A look at identifying and managing the condition
By Steve Lenier, contributing editor
Because keratoconus (KC) is a progressive condition that can lead to increasing astigmatism and, therefore, significant impairment in vision, diagnosing the condition early and intervening as soon as possible should be a priority when it comes to these patients.
“…I would love for there to be a tool that a school nurse or pediatrician could use, attached to a smart phone, that can take a picture and can tell if the eye is abnormal or not,” says Kathryn M. Hatch, MD, Massachusetts Eye and Ear and Harvard Medical School.
Here, corneal specialists discuss how to best identify and manage the condition.
The early diagnosis of KC is achieved in three ways:
1. Awareness of patient prevalence. Although KC can be seen in patients of all ages, it tends to present and be rapidly progressive during the teenage and pre-teen years, as well as in young adults in their 20s and 30s, say those interviewed.
“Younger patients initially may present with rapidly progressing myopia and astigmatism,” says Kenneth A. Beckman, MD, Comprehensive Eyecare of Central Ohio and Ohio State University. “When they have uncorrectable vision, meaning they have a lot of astigmatism and we can’t quite get them to 20/20 [vision] with glasses, that’s when we may do more advanced testing.”
Alan N. Carlson, MD, Duke University, agrees, saying he suspects a patient may have KC “if their prescription is changing, usually including an increasing myopic astigmatism. If the astigmatism is increasing over time, that tells you that you need to look further.”
He adds that KC should be watched in anyone who has a family history of the condition. That said, Dr. Carlson notes only 7% of patients with keratoconus have a family member with the disease.
Dr. Beckman offers that KC is commonly associated with people who have allergy problems.
2. Awareness of patient behavior. “We know there’s a very strong association with eye rubbing and corneal ectasia, offers Dr. Hatch.
Dr. Beckman adds that it is not known how much of the rubbing actually contributes to KC, though there’s a belief that constant pushing on the eye itself weakens the tissue of the cornea.
Sleeping position may also be a factor, Dr. Beckman says.
“A patient may sleep on one side, and the keratoconus on that side may be significantly steeper than the other, so it might be pressure being put on the eye while sleeping.”
Dr. Carlson adds that if somebody has asymmetric KC, and one side is much worse, about 85% of the time, the patients sleep on that side.
“If I see advanced keratoconus in a young patient in both eyes, I’ll suspect that they sleep on their stomach, face down,” he explains. “So, they’ve got REM sleep underneath their eyelids, but the eyes have pressure on them, so they’re rubbing their eyes.”
3. Diagnostic testing. Retinoscopy and corneal tomography aid in identifying KC, say those interviewed.
“There’s a particular pattern we commonly see with earlier keratoconus,“ Dr. Beckman asserts, “called scissoring. Light reflected from the retinoscope scissors instead of looking like a solid line, and that’s a clue that the cornea is distorted.”
He adds that clinical signs that may be seen in more advanced KC include a Fleischer ring, striae folds in the cornea or thinning of the stroma.
Dr. Hatch points out that corneal tomography offers highly sensitive imaging that “allows us to see very mild elevation changes and irregular astigmatism.”
“Younger patients initially may present with rapidly progressing myopia and astigmatism. When they have uncorrectable vision, meaning they have a lot of astigmatism and we can’t quite get them to 20/20 [vision] with glasses, that’s when we may do more advanced testing.” - Kenneth A. Beckman, MD, Comprehensive Eyecare of Central Ohio and Ohio State University.
Four management options are available for KC, say those interviewed:
• Rigid gas permeable contact lenses. Dr. Carlson says once he’s documented that a patient has KC, he assesses their vision in their glasses, and if the KC is even moderately advanced, the patient usually would see better with a rigid contact lens, either a hybrid lens that’s rigid in the center, a scleral lens, or a gas-permeable hard lens, depending on how advanced the condition is.
• Off-label use of the Intacs poly-methyl methacrylate ring implant. If patients have trouble with contact lenses, another option is the off-label use of the Intacs poly-methyl methacrylate ring implant, notes Dr. Carlson.
“This is an excellent treatment because it strengthens the cornea, and usually reverses a lot of the keratoconus, but one of the other benefits is it reminds patients not to rub because it feels different,” he explains.
• Deep anterior lamellar keratoplasty. Dr. Carlson says he will also perform a deep anterior lamellar keratoplasty in a patient who has fairly advanced disease, before they develop any breaks in Descemet’s membrane.
“It’s a procedure that allows you to leave endothelium, Descemet’s membrane, and Dua’s layer,” he offers.
• Corneal Cross-linking. “If you catch someone whose vision is still 20/20 or 20/25 and you can lock them in to that, that’s a home run,” Dr. Beckman asserts. “But in addition, they get flattening, and they get a reconfiguration, with steeper areas getting flatter, flatter areas getting steeper, so the cornea turns more spherical. We have a lot of patients who get a significant improvement in their vision, not just stabilization. And while we tend to think this stops at 40 years old, it doesn’t. I’ve treated patients in their 50s and beyond. If they’re progressing, they’re progressing.”
Dr. Hatch says that before moving forward with CXL, she looks at the age of the patient.
“If it’s an older patient who was recently diagnosed, or they’ve been stable for 30 years, I might follow them,” she explains. “No one is ever totally safe from progression, so it’s something we always have to monitor. When I see a teenager who has keratoconus, I almost never recommend observation. They need close following for any signs of change. Keratoconus doesn’t progress overnight, but you’re also not born with it. It’s something that takes months to years to get worse. So even if I don’t have documented prior imaging, which some insurance companies require, I will recommend young patients get cross-linking. Otherwise, you’re basically waiting for them to lose their eyesight.”
Dr. Beckman adds that corneal surgeons might benefit from a better understanding of what can be accomplished with cross-linking, as some who receive KC patients who have vision of 20/60 or worse, go directly to a corneal transplant.
“Even though they might get a great result with transplant, if their vision is bad because of steepness and distortion, I would always cross-link them before I would go to a transplant, unless a central scar is the cause of their decreased vision,” he notes.
He says he believes almost all patients can be fitted with a scleral lens, and even a contact lens-intolerant patient might tolerate a lens after a cross-linking procedure reshapes the cornea. Therefore, if there is no visually significant central scar, and a scleral lens can be fitted, the patient is very likely to obtain excellent vision and avoid a transplant, regardless of how advanced their cone is. CP
Special thanks to Michael Raizman, MD, for reviewing this article.