the above symptoms should therefore seek treatment without delay. Low Risk from Minimally Invasive Surgery Today s cataract patients need not worry too much, as modern cataract treatments are safe and simple. In a minimally invasive surgery, a high precision phacoemulsifier will put into the eye through a 2.2mm incision to break up the clouded lens. Emulsified pieces are then aspirated out with suction, followed by an implant of an intraocular lens (IOL). The IOLs used in the last generation of the procedure were about 10mm in diameter and hence, required a larger incision. New IOLs can now be folded up before implanting into the eye through the small incision. After that, it will expand itself to perform a lightfocusing function. The major risks in cataract surgery are bacterial infection and macula edema. The surgical incision is much smaller in size compared to that in old procedures and need not to be stitched. The risk for complication or serious hemorrhage stands at only 1 in 1,000. In addition, the smaller incision also helps preventing the cornea from deforming after the surgery. According to Cheng, it only takes 15 to 30 CGCC VISION AUG

6 minutes to complete the surgery. Patients can go home on the same day, and resume their normal life the next day. About 20-30% of the patients may suffer from secondary cataract, i.e. thickening of the membrane on the back of the lens, which may blur their vision. Yet, the condition can be treated with laser - no further invasive surgery is needed. IOLs can Correct Refraction Myopia, hyperopia, astigmatism and presbyopia, which are very common among Hong Kong people, are collectively known as refraction. Myopia is a condition when the eye has problems focusing on long distance objects. On the contrary, the focus of hyperopia patients fall behind the retina, as a result, they cannot see close or distant objects clearly. Astigmatism is a refraction error with distorted vision caused by an irregular cornea. Presbyopia, a condition in which patients cannot see close objects clearly, is attributable to the weakening of ciliary muscles that impairs the focusing control of the lens. Custom-made lens are now available to suit different curvatures and lengths of the eyeball, meaning that refraction symptoms can simultaneously be corrected during lens implantation. There are four main types of IOLs: monofocal, astigmatism correction monofocal, multifocal and astigmatism correction multifocal (see the table 1 for more details). How to Select a Right Lens An IOL is very much like a contact lens - its price varies with brands and functions. When selecting a lens, a patient should look mainly at its material, as well as his affordability and needs. The most expensive one is not necessarily the best one. At present, IOLs are imported and the materials have been in use for more than 10 years. About 40 million patients around the world have implanted this type of lens. The materials of the lens do not age easily and remain in good condition years after being implanted into children with congenital cataract. Prior to a surgery, an ophthalmologist would conduct a detailed eye examination for his patient. He would measure the vision, the corneal curvature, the anterior chamber s depth and eye pressure, check the back of the eye, and draw a map of the cornea surface. These are done to observe any surface irregularity on the cornea and decide on which type of IOL should be chosen. Cheng added that, the most basic monofocal IOLs are suitable for almost every one, while the more feature-packed multifocal variations are not. For example, patients with retina problems, diabetic retinopathy, water retention and macular degeneration are generally more suited for the monofocal type. Other factors to consider include life habits, work needs, preferences on vision quality, dependency on glasses, etc. This article is for reference only. Readers are recommended to seek professional medical advice for any questions on cataract

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