Overview of Scleral Fixation of Intraocular Lenses
When a patient’s eye doesn’t have enough natural support structure to hold an artificial lens, it becomes challenging for the surgeon. There are several options to place this lens, such as in the front chamber of the eye (ACIOLs), attaching it to the Iris (PCIOLs), or fixing it to the white part of the eye (SFIOLs). No one method has been proven to be the best.
However, placing it on the sclera (SFIOLs) forms a safer approach as compared to ACIOLs or PCIOLs. When we put the lens in the sulcus area, it stays closer to where the original lens was placed and this method is also safer for the cornea, which is the eye’s clear front surface, and the iris, which is the colored part of our eye.
Anatomy and Physiology of Scleral Fixation of Intraocular Lenses
The SFIOL technique is a medical process where an intraocular lens (IOL), or artificial lens, is placed in the back section of the eye, known as the posterior chamber. At the same time, part of this lens, called the haptic, is secured to the white part of the eye (the sclera) roughly 1.5 to 2 mm from the limbus, which is the outer edge of the cornea of your eye.
This method is believed to be safer for the inner layer of the cornea and the iris, which is the colored part of your eye. The haptic is usually positioned horizontally at what medical professionals might call the ‘3 and 9 o’clock direction’, similar to hands on a clock. However, in patients with larger eyes, like those with extreme nearsightedness or Marfan syndrome (a genetic disorder that affects connective tissue), the haptic can be positioned vertically at the ‘6 and 12 o’clock’ direction. This is because the vertical size of the cornea, the clear front surface of the eye, is smaller than the horizontal size.
Why do People Need Scleral Fixation of Intraocular Lenses
If you scheduled to have a specific type of eye lens implant surgery called in-the-bag PCIOL (Posterior Chamber Intraocular Lens), it might not be possible if you have certain eye conditions.
One example of such a condition is if your eye lens is displaced or moved from its normal position in a condition known as ectopia lentis. This can occur due to various reasons which include:
- Hereditary ectopia lentis with no other bodily symptoms – this includes conditions like simple ectopia lentis and ectopia lentis et papillae that are passed down through families.
- Hereditary ectopia lentis with other symptoms outside the eye – conditions like Marfan syndrome, Weill Marchesani syndrome, homocystinuria, hyperlysinemia, and sulfite oxidase deficiency which are also inherited, but cause other problems in the body.
- Acquired causes – Certain conditions can cause ectopia lentis, including eye trauma, high nearsightedness (myopia), a condition leading to increased eye size (buphthalmos), tumors in the front part of the eye, inflammations like chronic cyclitis and syphilis, and a condition called pseudoexfoliation syndrome where a flaky material is deposited on the eye’s front structures.
Another situation where this surgery might not be possible is when there isn’t enough support from the eye’s natural lens capsule. This usually happens after surgical removal of the natural lens because of cataract (a condition known as aphakia) or as a complication of cataract surgery, like issues with the “bag” that holds the natural lens (bag dialysis), problems with the fibers holding the lens in place (zonular dialysis), and large ruptures in the back part of the natural lens capsule.
When a Person Should Avoid Scleral Fixation of Intraocular Lenses
There are a few conditions that might make the surgery less safe or effective. These include thinning of the sclera (the white part of your eye), inflammation of the sclera (scleritis), inflammation inside the eye (uveitis), advanced glaucoma that has caused damage already, problems with the cornea (the clear part in the front of your eye), and any existing conditions affecting the retina (the back part of the eye that senses light).
If you have any of these conditions, your doctor will want to manage or treat those before proceeding with SFIOL (a type of surgery for certain eye problems). The goal is to make sure the surgery can be performed safely and effectively.
Equipment used for Scleral Fixation of Intraocular Lenses
The tools needed for this type of eye surgery include a special cutting device known as a vitrectomy cutter, a tool to keep the front part of the eye steady (anterior chamber maintainer), a small pair of forceps, blades, crescents (curved instruments used in surgery), a suitable intraocular lens (IOL – a lens that is implanted in the eye during surgery), and stitches that match the procedure being used. This is on top of the normal equipment that is usually needed for a type of eye surgery known as cataract surgery.
Preparing for Scleral Fixation of Intraocular Lenses
Before a medical procedure is carried out, the doctor will speak to the patient or, if the patient is a minor, their parent or guardian, to make sure they understand what the procedure involves and what the possible risks are.
Before an operation, doctors do several checks and tests to make sure the patient is healthy and ready. They ask questions about the patient’s general health and any eye problems they might have had in the past, as well as any treatments they may have received. If the doctor suspects that the patient has a hereditary disease like Marfan syndrome or homocystinuria, which can cause the lens in the eye to move out of place, they may also do some additional tests and ask for advice from other medical professionals.
They will thoroughly examine the patient’s eyes, which includes checking their vision with and without glasses or contact lenses, using a special instrument called a slit-lamp to look at the front part of the eye, measuring eye pressure, examining the shape of the cornea, looking at the back part of the eye, and if needed, performing an ultrasound scan of the eye if they can’t see the back of the eye properly. They will also measure the eye to determine the power of the artificial lens that would be implanted in the eye during the surgery.
For the actual operation, the doctor decides what kind of anesthesia to use based on the patient. If the patient is calm and can stay still, the doctor might use a peribulbar block, which involves injecting an anesthetic around the eye to numb it. But if the patient is agitated or has other health problems, the doctor might decide that general anesthesia, which causes the patient to sleep during the surgery, is the better option.
How is Scleral Fixation of Intraocular Lenses performed
During eye surgery, the operation site is cleaned and sterilized before the surgeon removes the eye’s lens. This process can be done through different techniques like phacoemulsification, phacoaspiration or lensectomy. If required, some of the gel-like substance in your eye (the vitreous humour) can be removed through a procedure called anterior vitrectomy. An intraocular lens (IOL) is then inserted into the eye and secured to the wall of the eye (sclera). If the patient doesn’t have a natural lens, the IOL is directly secured to the sclera.
The procedure to fix the IOL to the sclera can be done with or without the use of sutures (stitches). Sutures are tailor-made for eye procedures and come in different materials. Some are stronger and longer-lasting than others. However, all sutures have a risk of breaking over time. It’s also possible for the sutures to slightly irritate the eye if they’re not properly concealed, leading to an increased risk of inflammation (endophthalmitis). The procedure can also be performed without sutures. This method is useful for particular patients or circumstances but comes with its own set of pros and cons.
The IOL can be fixed at different points to ensure it stays in place. Doing a two-point fixation is more common, but this increases the chance of the lens tilting or moving off-center. A tilted or decentered lens can create vision problems. A four-point fixation reduces this risk but is more complex to perform.
The stitches or securing of the IOL can be done through different techniques. In the ab externo technique, the surgeon creates little skin folds (scleral flaps) and puts the stitches in under these. In the ab interno technique, the surgeon inserts the sutures through an incision under the iris. The endoscopy-assisted technique uses an endoscope for a better view during surgery. Lastly, the Hoffmann technique avoids the need for creating scleral flaps, making it a good choice for eyes with scarring or those that have undergone glaucoma surgeries.
Overall, the best choice of technique, whether to use sutures, and how many fixation points to use depends on various factors like the patient’s condition, their personal medical history, and the surgeon’s experience and preference.
Possible Complications of Scleral Fixation of Intraocular Lenses
Although surgeries to place secondary intraocular lenses (SFIOLs) have generally been successful over time, they can bring about some complications. These include:
* Temporary swelling of the cornea, which is the front surface of your eye.
* Hypotony, which means low pressure in the eye after surgery.
* Ocular hypertension, or high eye pressure.
* Cystoid macular edema, or swelling in the eye’s center (the macula) that causes blurry vision.
* The lens shifting out of place or tilting, leading to astigmatism, which is blurred or distorted vision due to the eye’s irregular shape.
* The lens getting trapped in the pupil, obstructing normal vision.
* Pseudophacodonesis, which is an unusual shaking of the implanted lens in the eye.
* Bleeding in and around the eye.
* Detachment of the retina, the layer at the back of your eyeball that senses light, especially in patients who are extremely nearsighted or who have a genetic disorder called Marfan syndrome.
* Endophthalmitis, a serious infection inside the eye.
In some cases, the tied knots used to secure the lens in sutured surgeries can erode the white part of your eye (the sclera). The sutures themselves can also break. In surgeries that don’t use sutures, the part of the lens that connects it to the eye (called the haptic) might erode or become dislodged. This can also cause complications.
What Else Should I Know About Scleral Fixation of Intraocular Lenses?
When eye surgery is needed and the lens in the bag (back part of the eye) can’t be replaced, SFIOLs (scleral-fixated intraocular lenses) are a safer option than ACIOLs (anterior chamber intraocular lenses) or iris-fixated lenses. These lenses are put in the ‘sulcus’ region, which is closer to where the natural lens sits. This is safer for the delicate front layer of the eye, called the corneal endothelium, and the iris (the colored part of the eye).
