Counselling patients for refractive surgery.
The popularity of refractive surgery has grown significantly over the years and the number of procedures performed globally is forecast to rise at an annual rate of 5.5%. (1) Many clinics now offer a spectrum of refractive surgery procedures depending on patient needs and expectations. This article will discuss the counselling process for suitable patients considering refractive surgery, which covers procedure details, postoperative visual expectations, lens selection (for all intraocular lens surgeries) and complications that may arise. Aftercare regime, which varies with procedure and clinic is also discussed and includes details on the medication regimen, eye protection, hygiene protocols and restrictions on exercise and other activities.
Laser vision correction
Laser vision correction (LVC) provides a safe, effective, treatment for refractive error. It is the world's most popular elective procedure, with more than 28 million laser-assisted in situ keratomileusis (LASIK) procedures having been performed worldwide. (2)
LASIK is the most conventional form of LVC and is suitable for patients with myopia up to--12.00D spherical equivalent (SE), and hyperopia up to +3.00D SE, with up to 3.00DC. (3) Treatment ranges can vary significantly with differing practitioners and laser platforms.
LASIK generally takes 10-15 minutes and is performed under topical anaesthesia. The first stage involves the creation of a protective flap, typically with a femtosecond laser. The laser separates the cornea at the level of the stroma and the flap is then lifted to allow reshaping of the stromal bed using an excimer laser. Previous iterations of LASIK involved the use of a mechanical microkeratome to create the protective flap, but this approach has largely been superseded due to improved visual outcomes through the use of femtosecond lasers. (4) Most patients will generally experience some discomfort for the first few hours following the procedure and are advised to sleep or rest at home during this time. Patients will have functional vision the following day, with many reaching driving standard or better.
Laser-assisted sub-epithelial keratectomy (LASEK)/photorefractive keratectomy (PRK)
In this form of LVC, the corneal epithelium is loosened using an alcohol solution and the excimer laser is applied. LASEK involves repositioning the epithelium back over the stroma, while in PRK the epithelium is discarded. A protective bandage contact lens is then placed over the epithelium, which allows the epithelial layer to heal with minimal disturbance over a period of three to five days. Patients are warned of a delayed visual recovery and increased discomfort after the procedure and are, therefore, cautioned to ensure sufficient time off work and normal day-to-day activities.
LASEK is recommended where the creation of a flap in the cornea is not advised. Clinical reasons may warrant this such as evidence of corneal scarring or insufficient corneal thickness for LASIK. Alternatively, a recommendation for LASEK/PRK can be made based on the lifestyle of patient, for example, those who actively participate in contact sports. The rationale behind this is to preserve the natural corneal biomechanical strength, which is normally compromised when a flap is created. (5)
Small incision lenticule extraction (SMILE)
SMILE is currently solely approved for treatment of myopia and astigmatism, and utilises a femtosecond laser for the entire procedure. It is only available using the Zeiss VisuMax femtosecond laser and involves the creation of a lenticule of stromal tissue, which is then removed via a small incision (see Figure 1). As no flap is created, the advantages are enhanced biomechanical strength and reduced disruption to the corneal nerve plexus, therefore, resulting in potentially less postoperative dry eye. (6) Consequently, SMILE can be recommended to patients who would not be ideal candidates for LASIK as aforementioned or those who may be predisposed to dry eyes postoperatively. General recovery with SMILE is similar to LASIK; however, visual recovery can be slower. The visual outcomes are typically similar for the two procedures at two to three week's postoperatively. (7)
LVC normally targets distance vision emmetropia. Patients are counselled on the effects of presbyopia and the need for near vision spectacles in the future. For those approaching or already experiencing presbyopia there are various options available:
* Full distance vision correction--this option would be recommended if uncompromised distance vision is required, for example, in certain occupations such as pilots or taxi drivers. It may also be a good option for those who are happy to wear near vision spectacles postoperatively
* Monovision--spectacle dependence is reduced overall by targeting distance vision in one eye (usually the dominant eye) and near or intermediate vision in the other eye. For those who have not experienced monovision previously, a period of neuroadaptation is required, which may take several months before patients appreciate the full benefits. Laser blended vision, which is offered on certain laser platforms, is an enhanced form of monovision which controls the postoperative spherical aberration in order to increase depth of focus; this essentially enhances the intermediate vision in both the distance and near eye which aids binocularity and improves tolerance. Overall the benefits of blended vision include reduced spectacle dependence, maintained contrast sensitivity and stereopsis. (8) The limitations include non-tolerance in some patients (which is normally determined preoperatively) and the reduction in near vision with increasing presbyopia which may necessitate the need for an enhancement in the future. Furthermore, if cataract formation occurs in the future, this will also interfere with the visual results of the treatment
* Multifocal laser correction--treatments available such as Presbymax aim to create multiple focal zones on the cornea which produces vision at all distances. Depth of field also remains high due to the aspheric nature of such treatments; however, compromises include night vision symptoms which may cause difficulty with night driving. (9)
Patients should always be provided with consent forms detailing complications of LVC to reinforce the verbal discussion carried out. Complications of LVC include:
* Dry eye--this is the most common side effect, which in most patients is easily managed with lubricating drops
* Glare/haloes--can be very common in the recovery period and usually settles in the first three months
* Infection--such a complication may reduce postoperative BCVA, but incidence rates are low, ranging from 0.02-1.5% (10)
* Inflammation--the most common variant is diffuse lamellar keratitis in LASIK. Incidence is between 2-4% and it is normally managed with steroid drops (11)
* Regression--as the cornea heals a residual prescription may return and an enhancement may be then be necessary
* Ectasia--this is characterised by a protrusion of the cornea through progressive weakening.
The incidence of this is very low at approximately 1/2000. (12)
Phakic intraocular lenses
Phakic intraocular lenses (pIOLs) are normally recommended for patients who are unsuitable for LVC, such as those with very high prescriptions or thin corneas. The procedure is typically carried out unilaterally and involves the insertion of an IOL into the anterior or posterior chamber (depending on the lens type) through a self-sealing corneal incision.
Anterior chamber IOLs include iris-fixated and angle-supported designs. Iris-fixated lenses are secured in the anterior chamber by two haptic claws, which clip on to the iris. Angle-supported lenses simply wedge into the iridocorneal angles. Anterior chamber lenses correct large prescription ranges, but iris-fixated lenses are unsuitable for patients partaking in contact sports due to the risk of lens dislodgement upon incidental ocular trauma.
Posterior chamber lenses, such as the Visian ICL are positioned into the ciliary sulcus, which is a space between the iris and ciliary body (see Figure 2).
Lens choice varies with each individual clinic and is based on prescription, anatomical data, and surgeon preference. Assuming no ocular morbidity occurs in the future, phakic IOLs should provide a long term distance correction and the only spectacles a patient should require are those for near vision once presbyopia arrives. However, it must be stated that each type of pIOL has a limited lifespan and this is due to the anatomical changes that occur with age, which eventually results in incompatibility issues with these IOLs. For anterior chamber IOLs the primary criteria is endothelial cell count (ECC). A patient requires a minimum ECC prior to surgery, which is denoted by the manufacturer. This must then be monitored annually postoperatively and if the ECC falls below 1500 cells/[mm.sup.2], the pIOL should generally be removed or this may lead to corneal decompensation. (13) Anterior chamber depth and lens rise are the biggest factors affecting pIOL lifespan.
The anterior chamber reduces by an average of 0.7mm over a 60-year period, (14) and the crystalline lens thickens anteriorly at an average rate of 18-20 [miro]m per year. (15) These anatomical changes are relevant because if the natural lens comes into contact with the pIOL it can result in the formation of a cataract. By measuring lens rise preoperatively, existing formulas can be used to give patients an estimate on how many years a pIOL can remain in the eye safely. (15) Although pIOLs are not advised to be a permanent correction, they represent a good option for patients due to the wide prescription range that can be corrected as well as the fact the procedure is reversible.
* Endophthalmitis--this is a sight threatening infection, but is exceptionally rare. Posterior chamber IOLs have a reported incidence of one in 6000 (16)
* Endothelial cell loss--the corneal endothelium naturally loses a small percentage of cells every year; however, this can be accelerated by potential interaction between the cornea and the IOL due to lens movement, eye rubbing or persistent inflammation. (17) Excessive cell loss will require removal of the pIOL
* Pupil block glaucoma--this is prevented by a Nd:YAG laser iridotomy or surgical iridectomy. Certain lenses such as the Visian ICL have a hole in the lens to aid aqueous flow (see Figure 2)
* Cataract--long term cataract formation is a risk with increasing lens rise, but may also occur if the lens curvature increases significantly on accommodation resulting in intermittent contact with the pIOL. (18) The incidence of cataracts after pIOLs are reported to be 1.29% with angle-supported lenses, 1.11% with iris-fixated lenses, and 9.60% with sulcus-fixated lenses (19)
* Chronic uveitis--iritis from pIOL movement is a factor for this complication as well as secondary pigment dispersion. (20) If the uveitis does not resolve with topical steroids, the pIOL may require removal.
Refractive lens exchange (RLE)
RLE is a procedure whereby the natural lens is replaced with an IOL. The IOL is calculated to correct the refractive error of the patient, thus enabling freedom from spectacles. RLE is normally reserved for patients that have reached presbyopia. Presbyopic patients are likely to have some lens changes manifesting in reduced accommodative power or lens aberrations.
Many clinics carry out RLE procedures unilaterally, but a smaller proportion may opt for bilateral treatment. During this interim period, patients are normally able to balance with an adjusted spectacle correction or with a contact lens in the untreated eye. The entire procedure can be carried out using topical anaesthesia or a subTenon's anaesthesia if preferred.
The procedure involves a small self-sealing incision on the cornea, followed by an opening created on the anterior capsule of the lens known as a capsulorhexis. The inner lens is then broken up using a phacoemulsification procedure and aspirated out. A folded IOL is inserted into the lens capsule, which then promptly unfolds.
While many surgeons perform the entire procedure manually, some clinics also offer femtosecond laser-assisted cataract surgery.
These lenses consist of a singular focal zone and will, therefore, only provide correction of vision at one distance. Depending on the spherical aberration profile of the IOL and the patient's cornea, some intermediate vision may also be obtained. As high contrast is maintained with these IOLs and night vision symptoms are not a concern due to the singular focal zone, monofocal IOLs are suited to patients whose priority is to achieve optimal distance vision as well as night vision.
For those looking to achieve the possibility of spectacle independence, multifocal IOLs are a good option as these lenses can correct the entire visual range, incorporating distance, intermediate and near (see Figure 3). However, there are compromises with such IOLs and these include the possibility of glare, haloes and dysphotopsia. Contrast may also be noticeably reduced, which can result in increased dependence on good lighting when reading. A patient's occupation and lifestyle should be discussed to establish whether the benefits of multifocal IOLs outweigh the risks. It must also be stated that spectacle independence can never be guaranteed and patients should be informed of the possibility of requiring spectacles postoperatively for certain tasks. Where possible, statistical data can be given to the patient, which should reflect the literature, or more ideally the audit data of the treating clinic.
Other types of IOLs used include extended depth of focus IOLs, accommodative IOLs and light adjustable IOLs. For any RLE procedure, practitioners should accurately outline the benefits and risks of all IOLs available to the patient and where possible make a recommendation of the IOL that will best match their needs.
The results of an RLE procedure can be permanent, providing no ocular morbidity occurs in the future. The need for any potential future cataract surgery will also be obviated. The aim of the procedure is to reduce or eliminate the refractive error of a patient and if a residual refractive error occurs postoperatively, patients are counselled regarding remedial procedures, which may include a laser enhancement or piggyback IOL. The counselling process on visual expectations can vary from case-to-case depending on the clinical findings. For example, those who have had previous laser vision correction should be warned of the increase in unpredictability of the IOL calculations and as a result a higher risk of a possible residual postoperative refractive error. Piano presbyopes who are keen on multifocal IOLs to eliminate the need for reading glasses should be cautioned of the increased risks as these patients are starting out with good unaided distance vision, which may be compromised if there is anything less than an optimal outcome. Less than 1% of patients may be intolerant of multifocal IOLs and in such cases a lens exchange to a monofocal lens may be required. (21)
As well as discussing the documented complications of RLE procedures, it is also essential to inform patients of any additional risk due to existing ocular comorbidity or IOL type. The most significant complications of RLE include:
* Endophthalmitis--this is an infection, which may necessitate removal of the IOL. The incidence of endophthalmitis is significantly lower than 1%, especially since the introduction of intracameral antibiotics (22,23)
* Retinal detachment--a long-term study conducted over 10 years reported retinal detachment occurring in 1.17% of cases following cataract surgery, with the risk being greater in those under the age of 50 and higher axial lengths >26mm. (24,25) It is, therefore, important to highlight the additional risks for patients falling into these groups
* Posterior capsular tear--the Royal College of Ophthalmologists reports a tear of the posterior lens capsule as perhaps the most common surgical complication occurring in approximately 1.6% of cases. (26) Such an outcome may affect the lens selection as the IOL will need to be housed in the ciliary sulcus, whereupon a monofocal IOL is most commonly used. This is particularly relevant for counselling patients opting for a multifocal IOL at the outset
* Cystoid macular oedema (CMO)--within one year of RLE surgery, the incidence of CMO is 1-3%, most commonly occurring between two to four months. (27) This condition occurs when fluid accumulates at the macula and forms cystoid spaces and leads to a reduction in vision overall. Management includes topical steroidal and nonsteroidal anti-inflammatories
* Posterior capsular opacification--a thickening of the posterior capsule can occur long after RLE surgery and leads to blurring of vision, glare and reduced contrast. The incidence varies with IOL material and design, as well as surgical technique. (28) It is easily treated with a Nd:YAG laser capsulotomy.
In many clinics, counselling will be done either by ophthalmologists or specialist optometrists working alongside ophthalmological colleagues. Ultimately it is the treating surgeon that has final responsibility. However, it is still incumbent upon optometrists involved in the counselling process to address the areas of discussion outlined in this article. Refractive surgery can have a positive effect on the quality of life of many patients and in some cases can even be life-changing. However, as these are elective surgeries, practitioners should always guide patients appropriately on the risks and benefits of the procedures available to them. This creates a structured consent process allowing patients to make well-informed decisions.
Exam questions and references
Under the enhanced CET rules of the GOC, MCQs for this exam appear online at www.optometry.co.uk. Please complete online by midnight on 8 December 2017. You will be unable to submit exams after this date. Please note that when taking an exam, the MCQs may require practitioners to apply additional knowledge that has not been covered in the related CET article. Visit www.optometry.co.uk, and click on the 'Related CET article' title to view the article and accompanying 'references' in full.
* Sundeep Vaswani is a specialist refractive optometrist. He currently works in a private hospital setting, which offers multidisciplinary ophthalmic services. He has nearly a decade of experience in refractive surgery covering areas of laser vision correction and intraocular lenses.
* Jay Bhatt is a specialist refractive optometrist. He graduated from Aston University in 2004 and currently works in a private hospital setting that offers multidisciplinary ophthalmic services. He has worked within the field of refractive surgery for over 10 years.
* Vicky Roberts currently works in a private hospital setting as a specialist refractive optometrist. She has over a decade of experience in refractive surgery covering areas of laser vision correction and intraocular lenses.
* Be able to counsel patients on refractive surgery options (Group 1.2.4)
* Be aware of advances in refractive surgery options (Group 2.5.3)
* Understand treatment options for refractive error (Group 6.1.11)
* Be able to inform patients about refractive surgery techniques (Group 1.2.4)
* Be aware of advances in refractive surgery options (Group 2.5.3)
* Be aware of treatment options for refractive error (Group 8.1.3)
Caption: Figure 1 Creation of lenticule and side cut in SMILE (left) and removal of lenticule (right).
Caption: Figure 2 Anterior segment OCT showing Visian ICL in ciliary sulcus (top), and Visian ICL showing KS-Aquaport to aid aqueous flow (bottom)
Caption: Figure 3 Image of Zeizz Trifocal IOL
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|Title Annotation:||Refractive surgery: CET|
|Author:||Vaswani, Sundeep; Roberts, Vicky; Bhatt, Jay|
|Date:||Nov 1, 2017|
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