by Professor Charles Claoué MA (Cantab), MD, DORCS, FRCS (Eng), FRCOphth, FEBO, MAE.
With the demographic changes to an older population, cataracts (which is predominantly age-related) is becoming commoner. The only effective treatment is surgery, and this is so successful that cataract surgery (phakoemulsification with intraocular lens implantation) is now the commonest surgical procedure in all developed countries.
Inevitably, there are cases where tort occurs, and these will probably become commoner in the near future. To understand this, it helps to have a basic understanding of what cataract is, and the surgical pathway before reviewing the commonest errors.
Inside the eye there is a crystalline lens which should be transparent. This lens becomes progressively opaque with the passage of time, and when this is noticed and causes visual symptoms, is then referred to as “cataract”. Patients very typically refer to “misty” vision. It should be noted that ophthalmologists use the term in a stricter technical sense to denote any opacity within the crystalline lens whether visually significant or not. The surgery is technically complex and demanding although the procedure lasts only about 30 minutes. It is usually performed under local anaesthetic as a day-case. There is minimal if any pain. The contents of the crystalline lens are liquefied by an ultra-sound probe (“phakoemulsified”) and then aspirated via a 1mm cannula, leaving the capsule of the lens. This capsule is used to support an intraocular lens implant (IOL) which is injected and which unfolds within the eye. Typically no sutures are required for the 2.3mm incision which is constructed to be valvular, and the procedure is completed with intraocular antibiotics. The patient uses antibiotic and anti-inflammatory eye drops for about a month, and in the majority of cases the results are outstandingly good. This of course has created the expectation that “my” surgery will have a good outcome, and when this is not the case there is the expectation that an error must be the cause. Indeed, the surgery is so successful and predictable that a variant has evolved called “refractive lens exchange” where essentially the identical surgery is undertaken in the absence of any significant cataract with the sole intention of changing the refraction of the eye and the need to be spectacle dependent. This is because the crystalline lens is one of the 2 structures of the eye (the other being the cornea) which are amenable to surgical treatment to change the need for spectacles; such surgery is called “refractive surgery” and whereas corneal refractive surgery such as LASIK is ideally undertaken between the ages of 21 and 40, lens-based surgery is usually restricted to those over 45. The author described the first case of such surgery to treat presbyopia – the need for glasses for near-vision tasks required from about the age of 45 onwards.
This procedure is now widely practised and is called PREsbypic Lens EXchange or PRELEX. It is a procedure that has found favour with “baby boomers”. The issues of potential negligence are virtually identical as for cataract surgery, except that of course there s no cataract and the diagnosis is refractive error! In assessing where things go wrong, it is helpful to look at the various steps of the procedure in turn.
Diagnosis & Pre-operative Management
The diagnosis is not frequently questioned. The patients are typically referred by opticians thereby providing corroboration. However, there may be missed co-morbidity which means that the patient does not achieve good vision after successful surgery. Since the cataract obstructs a clear view (and often any view) of the retina, a regular scenario is the patient with cataract and undiagnosed age-related macular degeneration who is unhappy with their post-operative vision. So long as an attempt has been made to view the retina, and if (ideally) the patient has been warned that they have a guarded prognosis because of the lack of retinal view, then this would not be negligence.
However, the next major part of the work-up is to measure the eye for the IOL power, and this is a common cause of issues. The IOL is effectively a tiny lens, and as such has an optical power. This power varies from eye to eye, and to achieve an optimal optical outcome (usually freedom from glasses for distance vision: emmetropia) careful measurements are required which are the basis for a calculation of the IOL power required; this process is called “biometry”. Obvious sources of error include wrong measurements (wrong eye, wrong patient, bad technique), and inaccurate calculation. Sadly, even when this is undertaken perfectly, the wrong IOL can be implanted due to human error. In addition, the calculations are less accurate for specific eyes that are severely short or long-sighted, and also eyes that have had laser vision correction. This last scenario is likely to become a bigger problem, as patients frequently forget to tell their ophthalmologists who also frequently fail to ask! Since it is extremely easy to miss on examination, the first time it becomes manifest is an unhappy patient post-operatively!
Consent is of course fundamental. However, given that most surgery is undertaken on conscious patients, the lack of a written consent is not insuperable, even if this occurs rarely. What is much more common is inadequate information on a consent form, although this has improved of late. Exemplary consents include wording that patients can understand such as “no improvement” or “worse vision”. Part of the consent should be agreement on the target optical outcome, and this will be considered below.
One still sees “Routine procedure” as the sole operative record whereas it is quite obvious that this was not the case! In view of the repetitive nature of the operation, it is understandable that surgeons use abbreviated operation notes. I recommend the use of pre-printed adhesive stickers covering the main stages, which can then be annotated to complete the record in about 30 seconds. The laterality, use of antisepsis, adequate closure and use of antibiotics are often weaknesses if not recorded.
Despite the widespread introduction of the WHO (World Health Organisation) checklist, wrong side surgery (a “Never Event”) still occasionally happens, usually in association with a general anaesthetic and a patient the surgeon has never met but which was put on their list to “meet service needs”. It should be universal that the laterality is marked with an indelible pen pre-operatively by asking the patient to point to the eye on which they expect surgery, and since the pupil has to be dilated for surgery, this should provide a second laterality “mark”. Wrong eye surgery is indefensible.
The selection of the IOL to be implanted can be problematic. It is common for mistakes to be made “+27” for “+21” or the correct IOL for the left eye to be implanted in the right eye. There are a variety of styles of IOL with resultant differing powers for any given eye, and this also causes problems.
Surgical complications are not negligence, but their management needs to be well documented and reasonable. The commonest is the need to surgically amputate part of the vitreous body (“vitrectomy”), and this occurs in up to 5% of routine cases. Unfortunately, this worsens the prognosis and predisposes to post-operative complications such as retinal detachment. As such, meticulous surgery is required and this also needs to be meticulously recorded despite the fact that the operating list is now probably running late!
Often, the first time that it becomes apparent something has gone wrong is in the post-operative period. Despite all our improvements and efforts, intraocular infections (endophthalmitis) still occur with a frequency of about 1 in 3,000. Sadly, despite optimal therapy, the outcome is often poor, and patients frequently believe they have been treated negligently. My experience over ten years is that management has improved and in general the poor outcomes are related to the disease rather than the procedures. The other two common issues relate to binocular vision problems and IOLrelated difficulties.
If a patient has binocular double vision (diplopia) and then develops a cataract in one eye, the diplopia becomes less problematic as the image in the cataractous eye fades. However, if this eye undergoes a successful cataract operation, the diplopia will return and may be disabling. Unfortunately it is not always possible to find a solution in this situation without further surgical procedures which might include squint surgery, botulinum toxin injections (which may have to be repeated) or the insertion of an opaque IOL to render the eye “blind”. Unless the problem has been identified pre-operatively and the patient suitably consented, this can be a valid reason for a negligence action.
A major source of patient unhappiness and negligence procedures are IOL-related. Since an IOL is a lens and frequently changes the need for spectacles, it is essential that the patient understands the optical target and agrees to it. A common and indefensible scenario relates to patients under 45 year of age. Such patients are pre-presbyopic; they can accommodate and see well for near and distance with the same (if any) spectacle correction. Since the majority of IOLs are monofocal and fixed focus, following surgery and if targeted on emmetropia, such eyes will need reading glasses for all near work. This is often poorly tolerated, especially if unexpected. If not informed and consented this can be indefensible. However, the majority of patients having cataract surgery are over 45 and adapted to the need for reading glasses. Another “binocularity” scenario is the patient with unilateral cataract; since almost all eyes are targeted on emmetropia, it happens that the optical status of the other eye is not taken into account. If the other eye has no cataract but needs a strong optical correction then the 2 eyes will be so different that the brain will not tolerate a spectacle correction (anisometropia) and the patient will be unhappy. Similarly, if a patient has been short-sighted all their life and can just take off their glasses to read, if they are rendered emmetropic and spectacle-dependent for reading they can react very badly if not previously counselled. Indeed, even if a short-sighted outcome has been discussed and agreed, because almost all eyes are targeted on emmetropia, this planned outcome can be “forgotten” at the time of surgery
Finally, there is the “refractive surprise” scenario. In such circumstances, the planned optical outcome is not achieved. There are limitations to biometry, but the majority of outcomes should be within +/- 1 dioptre of planned. Unfortunately, this becomes much less likely in eyes that are severely long or short-sighted or have had laser vision correction, and appropriate pre-operative counselling should have been given. There are still cases where the optical outcome is very different from that planned despite good biometry and allowing for other factors; such cases are called “refractive surprises” and providing all procedures have been carried out to a high standard are not negligent. Nevertheless, the patient will be unhappy, and if active management is not undertaken (commonly an IOL exchange) then they may initiate proceedings for alleged negligence. Matters can be worse if the IOL implanted was mislabelled; if the surgeon implants a +30 IOL from a box labelled +13 the eye will be severely myopic; to correct this he now removes the first IOL, and unaware that it was mislabelled by the manufacturer, implants an IOL substantially lower power than the +13 desired, and the patient suffers a second refractive surprise and is severely long-sighted this time! Unless the first IOL is examined at a specialised laboratory, the error is difficult to prove and after a second refractive surprise the patient has lost all faith in their surgeon and wants to see a solicitor! This is even more likely if the patient has paid for their surgery and specifically if they have had a refractive lens exchange rather than cataract surgery.
In summary, cataract surgery is such a safe and successful procedure that it has become both trivialised as well as the commonest surgical procedure. The surgical planning and actual performance have potential pitfalls and some negligence scenarios are sadly repeated. Given the ageing population and the ever higher expectations, it is likely that we will see a steady increase in alleged negligence actions by unhappy patients. I am most grateful to Miss Hanifa Azri, Barrister (Inner Temple) for reading and commenting on this article. ?