Medical Questions & Answers » color blindness

Eyesight : Spectacles

medicalquestions — Thu, 19 Jun 2008 06:00:08 +0000

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

medicalquestions — Sun, 01 Jun 2008 06:00:32 +0000

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.

Pterygium in the eyes

medicalquestions — Sun, 01 Jun 2008 06:00:22 +0000

Question: I would appreciate your opinion on the cause of a pterygium in the eyes. Some say it is glare, others sand or other foreign matter in the eyes. How is this condition caused, and how do you prevent it?
A pterygium is a fleshy overgrowth of the white part of the eye (cornea) that grows across the colored part of the eye (iris). They develop very slowly over many years, but once they are half way across the iris, they should be removed in a simple operation to avoid growth across the pupil and blindness.
Pterygium are very common in Australia, but more so in the north than the south, as they are caused by recurrent mild sunburn to the cornea. The irritated tissue overgrows, and spreads across the eye. Farmers, sailors, drivers, outdoor workers and sports people are most prone to pterygium as glare and sun exposure are the prime cause. The problem can be prevented by wearing good quality (polarized) sun glasses.
A pterygium may become irritated, red and itchy at times. Simple drops available from chemists will ease this problem. Once present they will remain until removed surgically. There are no drops that will make them go away.

Question: My mother is having a vitrectomy. What sort of operation is this?
The eye contains a clear jelly-like substance called the vitreous. If this becomes discolored, the vision in that eye will be remarkably reduced, possibly to the point of blindness.
The most common cause of discoloration of the vitreous is bleeding into the eyeball. This can occur in high blood pressure, diabetes and injury. In the last few years, a very delicate operation has been devised in which the blood-stained vitreous can be removed from the eye and a new artificial substance substituted, allowing normal vision again. It is performed under a general anaesthetic by an ophthalmologist (eye doctor) who has had specialist training in this procedure.

Treatment of Glaucoma

medicalquestions — Fri, 30 May 2008 09:45:48 +0000

Question: My mother has been diagnosed as having mild glaucoma, but all the doctor has done is give her some eye drops. How is glaucoma treated?
Your sight is one of your most valued possessions. Any disease that can reduce your vision, or worse still, make you blind, is of great concern. One such disease is glaucoma.
Glaucoma is an increase in the pressure of the fluid inside the eye. If this pressure becomes too high, the eye can be permanently damaged. It is diagnosed by measuring the pressure inside the eyeball. There are two methods of measuring the eyeball pressure. In the older method, special drops to numb the eye are used, and then an instrument is rested on the eye for a few seconds. A more sophisticated method is to use a machine that puffs air onto the eye for a fraction of a second and measures the amount of air pressure reflected from the eye. Both can give very accurate measurements of the eye pressure. Looking at the outside of the eye at different angles, and examining the back of the eyeball with a magnifying instrument also help make the diagnosis. There are more than 20 different types of glaucoma, with different causes and therefore different treatments. It is a complex area, that once suspected or diagnosed, is best dealt with by an ophthalmologist (specialist eye doctor).
Treatment involves the use of one or more eye drops on a regular basis, every day, usually for the rest of the patient’s life. Some types of glaucoma may also require the taking of tablets. Occasionally the disease settles spontaneously in old age. Glaucoma cannot be prevented, but it can be controlled successfully in nearly all patients, and sometimes it can be cured by surgery. The surgery increases the rate of drainage of fluid from the eye, and may involve the use of lasers to burn microscopic drain holes in the corner of the eye. With modern treatment techniques, the outcome for patients with glaucoma is normally very good, but continued follow-up by a doctor is essential.

Causes of Glaucoma

medicalquestions — Fri, 30 May 2008 09:27:12 +0000

Question: I have just been diagnosed as having glaucoma. My mother had it too. What causes this disease?
Your eyeball contains a transparent liquid that has the consistency of half-set jelly. This liquid is produced by special cells that sit just behind the iris (the colored part of the eye). There is a slow circulation of this fluid around the eyeball and out through the pupil to the area in front of the iris. Here the fluid is absorbed back into the bloodstream.
The fluid in the eyeball is under pressure to maintain the shape of the eye and prevent distortion of the light waves entering the eye. If the pressure of the fluid increases, the light-sensitive cells inside the eye will be damaged and vision will decrease possibly to the point of blindness. Glaucoma is the disease caused by an increase in the pressure of the fluid in the eye. The most common type of glaucoma has a slow onset over many months or years. The patient may not be aware that there is anything wrong unless a routine test by a doctor detects it.
Unfortunately, the first symptom is often deteriorating vision, and by then it may be impossible to reverse the existing damage, but any further damage can be prevented by the correct treatment. There is an hereditary tendency to this type of glaucoma, and anyone who has parents with glaucoma should have their eyes checked every couple of years after the age of 35.

Question: What is color blindness?
The normal form of color blindness is an inability to differentiate between the colors red and green. In some men, other colors may be involved, but only rarely is all color vision lost with the person seeing in black and white. Color blindness is hereditary, and occurs nearly always in men.
Special cards covered in colored dots, with numbers hidden amongst the dots, are used by doctors to diagnose the condition. There is no treatment available, but most patients can live quite happily with the problem, and may have adapted so completely to the problem, that they are not aware of its existence. Those planning a to work as an electrician or commercial pilot, or in some other areas where color differentiation is vital, may not be allowed to undertake these careers.

Pterygium in the eyes

medicalquestions — Fri, 02 May 2008 06:00:46 +0000

Question: I would appreciate your opinion on the cause of a pterygium in the eyes. Some say it is glare, others sand or other foreign matter in the eyes. How is this condition caused, and how do you prevent it?
A pterygium is a fleshy overgrowth of the white part of the eye (cornea) that grows across the colored part of the eye (iris). They develop very slowly over many years, but once they are half way across the iris, they should be removed in a simple operation to avoid growth across the pupil and blindness. Pterygium are very common in Australia, but more so in the north than the south, as they are caused by recurrent mild sunburn to the cornea. The irritated tissue overgrows, and spreads across the eye.
Farmers, sailors, drivers, outdoor workers and sports people are most prone to pterygium as glare and sun exposure are the prime cause. The problem can be prevented by wearing good quality (polarized) sun glasses. A pterygium may become irritated, red and itchy at times. Simple drops available from chemists will ease this problem. Once present they will remain until removed surgically. There are no drops that will make them go away.

Question: My mother is having a vitrectomy. What sort of operation is this?
The eye contains a clear jelly-like substance called the vitreous. If this becomes discolored, the vision in that eye will be remarkably reduced, possibly to the point of blindness.
The most common cause of discoloration of the vitreous is bleeding into the eyeball. This can occur in high blood pressure, diabetes and injury. In the last few years, a very delicate operation has been devised in which the blood-stained vitreous can be removed from the eye and a new artificial substance substituted, allowing normal vision again. It is performed under a general anesthetic by an ophthalmologist (eye doctor) who has had specialist training in this procedure.