In our tertiary care setting at Children’s Mercy Hospital in Kansas City, Missouri, we evaluate and treat patients with pediatric keratoconus every day. But for those in primary care practices, this sight-threatening disease is seen or detected much more rarely, and it can be tough to know when a referral is warranted.

The short answer is that there is no such thing as an unnecessary referral. Patients who have suspicious topography, clinical signs with the retinoscope or at the slit lamp, rapidly changing or irregular astigmatism, or can’t correct to a sharp 20/20 (with no other explanation for their reduced vision) should be referred for a full evaluation of both the anterior and posterior cornea. We would much rather have a keratoconus suspect turn out to be normal than miss a case of progressing keratoconus.

PATIENT CASE EXAMPLES

Case No. 1

We recently saw a 7-year-old patient who had some behavioral issues and was difficult to examine. The child’s BCVA was 20/20 OU, but the referring doctor was concerned that the high astigmatism could be due to keratoconus. A cycloplegic retinoscopy refraction showed that the patient had significant refractive error (+1.00, -6.00 x 005 OD and +2.50, -7.50 x 175 OS). However, anterior segment tomography shows that the astigmatism is regular (Figure 1). This patient has a normal cornea, albeit one with high cylinder. This was a happy outcome: The mother had been anxious and was happy to learn that her child didn’t have a progressive eye disease, and we were happy to send the patient back to the referring optometrist for new glasses.

Figure 1. Anterior segment tomography with the Pentacam (Oculus) shows that the patient’s astigmatism is regular, with a Kmax of 46.3 D OD (A) and 47.3 D OS (B).

It’s important not to overly worry the patient (and parents) when referring for a cornea consult, especially if the diagnosis is unclear. A great way to handle the referral is to say something along the lines of, “Your cornea looks a little bit steeper than I like to see. This may just be your version of normal, but I’d like to send you to someone who can give you a definitive answer.”

Case No. 2

A highly astigmatic teenage patient we saw recently had a retinoscopy refraction of -1.00, -3.00 x 015 OD and +1.00, -7.00 x 180 OS. The referring doctor was unable to improve the patient’s vision with glasses (20/70 OD; 20/50 OS). Retinoscopy showed an oil droplet appearance, which is characteristic of keratoconus. Iron lines indicative of tear stagnation at the base of a cone area were also visible superiorly and inferiorly at the slit lamp. Anterior segment tomography shows a Kmax of 61.9 D OD and 59.1 D OS (Figure 2). Corneal collagen cross-linking (CXL) was recommended for both eyes due to progressive keratoconus.

Figure 2. This patient, who had a Kmax of 61.9 D OD (A) and a 59.1 D OS (B) was diagnosed with progressive keratoconus and recommended to undergo cross-linking.

This is an urgent referral because the risk of rapid progression is higher in this young population.¹ Young patients can be referred to either a pediatric ophthalmologist or a cornea specialist. However, some pediatric ophthalmologists focus more on strabismus and don’t have topography or tomography devices or perform CXL, so it is best to refer to a specialist who regularly treats keratoconus with FDA-approved technology and equipment. It is always a good idea to keep the lines of communication open to understand the latest developments in CXL, the cornea specialist’s treatment patterns, and what information is desirable when making referrals.

SHARING CARE

Keratoconus presents a good opportunity for collaborative care. Patients can be referred to a specialist to confirm the diagnosis and undergo treatment, and then returned to their referring optometrist for ongoing monitoring and vision care. Because there is no global period for CXL, there is also no comanagement fee as there is with surgical procedures. Instead, both doctors bill for the examinations and diagnostic testing as needed.

REFERRAL MYTHS

We regularly hear three common misconceptions regarding the referral of patients with keratoconus from colleagues that contribute to what we believe is significant underdiagnosis and underreferral of these patients.

Referral myth no. 1: A keratoconus diagnosis must be confirmed before the patient can be referred.

Certainty is not required! Even the suspicion of keratoconus is sufficient to refer the patient for further evaluation. Cornea specialists can repeat diagnostic tests and/or order additional exploratory corneal imaging to help diagnose or rule out keratoconus and determine treatment options. By the time you achieve certainty by confirming the presence of corneal striae at the slit lamp, for example, the condition may have already advanced to the stage of permanent vision loss. If you want to have more confidence in your diagnostic abilities, topography is helpful, but you can also dust off your retinoscope and perform a dilated retinoscopy. Retinoscopic changes typically occur much earlier than corneal signs or refractive changes. Any warpage on retinoscopy warrants a referral for further evaluation.

Referral myth no. 2: The patient is too young to have keratoconus or to be treated.

Although keratoconus usually manifests in patients who are in their early to late teens, we have seen patients with keratoconus as young as 4 years of age, particularly those with complicating genetic conditions. The FDA-approved iLink CXL procedure (Glaukos) using riboflavin 5’-phosphate ophthalmic solution 0.146% (Photrexa, Glaukos) and riboflavin 5’-phosphate in 20% dextran ophthalmic solution (Photrexa Viscous, Glaukos) in combination with the KXL system that is approved for use in the United States, was studied only in patients 14 years of age and older.

Referral myth no. 3: The patient needs to have failed contact lens wear first.

Historically, a referral to a cornea specialist was deferred until a patient could no longer achieve 20/20 vision or could not tolerate contact lenses. Although contact lenses are a great tool for managing the visual needs of patients with keratoconus, they aren’t actually treating the underlying condition. In contrast, CXL has been shown to slow or halt keratoconus progression,² so the sooner a patient with progressive keratoconus undergoes CXL, the more likely we are to be able to preserve their corneal stability, vision, and vision correction options for the future. Soft, rigid gas permeable, or scleral contact lenses can continue to be prescribed after CXL as needed for vision correction.

ERR ON THE SIDE OF CAUTION

The bottom line is that there is really no reason to wait to refer a patient—especially a young one whose cornea or refractive changes look suspicious for keratoconus. A family history of keratoconus, Down syndrome, or history of eye rubbing should increase the level of suspicion. With keratoconus, that simple referral can literally be sight-saving.