Posts Tagged ‘color blindness’

Eyesight : Spectacles

Thursday, June 19th, 2008

Alternatives to spectacles: There are four main options available to overcome the disadvantages of spectacles:
Contact Lenses
These are small polymer lenses, which are placed directly over the cornea. They are of two main types — soft and semi soft. Soft contact lenses are pliable and therefore very comfortable, but require utmost meticulous care and maintenance. Infections and allergy (GPC : giant papillary conjunctivitis) are the likely complications. Semi soft lenses (or Rigid Gas Permeable) are rigid and thus, initially, slightly uncomfortable to wear, but they do not require too much care. Complications like infection and allergy are uncommon with these lenses. However, in the Indian context infection, GPC, mishandling, dust and pollution associated conjunctivitis continue to be major causes of contact lens intolerance. Patient compliance is generally not satisfactory relating to the lens care and maintenance schedules.
• High degree of astigmatism cannot be corrected by contact lenses.
• Extended wear lenses are not suitable for Indian conditions.
• Hard lenses are obsolete and should not be used as they prevent oxygen supply to the cornea.
Refractive Kartotomy (RK)?
This is an operation where 4 to 8 (rarely 16) incisions are made on the cornea using a diamond knife. This results in flattening of the complications caused by RK.
Excimer LASER (PRK) technique
Using a computer controlled LASER (mostly Argon Fluoride 193 nm) the surface of the cornea can be reshaped imparting a predetermined curvature. This leads to correction of both myopia and hypermetropia, and also moderate amount of astigmatism, the procedure is short and simple and being computer controlled is highly accurate. The patients suitable for PRK are the ones above 18 years of age, with refractive error between 1 to 6 D and whose error has been stable for the last 1 year. There should not be any other complicating factor or disease in the eye. PRK, although a little expensive, is relatively safe in comparison to RK. The complications are postoperative pain (due to removal of epithelium during surgery), prolonged healing time and need to use steroids, slight corneal haze and late regression of the effect seen in some patients. It is not useful for high refractive errors and high astigmatism.
LASIK is an acronym for Laser Assisted In-situ Keratomileusis.
It combines all the advantages of the above procedures and virtually eliminates all their disadvantages. In LASIK an ultra-thin flap/ layer of cornea is raised using an automated cutting device called the microkeratome, and then Excimer laser is delivered to reshape the corneal stroma (inner layer of cornea) into desired curvature. The flap is repositioned back where it self seals without any stitches.

Cataract Operation

Sunday, June 1st, 2008

Question: My GP said that I have a cataract and It will need an operation. Is this the best treatment for a cataract?
Behind the pupil in your eye is the lens. This is transparent and able to change its shape with the aid of tiny muscles attached to its edge. The change in shape enables it to focus on objects near and far.
A cataract is the clouding over of this lens. Once the vision has deteriorated sufficiently to cause significant sight impairment in both eyes, the worst eye will be operated upon, because this is the only way of treating a cataract. There are no medications or drops that will help. The operation is technically difficult, but can be completed in half an hour and is often done under local anesthetic. The cloudy lens is removed, and a new clear plastic lens is inserted. This new lens is not mobile, and cannot change shape, thus spectacles are normally required for close work, and sometimes distant vision as well.

Question: What is the best time to have a cataract operation? When it is only slightly annoying, or should I wait until later?
A cataract is the slow clouding of the lens in the eye, until it becomes like frosted glass, and impossible to see through.
There is no urgency about having a cataract operation until your sight has deteriorated to the point where glasses are unable to compensate for the clouding of the lens. Usually one eye deteriorates faster than the other, and when reading, driving or other skills become difficult, the worst eye will be operated upon. Only very rarely are both eyes done at once.
Once the bad eye has recovered, the other eye will be treated, and most patients find a dramatic improvement in their sight. One of the most common comments by patients after a cataract operation is that they find colors far brighter and more vibrant. The slow progression of the cataract over many years has had the same effect as slowly turning down the color control on a television to give a very washed-out effect.