Cataract is opacities of the lens inside the eye. The human eye has a lens inside it, located behind the iris. The lens is the “zoom” of the eye and it helps focusing the light rays on to the retina.
With age, this lens becomes larger and harder and eventually gets different degrees of opacities. These opacities block some the light rays reaching the retina to different degrees and cause blurred vision. These opacities could be located at the peripheral part of the lens and have minimum effect on vision. On the other hands, they might be located in the central part of the lens and have huge impact on vision despite the limited size of the opacities. The central type of cataract gives often blurred reading vision and glare while driving at night despite having good distance vision. Having said that, the above symptoms are not limited to this type of cataract.
Most of people will develop age-related cataract over the spam of their life. It is thought that the age when age-related cataract might develop is from 40 years old onward, thought the most common age is 60 years old onward.
- Gradual deterioration of vision: distance, reading vision or both. Sometimes people notice that they need more light to see better. Also some patients, find that is becoming more difficult to distinguish colours
- Glare while driving at night or in sunny days
- Double vision or more commonly shadow around things. This usually persist even if you cover the other eye
- Seeing better for reading with the affected eye without glasses: Due to the increased size and hardening of the lens, the cataract could make the affected eye short-sighted and hence make the eye see better for reading without glasses. Over time this usually gets worse. For the same reasons i.e. increase size and hardening of the lens, some patients have to change their glasses more often to keep satisfactory vision.
Causes of cataract
The most common cause of cataract development is age. It is a “natural history” development and all of us at some point will develop cataract but the development of cataract is not an indication for cataract surgery (please see below the indication). There are other causes for cataract development like injury, different medicines side effect and congenital (born with cataract).
Indications for surgery
The indication for cataract surgery is patient’s dissatisfaction with her/his vision enough to justify the small risks of surgery. Nowadays, we do not wait for the cataract to “ripe” nor “until it is ready to be removed”. The technology and techniques of cataract surgery has developed enough to offer surgery when the patient is bothered with his/her cataracts.
There are rare other indications for cataract surgery like helping reducing the intra-ocular pressure in some circumstances, or to balance the refraction (the power of glasses) with the other eye. It is also done for refractive reasons for instance in high short-sighted or long-sighted people who are not willing to wear thick glasses or contact lenses and who are happy to accept the small risks of surgery.
Like anything in medicine, there are many risks involved in cataract surgery, some of them are insignificant and resolve quickly and others are very serious. I will write in brief the most common risks. For detailed and more information, please read extra literature available widely on the web including different videos.
- During the surgery
- Break in back part of the lens capsule with prolapse of the gel of the eye to the site of surgery. If this occurs the operation will take longer than usual to remove the gel from the front of the eye before an implant can be inserted
- Drop of all or part of the cataract into the back of the If this happen, the patient will need another operation to get it from the back of the eye, usually done by a vitreo-retinal surgeon
- Bleeding inside the eye: This is very rare and I can not re-call seeing one for the last 10 years. If it happens, it can lead to loss of vision
- After the surgery
- High pressure inside the eye: Usually transient and not serious.
- Swelling of the cornea: This is not common and if it happens, it is usually for a short period of time, rarely permanent. Patients with a condition called Fuch’s endothelial dystrophy are at a higher risk of this complication but with the available substances and surgical techniques, even in this category of patients this complication is not common.
- Incorrect strength or dislocation of the implant: If not correctable with suitable glasses it may require a further operation to change or reposition the implant.
- Macular oedema: The macula, is the central part of the retina responsible for central vision. Swelling of the macula occurs in up to 5% of patients but usually transient and clinically in-significant. In 2% of cases, it needs treatment and might delay the full recovery of vision on average but not always for 3 months. The treatment usually is with eye drops and tablets, and minority of patients might need special treatment with injections of steroids.
- Retinal detachment: Very rare, if it happens, will need another surgery and can lead to loss of sight.
- Infection in the eye – endophthalmitis: This is a very serious but rare complication. The current rate of endophthalmitis in the UK is around one in 1000 to 1400 It can lead to loss of sight or even the eye. It requires immediate intensive treatment with injections of antibiotics inside the eye and may require a further operation.
- Allergy to the medication: Redness, itchiness and soreness of the eye, longer than the expected few days for post-operative usual recovery. Usually changing the eye drops is sufficient.
Please, note that the above are the most common but not all possible risks.
Phacoemulsification, is the standard surgery performed for cataract surgery.
- Before the operation:
Before the operation, a nurse or a technician will do some measurements of different parameters of the eye – biometry. These measurements will help the surgeon calculating the power of the intraocular lens (IOL) you will have implanted into your eye after removing your cataract. As mentioned above, the lens in the eye has some refractive power to focus the light rays on to the retina. The IOL which is a lens made from Acrylic material will do the same function as your lens (now called cataract after becoming opaque) that we will remove during cataract surgery i.e. focusing the light rays on to the retina. All modern cataract surgeries include implanting IOLs. The measurements are not always 100% accurate but they will provide you with the best possible power of IOL that suits you. There are different forms of IOL:
Monofocal: These lenses give you the best possible vision for either distance (TV, driving ect), or reading (books and newspapers) or intermediate vision for computers – one particular distance – not all distances.
Toric IOLs: These are the same as monofocal or multifocal IOLs but also correct some irregularities in the shape of the cornea if you have such irregularities.
Multifocal IOLs: Roughly speaking these are like varifocal glasses. They are called premium IOLs because they are expensive. There are many designs of multifocal IOLs. Please check with your surgeon.
Some people choose monovision, i.e. one eye usually the dominant eye sees for distance and the other non-dominant eye sees for reading.
- During the surgery:
The surgery in most of cases is done under local anaesthetic. This includes numbing drops and solution irrigated into the eye. Sometimes, the surgery is done under anaesthetic injection done behind the eye with a blunt tube – this is called sub-Tenon’s anaesthesia. It stops the eye from moving but also stops the eye from seeing for a few hours until the anaesthetic wares off. Rarely, often with medical indication, cataract surgery is done under general anaesthetic.You will go into the operating room walking if you can walk, you will be laid down on the operating table, the eye and surrounding skin cleaned with Iodine solution, a drape placed over your face. The operation is done under the microscope with bright light so you will not see what the surgeon is doing. You might feel some water going on your face, that is normal. The simple straightforward cataract operation takes about 15-20 minutes to do but many cataracts/eyes are not straight forward cases. Some of those cataracts might take longer to carry out safely.
- After the operation:
After the operation, you will be taken walking if you can walk to the post-operative room where you will be given the post-operative instructions and treatment and sent home. The post-operative treatment is usually with eye drops for a few weeks.