Pediatric Keratoconus

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Article initiated by:

Brad H. Feldman, M.D., Olivia F Dutton

All contributors:

Hannah Brosman, BS, Brad H. Feldman, M.D., Vatinee Y. Bunya, MD, MSCE, Colleen Halfpenny, M.D., Zeba A. Syed, MD, S. Grace Prakalapakorn, MD, MPH, Angeline Nguyen, MD, Mary Daly, MD

Assigned editor:

Review:

Assigned status Up to Date

 by Angeline Nguyen, MD on September 6, 2025.

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Disease Entity

Disease

Keratoconus is a progressive disease that can create a conical shape of the cornea due to corneal thinning and resulting ectasia. This results in poor visual acuity, progressive myopia, and irregular astigmatism. Pediatric keratoconus has been shown to be more aggressive than keratoconus in adult patients which creates a greater importance on early intervention in pediatric patients.

Etiology

The etiology of pediatric keratoconus is poorly understood, although it involves a combination of genetic and environmental variables. It is thought that rubbing of the eyes may further the steepening of the cornea by way of creating microtraumas. Inflammatory markers that react to the microtrauma may induce apoptosis of cells in the cornea. Rubbing can be induced by hay fever, allergic conjunctivitis, or vernal keratoconjunctivitis among other reasons.

Risk Factors

Risk factors include environmental factors, family history, as well as associated genetic syndromes.

Environmental factors include eye rubbing, atopy, and sun exposure.

When inherited, keratoconus is believed to follow an autosomal dominant pattern, although autosomal recessive inheritance has also been suggested. A positive family history has been reported in 20.5% of first-degree relatives. The role of genetic factors in the development of keratoconus however it is not yet clear.

Down syndrome has the highest association with keratoconus. Marfan Syndrome, Ehlers-Danlos Syndrome, vernal keratoconjunctivitis, retinitis pigmentosa, leber congenital amaurosis, sleep apnea and mitral valve prolapse are all associated with keratoconus.

General Pathology

All layers of the cornea may show pathological findings of keratoconus. Pathological findings include thinning of the epithelium, fibrillations and breaks in the Bowman’s layer, altered collagen fibrils and loss of lamellae in the stroma, ruptures and folds in Descemet’s membrane, and rarely elongation of cells in the endothelium. Eye rubbing can create microtrauma to the epithelium leading to an inflammatory mediator response from the epithelium and stromal layers. Additionally, ocular allergies may induce an inflammatory response through the release of the allergen into the body. Keratocytes are also reduced in eyes with keratoconus due to apoptosis.

Pathophysiology

The rigidity of the cornea is inversely proportional to age, allowing for the biochemical component of pediatric corneas to be more susceptible to degradation. Upregulation of matrix metalloproteinases (MMP‐14, MMP‐1, MMP‐7, MMP-13and MMP‐2) due to eye rubbing can cause degradation of type I and type II collagen, fibronectin, and glycoprotein in membranes. Additionally inflammatory markers IL‐6, TNF‐α, and MMP‐9 are increased in keratoconus patients’ tears. Ocular allergies react with IgE on mast and basophil cells leading to the release of histamine, proteases, and TNF-alpha. These inflammatory markers are thought to play a role in inducing keratocyte apoptosis which leads to thinning of the extracellular matrix, a reduction in corneal collagen cross-linking stromal volume loss, and ectasia.

Primary Prevention

Prevention of keratoconus is limited at this point. However, avoiding allergens and rubbing of the eyes may prove effective at preventing progression. Awareness of genetic risk factors of keratoconus may allow for early intervention and stabilization of keratoconus in children. Halting the steepening of the cornea may help prevent corneal scarring. New genetic testing is becoming more widely available and may be used to determine prevalence of genes that predispose patients to development of keratoconus.

History

Keratoconus typically begins progression in patients' 20's, with most research finding disease onset occurring after puberty. However, there have been case studies of onset as early as 4 years old. The corneal disease typically presents bilaterally; however, it rarely progresses symmetrically at the same rate in both eyes. The estimated prevalence of keratoconus in the pediatric population is estimated to be 0.16% , but many experts believe the prevalence to be higher, thus emphasizing the need for early, sensitive testing. Pediatric keratoconus affects both genders equally. Studies on pediatric keratoconus suggest that at the time of diagnosis, 27.8% are at an advanced stage and 88% progress.

Symptoms

Patients may experience a progressive decrease in visual acuity, distortion of images, increasing halos and starbursts around lights. Rapidly changing astigmatism or myopia may also be seen in patients. In more extreme cases, patients can experience acute corneal hydrops causing impairment of vision, redness, pain and photophobia.

Examination

Patients suspected of having keratoconus should have a full eye exam including measurements of corneal curvature and thickness. Visual acuities at distance with and without correction should be obtained as well as a refraction to assess progressive astigmatism and myopia. Retinoscopy findings of scissoring and corneal topography can be used to detect early-stage keratoconus.

A slit lamp exam should also be performed for signs of keratoconus. The slit lamp exam findings may include central and paracentral thinning, inferior steepening, corneal scars, corneal haze, Fleischer ring and Vogt’s striae. In more severe cases, external indicators include the Munson sign and Rizzuti sign. It has been noted that cones appear to form more centrally in pediatric patients compared to adolescent or adult patients.

Diagnosis

Clinical diagnosis

Diagnosis of keratoconus requires a thorough slit lamp examination, supported by corneal topography. Topography images allow for early diagnosis of keratoconus as well as tracking the progression of irregular astigmatism and high K values. Ultrasound pachymetry can also be used to determine the central and paracentral thinning of the cornea. Due to the rapid severity of keratoconus in pediatric patients, some studies recommend a shorter follow-up time frame such as 1-3 months versus 6-12 months in adult patients.

The ABCD grading system developed in 2016 incorporates: (A) average anterior radius of curvature, and (B) posterior average radius of curvature, both measured in a 3-mm zone centered on the thinnest point of the cornea, along with (C) the thinnest pachymetry measurement (C), and (D) the best spectacle-corrected distance visual acuity. This grading scale utilizes Scheimpflug imaging and slit-scan tomography, which are highly effective at measuring anterior and posterior curvature and thus increasing early diagnosis.

Family history and past medical history may be considered in the diagnosis.

Diagnostic Procedures

Retinoscopy in patients with keratoconus will demonstrate a scissoring reflex in which the light reflex will split into two separate bands. Keratoconus patients may also demonstrate a Charleaux or "oil droplet" sign upon examination and show a bright reflex at the conical apex surrounded by a dark shadow.

Slit lamp examination may reveal a ring of iron deposition, known as Fleischer's ring, around the base of the conical cornea. Additionally, Vogt striae, vertical lines in the deep corneal stroma, may be a feature seen in early keratoconus.

Corneal topography images are more helpful in early diagnosis of keratoconus, especially in pediatric patients when visual acuity may still be corrected using spectacles. When looking at topography images, it is especially important to consider the inferior steepening as well. Progression of the K values as measured by the topography imaging occur rapidly, and differences in K's can be measured in as few as three months.

Scheimpflug Imaging creates a 3-dimensional model of the anterior segment of the cornea. Pentacam and Galilei cameras take over 25,000 elevation points to create the model without any contact to the surface of the cornea. These image representations give information regarding anterior instantaneous curvature, pachymetry, anterior elevation, posterior elevation, and pupil indices to aid in keratoconus detection. The Pentacam’s CAIRO 8 index (the corneal assessment index from the relational thickness and other OCULUS values analyzed for 8 mm zone) has shown utility in diagnosing pediatric keratoconus. This index is derived through regression analysis and incorporates corneal elevation and thickness to enhance diagnostic accuracy.    

Belin Ambrosio Display (BAD) combines the information from the posterior and anterior elevations and corneal thickness in a single map.

Ultrasound pachymetry using a probe is an effective and efficient way to determine the thickness of a patient's cornea. Pachymetry values can also be found using Scheimpflung imaging, confocal microscopy, scanning slit topography, optical coherence tomography (OCT), partial coherence laser interferometry (PCI), and optical low-coherence reflectometry (OLCR).

Laboratory test

Next generation sequencing is currently being used in research to identify genes associated with predisposition to keratoconus.

Differential diagnosis

Axial Myopia in children may progress through the first and second decade of life. Combined with astigmatism, these patients should be monitored closely for keratoconus due to the rapid nature of pediatric keratoconus. Patients with high myopia have been shown to have a greater risk of developing keratoconus. One study sites almost double the risk in high myopic patients compared to control patients .

Pellucid Marginal Corneal Degeneration (PMD) is often confused with keratoconus. PMD causes abnormal thinning of the periphery of the cornea and severe inferior steepening on anterior corneal maps, as opposed to more central thinning in keratoconus. Also, PMD usually presents in a person’s 20s or 30s, whereas keratoconus usually presents at a younger age, albeit it may present at any age.

Keratoglobus is the bilateral thinning of the cornea and an abnormal globe-shaped (globular) or spherical form to the cornea. Unlike in keratoconus, fleischer rings, Vogt striae, and anterior stromal scarring are not typical. Descemet membrane thickening and folds are common in keratoglobus.

Management + Treatment

Management of keratoconus includes avoidance of recurrent ocular microtrauma by making sure to prevent eye rubbing and nocturnal pressure on eyes as much as possible. Ocular allergies should be controlled adequately prior to surgical interventions due to the increased likelihood of infection. If the disease has not stabilized, corneal collagen cross linking is the recommended surgical option to halt progression of the steepening of the cornea and worsening visual acuity. Management of keratoconus, once stabilized, includes follow ups with topography and pachymetry testing as well as management through spectacle or contact lens usage.

Corneal Collagen Crosslinking (KXL) has quickly become the most popular treatment option for adults with progressive keratoconus, and standard epithelium-off KXL treatment has been reviewed for pediatric patients as well. The goal of the treatment is to increase the biomechanical rigidity of the cornea using riboflavin and UV light. Riboflavin increases the absorption of UV‐A by the corneal stroma. The riboflavin generates reactive oxygen when exposed to UV-A light. The reactive oxygen then reacts with available groups to create chemical bonds between amino acid residues thus increasing "cross‐linking between proteoglycans and collagen with the resultant photopolymerization of collagen fibrils improving biomechanical properties". Standard Epithelium-off KCL has proven to stabilize the corneas in both pediatric and adult patients; however, pediatric patients have a higher rate of progression after the procedure. This procedure has stability reported up to five years in pediatric patients with studies reporting 80% of pediatric patients had improved visual acuity and Kmax values reducing over the span of four years after KXL. An analysis over a follow-up period of 6 to 36 months demonstrated that standard epithelium-off and accelerated epithelium-off corneal collagen crosslinking are comparable in their effectiveness for treating pediatric keratoconus.

Epithelium-on KXL has been used in pediatric patients because it reduces pain postoperatively and has a reduced risk of infection., which is important for pediatric patients, as compliance with postoperative antibiotics may not be as high as with adult patients.

Keratoplasty options for treatment of advanced keratoconus include deep anterior lamellar keratoplasty (DALK) and Penetrating keratoplasty (PK). However, keratoplasty in pediatric patients has a poorer prognosis than in adult patients. In adult patients, studies report that PK provides greater improvement in visual acuity and is associated with fewer complications due to suturing when compared to DALK. In contrast, PK is associated with a higher rate of graft rejection than DALK.

Intracorneal ring segment (ICRS) implantation has been shown to improve vision of pediatric patients with keratoconus, and the procedure has been undergoing advances to improve outcomes. Specifically, corneal allogenic intrastromal ring segment (CAIRS) implantation has been investigated as a treatment for adult keratoconus. The procedure implants a ring of corneal tissue from a donor to the peripheral cornea to flatten the central cornea, and the use of allogenic tissue may offer advantages over synthetic segments. Although early results are promising, further research into long-term outcomes and use of CAIRS for pediatric patients is required.

Contact lenses do not treat the progression of keratoconus, but they may offer keratoconus patients the best visual acuity before or after a treatment procedure. Spectacles and soft toric lenses can be used to correct astigmatism in mild and stable cases of keratoconus. However, in moderate to severe cases of keratoconus, rigid gas permeable contact lenses are needed to offer improvement in visual acuity by neutralizing the irregular astigmatism. These contact lenses may be uncomfortable to keratoconus patients and cause dryness, pain, and itching. To alleviate such symptoms, specialty contact lenses that are customized to each patient such as RoseK, or other options such as semi-scleral contact lenses, piggyback lens use (hard lens over soft lens), scleral lenses, hybrid lenses, and PROSE (prosthetic replacement of the ocular surface ecosystem) may also be a better fit for irregular and steep corneas found in keratoconus.

Prognosis

Most patients, given proper treatment and early intervention, have good visual acuity with correction. Due to differences between pediatric and adult keratoconus, pediatric patients have a higher risk of requiring recrosslinking and corneal transplantation. Therefore, early detection is crucial for improving prognosis.