A cataract is an opacity of the natural lens of the eye. This causes blurred vision because it prevents light from entering the eye. Most cataracts develop because of natural aging.
Cataracts can be removed to restore vision. For most patients, the treatment of choice is a minimally-invasive procedure, called phacoemulsification, which lasts about 30 minutes.
Cataract surgery has a very high success rate, and the risk of a complication is low. Mr Hu benchmarks his outcomes against national standards.
Facts about Cataract Surgery
• Blurring of your vision, glare, and difficulty reading which develop over months or years are symptoms that warn that you may be developing cataracts.
• Cataracts commonly affect us and become more noticeable as we get older.
• Cataracts can be diagnosed by your optician or doctor by examining the eyes with specialized viewing instruments.
• Cataract surgery is not necessary if your cataracts do not affect your daily activities such as driving, reading, watching TV or sporting pursuits, or if you are not keen to have surgery.
• Cataracts are treated by the removal of the cataract by a specialist eye surgeon with implantation of an artificial lens.
• A variety of intraocular lens types can be implanted to restore vision in different ways.
• In the best hands, cataract surgery is a safe and effective way to restore vision and serious complications are unusual.
What are Cataracts?
A cataract forms when the normally clear lens of the eye becomes cloudy, causing blurry vision. The normal lens focuses light onto the back of the eye so that images appear sharp. The clouding of this lens when a cataract forms distorts vision. Cataracts usually form gradually and are age related but can also develop rapidly. They often affect both eyes, but it is not uncommon for a cataract in one eye to form more quickly. Cataracts become more common, as people become older.
It is uncertain precisely why cataracts occur. Most cataracts are thought to be caused by changes in the protein structures within the lens over a period of years so that the lens become cloudy. Rarely, early childhood cataracts or cataracts in the new-born may be a result of genetic disease, hereditary enzyme defects, or systemic congenital infections. Formation of cataracts can also be hastened by severe trauma to the eye, eye surgery, or intraocular inflammation. Excessive ultraviolet light exposure, exposure to ionizing radiation, smoking, diabetes mellitus, or the use of certain medications, such as oral, topical, or inhaled steroids, & statins have been thought to be associated with promoting cataract formation.
What Symptoms suggest that I have a Cataract?
Apart from blurred vision, cataracts cause difficulty with glare (in bright sunlight or vehicle headlights when driving at night), dull colour vision, difficulty with reading and near vision, and frequent changes in spectacles prescription. Initially, a change in glasses may help when vision begins to change from an early cataract. However, stronger glasses or contact lenses will no longer improve the vision as the cataract develops and becomes more dense and cloudy.
Eye pain, redness or tiredness is usually not associated with cataract. As cataracts usually develop gradually over months or years, any more rapid or painful changes in vision suggest other eye diseases. If in doubt, there should be an urgent or early evaluation by an ophthalmologist.
How can my Doctor tell that I have a Cataract?
An optician or ophthalmologist can diagnose cataracts by detecting opacities in the lens during a medical eye examination. The lens of the eye affected by cataract formation can be seen using a variety of specialized viewing instruments. An eye care specialist is able to tell how much a cataract may be affecting vision by employing the usual eye tests include testing visual acuity using a Snellen chart, colour vision, glare & contrast sensitivity, and a thorough examination of all other parts of the eye. It is important for the ophthalmologist to exclude diabetes mellitus, glaucoma and macular degeneration by performing a thorough examination.
If your cataract does not affect your daily life in any way, or if you are not keen to have surgery, it is not imperative to undergo cataract surgery. Most cataracts develop slowly with age, and many patients do not notice loss of vision until it is quite advanced. It is not possible to predict with certainty how rapidly cataracts will develop and some cataracts remain less dense and do not progress to the degree where they cause blurred vision severe enough to require cataract surgery. Some cataracts progress more rapidly. Your ophthalmologist will assist you in making your own individualized choice about whether and when to proceed with cataract surgery. The ophthalmologist will be able to advise you how much of your loss of vision is due to cataracts and what sort of visual improvement you can expect if you choose to have cataract surgery.
How do I know that I need Cataract Surgery?
Cataracts are uncommon before the age of 40, but once cataracts do develop, an eye care specialist may mention during a routine eye examination that you have early cataracts, even if you have not noticed visual blurring or other symptoms. However, generally you will be the first one to notice changes in your vision that may require cataract surgery. Most people will not begin to have symptoms from their cataracts until many years after the cataracts start to form. It is reasonable to consult your ophthalmologist at regular intervals to monitor your cataracts. A cataract can be safely observed without treatment until you notice changes in your vision.
When you develop significant vision loss directly because of the presence of cataract, then cataract surgery is normally recommended. However, your ophthalmologist may not recommend surgery if you also have other significant eye disease, unconnected to cataracts, that impairs your vision. If it is necessary to perform cataract surgery to remove a cataract that resulted from eye trauma or previous eye surgery, so that the eye specialist is able to see the retina at the back of the eye, this may be appropriate in order that the ophthalmologist can assess the retina or optic nerve for further treatment. Cataract surgery is usually performed under local anaesthesia and typically takes less than 30 minutes, but account is taken of the individual’s coexisting medical conditions and the mode of cataract surgery is personalized for the individual.
Are there Different Types of Cataract Surgery?
Nowadays, the most common form of cataract surgery involves a process called phacoemulsification. Using an operating microscope, your ophthalmic surgeon will make a very small incision in the surface of the eye in or near the cornea and then inserts a thin probe into the eye. The ultrasound probe uses ultrasonic vibrations to dissolve the clouded lens. These tiny fragments are then suctioned out through the same ultrasound probe, following which an artificial lens is placed into the thin capsular bag that the original lens previously occupied. This artificial lens is required to help your eye focus following cataract surgery. Other less common techniques for cataract surgery nowadays are Extra-capsular cataract surgery and Intra-capsular cataract surgery, but may be appropriate in such cases as extremely advanced and dense cataracts, or where there has been previous significant eye trauma.
Why are there Different Types of Artificial Intraocular Lenses used in Cataract Surgery?
The natural lens of the eye helps focus the light for sharp vision, An artificial lens is implanted at the time of cataract surgery as a replacement for the natural lens because it gives the best visual outcome. As the artificial lens implant is placed in or near the original position of the removed natural lens, virtually normal vision is restored. Artificial lenses typically stay permanently in place, are maintenance free, and are not felt by the patient and not noticed by others.
The following is a summary of the available types of artificial lenses:
1. Mono-focal lens are the most commonly implanted lenses nowadays. They can provide very good distance vision, supplemented often with a light pair of glasses. Mono-focal lenses provide sharpest focus at only one distance and they do not correct pre-existing astigmatism, which is due to irregular corneal shape that tends to distort vision at all distances. Reading glasses are often needed by patients who have had mono-focal intraocular lenses implanted. With mono-focal lenses, it is possible to choose to aim for good close vision instead, as this is particularly suitable for those who wish to do a lot of detailed close work or prefer to be able to read without glasses. Glasses for distance will then be required. A final option, using mono-focal lenses, is so-called “Monovision”, which aims to provide a combination of distance vision in one eye and near vision in the other. The purpose is to minimize the need for glasses, but Monovision may result in some visual difficulties which may be difficult to get used to. Monovision is not always ideal and should be chosen only after very careful consideration.
2. Toric lens are suitable for correcting astigmatism as well as short-sightedness. Due to the difference in lens power in different areas, the correction of astigmatism with a toric lens requires that the lens be positioned in a very specific configuration. There is a risk that if the toric lens rotates, a second operation may be needed to rotate it back into position for best vision, or sometimes to remove it and replace with a standard lens. With toric lenses, patients are still likely to need corrective glasses for all near tasks, such as reading or writing.
3. Multifocal lens, one of the latest advances in lens technology, may allow some individuals to see at a variety of distances, including near, intermediate & distance. However, multifocal lenses are not suitable for everyone as they cannot correct astigmatism, and patients may still require spectacles or contact lenses for clearest vision.
What happens just before & on the day of the Cataract Surgery?
Just before surgery, your ophthalmologist or associate staff member will inform you about the steps that will occur during surgery, ask you about your medical history and perform a brief physical examination. Always inform your ophthalmologist about medications you are using and discuss if any should be avoided prior to surgery. Always inform your ophthalmologist if you have had previous laser treatment (e.g. LASIK and PRK) to your eyes, because it affects the calculations used in the selection of the power of the lens implant best suited to you. Prior to surgery, it would help to discuss your refractive requirements with your ophthalmologist because this will also affect the selection of the most suitable artificial lens to be implanted for you. To make this selection, special tests are done usually prior to the operation day but they may also be done when you first attended the clinic or a few weeks prior to surgery. In preparation for these special test measurements, contact lens wearers must leave their contact lenses out for 2 weeks, if using soft contact lenses, or 4 weeks, if using gas permeable or hard contact lenses.
Follow all of your preoperative instructions, including not eating or drinking anything after midnight the day prior to your surgery. Arrange for family or friends to transport you home after the surgery is complete as cataract surgery does not usually require an overnight stay in hospital. You will normally be required to report several hours before the scheduled time for your surgery. An anaesthetist may work with the ophthalmologist to determine the type of sedation, where necessary. Most cataract surgery is done under local anaesthesia or with only minimal sedation without being put to sleep. To reduce sensation of the eye during cataract surgery, numbing drops or an injection around the eye may be used.
Cataract surgery will normally take approximately 20-30 minutes. It is performed while you are lying down on your back and your face partially covered by a sterile sheet. The surgeon uses a microscope with a bright light, and although you do not see the operation or the instruments used, you may be aware of a bright light, see moving shapes, and often interesting coloured lights and shadows. During the surgery, you may also notice the sensation of pressure from the various instruments used. After leaving the operating room, you will be prescribed several eye-drops to be used for a few weeks postoperatively. Although you may notice some discomfort, most patients do not experience significant pain following surgery. You should contact your ophthalmologist or local eye casualty department urgently if you experience distorted vision, increasing blurring or decreasing vision, increasing eye redness, soreness or significant pain, an enlarging shadow in your field of vision, especially with increasing floaters or flashing lights, or a yellow / green eye discharge following cataract surgery.
After Cataract Surgery, What then?
>Expect your operated eye to be protected with a clear plastic shield, possibly with an eye pad which you will be told when to remove yourself. The plastic shield is usually worn during sleep for about 1 week after surgery.
>After surgery, the doctor or nurse will ensure you are given the postoperative instructions, the eye drops, and check that you are ready to be discharged from hospital, and this all takes about 30-60 minutes.
> Avoid strenuous activity for 2 weeks & avoid heavy lifting for 4 weeks, to allow time for the self-sealing incisions, made during cataract surgery, to heal
> Use the eye drops prescribed to you as instructed – you will be shown how to clean your eye and put in the eye drops correctly. In summary, it involves tilting your head back, pulling your lower eyelid down gently, looking upwards and then, without letting the tip of the bottle touch your eye, placing the drops inside the lower lid. Avoid rubbing or touching the eye in the first 2 weeks after the surgery. Dark glasses may be worn if you find that you are sensitive to light.
You will be advised when you should return for re-assessment during the period after cataract surgery. During this period, you will be using several eye-drops which help protect against infection and inflammation. Within a few days, most people notice that their vision is better and good enough to return to work. During follow-up visits, your ophthalmologist will check for complications. Appropriate glasses may be prescribed, if needed, for optimal vision, usually about 4-6 weeks after the surgery.
Tell me about the potential Risks of Cataract Surgery
Cataract surgery is one of the safest procedures available with a high rate of success. After cataract surgery, 90% of patients will have vision of 6/12 or better. Although the pre-operative measurements usually enable the surgeon to select a lens implant which provides the desired near or distance vision, the variability of individual responses means that it is not possible to guarantee absolute accuracy, so that there may sometimes be an unexpected need for strong glasses. There is commonly a change in colour vision such that colours look brighter or bluer. Also, rare complication can occur, including one person in every 1000 going blind in that eye as a direct result of the operation, and one in 10000 losing the operated eye. There is a 1:100 risk of needing additional surgery to rectify a problem, such as the loss of all or a part of the cataract into the back of the eye. Before you sign the consent form for the surgery, your ophthalmologist will discuss the potential complications of the procedures that are unique to your eye. The complications that can arise after cataract surgery are persistent inflammation, infection, changes in eye pressure, or swelling or detachment of the retina at the back of the eye. In rare instances, the delicate bag the lens sits in is injured (posterior capsular rupture), so that the artificial lens may need to be placed in a different location, or the artificial lens moves or malfunctions and may need to be repositioned, exchanged, or removed. All these are some of the large number of possible complications of cataract surgery but the list is not comprehensive. Many are very rare complications but even so can lead to a poor visual outcome and so close follow-up is required after cataract surgery.
The thin lens capsule may in some cases become cloudy some months or years after cataract surgery, causing a return of blurred vision. This process is called posterior capsular opacification. 1 in 10 patients require treatment with a laser procedure known as YAG laser capsulotomy, taking only minutes during an outpatient visit, to painlessly create a hole in the cloudy lens capsule and vision usually improves rapidly.
YAG LASER CAPSULOTOMY for POSTERIOR CAPSULAR OPACIFICATION
One of the commonest complications which can occur after cataract surgery with an artificial IOL (intraocular lens) implantation is Posterior Capsule Opacity (PCO). This can happen typically 2-3 years following the surgery, in up to 50% of patients who undergo otherwise routine cataract surgery & IOL implantation. The PCO is an opaque or clouded thickened membrane which replaces the previously transparent capsule behind the IOL, causing the previously clear vision to deteriorate and become blurry or cloudy, and causing glare from lights at night-time or from bright lights. If your eye surgeon has recommended YAG Laser Capsulotomy, it is because this laser procedure will create a clear opening through the clouded posterior capsule so that your vision will be restored to its previous clarity.
2. WHAT IS YAG LASER CAPSULOTOMY?
YAG Laser Capsulotomy is a simple, commonly performed and very safe laser treatment, which is used to improve your vision, if a posterior capsule opacity forms after you have had cataract surgery with an artificial intraocular lens implant. In a YAG Laser Capsulotomy, the ophthalmologist uses a special lens to apply a laser beam to the centre of the opaque, clouded capsule. This creates a small hole in the centre of the thickened capsule so that there is a clear pathway for light to get through. Currently, YAG Laser Capsulotomy is the only non-invasive way to treat this condition.
3. WHAT ARE THE RISKS?
It is very uncommon to have complications after YAG Laser Capsulotomy.
Nevertheless, the following complications are possible following the procedure and careful monitoring is a routine part of the post-treatment care:
Increase in floaters: These appear like dots or wavy lines in the vision and they are the commonest side effect of this treatment, but they are not serious, and people learn to ignore them after a little while.
Increased pressure in the eye: This can occasionally occur immediately after the laser treatment. Before you are discharged to go home, additional treatment with eye drops or tablets will be provided, and you may be asked to remain in the clinic until the eye pressure has dropped to a satisfactory level. Typically this may take a few hours at most.
The laser capsulotomy opening is not large enough or is incomplete: The treatment will need to be repeated at a later date.
Extremely rarely, macular oedema (swelling) and retinal detachment have been reported as possible complications. Retinal detachment can produce a shadow in the vision or flashing lights accompanied by large floaters. Such symptoms, or any new blurring or distortion of vision should be reported urgently to your doctor for further investigation. Mild eye inflammation, lens dislocation and lens damage (pitting) which reduces the clarity of the new artificial lens have also been reported as rare complications.
4. BEFORE YAG LASER CAPSULOTOMY
Continue using your usual drops and medications, including blood thinning medications like Aspirin, Warfarin and Clopidogrel, until the day of surgery.
At your pre-treatment assessment, check that any underlying medical conditions you may have such as diabetes, hypertension or cardiac disease have been disclosed and discussed. Special preparations such as fasting or wearing operating theatre clothes will not be required as the treatment will be done as a day case outpatient procedure, lasting for about half a day.
You will be asked to sign a consent form which will set out the risks and benefits of the treatment, after they have been discussed with you. Measurement of your vision and eye pressure will be done. You will have some drops put into your eye to widen the pupil, and an anaesthetic eye drop to numb the surface of the eye. As a result of these drops, your vision may be blurred for about 4 hours. You may have drops of apraclonidine (“Iopidine”) before the treatment to help prevent rises in eye pressure, but this may be omitted if you have a history of ischaemic heart disease (heart attack or angina). If you have heart problems, especially severe angina that has required surgery or vascular stenting, it is important to ensure that your doctor is aware of this.
5. DURING YAG LASER CAPSULOTOMY
YAG Laser Capsulotomy takes about 10 – 20 minutes. You will be seated at a “slit-lamp” – a machine likely to be similar to the one used to examine your eyes when you visit the eye clinic for your routine eye checks – this one will have a special laser attached. A special lens will be placed on your eye by your ophthalmologist, before applying the laser beam. This lens enables the ophthalmologist to see the membrane clearly before applying the laser and creating a small hole in it to clear the vision. You will be instructed to look at a target in front, and to keep still while the treatment is performed. This is important because movement during the procedure can cause problems such as lens pitting. You will see a bright, white light as it is shone into the eye by the ophthalmologist, to see the spot where the treatment is being applied. This may cause your vision to be dimmed for up to 30 minutes afterwards. The YAG laser machine makes a clicking noise and gives a very short “flicking” sensation when activated. The ophthalmologist will need to adjust the laser power depending on the thickness of the capsule. After the procedure, you will return to the waiting room to await a further check on your eye pressure about an hour later. The treated eye is also re-examined to assess the outcome of the laser procedure.
6. AFTER YAG LASER CAPSULOTOMY
After YAG laser capsulotomy, most patients find that their vision is blurry for about four hours as a result of the drops and some are bothered by the glare from bright lights. It will therefore be helpful for someone to accompany you home, but this is not essential. Avoid driving or riding a motorcycle or bicycle for the rest of the day. Typically, no special treatment is required following the procedure, and you can go back to your normal daily activities straight away. Sometimes, if the eye pressure remains high following the procedure, you will be given tablets and/or drops to use for a few days. You will sometimes be advised to use anti-inflammatory eye drops for 1 week to prevent inflammation in the eye. If you routinely wear contact lenses, you will need to use preservative free drops, or stop wearing contact lenses for the week. Those with glaucoma should continue to use their normal glaucoma medication for both eyes unless specifically told not to.
You should urgently report the following symptoms: Excessive pain, increasing redness of the eye, loss of vision, a shadow in the vision, flashing lights, sudden appearance of large floaters.
You may take your usual pain relieving tablets following the instructions on the pack, if you have some discomfort when you are at home. It is normal to have itchy, gritty or sticky eyes and mild discomfort for the remainder of the day after the treatment. You will be given a follow-up appointment a week or so after your laser treatment to ensure that the eye has settled down normally and to assess the success of the treatment.
7. IN SUMMARY
YAG Laser capsulotomy helps restore clear vision in people who develop hazy vision as a result of developing a posterior capsule opacity following cataract surgery with an intraocular lens implant.
This outpatient laser procedure is simple, commonly performed and very safe.
Complications resulting from YAG laser capsulotomy can sometimes occur but they are very uncommon.
Glaucoma is a disease of the main nerve of the eye that causes irreversible loss of vision. Usually, glaucoma is associated with an excessively high pressure within the eye.
In its early stages, glaucoma affects peripheral vision and may go unnoticed. However, in its later stages, glaucoma can also affect central vision, affecting the ability to recognise faces and read.
Glaucoma can be treated to prevent its progression. This involves reducing the pressure inside the eye. A wide range of treatments is available including medicines, laser treatments, and surgery.
Facts about Glaucoma
• GLAUCOMA IS GLOBALLY THE SECOND LEADING CAUSE OF BLINDNESS: Over 60 million people are estimated to be the total number of suspected cases of glaucoma worldwide, and of these a significant proportion, at least half of them, are unaware that they have the condition. Left untreated, glaucoma can result in loss of vision and this is why glaucoma is a leading cause of blindness.
• GLAUCOMA STILL HAS NO CURE: The first crucial step in preserving your sight is to find out if you have glaucoma, in other words, to get a diagnosis. This is because, with treatment, it is possible to halt further loss of vision, but once vision is lost, it’s too late – it cannot be regained or restored by any means.
• EVERYBODY IS AT RISK OF VISION LOSS DUE TO GLAUCOMA: If you are over 60, or have a family member diagnosed with glaucoma, or are diabetic, or are very nearsighted (highly myopic), or are of African or East Asian descent, you are at greater risk of having glaucoma. However, everyone from babies to senior citizens is at risk of glaucoma.
• GLAUCOMA USUALLY GIVES NO EARLY WARNING SYMPTOMS: There may be virtually no symptoms to warn you that you have glaucoma. Getting tested & screening by an ophthalmologist or eye care specialist is the best way to prevent blindness as a result of untreated glaucoma.
What is Glaucoma?
Glaucoma, the second leading cause of blindness in the world according to the WHO (World Health Organization), is a complicated disease, made up of a group of eye (ocular) disorders in which damage to the optic nerve leads to progressive, irreversible loss of sight. Glaucoma is often, but not always, associated with increased fluid pressure in the eye (intraocular pressure – I.O.P.)
What are the different types of eye disorders that are all called Glaucoma?
Glaucoma is actually made up of a group of eye disorders and they are known as follows:
> Primary open-angle glaucoma
> Angle-Closure Glaucoma
> Normal-Tension Glaucoma
> & Other Types of Glaucoma
Primary Open-Angle Glaucoma
In this form of glaucoma, clogging of the eye’s drainage canals happen gradually and it is the most common form of the disease.
As the condition develops slowly over a period of time, giving most people with the condition virtually no symptoms and no early warning signs, it often causes a gradual but progressive loss of sight which may initially go unnoticed over some years.
As the eye’s drainage canals become clogged over time, the inner eye pressure (also called intraocular pressure or IOP) rises because the correct amount of fluid is unable to drain out of the eye. It is this increase in I.O.P. which can be detected by the ophthalmologist or other eye care specialist, using specialist measurement tools. Any loss of vision can also be assessed and monitored using perimetry – the visual field test.
This condition is treatable & it usually responds well to medication, especially if detected early and treated.
The eye pressure in angle-closure glaucoma, also known as acute glaucoma or narrow angle glaucoma, usually rises very quickly, quite unlike the gradual rise in I.O.P. in open-angle glaucoma. Fortunately, acute glaucoma is also relatively uncommon.
The symptoms of angle-closure glaucoma may include a painful eye, headaches, nausea, halos around lights at night, and very blurry vision.
Acute glaucoma is due to blockage of the drainage canals, much like a washbasin with something covering the plughole, & is associated with the iris not being as wide and open as it should be. When the pupil suddenly or excessively enlarges, as could happen when one enters a dark room, the outer edge of the iris bunches up & obstructs the eye’s drainage canals.
Using a specialist viewing device, an ophthalmologist can tell if your angle is normal and wide or abnormal and narrow. Treatment involves surgery or laser so as to create an opening through a small part of the outer edge of the iris, to unblock the eye’s drainage canals. Glaucoma surgery may also be recommended as a precautionary measure for the other eye, once acute glaucoma has occurred in the first eye.
Although glaucoma surgery for acute glaucoma is usually successful and long lasting, it is sensible to undertake regular follow-up checks as a chronic form of glaucoma could still occur.
Normal-tension glaucoma is diagnosed when the optic nerve is damaged even though the pressure in the eye is not very high. The optic nerve damage is revealed by a direct examination of the eye and assessment of the appearance (shape & colour) of the optic nerve by an ophthalmologist. A nerve that appears cupped or does not look a healthy pink colour could raise concerns, as would an abnormal visual field test, which involves mapping out the person’s whole field of vision, typically using specialist equipment.
The cause of damage to the optic nerves even though they have almost normal pressure levels of between 12-22 mm Hg. is unclear, but it seems to be associated with people with a family history of the same condition, people with a history of systemic heart disease and those of Japanese descent.
Typically ophthalmologists today would treat normal tension glaucoma by reducing the eye pressure as low as possible using medications, laser treatments and conventional surgery, although research is still underway to clarify why some eyes are susceptible to damage even when the I.O.P. appears to be within the normal range.
Other Types of Glaucoma
These other types of glaucoma can occur in either one or both eyes and could be like either the open-angle or the angle-closure kind. They include the following:
Secondary Glaucoma: where the raised I.O.P. is a result of another disease process such as eye inflammation, eye trauma & injury, diabetes mellitus, tumour, advanced cataract, or taking prescribed drugs like steroids, and it still results in damage to the optic nerve and loss of sight. The severity of secondary glaucoma is variable, but the treatment depends on whether it is found to be of the open-angle or the angle-closure variety.
Pigmentary Glaucoma: Pigmentary Glaucoma, also a type of secondary open-angle glaucoma, occurs when the pigment granules in the back of the iris are shed into the clear fluid in the eye and these tiny pigment granules subsequently clog up the drainage canals in the eye, resulting in a raised I.O.P. Treatment could involve medications, laser, or glaucoma surgery.
Pseudoexfoliative Glaucoma: This occurs when a flaky material is shed from the outer layer of the lens within the eye, producing a form of secondary open-angle glaucoma. The material clogs the drainage system of the eye by collecting in the angle between the iris & the cornea, causing the I.O.P. to rise. It is treated usually with medications or surgery.
Neovascular Glaucoma: This happens typically in diabetic patients when the abnormal formation of new blood vessels on the iris and over the eye’s drainage canals causes a form of secondary open-angle glaucoma, which is difficult to treat.
How can my Doctor tell that I have Glaucoma?
Diagnosing glaucoma requires careful evaluation of the optic nerve. A correct diagnosis is crucial for protecting your sight, and ophthalmologists need to consider many factors before making decisions about treatment. If your condition is particularly difficult to diagnose or treat, you may be referred to an ophthalmologist who specializes in glaucoma screening & treatment.
As early detection of glaucoma is the key to protecting your vision from damage, a complete eye examination which includes the following common tests to detect glaucoma should be performed at regular intervals. This is best discussed with your own doctor, optician or ophthalmologist as there is currently no national glaucoma screening programme in the UK.
Tests for glaucoma:
Tonometry measures the pressure within your eye and this is done using an instrument called a tonometer. Eye drops to numb the surface of the eye are first instilled into the eye and then a small amount of pressure is applied to the eye by a tiny device or by a warm puff of air.
A pressure of 12-22 mm Hg (“mm Hg” refers to millimeters of mercury, a scale used to record eye pressure) is considered to be within the normal range and most glaucoma cases are diagnosed with pressures greater than 20mm Hg. However, some people with Normal-Tension Glaucoma can have optic nerve damage even at pressures between 12 -22mm Hg. Eye pressure can vary during the course of the day and is unique to each person.
Slit lamp examination
This diagnostic procedure is a direct visual examination of your optic nerve for glaucoma damage. The shape and colour of the optic nerve can be assessed by the ophthalmologist, typically nowadays using a slit lamp, to look through the pupil of the eye, which often first needs to be dilated using eye drops.
Perimetry and gonioscopy may then additionally be recommended, should there be a concern about the outcome of the tests above.
Perimetry is a visual field test. It maps your whole field of vision so that your ophthalmologist can tell whether your vision has been affected by glaucoma. The test involves looking straight ahead and indicating when a moving light passes your peripheral (or side) vision. It is very helpful if you can relax and respond as accurately as possible during the test. It is usual to be asked to repeat the test to see if the results have changed the next time you take it, as this will help to monitor any changes in your vision.
Gonioscopy helps the ophthalmologist determine if the angle where the iris meets the cornea is wide & open or narrow & closed. First, eye drops are used to numb the eye and then a hand-held contact lens with an integrated mirror is placed gently on the eye so that the ophthalmologist can tell if the angle between the iris and cornea is wide and open (a possible sign of open-angle glaucoma) or closed and blocked (a possible sign of angle-closure glaucoma).
The thickness of the cornea is measured by the simple, pain free test called pachymetry, involving the placing of a probe called a pachymeter on the front of the eye (the cornea). Corneal thickness can potentially influence eye pressure readings and so needs to be taken into account when evaluating your I.O.P. reading so that your treatment plan can be personalized for you. It takes only about a minute to perform pachymetry for both eyes.