When Keratoconus Does the Crime, iDetectives Get There in Time

Any increase in corneal cylinder or manifest cylinder by 1.00 D or more warrants corneal topography to rule out keratoconus.

The suspicion of keratoconus increases significantly in patients with corneal cylinder or manifest cylinder ≥2.00 D.

Because irregular, oblique, or ATR astigmatism has been associated with keratoconus, topography is therefore highly warranted.

If a patient has ≥2.00 D cylinder in the spectacle prescription, then I question, “Is this a normal cornea?” If the manifest refraction cylinder is ≥2.00 and I see an increase of 1.00 D in cylinder compared to last year, then I highly suspect keratoconus caused this crime.

-Dr Saenz, iDetective

Error messages or unusual findings may result from corneal distortion and irregular astigmatism. Topography may be needed if repeated attempts at measurement fail.

Keratoconus should be considered if a patient experiences a myopic shift or MRSE change ≥0.50 D from visit to visit. Unexpected changes in prescription could indicate corneal shape changes or steepening, as seen in progressive keratoconus.

MRVA worse than 20/20 or repeat complaints about glasses prescription needing to be updated or “being wrong” may indicate keratoconus.

Because most patients are routinely screened using auto-refraction, changes in refractive error may be the first clue of keratoconus. However, presence of refractive error and/or refractive shifts are not mandatory findings of keratoconus.

-Dr Schroeder Swartz, iDetective

Average steep K is 43.00-43.50 D. Once steep K is >47.00 D, ectasia should be suspected.

An error message occurs when the auto-keratometer cannot accurately read an abnormal cornea. Corneal distortion may be the culprit.

Difference in Ks points to corneal astigmatism. Corneal astigmatism ≥2.00 D correlates to a higher prevalence of keratoconus, which warrants topo-tomography.

Keratometry/auto-keratometry is a keratoconus diagnostic tool available in almost every optometric practice. Watch out for K values >47.00 D, keratometry mire distortion or auto-keratometer error messages, ocular asymmetry between K values, and keratometry values increasing >1.00 D between visits.

-Dr Ibach, iDetective

Eye rubbing shows consistent association with keratoconus and keratoconus progression, even though a causal relationship has not been determined. CLEK study findings showed that 50% of keratoconic patients reported eye rubbing in one or both eyes vigorously. ¹

Treating associated atopic eye allergy symptoms may be more effective than asking patients not to rub their eyes.

Vernal keratoconjunctivitis, allergies, atopic dermatitis, dry eye disease, and eye rubbing are all associated with keratoconus.²

Even in those with no other associated pathology and with negative family history of keratoconus, keratoconus screening with corneal tomography should be considered in children with atopy and eye rubbing behavior, regardless of age.

-Dr Tullo, iDetective

1. Wagner H, Barr J, Zadnik K. Collaborative longitudinal evaluation of keratoconus (CLEK) study: methods and findings to date.Contact Lens Anterior Eye. 2007;30(4):223-232.
2. Robati RM, Einollahi B, Einollahi H, Younespour S, Fadaifard S. Skin biophysical characteristics in patients with keratoconus: a controlled study. Scientifica (Cairo). 2016;2016:6789081.

Segregation analysis identifies keratoconus as a complex polygenic disease. There is evidence to associate more than 100 genes with keratoconus.

Some studies have reported keratoconus prevalence in first-degree relatives 15 to 67 times greater than in the general population. The CLEK study found that 14% of study patients had a family history positive for keratoconus.¹

Like many diseases, keratoconus results from a combination of genetics and environment. When screening patients, ask if any family members have the condition or other eye problems. A “yes” answer warrants further investigation.

-Dr Gromacki, iDetective

1. Gordon-Shaag A, Millodot M, Shneor E, Liu Y. The genetic and environmental factors for keratoconus. Biomed Res Int. 2015;2015:795738.

Keratoconus typically presents asymmetrically. Individuals may notice greater shadowing and doubling of images from the more advanced eye.

Corneal distortion and higher-order aberrations due to keratoconus may contribute to halos and glare, usually more noticeable at night.

Irregular astigmatism related to keratoconus makes vision correction difficult with glasses. Further investigate poor quality of vision to rule out ocular disease.

Even with 20/20 vision, the presence of glare or shadows may indicate ocular pathology from the front or back of the eye. Suspect keratoconus in young individuals with worsening visual complaints in the absence of cataracts and retinal disease.

-Dr Chiu, iDetective

In one study, retinoscopy was found to have 98% sensitivity and 78% specificity when compared with Pentacam’s Belin/Ambrósio Display Final D index of ≥2.69.¹

If a patient has keratoconus, a total internal reflection of light due to the conical cornea may produce the oil droplet reflex.

When suspecting keratoconus, we can’t forget that retinoscopy or direct ophthalmoscopy can be incredibly helpful to aid in keratoconus detection, especially if you don’t have a topographer.

-Dr Saenz, iDetective

1. Al-Mahrouqi H, Oraba SB, Al-Habsi S, et al. Retinoscopy as a screening tool for keratoconus. Cornea. 2019;(4):442-445.

Keratoconus is a disease of corneal asymmetry. An example of asymmetry that may indicate keratoconus is when the I-S ratio is >1.5 D. The I-S ratio is the inferior-superior dioptric asymmetry value—the numerical differences between the average Ks in the inferior hemisphere and the superior hemisphere. Asymmetry between eyes (Kmax or average K ≥1.00 D) is an important clue.

Keratoconus is a disease causing the development of nonorthogonal (irregular) astigmatism over time. Any SRAX >10 degrees, and/or subsequent increases in SRAX over time, may indicate corneal ectasia.

Keratometry should not significantly change over time in healthy patients. Increases in curvature >1.00 D may indicate biomechanical weakness (ectasia) and should be further investigated using tomography or topography, and then monitored for further progression.

Corneal asymmetry (I-S ratio >1.5 D), irregularity (SRAX >10 degrees) or increase in K readings (≥1.00 D) over time require further evaluation with corneal tomography to rule out keratoconus. Additionally, Kmax or steepest K >47.00 D and unexplained BCVA worse than 20/20 require further investigation with corneal tomography. Keratoconus is a disease of asymmetry, so always compare findings with the other eye.

-Dr Tullo, iDetective

Studies have shown that the risk of keratoconus is at least 10 times greater in the Down syndrome population.¹

You may observe that patients with Down syndrome who also have keratoconus frequently rub their eyes.

An autorefractor/ keratometer and retinoscopy are quick and effective tools for uncovering keratoconus warning signs in patients who may be less likely to report changes in vision.

Keratoconus must be ruled out in patients with Down syndrome. Due to the increased incidence coupled with an even worse keratoplasty prognosis in a patient with Down syndrome, this group of patients should have a yearly topography or tomography.

-Dr Ibach, iDetective

1. Alio JL, Vega-Estrada A, Sanz P, et al. Corneal morphologic characteristics in patients with Down Syndrome. JAMA Ophthalmol.2018;136(9)971-978.

Because the cornea is composed of collagen, keratoconus may be a manifestation of an underling systemic condition.¹

It has been recently reported that patients with EDS may have a genetic predisposition to keratoconus; the association between the two conditions has been previously suggested.²

Marfan syndrome is responsible for reduced collagen strength affecting the eyes, bones and joints, skin, lungs, and heart. Patients with Marfan syndrome may have corneas that are soft and weak.³

Attention to patient history and reports on connective tissue disorders should alert you to be attentive for signs of ocular manifestations including keratoconus.

-Dr Schroeder Swartz, iDetective

1. Beene LC, Traboulsi EI, Seven I, et al. Corneal deformation response and ocular geometry: a noninvasive diagnostic strategy in Marfan syndrome. Am J Ophthalmol. 2016;161:56-64.
2. Fransen E, Valgaeren H, Janssens K, et al. Resequencing of candidate genes for keratoconus reveals a role for Ehlers–Danlos Syndrome genes. Eur J Hum Genet. 2021;29(12):1745-1755.
3. Kara N, Bozkurt E, Baz O, et al. Corneal biomechanical properties and intraocular pressure measurement in Marfan patients. J Cataract Refract Surg. 2012;38(2):309-314.

Corneal ectasia causes irregular astigmatism, which makes correction in toric soft contact lenses difficult. If fit and vision are unstable, consider keratoconus screening.

If rigid gas-permeable, hybrid, or scleral lenses significantly improve vision compared with glasses or soft contact lenses, it might be due to an irregular cornea or keratoconus.

Rigid lenses that touch the cornea may temporarily flatten the cornea. Topography taken immediately after lens removal may not be accurate and might mask keratoconus progression.

While soft lenses may work well for early keratoconus, specialty lenses are typically required to achieve best corrected vision in more advanced cases. With early detection and treatment to minimize progression, quality of vision might be preserved with even glasses or soft contact lenses.

-Dr Chiu, iDetective

Fleischer ring is an iron ring within the epithelium at the base of the cone. It is brown in color and best visualized using the cobalt blue filter.

If you suspect keratoconus, look for vertical lines within the posterior stroma or Descemet membrane.

Stromal thinning is often present in the cone. It may initially be subtle, but it can become more pronounced over time.

In the CLEK study of 1209 KC patients, 86% of the subjects presented with a Fleischer ring; 65% with Vogt striae; and 53% with scarring. If any of these are seen, suspect keratoconus. Munson sign (protrusion of the lower eyelid upon downgaze) generally does not manifest until severe keratoconus, if at all.

-Dr Gromacki, iDetective