Abstract
It is estimated that over 40 million people have had laser vision correction worldwide since 1991. Laser-assisted subepithelial keratomileusis is commonplace in the UK in high street chains and from more bespoke suppliers. The standards around this treatment have always been regulated by the General Medical Council (GMC), but litigation cases have been common. The recent GMC guidance for cosmetic procedures and subsequent guidelines by the Royal College of Ophthalmologists cover advertising, facility regulations, equipment, consent and surgeon training which should improve industry practices and deliver improved patient safety standards.
Lasers are used extensively by Ophthalmologists for a variety of diagnostic and therapeutic tasks. All lasers are not the same, but they all produce a coherent, unidirectional, monochromatic light which can be precisely focussed. A laser utilises photochemical (breaking bonds) or photomechanical (disruption) or photothermal (heat) effects to promulgate changes in the tissues of the eye.
In this article, laser eye surgery refers to refractive surgery on the cornea only and not to any of the other manifold uses of laser for eye surgery.
Refractive surgery is surgery performed with the primary aim to alter the refracting power of the eye rather than to treat or cure any inherent disease process. By this definition, most eyes undergoing laser eye surgery will be otherwise healthy, the motivation for the patient will be to lose dependence on spectacles or contact lenses.
The eye in its simplest construct has a cornea (the clear window of the eye), and a natural lens within the eye which together refract light to focus onto the retina at the back of the eye (analogous to the film in an old fashioned camera). If the cornea and lens refract the light too much or too little and do not focus light precisely onto the retina, then spectacles or contact lens are required to achieve this or vision will be suboptimal.
In laser eye surgery, rather than using spectacles or contact lenses to refract light, the shape of the cornea is altered to improve the focus of the eye. This is achieved using principally two types of laser in varying combinations with many confusing acronyms.
Femtosecond laser
This laser uses photo disruption to create accurate cleavage planes within the corneal tissue. In the predominant form of laser vision correction (LVC) laser-assisted in situ keratomileusis (LASIK), the femtosecond laser creates a flap in the cornea with a hinge so it may be lifted without being lost, and the cornea underneath is reshaped with a second laser (excimer – see below).
A newer procedure on the market (but not proven to be particularly better or worse with respect to outcomes or complications at this time), SMILE by Zeiss, 1 uses the femtosecond laser to create a thin lenticule within the cornea which when surgically removed is calculated to create a beneficial change in the surface profile of the cornea post operatively, and hence improved unaided vision.
Excimer laser
This laser uses photo ablation to reshape the cornea in a controlled manner. When this occurs, the cornea becomes thinner and therefore the available thickness of the cornea preoperatively is an important factor which may limit the available correction achievable in some people and increase the risk of ectasia in others (in some people post operatively the treated cornea may continue to steepen this is due to mechanical weakness of the thinned cornea and produces poor visual outcomes). The excimer laser is used in LASIK after the femtosecond laser has produced a flap and the surgeon has lifted the flap. The excimer laser is also used without a femtosecond laser created flap in photo refractive keratectomy (PRK) and LASEK (laser-assisted subepithelial keratomileusis). In PRK and LASEK, the surface of the cornea is removed firstly either with dilute alcohol or a uniform ablation with the excimer laser (trans epithelial) followed by secondly a refractive ablation with the excimer laser to reshape the cornea.
Risk management in the pre-operative consultation
The assessment for LVC is performed to exclude those patients who if they had LVC performed would not have a good outcome. These exclusions are lengthy and may vary between patients (i.e. are not an absolute contraindication always).
History
A detailed history is required, specifically previous ocular symptoms, treatments and surgeries. Probably the commonest post-operative symptom is dry eye. 2 LVC is likely to worsen any pre-existent symptoms of dry eye as the nerves to the ocular surface are sectioned when the flap is created and may not heal for many months. The healed nerves often do not function to the same level as pre operatively and therefore symptomatically the patient may be worse, possibly permanently, and should know this.
Issues which may prevent the creation of a perfect flap should be disclosed, such as previous corneal scars, dystrophies (a congenital dysfunction of the cornea), and recurrent corneal erosions which although not an absolute contraindication to LVC, would direct the surgeon to suggest PRK surface laser and a more detailed discussion of the risks.
Lifestyle factors can help the surgeon and patient understand whether LVC is suitable. Professional drivers, pilots, military and others with known visual standards for their occupation must understand the limits of the treatment that is proposed and whether this is prohibited for their occupation, or if authorised how long this may prevent them working before resuming work. For instance, pilots with a class 1 licence undertaking LASIK may be restricted from flying up to three months, dependent upon satisfactory examination and refraction by a CAA registered Ophthalmologist. 3
A longer conversation is required for the middle-aged patient. Due to the ageing process, the natural lens of the eye loses flexibility (presbyopia). Prior to this, the natural lens can change the focus from far to near like the zoom on a camera. After middle age, the zoom is fixed. This means that the outcome after LVC will be different in comparison to younger patients. In younger patients after LVC, the likely outcome will be good vision in the distance and for near. In the middle aged, it will be either near or far (dependent on choice) but not both. Therefore, middle-aged patients may still need spectacles for some distances after LVC.
Ocular factors which may prevent successful LVC include non-stable refraction (a lower age limit is not as important as the refraction being stable, although most practitioners would not operate below aged 18 years without an exceptional reason), the various causes of dry eyes, irregular corneas and scars, corneal dystrophies, lid disease, blepharitis, that may increase the risks of inflammation post operatively 4 (deep lamellar keratitis).
The patients general health is important as those with active rheumatological and some autoimmune conditions (i.e. rheumatoid arthritis, SLE, etc.) will need to be excluded. These conditions target collagens, which can potentially cause corneal melting. 5
Any of the above if an absolute contraindication would clearly prevent LVC from being performed, whilst a relative contraindication would need to be placed within context and discussed as part of the consent process, individualised and set against the expectations of the patient.
Examination
The examination should as a minimum consist of visual acuity measurements unaided and with refraction. A cycloplegic refraction is performed (with the ciliary muscle paralysed with cyclopentolate) in certain groups, particularly hyperopic prescriptions, as a degree of hyperopia may otherwise be hidden by the action of accommodation. The eyelids are examined to exclude blepharitis (which may promote infection or inflammation, or predispose to evaporative dry eye). The tear film should be good volume and non-evaporative. The cornea should be examined for signs of scarring which may cause issues with flap creation, dystrophies which may create flap issues, or poor outcomes due to recurrence within the interface. Pupil sizes were an issue in the past, as the optical zone of the ablation was within the pupillary zone creating an edge effect and symptoms of glare and haloes for patients. With modern laser systems the blend zone on the excimer ablation is wide, and pupil size is not now often an issue.
If a cataract were present (an opaque crystalline lens within the eye), any LVC performed would not have a beneficial effect and therefore must be excluded with dilated examination pre operatively.
Retinal issues have been contentious. The predominant group undertaking LVC are young myopic (short sighted) individuals. This group has a higher incidence of retinal detachment than general population, 6 but there has at this time been no proof of cause and effect after LVC. Nonetheless, a dilated examination is required to examine the retina and refer for treatment of any pre-existent retinal lesions. 7
Diagnostics
Imaging of the eye pre operatively is necessary for: (1) risk management and (2) as part of the treatment episode.
Risk management
When the cornea is ablated and reshaped by the excimer laser, the cornea is thinner post operatively. The biomechanical strength of the cornea depends upon the thickness of the cornea and its intrinsic biomechanical properties. The thickness of the cornea can be easily measured by ultrasound, Optical Coherence Tomography (OCT) or Scheimflug photography. This must be performed. The intrinsic biomechanical properties of the cornea are less easily measured, although devices do exist to measure corneal elasticity and hysteresis, there is a large overlap within the general population and therefore it has not proven clinically useful at this time.
Corneal shape can be measured with topography or tomography and must be performed. The shape of the cornea can sometimes reveal if there is a predisposition to ectasia post operatively. Ectasia is a progressive steepening of the cornea post operatively. All the factors leading to ectasia are unknown, but treating a cornea that is too thin or with a characteristic shape (forme fruste keratoconus) preoperatively would be negligent.
Tear film levels may be measured with various tools, including paper strips (Schirmers test) and tear film aberrometry. The issues with these are that just as the tear film may be variable, so are the test results. Nonetheless, particularly in some groups, it may be wise to perform these pre operatively. For instance, in contact lens wearers with dry eye, the issue may not be hypo secretory, but due to the contact lens in which case LVC may be indicated. Therefore, objective evidence of this would help defend a claim if subsequently the patient developed dry eye incidentally.
Retinal photography pre operatively to demonstrate that the retina did not have pre-existent lesions, and if there are lesions to have these checked and treated by a vitreo retinal expert would be good practice.
Diagnostics for treatment purposes
In addition to those listed above, patient may also require tests such as wave front aberrometry. These measure the creation of higher order aberrations by the eye (how the eye distorts light, try looking at the red round on/off light on a television and notice the star burst effect your eye creates), and the wave front is divided mathematically (by Fourier or Zernike method) to allow creation of a customised ablation pattern by the excimer laser. These wave front treatments aim to minimise the intrinsic aberrations produced by the eye, so post operatively there is a reduction in glare and haloes symptoms.
Consent issues
Following the report on the cosmetic surgery industry by Sir Bruce Keogh in 2013, 8 the General Medical Council (GMC) subsequently published guidance for doctors who offer cosmetic interventions in 2016. 9 Whilst these guidelines were not established for refractive surgery (cosmetic surgery was defined as any intervention, procedure or treatment carried out with the primary objective of changing an aspect of a patient’s physical appearance) in which the physical appearance is unchanged nonetheless the GMC has indicated that they consider refractive surgery to be within its remit, as it had been recognised that similar issues coexisted in the refractive surgery industry and the Royal College of Ophthalmology commissioned a working group to provide guidelines which were published in April 2017. 10
The process of consent may begin with the initial contact through advertising. In the past, adverts had made extraordinary claims such as 100% 20/20 vision that imply the procedure is risk free without information that this was in a small subset of patients and without the knowledge that there is the 20/20 unhappy patient. Adverts must now comply with the Committee of Advertising practices regulations. 11 Bait and switch tactics such as advertising £395 per eye without explaining that this is only available for a particular technology and a narrow refractive indication are now prohibited. All material information should be disclosed to allow the patient to make an informed choice including an explanation of the range of prices and the eligibility criteria. Surgery should not be trivialised and regarded as a competition prize or a two for one offer.
Consent is a process, performed by the operating surgeon, to inform the patient of the benefits and the risks to them personally of the proposed procedure and any reasonable alternatives. Patient expectations must be ascertained, and if unreasonable then informed so. This patient-centred approach is enshrined in the GMC Good Medical Practice and Consent: Patients and Doctors Making Decisions Together.
12
Following Montgomery vs Lanarkshire Health Board, material risks must also be discussed, defined as: The test of materiality is whether, in the circumstances of the particular case, a reasonable person in the patient’s position would be likely to attach significance to the risk, or the doctor is or should reasonably be aware that the particular patient would be likely to attach significance to it.
Although this is a surgical procedure, it is also a commercial transaction. It must be made clear during the consent process, that although payment is taken, that payment does not guarantee success. The costs of treatment and any potential subsequent costs for remedial treatment that could reasonably be predicted must also be declared in advance of treatment.
Surgical treatment
Successful surgery is dependent upon many factors including equipment, surgical skill, patient factors within treatment parameters, correct pre-operative preparation, correct post-operative treatment and early management of any complications.
Negligent treatment, conversely, may be due to incorrect or poorly maintained equipment in an incorrect environment (humidity and temperature are essential for good laser function and a record should be kept) or, poor surgical skill such as incorrect management of an intraoperative complication (the having an intraoperative complication is not necessarily in itself negligent although it may be if it was caused by failure to prevent by omitting a certain pre-operative preparation). Poor outcomes may be expected when treating patients outside the limits of the technology, or with contra indications as discussed in the history, examination or diagnostics sections of this article.
Infection after LASIK is less likely than infection in contact lens wearers. 13 But, nonetheless, infections do occur approximately 1 in 20,000 LASIK cases. Good outcomes depend upon prevention of complications with antimicrobial prophylaxis including fourth generation fluoroquinolones pre and intraoperatively and broad spectrum antibiotics post operatively. Steroid eye drops are applied post operatively to prevent inflammation, but occasionally steroid-induced glaucoma (raised intraocular pressure) occurs and a follow-up visit where intraocular pressure is measured should be arranged on discharge.
Occasionally, early post-operative issues may arise which when dealt with early provide good outcomes. The LASIK flap may have fine wrinkles (striae) which affect the quality of vision necessitating flap lift and occasional suturing of the flap, growth of the epithelial lining of the cornea under the flap requiring flap lifting and removal (epithelial ingrowth) is best dealt with early to prevent progression and flap melt. It may be difficult to distinguish inflammation (diffuse lamellar keratitis) and infection (microbial keratitis) in the early post-operative period. Each has very different treatments, and failure to perform adequate sampling to exclude infection would be negligent. This requires the LASIK flap to be lifted and samples taken for microbiological sampling to exclude bacterial infection.
After LVC has been completed, most patients are satisfied and become spectacle free. However, a small percentage may still be a little short- or longsighted. A retreatment may be offered by the practitioner, but this should be considered a separate event, with re-evaluation of the cornea, repeat refraction and imaging, and a repeated consent process focussing on the risks and alternatives. The risks of a second procedure are not the same as the primary procedure, particularly with respect to epithelial ingrowth if the flap is lifted, and this should be made clear.
Summary
Laser vision correction provides excellent outcomes for well screened people with realistic expectations, within the parameters of the technology. New rules and guidance are available from the GMC and Royal College of Ophthalmologists covering advertising, consent and standards of care expected.
Footnotes
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
Guarantor
DL.