Commencing with cylinder correction
A pediatric patient comes into your practice with a meaningful amount of astigmatic error—how should you approach correction?
Although you might first think to limit initial discomfort by only prescribing a certain percentage of cylinder, Dr. Rueff advises against this. “Prescribe as much of the patient’s true refractive error as they can tolerate to allow their eyes to both adapt to the cylinder and develop normally,” she says. “If a pediatric patient has high cylinder in both eyes that goes uncorrected, they may be unable to adapt to the full cylinder correction as they move into adulthood. There may be other consequences, such as meridional amblyopia, or if the astigmatism is asymmetrical between the patient’s eyes, amblyopia in just one eye.” You should aim to ultimately correct the full magnitude of the cylinder, though this may require an iterative approach whereby you ease the patient into this over time as they adapt.
There are other factors to take into account, especially when correcting high amounts of astigmatism. “Alongside the prescription, we need to consider the materials used,” explains Dr. Rueff. “Alongside impact-resistant materials, we need to think about the weight of the glasses, glare, aberrations—and if the patient has a large magnitude of astigmatism, the astigmatic orientation, which may affect the amount of lens disruption that’s experienced.”
Making contact early
Not opting for glasses may be one way to navigate these considerations. “Contact lenses can eliminate a lot of the downsides that are associated with prescribing full astigmatism for pediatric patients, especially when you’re correcting greater astigmatic errors,” says Dr. Rueff. “Generally, wearing higher amounts of cylinder with contact lenses is going to be easier to adapt to than with glasses. Additionally, if the astigmatism you’re correcting is very asymmetrical between the two eyes, a corrective pair of glasses may cause some aniseikonia, something that doesn’t occur with contact lenses.”
Despite the misconception, especially in the general populace, that patients need to age up to teenagehood to effectively use contact lenses, younger patients may actually fare better with these modalities. “The Clay Group has shown that children aged between 8 and 12 are much less likely to have complications related to contact lens wear than older children and younger adults,1 with this risk peaking at around age 20,”2 highlights Dr. Rueff.
This knowledge isn’t new—16 years ago, Dr. Moody was part of the Contact Lenses in Pediatrics (CLIP) study, which evaluated 8–12-year-old patients in Singapore, China, and Chicago.3 “We found both that these patients had incredibly low, almost nonexistent adverse events, and that ability and time to insert and remove contact lenses were the same regardless of location,” he explains.
Contact lenses can offer additional quality-of-life improvements, such as increased self-perception,4 presenting additional reasons to consider these options earlier on. “Not having a heavy pair of glasses that easily break, fall off, cause glare or halos, or the feeling of looking different; and giving a child the option for a contact lens early, can really impact them in meaningful ways, maybe even beyond our ability to quantify in the long term,” Dr. Rueff says. “Don't be afraid to start with contact lenses early, especially for those unique refractive errors.”
A choice in correction
But when it comes to contact lenses, there’s also the choice between rigid gas-permeable lenses, which offer superior quality, or soft torics, which offer a more comfortable experience often favored by patients. “When I practiced, for patients with up to 2.0 D of refractive error, I typically favored a soft toric lens. But above this, I’d then suggest the gas-permeable,” Dr. Moody says—as a reminder, the vast majority of astigmatic patients, have errors below 2.0 D.
It's also important that the lenses fit comfortably and remain correctly aligned, two factors that Dr. Moody says lead a quarter of patients to drop out of contact lens use within a year of being fit. “30 degrees of mis-rotation results in you inducing the same amount of astigmatic error that you’re trying to correct; the ramifications are greater for patients with higher amounts of cylinder,” he explains. “Although 30 degrees of mis-rotation is unlikely to occur when a patient’s head is perfectly vertical, such as when we’re looking at them in the slit lamp, when a patient’s head moves back and forth—as happens during everyday activities such as lying down on a couch, looking in a rearview mirror, or playing sports—a contact lens can mis-rotate, and some more than others.”
To check for mis-rotation, Dr. Moody will not only have patients look up, down, left, and right, but also at orthogonal angles. “The slit lamp is also only a moment in time,” reminds Dr. Rueff. “A patient may complain about not liking a lens that seems to look great, but even five degrees of rotation, which isn’t much at all, can cause noticeable blur for patients.”
In cases where patients are fit with a spherical lens in one eye and a toric lens in the other, practitioners should also remember that the majority of lenses on the market—being either prism ballast or peri-ballast—create some amount of prismatic imbalance. “Data presented at the American Academy of Optometry conference showed that, out of the leading lenses in the market, only the Johnson & Johnson lenses are prism-free in the optic zone,”5 says Dr. Moody. “Although there’s no ANSI standard for contact lenses, for glasses it’s 0.33 D of prism; prismatic imbalance as low as 0.5 D can cause headaches and discomfort.”6
Considering surgery
Finally, there are the surgical options. “The decision to suggest refractive surgery requires a multifactorial decisional approach,” explains Dr. Rueff. “I consider corneal thickness, systemic issues, medications, and potential presbyopia—and for astigmatism, I make sure that there aren’t signs of irregularity. I also like to see 2.0 D or less of corneal astigmatism to reduce the likelihood of postoperative glare, halos, or aberrations. Our refractive surgery technologies are better today than ever before, but I still want to make sure I'm sending someone for surgery that's going to have the best outcome possible.”
And what if your patient requires cataract surgery? “When weighing up the option between a standard toric lens and a standard spherical intraocular lens (IOL), ophthalmologists more strongly lean towards the former when there’s 1.5 D or more of corneal astigmatism, with some having this preference even starting at 1.0 D,” offers Dr. Moody. As a note, presbyopia-correcting IOLs are typically favored at 1.0 D of corneal astigmatism. As Dr. Moody explains, understanding these considerations can help you to fully equip your patients with the information that they need: “all of these lenses are getting great results. It's really down to us to educate patients on all the available options so that they can make informed decisions.”
