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FYI on ICLs: surgical options for the extreme Rx: This article considers the indications, assessment, surgical procedure and follow-up of patients undergoing phakic intraocular lens implantation for the management of high refractive error.

Optometrists [COMMUNICATIONS] [OCULAR DISEASE]

Therapeutic Optometrists [SELF & OTHERS]

Dispensing Opticians [COMMUNICATIONS] [OCULAR ABNORMALITIES]

Introduction

Clinically significant refractive error affects nearly half of the population in the UK. (1) While many of these individuals are happy to wear glasses or contact lenses, some wish to pursue refractive surgery to decrease their reliance on vision correction aids. Laser in situ keratomileusis (LASIK) and small-incision lenticule extraction (SMILE) have been shown to be safe and effective options of vision correction for these patients. (2,3) While the majority of patients have a prescription that is well within the treatment range for most modem lasers, there are a small number that do not meet treatment parameters due to their prescription or corneal characteristics. One option to discuss with these patients is correction with a phakic intraocular lens (pIOL), which has the ability to treat prescriptions up to -20.00D, and even more if combined with corneal refractive surgery.

Artisan (Johnson & Johnson, Santa Ana, CA) lenses were the first widely used pIOLs. These initial lenses were designed as anterior chamber (AC), iris fixed, intraocular lenses. While the lenses provided great visual results, the lens itself was not foldable and thus required a large incision for implantation; this meant that sutures were necessary, often resulting in a long recovery process and unwanted residual astigmatism.

In 1997, the V4 Implantable Collamer (or contact) Lens (ICL) (Staar Surgical, Monrovia, CA) was approved for use in the UK. ICLs are extremely small and thin lenses implanted inside the eye (see Figure 1). In the UK, these lenses are available to treat myopia from -0.50 to -20.00D, hyperopia from +0.50 to +10.00D, and astigmatism up to +6.00D. The lens comes in four different sizes to accommodate a range of eye sizes. Lenses for myopia have a small hole in the centre that allows for improved aqueous flow. The lens sits behind the iris and in front of the natural crystalline lens (see Figure 2), and is anchored in place by footplates pushing into the junction between the iris and the ciliary body, that is to say, the sulcus.

Patient selection

Patients who are interested in pursuing a surgical vision correction should always undergo a full ophthalmic assessment including refraction, slit lamp, and dilated fundus examination with binocular indirect ophthalmoscopy; this is especially important for myopic ICL patients as they are more likely to have an elongated axial length due to their high prescription. If there is any concern regarding the far peripheral retina, it is recommended that the patient has wide field retinal imaging and evaluation with a retinal specialist using scleral indentation. In addition to the aforementioned examination, the following criteria for prospective ICL patients must be met:

* At least 21 years old

* Anterior chamber depth (ACD) greater than 2.8mm --ACD is defined as the distance from the corneal endothelium to the anterior surface of the crystalline lens

* Stable refraction--an unstable refraction is not an absolute contraindication and can be discussed with the treating surgeon.

It is also important, as the patient's eye care provider, to share any part of their ocular history that may affect the outcome of the surgery with the treating surgeon. Contraindications for ICL surgery can be broken down into two categories: absolute and relative. Absolute contraindications include, but are not limited to:

* Ocular pathology that affects the safety and outcome of the surgery:

* History of iritis

* Synechiae

* Pigment dispersion syndrome

* Pseudoexfoliation syndrome

* Ocular hypertension

* Glaucoma

* Fuchs' endothelial dystrophy

* Low endothelial cell count or abnormal endothelial cell appearance.

Relative contraindications include, but are not limited to:

* Pupil size--the optic portion of the implant varies depending on the power of the lens. Patients with pupils larger than 7mm may have an increased risk of haloes after surgery. While it is rarely bothersome, it is important to have this discussion with every patient prior to surgery. Most prospective ICL patients already experience glare or poor peripheral vision due to distortions from their glasses so if they experience haloes at night after surgery it typically does not affect them

* Expectations--while this seems straightforward, it is essential to cover visual expectations. Some patients with a high prescription will have mild amblyopia in one or both eyes. It is important to reinforce that, while an ICL will drastically improve their uncorrected vision, (4,5) the goal for best corrected visual acuity is the same as with glasses or contact lenses. While that is true for most patients, a small number (approximately 10% of high myopic patients) will gain one or more lines of best corrected visual acuity after surgery because the correction is moved closer to the nodal point of the eye (4)

* Contact sports--direct contact to the globe during a physical activity may cause the implant to become displaced or come in to contact with the natural crystalline lens, which can increase the chance of a cataract.

ICL surgery

The power of the lens that will be implanted determines the surgical course and number of clinic visits that is required of the patient. Lenses to correct myopia have a small hole in the centre to allow for aqueous flow; however, lenses for hyperopia do not. If a patient is having a myopic ICL there are no further visits necessary prior to surgery. If a patient is having a hyperopic ICL they will need to have a peripheral iridotomy (PI) either prior to surgery or on the day of surgery. The PI is performed to help aid aqueous flow around the lens and decrease the chance of pupillary block. A PI can be performed with a laser prior to the ICL surgery or mechanically on the same day as ICL surgery; each surgeon has their own preference in this regard taking into account the following:

Laser PI (prior to ICL surgery)

* Advantages: easy to perform for the surgeon; ICL surgery time is kept to a minimum because it is performed at a separate visit; and the opening can be reviewed prior to surgery to make sure it is patent and fully functional

* Disadvantages: may generate complaints of discomfort that can last hours or days; harder to control size and location of the opening; and can be difficult to determine if patent, especially in light coloured eyes.

Mechanical PI (same day as ICL surgery)

* Advantages: does not require any extra visits; painless procedure; the size and location can be well controlled, patency is easily determined by the operating surgeon

* Disadvantages: more difficult to perform for the surgeon; slightly increases total surgical time; and more likely to bleed.

ICL surgery is typically performed on one eye at a time with one to three days between eyes. However, there are some providers that operate on both eyes on the same day. The surgery takes approximately 10 minutes. First, a small 2.5-3mm incision is made into the cornea near the limbus (see Figure 3A). Next, the injector is inserted into the small incision (see Figure 3B). The lens, which is folded inside the injector, is pushed into the AC. The lens slowly unfolds as it leaves the injector (see Figure 3C). Once the lens has been completely inserted (see Figure 3D), a second instrument is used to manoeuver it into position. The position and rotation of the lens is then double checked before the surgery is completed.

After surgery, the patient remains at the clinic for anywhere between 30-60 minutes before receiving a final check which includes intraocular pressure (IOP) and incision review. The exact set of postoperative medications given to a patient will vary between clinics but typically includes an antibiotic and anti-inflammatory eye drops for one week. Some patients may also receive an IOP lowering drop and topical or systemic pain control to use as needed for the first day or two.

Postoperative

ICL patients can return to most normal daily activities the morning after surgery with a few restrictions such as: no eye rubbing, swimming intense physical activity, and avoiding dusty or dirty environments. If the eye is stable at one week, all restrictions are lifted. Patients are usually seen one day, one week, one month, three months, and six or 12 months after treatment. The visits include the following:

Day one visit

* Visual acuity

* Slit lamp examination to check lens position, incision site, and AC for any inflammatory cells or red blood cells

* Tonometry.

Week one visit (and beyond)

* Visual acuity

* Manifest refraction

* Slit lamp examination to check lens position

* Tonometry

* Dilation between six and 12 months (or as deemed clinically necessary).

After the one-year visit, it is important to continue to see the patient for annual review, including a dilated fundus exam. Patients must understand the long-term risks of ICLs as well as high myopia. While the vision and prescription may be vastly improved, it does not change the fact that a high myopic patient has a lifelong increased risk of retinal tears and detachments. (6)

Risks and complications

Risks of ICLs include pupillary block, cataract formation (see Figure 4A) and increased IOP. (5,7,8) The IOP increase can be transient secondary to surgery or pupillary block, or may be due to long-term anatomical changes, most often pigment dispersion (see Figure 4B). While, these risks are low, (8) the majority are associated with ICL sizing.

Lens sizing

The lens size is chosen based upon diagnostic measurements taken at the surgery centre during the preoperative evaluation. The majority of providers, both in the UK and internationally, still use external ocular measurements to determine lens size. However, the sulcus, where the lens sits inside the eye, does not always correlate with the external measurements. (9-12) The most advanced method to take measurements is using ultrasound biomicroscopy (UBM), which directly measures the sulcus and other anatomical landmarks behind the iris (see Figure 5), rather than extrapolating the size based on other measurements. Having the correct lens separation, the space between the ICL and the natural crystalline lens, decreases the risk of most complications (see Figure 6).

Clinical pearls

Lens separation: as mentioned previously, the lens position inside the eye is important and should be recorded at every follow-up visit. There are multiple devices on the market that allow for accurate lens separation measurement including anterior segment OCT (see Figure 6) and UBM. If these devices are not available, it is still possible to estimate the lens separation distance. During the slit lamp examination, create a very thin optic section beam and turn up the brightness. Angle the beam around 30[degrees] to the temporal side and look at the thickness of the cornea (the average cornea is between 500-550fjm) as this will be your guide. Then slowly push the focus towards the pupil. Once you have found the space between the ICL and the natural lens you can estimate what that distance appears to be in comparison to the thickness of the cornea (see Figure 7, page 74). For example, if the separation between the ICL and natural lens looks to be about the same as the thickness of the cornea you can record 100% separation. While there is no hard evidence to suggest what a 'safe' lens separation would be, the general consensus among surgeons is between 100-1000[micro]m (1mm).

Refractive error: some patients may have a small amount of refractive error remaining after ICL surgery. Residual refractive error tends to be very small but can be addressed should the patient want additional help for specific tasks. After ICL surgery there are no restrictions on the type of glasses or contact lenses a patient can wear. In addition, the patient can also consider laser refractive surgery to treat any residual prescription.

Glare/haloes: most patients experience a small amount of glare and haloes in the early postoperative period but usually they will adapt to this after a few weeks or months. However, if a patient complains of glare and haloes after six to 12 months there are a few things to evaluate. The first consideration is to refract very carefully. These patients often began with an extremely high prescription and refraction can be difficult, even after treatment. It is worth considering correcting even a small amount of myopia or cylinder for a chance of improved nighttime vision if the patient wishes. Another option is to provide the patient with a drop to help constrict the pupil. In most cases the pupil needs a very small amount of constriction to drastically improve the haloes. The most popular drop to begin with is brimonidine (Allergan, Marlow, UK). The drop is not something that needs to be taken every day but is often reserved for times when the patient might be going out for a long evening in low light or is driving at night. Finally, the patient can elect to have the lens removed. It is extremely rare to remove a lens because of subjective patient complaints, (13) but since an ICL does not alter the natural state of the eye it can be easily taken out and the patient can go back to wearing glasses or contact lenses.

Conclusion

Patients who pursue refractive surgery, especially those with high refractive errors, have often struggled with vision correction for many years and an inability to perform even the simplest functions while unaided. As a result, having ICLs can lead to an increased quality of life after treatment. (14) ICLs expand the treatment range for your patients who wish (or need) to decrease their dependency on glasses or contact lenses.

Exam questions

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 20 September 2019. 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.

CET points will be uploaded to the GOC within 10 working days. You will then need to log into your CET portfolio by clicking on 'MyGOC' on the GOC website (www.optical.org) to confirm your points.

References

Visit www.optometry.co.uk, and click on the 'Related CET article' title to view the article and accompanying 'references' in full.

Dr Ryan S Vida OD, FAAO

Dr Ryan Vida is part of the ophthalmic research department at the London Vision Clinic. Prior to taking a research position, he was the clinical director of a surgery centre in Los Angeles, CA, which was the number one implanter of ICLs in the US.

Course code: C-71316 Deadline: 20 September 02019

Learning objectives

* Be able to advise patients with high refractive errors on the surgical options for vision correction (Group 1.2.4)

* Be able to recognise complications relating to phakic IOLs (Group 6.1.5)

* Be able to recognise complications relating to phakic plOLs and work with ophthalmologists to ensure appropriate management of the patient (Group 9.1.1)

* Be able to outline the surgical options available for patients with high refractive errors (Group 1.2.4)

* Be aware of the complications that can arise from phakic IOLs (Group 8.1.3)

Caption: Figure 1 Slit lamp photograph using retro-illumination to highlight the ICL inside the eye. Image courtesy of Daniel Elies I Amat, via Staar Surgical

Caption: Figure 2 Image of the ICL resting between the iris and natural crystalline lens. Image is property of and reprinted with permission from Staar Surgical

Caption: Figure 3 A series of images showing: 3A The primary incision near the limbus; 3B Injector inserted through the small incision; 3C The lens being slowly pushed into the AC; 3D Unfolding completely. Images are screen captures taken from a surgery video courtesy of Greg Parkhurst

Caption Figure 4A Slit lamp photograph of an anterior capsular cataract; 4B Excessive pigment in the angle

Caption Figure 5 Sulcus-to-sulcus measurement with the Insight 100 very high-frequency digital ultrasound (Arcscan Ine, Golden, CO)

Caption: Figure 6 Corneal OCT B-scan (MS-39, CSO, Florence, Italy) showing the distance between the ICL and the natural crystalline lens

Caption: Figure 7 Slit lamp images showing: 7A An optic section of the cornea; 7B The space between the ICL and natural crystalline lens. The distance (separation) between the ICL and crystalline lens is approximately the same as the thickness of the cornea on optic section
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Title Annotation:Refractive surgery
Author:Vida, Ryan S.
Publication:Optometry Today
Geographic Code:4EUUK
Date:Aug 1, 2019
Words:2719
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