This indepth analysis of cataract and cataract surgery was written by Simon G. Levy MD MRCP FRCS FRCOphth, Consultant Ophthalmologist for a lecture given to optometrists (opticians). It provides a detailed analysis of the history of cataract surgery, pre-operative workup, surgical technique and post-operative management of cataract.

UNDERSTANDING CATARACT: A GUIDE FOR THE PERPLEXED

(Slide show and notes)

SIMON G LEVY MD MRCP FRCS FRCOphth

INDEX

Types and causes of cataract
Symptoms
Lens anatomy
History of cataract surgery
Phacoemulsification/small incision surgery
The cataract surgeons job
Maximising unaided distance acuity
     Pre operative biometry
     Managing astigmatism
Maximising unaided near acuity
     Calculated astigmatism for good near acuity
     Multifocal IOLs
Minimising psychological distress
Minimising recovery time
When to have surgery
Refractive outcomes
Risk
Comorbidity
Anaesthesia for cataract surgery
Cataract in children
Post op cataract medication
Secondary Cataract
Lensectomy for high ametropes and Phakic IOLs
The optometrists role

Nuclear sclerosis is the commonest type of cataract and usually age related.

Posterior subcapsular cataract is found in younger patients. It is sometimes due to oral/topical/? inhaled steroids. So medical conditions such as asthma for which oral steroid has been prescribed can have a profound indirect effect on vision.

Generally speaking most cataracts are age related. Everyone gets them eventually!

Unusual types e.g. crystalline, sutural maybe genetic but this is rare.

All types of cataract occur earlier in high myopes.

Trauma, uveitis, steroid use and diabetes can all cause cataract.

The role of UV light 'ageing' the lens is unclear, but it may be important.

The extent to which a patient is symptomatic from cataract depends on many factors. Obviously the younger the patient, the more likely they are to be aware of visual loss. Converseley elderly patients with modest visual requirements are often remarkably unaware of their cataract. The speed of onset of the cataract also plays a part. Classically nuclear sclerosis comes on slowly so the patient has plenty of time to get used to the change it has caused, and may not notice it all. Drivers have early symptoms because of glare from oncoming headlights. Some types of cataract cause symptoms quicker than others. Classically this applies to posterior subcapsular catataracts which are frequently right in the centre of the lens. These cataracts scatter light so causing glare very early. Also on a bright day when the pupil closes down a patient may suddenly have count fingers vision when he may still be 6/6 in dim illumination. The presence of comorbidity, for example macular degeneration, also affects a patients ability to perceive the extent to which cataract has reduced vision.

LENS ANATOMY

All the clinician/optometrist needs to know for practical purposes about lens anatomy is that the lens substance is wrapped up in an elastic capsule. The capsule is immensely important from the surgeons point of view because (1) the anterior capsule has to be removed very carefully during cataract surgery (2) the integrity of the posterior capsule must be protected at all costs during cataract surgery.

You will all be aware of the zonular/ciliary body apparatus and its role in accommodation. Accommodation is largely academic in the context of cataract since most patients are already presbyopic. However see the discussion on 'pseudo-accommodation' in the section on maximising unaided near acuity.

HISTORY OF CATARACT SURGERY

Couching was the practice of making a crude cut in the eye and then inserting an object such as a finger, stick or spoon-handle into the eye and pushing the lens to the bottom of the eye. A technique to be used only in extremis obviously! Perhaps better than blindness in advanced cataract although presumably quite capable of causing blindness in itself. So long as the lens capsule was not ruptured, so releasing lens matter, there was surprisingly little intraocular inflammation and perhaps some positive benefit to the patient might result.

Intracapsular surgery was the first type of modern cataract surgery. In this technique a wide surgical incision is made at the limbus and a surgical instrument used to grip the lens and remove it in toto from the eye. A major step forward from couching but still quite traumatic especially since in the early days there were no sutures suitable for closing the incision. The wound was therefore left open and the patient had to be kept in bed for up to a fortnight with his head sandwiched between pillows to stop him moving until the wound healed.

Until the advent of the mass availability of contact lenses (1960s onwards) ICCE surgery was inevitably aphakic. Patients wore +12 glasses which were optically highly unsatisfactory causing magnification, distortion and peripheral scotomas. Anisometropia was such a problem that uniocular cataract surgery was contra indicated. The early types of contact lenses were not much help because most elderly patients found them too inconvenient to handle. The advent of soft contact lenses made an enormous difference to ICCE cataract surgery but constant supervision was required if they were to be worn on an extended wear basis and complications such as corneal infections were not infrequent.

Sir Harold Ridley invented the first intraocular lens in 1948, the operation being performed at St Thomas Hospital London. This was one of the most important discoveries of modern medicine, ranking with antibiotics, vaccines, anaesthetics, viagra, etc. in its capacity to improve the quality of human life. However partly because of the relatively crude nature of the early designs and party because of a rather conservative attitude amongst ophthalmologists, IOLs were not widely adopted until the 1980s.

Extracapsular (ECCE) surgery arrived in the 1980s. This was a big step forward over ICCE because, after the same rather gross corneal incision, the lens was removed in such a way that the posterior capsule was left intact. This was much less destructive to the eye with improved outcomes as a result. Also by this time most cataract surgery was performed with the benefit of an IOL.

Phacoemulsification (small incision cataract surgery) was discovered in the mid 1960s by the brilliant American ophthalmologist Dr Charles Kelman. This extraordinary man revolutionised cataract surgery by inventing phacoemulsification. Just as with Sir Harold Ridley's invention of the IOL, phacoemulsification was only slowly introduced partly because the initial phaco machines were technically crude so that the surgery was exceptionally difficult and partly because of suspicion amongst the ophthalmic community. However from the 1990s onwards phaco became the treatment of choice for cataract and in my opinion extracapsular surgery is now utterly outmoded.

PHACOEMULSIFICATION - HOW IT'S DONE

Phacoemulsification surgery time depends on factors such as surgical skill, the quality of the available equipment and factors relating to the patient such as the type of cataract. An average figure is 20-30 minutes. This does not include the time spent in the operating theatre preparing the patient before surgery and preparing the patient for return to the ward post-operatively. Altogether patients should expect 50-60 minutes in the operating theatre.

Less astigmatism: the phaco incision is 3mm or less whilst the ECCE incision was 10-12mm. Induced astigmatism is proportional to the incision length². Generally an unsutured phaco incision causes 0-0.5 dioptre flattening when made on the temporal side of the eye. The same 3mm incision made superiorally i.e. at the 12o'clock position causes 0.5-0.75 dioptres of flattening. Incisions made in the sclera cause less flattening than those made in the cornea.

Much safer: the small phaco incision is completely filled by the phaco probe. Because of this and the sophisticated fluidics of the modern phaco machines, virtually all intraocular events during surgery are under the control of the surgeon. The result is therefore down to the surgeons skill. In the days of ECCE surgery, the huge incision made in the eye created completely unstable intraocular dynamics over which the surgeon only had limited control. This was one of the reasons why ECCE surgery is much more dangerous than phaco with events such as vitreous loss and cornea damage much more common.

Quicker recovery: The small phaco incision is gentle to the eye. No stitches are required which might cause induced astigmatism and require removal at a later date. The incision heals quickly so that glasses can be prescribed soon after surgery.

Biometry is the process of measuring the eye prior to cataract surgery to select the correct strength of intraocular lens to insert during surgery. See below for more details.

Biometry is such an important aspect of cataract surgery that numerous complete text books have been written about it.

Axial length is measured with an A-scan ultrasound machine. This is not 'automatic' and requires great skill and judgement to use properly. An error of 0.4mm in the axial length will cause 1 dioptre of ametropia.

Keratometry is very important. A 1 dioptre error in the Ks equates to 1 dioptre ametropia post op. Ks can be difficult to measure accurately e.g. greasy tear films, cornea scars, pterygium, trachoma, keratoconus and poor fixation. Contact lenses must be out before Ks are taken. Soft lenses - 1 week. Gas permeable lenses - 2 weeks. PMMA lenses - 3 weeks.

Axial length and Ks are fed into a computer loaded with one of several biometry formulae. The best is 'SRK(T)' which is an acronym for its authors.

The biometry formulae become inaccurate if the eye is 'diseased' e.g. cornea scars or previous refractive surgery. Refractive surgery patients e.g. LASIK will require new formulae which are currently under development. Alternatively some educated guess work is needed.

RANGES OF IOL POWER

'Normal' eyes +21 to +24 dioptres
Myopes may be as low as -5 dioptres.
Hyperopes may be as high as +40 dioptres. Because IOLs are only made up to +30 dioptres power it may be necessary to insert 2 ('piggy backing') into the eye.

TYPES OF IOL

All are made from plastic (not glass!). Newer models are flexible e.g. silicone so that they can be folded in half and inserted through the 3mm phaco incision. They unfold to a diameter of 5-6mm.

MANAGING ASTIGMATISM

Note - see below for more information on calculated astigmatism in cataract surgery to increase near vision.

The cornea is the eye's main focusing organ. It's shape is critical for the eye's refractive power. Any change in cornea shape caused e.g. by an incision, sutures, scar, etc. may cause astigmatism.

Remember that astigmatism may be pre-existing or induced by surgery. Phacoemulsification provides an opportunity to reduce pre-existing astigmatism as well as surgically induced astigmatism.

Small incision: Phaco incision is 3mm wide, ECCE incision 10-12mm wide. Induced astigmatism is proportional to incision length ². Phaco is obviously therefore much better.

No sutures: no sutures are (usually) used after phaco whilst ECCE required 5 to 7. Sutures distort/tighten the incision and cause unpredictable astigmatism.

Place incision on steep meridian: any surgical incision made in the cornea weakens the cornea causing flattening. Flattening reduces the corneas focusing power. The amount of flattening is proportional to the incision depth, length and closeness to the corneal apex. These parameters can all be manipulated by the surgeon. The surgeon will place the incision on the steepest meridian of cornea power (at 90% to the axis of the astigmatism on refraction!).

Astigmatic keratotomy: these are additional incisions, usually paired, placed on the steep meridian of astigmatism. These cause flattening of the steep meridian.

Toric IOLs. IOLs which incorporate a correction for astigmatism. A nice idea but expensive and difficult to use because even a slight misalignment between the axis of the IOL and the axis of the astigmatism will cause an unpredictable refractive outcome.

Calculated myopia: useful for patients who have always been 2 - 4 dioptres myopic and who prefer good unaided near vision and don't mind wearing distance glasses.

Monovision: after cataract surgery monovision is permanent! The patient must be familiar with it beforehand and able to cope with anisometropia of about 2.5 dioptres i.e. quite a lot. Given that the post-op refraction can never be guaranteed to be exactly what is planned, the patient could end up with more anisometropia than 2.5 dioptres. Generally this option is not favoured by cataract surgeons.

Calculated astigmatism: see 'Calculated Astigmatism and Near Acuity' below.

Multifocal IOLs: see information on this subject below.

Small pupils: pupil diameter is always smaller in older patients. This has a pin hole effect of increasing the depth of field and is probably the major reason for some patients having much better unaided near acuity than would be expected given their refraction.

Pseudo-accommodation: amazing but true! As shown by ultrasound studies. Ciliary muscle contraction occurs post-op causing anterior movement of the IOL and therefore 'pseudo-accommodation' of up to 1 dioptre in some patients. There is no way of predicting which patients will enjoy this extraordinary effect.

CALCULATED ASTIGMATISM AND NEAR ACUITY

One focal plane will be on the retina for distance vision and the other will be in front of the retina i.e. useful for near vision. 0.75 dioptres may not seem enough to enable the patient to read, but remember they have small pupils and sometimes pseudo-accommodation.

Software packages (such as Mr Paul Chell's 'kill the cyl' or Mr Julian Steven's 'Vector Inspector' packages) enable the surgeon to manipulate the location, depth and length of the main incision and the same parameters for astigmatic keratotomy in order to leave a calculated amount/axis of astigmatism post-operatively.

MULTIFOCAL IOLS

MAXIMISING PSYCHOLOGICAL DISTRESS
OR: HOW TO MAKE FRIENDS WITH YOUR PATIENT

This is an extremely important aspect of cataract surgery and sadly one that is all too often partially or completely neglected. Cataract surgery can be a relatively happy and painless experience, psychologically speaking, if the patients feelings are borne in mind. If not it can be something of a nightmare for the patient and his/her family. Basically the ophthalmologist should possess enough imagination/sympathy to empathise with the patient and treat the patient accordingly. Frequently and sadly ophthalmologists believe that only the 'technical' aspects of the job such as avoiding surgical complication, getting the post-op refraction right etc. matter.

INFORMATION. The main problem is often simply that patients have no knowledge of what is involved in cataract surgery and are terrified of the unknown. I provide information on cataract surgery, what to do beforehand, what to expect afterwards, etc. both in printed form and via my website. Whilst not all patients will want to read this information, in my experience the majority do.

PRE-CONCEPTIONS. I try to get some idea during the pre-operative consultation of whether there is something on the patients mind that they find particularly bothersome about their forthcoming surgery. For example there is sometimes something terrible in the patients family history such as a cataract operation that went badly wrong. Discussing this will often enable me to put the patients mind at rest - for example pointing out that cataract surgery is now much safer than it used to be.

TALKING TO OTHER PATIENTS . Occasionally it is helpful to put a patient in touch with someone who has already had cataract surgery. However most patients already know someone to whom they can talk.

TALK TO THE PATIENTS BEFORE THEIR SURGERY. This is very important. I make an absolute rule of chatting to the patients for a few minutes just before to their surgery and 'walking them through' what will happen. I give a brief overview of what to expect, in particular pointing out things like the cataract machine making a hissing noise, water from the cataract machine trickling down their ear during the operation (no, its not blood) and the fact that the eye will not have good vision for sometime after the surgery (no, nothing has gone wrong, this is normal).

RELATIVES IN THE OPERATING THEATRE. Generally speaking I have no objection to a relative holding the patients hand in the operating theatre. This is very reassuring, especially if the patient does not speak English.

'VOCAL LOCAL'. I talk to the patient during the surgery. Most patients find this very reassuring. The sort of thing I say to the patient includes (1) what are the noises they can hear (2) what stage is the operation at e.g. 'I am just finishing the stage of removing the cataract' or 'I am just about to insert the replacement lens' (3) how much longer the operation will last. (4) 'everything is going well'. The Americans coined the phrase 'vocal local' (anaesthesia).

TOPICAL ANAESTHESIA. The best way, in my opinion, of doing most cataract surgery is to use powerful anaesthetic eye drops rather than an anaesthetic injection. This is comfortable for the patient and the eyes look better after surgery. Psychologically, patients are often hugely reassured to be told that 'no needle' will be used for their local anaesthetic.

DE-BRIEFING PATIENTS. A brief chat half an hour or so after the operation to tell the patient that all went well serves as 'closure' for a stressful event.

VISION RECOVERY TIME. It is extremely important to remember to warn patients that the eye will not regain vision until 12 to 24 hours after the operation. They will be reassured to know that this does not indicate that there has been a complication.

MINIMISING RECOVERY TIME

Remember - time is precious in elderly patients!

Generally vision returns within 12-24 hours after phaco. A substantial proportion of post-operative recuperation has already occurred by one day although healing will continue for a month or sometimes longer. Glasses are prescribed after 2-4 weeks.

Phaco recovery faster than ECCE because of the small incision.
(1) gentle to the eye - less cutting = less healing after
(2) Much less astigmatism
(3) No sutures to remove
(4) Less chance of a complication than with ECCE

Recovery after local anaesthesia much quicker than general anaesthesia.

See 'Minimising Psychological Distress' above for other tips.

WHEN TO HAVE SURGERY

The risk of phaco is sufficiently small (see discussion on risk below) that early (even very early) surgery is now appropriate. Local anaesthesia is very safe for the patients general health especially if topical anaesthesia is used. Therefore the age and health of the patient are usually irrelevant. Again this supports a policy of early surgery.

Surgery is appropriate as soon as the cataract becomes troublesome to the patient. Do not wait until the cataract is advanced ('ripe'). It is best to let the patient decide when to have surgery. However remember that elderly patients are often unaware of slowly progressive nuclear sclerosis even when the process has become advanced. It is appropriate for the surgeon/optometrist to encourage the patient to undergo surgery in this circumstance even if the patient is reluctant.

Remember that time is precious in elderly patients. The sooner the surgery is done the longer they will have to enjoy the visual improvement.
Another factor supporting early surgery is that the risk of surgery increases sharply if nuclear sclerotic-type cataracts are allowed to advance. The lens becomes very hard making the surgery technically much more difficult.

Symptoms justifying surgery include -

1. Reduced vision. Remember that Snellen visual acuity is often remarkably well preserved in nuclear sclerosis, despite severe loss of contrast sensitivity, the latter being a much better measure of visual performance. Also a posterior subcapsular cataract patient may have normal vision and no symptoms in dim illumination but count fingers vision and severe glare on a bright day when the pupil shuts down. This is because early nuclear sclerosis often occupies only the central portion of the lens.
   
2. Troublesome 'index' (cataract - induced) myopia or other refractive change.
   
3. Blunting of colour perception.
   
4. Glare when driving or on a sunny day.
5. Anisometropia.
6. Monocular diplopia.
   
7. The legal requirement for driving is relatively rigorous, equating to about 6/10 aided in at least one eye

REFRACTIVE OUTCOMES

Generally refractive outcomes after phaco are excellent. My impression is that optometrists share this opinion especially if they have been in practice long enough to have refracted many patients who have undergone ECCE surgery.

Good biometry is crucial to a good refractive outcome as it determines the power of the IOL inserted and so the spherical refraction post-op. Phaco permits pre existing astigmatism to be reduced during the operation (see 'Reducing Post-op Astigmatism' above) and induces very little astigmatism.

RISK

Phaco is much safer than ECCE because the surgeon controls the operation rather than vice the versa. See 'Phacoemulsification - Why It's So Good' above for a discussion on why this is so.

Complications are usually avoidable by a good surgeon (but not always! See below).

Intra-operative complications include -

1. Corneal oedema
   
2. Iris damage
   
3. Vitreous loss following posterior capsule tear
   
4. Dropped lens
   
5. Expulsive haemmorage.
   
6. Inability to insert an IOL

Post-operative complications include -

1. A scratchy/red eye
   
2. Cystoid macular oedema (CMO)
   
3. Poor refractive outcome
   
4. Leaking incision
   
5. Prolonged uveitis
   
6. Endophthalmitis
   
7. Retina detachment

1. A scratchy/red eye is the commonest post-operative problem. It is a nuisance but will disappear after one day - 2/3 months. Causes are discomfort from the incision, post-operative uveitis, recurrent cornea erosion syndrome from corneal epithelial trauma during surgery and post-op eye drop allergy. Sometimes unrelated problems such as blepharitis are 'brought to the patients attention' by the operation. Treatment is reassurance (vocal local!); topical anaesthetics; topical steroids; Acular (a non-steroidal analgesic/anti inflammatory agent); topical lubricants; occasionally a bandage contact lens.
2. CMO is probably the commonest severe post-operative complication. It comes on after about a week post-op. Vision drops from 6/6 to 6/36 or so. It is more common if a complication has occurred during surgery such as vitreous loss. Diabetics may have CMO as a component of diabetic retinopathy but they are also more prone to get it as a result of cataract surgery. CMO may occur after completely uncomplicated surgery. It usually disappears when treated with a combination of G. Acular and G. Maxidex QID for a month.

How frequent are complications?

The National Cataract Survey 1998 carried out by the Royal College of Ophthalmologists of 18,500 cases identified a 7.5% of intraocular complications!!! This is a very high figure, hence my comment on the slide that the risks associated with cataract surgery should never be trivialised. However I must say that most experienced phaco surgeons find these figures surprisingly high. I find that the risks of a significant intra-operative complication with most eyes is about 1:200. The risk of a serious post-operative complication (mostly CMO) is about 1:100.

The risk of phaco is reduced by:

1. Surgical skill and experience.
   
2. The quality of surgical equipment and nursing support available

The risk of surgery is increased by many factors including:

1. Short (hyperopic) eyes, less than 20mm axial length
   
2. Long (myopic) eyes, greater than 28mm axial length
   
3. Opaque corneas
   
4. Hard (long standing) cataract
   
5. Deep set eyes
   
6. Pupils that don't dilate
   
7. Very elderly patients (older than 90-something who will have fragile ocular tissues)
8. Pseudoexfoliative glaucoma in which there is a tendency for the lens to come adrift during surgery and sink to the bottom of the eye.

COMORBIDITY

The standard approach is to offer phaco to optimise ocular performance unless the retina/optic nerve are completely unfunctional. The patient must be told not to expect an unrealistic outcome. Peripheral vision in AMD is better than none.

General anaesthesia used to be ubiquitous but is now hardly ever used because it is unpleasant for the patient, dangerous for those in poor health and expensive for the health service. It is usually unnecessary. I still use it in patients who (1) insist (2) are claustrophobic (3) have an uncontrollable head or body tremor (4) are demented (5) are mentally subnormal (6) children.

Patients (perhaps surprisingly) generally have no difficulty keeping their head and body still during cataract surgery under local anaesthesia. There is virtually no risk to the patients general health from the LA, the patients feel much better after if they have not had a GA and they can go home immediately after surgery so that overnight stays are a thing of the past.

Local anaesthetics used to be given by injection. This often hurts, the prospect frightens the patient and the injection is in my opinion not 'good for' the eye. I now almost always use topical anaesthesia. Several potent anaesthetic eye drops (Amethocine) are administered and additional intracameral anaesthetic is given via the main incision. This technique is usually painless and the patients appreciate the 'no needle' approach. To the surgeon the eyes feel better whilst the surgery is done and they certainly look better afterwards since injecting local anaesthesia sometimes causes ferocious conjunctival haemorrhage. Post-operative recovery is quicker after topical anaesthesia since the eye is not 'asleep' to the same extent and disconcerting post-op diplopia never occurs as it often does with injection local anaesthesia. More surgical skill is required since the eye can rove around during the operation although usually it doesn't because (1) the patient is asked to look at the light from the operating microscope and this keeps the eye still (2) because the surgical instruments inside the eye control the eye's movements.

Poor refractive outcome after phaco is unusual. The best way of avoiding it is for the surgeon to practice 'refractive cataract surgery' and to be aware of all the potential pitfalls and so avoid them.

As always good pre-operative biometry is essential.

There are two types of poor outcome -

1. Subjective - an unhappy patient but a reasonable refractive outcome. The main cause is an unrealistic expectation of the outcome e.g. total glasses independence. The management is avoidance - it is essential to educate the patient before surgery as to what can be reasonably expected.
2. Objective - a genuinely poor refractive outcome. There are many types e.g. (1) high sphere especially if it is hyperopic (any residual hyperopia is a poor outcome). (2) high cyl especially if it is so high that glasses are no good. (3) anisometropia.

The causes of a poor refractive outcome include (1) pre-operative biometry done badly (2) pre-operative biometry done well but in difficult circumstances such as pre-existing cornea scars. (3) High pre-existing cyl which is difficult to reduce surgically during the operation (4) induced astigmatism caused by outdated ECCE techniques - THIS USED TO BE THE COMMONEST CAUSE OF POOR REFRACTIVE OUTCOME BEFORE PHACO. (5) inserting the wrong IOL during surgery (6) manufacturer mis-labelling IOL so that the wrong power is implanted into the eye (7) unusual pre-operative circumstances. For example unilateral cataract in a high myope. Should the surgeon make the patient emmetropic in the operated eye so causing anisometropia or render the operated eye as myopic as previously so missing the chance to cure the patients myopia?

The treatment of an unsatisfactory refractive outcome includes -

1. Avoidance
2. Encourage the patient to use glasses if practical
3. Contact lenses are ok but frankly often a nuisance in elderly patients. This is especially true if the new silicone soft extended wear contact lenses are inappropriate for example because of high astigmatism.
4. Explant the IOL from the eye and replace it. This is a high risk surgical strategy.
5. Implant an additional IOL to correct spherical error
6. Do astigmatic keratotomy to treat residual astigmatism.
7. LASIK is generally safe and effective. LASIK should be done at least two months after the initial surgery so that the phaco incision doesn't split when the LASIK flap is made.

 

CATARACT IN CHILDREN

Paediatric Cataract Rare Various causes Surgery similar to adult Amblyopia = main problem

Care of children with cataract is best undertaken by specialist paediatric cataract surgeons e.g. those at Great Ormond Street Hospital. The surgery is similar to that done in an adult including the nowadays routine implantation of IOLs. The surgery can be 'tricky'. It is always done under GA. One of the difficulties is judging the correct IOL power to implant. This is because the eye will obviously grow as the child gets older. It is best to deliberately induce hyperopia so that as the eye gets larger it gradually becomes more emmetropic.

The main problem with paediatric cataract surgery is amblyopia because of anisometropia and ametropia, especially in unilateral cataract. Constant patching may be necessary.

A 6/6 outcome is perfectly possible but the child will inevitably be 'presbyopic'.

POST OPERATIVE CATARACT MEDICATION

Secondary cataract is very common, some estimates being as high as 50% of all cases. It is more frequent in children and young adults. It is also more frequent when the primary pathology is posterior subcapsular cataract.

It is a relatively trivial problem in the developed world. Treatment is Nd:YAG laser capsulotomy. This is quick, painless, simple and almost completely safe. Occasional complications are retinal detachment, cystoid macular oedema and severe elevation of IOP. However these are extremely uncommon.

The laser vaporises/cuts the thickened posterior capsule restoring vision to its post-operative level almost immediately.

Secondary cataract is a huge problem in the developing world where resources for laser capsulotomy are not available.

Lensectomy has become established as the treatment of choice for high myopes/hyperopes who are (1) presbyopic (2) beyond the reach of LASIK i.e. more than about 4 dioptres hyperopic or 9 dioptres myopic.

These patients are (1) often highly motivated (2) tend to get cataract sooner than in normal eyes. Patients need to be told about (1) the surgical risk (probably no greater than for LASIK and (2) presbyopia post-op.

An IOL is implanted into the eye. The natural lens is left in situ. Various models are available eg the 'Artisan'/'Implantable Contact Lens'.

I use the Artisan which clips onto the iris. It will correct any degree of myopia. For example I have rendered patients who were almost 20 dioptres myopic emmetropic using this technique. It is the treatment of choice for pre-presbyopic myopes beyond the range of LASIK (more than 9 dioptres or so). These patients are often highly motivated.

Accommodation is preserved using this technique which is why it is appropriate for younger patients. The IOL can be removed if necessary i.e. the procedure is reversible/adjustable.

Great surgical skill is necessary to avoid damage to the lens and cornea. The patients must be made aware of the risk associated with this procedure especially being told not to rub/put pressure on the eye which might force the cornea into contact with the IOL. The possibility of long term damage to the cornea endothelium is a reason why this technique is not generally advised for high hyperopes who have very small eyes.

Abroad, especially in North America, optometrists are involved in many aspects of cataract management other than providing glasses afterwards. This includes diagnosis of cataract, direct referral to ophthalmologists, pre-operative counselling and post-operative care such as prescribing/discontinuing medication.

The recent government consultation paper 'Action on Cataract' suggested much greater optometric input into cataract in the UK for example direct referral.

I would welcome these changes and I imagine many optometrists would too.

Optometrists are well able to judge how good a cataract surgeon's outcomes are!