When Keratoconus Does the Crime, iDetectives Get There in Time
In a world of ocular diseases, iDetectives are on the case, hunting down sight-threatening conditions and arresting them in their tracks.
#FollowTheClues to help slow or halt the progression of keratoconus…before it’s too late!
Keratoconus care starts with optometry. That’s why it’s critical for optometrists to take on the role of iDetective and look for the clues through a new lens so that patients can be diagnosed as early as possible.
Examination Findings
When your patient history and examination findings present any of the following, consider keratoconus.
Increasing and/or
Unusual Astigmatism
Increase in cylinder ≥1.00 D
Any increase in corneal cylinder or manifest cylinder by 1.00 D or more warrants corneal topography to rule out keratoconus.
Cylinder ≥2.00 D
The suspicion of keratoconus increases significantly in patients with corneal cylinder or manifest cylinder ≥2.00 D.
Irregular, oblique, or ATR astigmatism
Because irregular, oblique, or ATR astigmatism has been associated with keratoconus, topography is therefore highly warranted.
Increasing and/or
Unusual Astigmatism
From the Case Files of
iDetective Bobby “Eye Spy KC” Saenz
OD, MS, FAAO
iDetective’s Notes:
Unusual Auto-refractor Reading
Error messages
Error messages or unusual findings may result from corneal distortion and irregular astigmatism. Topography may be needed if repeated attempts at measurement fail.
≥0.50 D increase in myopia or MRSE
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.
Frequent changes in prescription
MRVA worse than 20/20 or repeat complaints about glasses prescription needing to be updated or “being wrong” may indicate keratoconus.
Unusual Auto-refractor Reading
From the Case Files of
iDetective Tracy “Tracker” Swartz
OD, MS, FAAO
iDetective’s Notes:
Unusual
Keratometry (K)
Steepest K >47.00 diopters (D) or radius of curvature <7.2 mm
Average steep K is 43.00-43.50 D. Once steep K is >47.00 D, ectasia should be suspected.
Error messages on auto-keratometry
An error message occurs when the auto-keratometer cannot accurately read an abnormal cornea. Corneal distortion may be the culprit.
Difference of ≥2.00 D between K1 (flat K) and K2 (steep K)
Difference in Ks points to corneal astigmatism. Corneal astigmatism ≥2.00 D correlates to a higher prevalence of keratoconus, which warrants topo-tomography.
Unusual
Keratometry (K)
From the Case Files of
iDetective Mitch “Private Eye” Ibach
OD, FAAO
iDetective’s Notes:
Eye Rubbing &
Ocular Allergy
Eye rubbing is associated with keratoconus
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
Atopy is commonly observed with keratoconus
Treating associated atopic eye allergy symptoms may be more effective than asking patients not to rub their eyes.
Other conditions linked with eye rubbing
Vernal keratoconjunctivitis, allergies, atopic dermatitis, dry eye disease, and eye rubbing are all associated with keratoconus.2
References
- 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.
- 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.
Eye Rubbing &
Ocular Allergy
From the Case Files of
iDetective Bill “Bond” Tullo
OD, FAAO
iDetective’s Notes:
Genetics
Keratoconus is a genetic eye disease
Segregation analysis identifies keratoconus as a complex polygenic disease. There is evidence to associate more than 100 genes with keratoconus.
Keratoconus is found in families
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
Reference
- Gordon-Shaag A, Millodot M, Shneor E, Liu Y. The genetic and environmental factors for keratoconus. Biomed Res Int. 2015;2015:795738.
Genetics
From the Case Files of
iDetective Susan “Super Sleuth” Gromacki
OD, MS, FAAO, FSLS
iDetective’s Notes:
Visual Quality
Complaints
Monocular diplopia or ghosting
Keratoconus typically presents asymmetrically. Individuals may notice greater shadowing and doubling of images from the more advanced eye.
Halos and glare
Corneal distortion and higher-order aberrations due to keratoconus may contribute to halos and glare, usually more noticeable at night.
Vision that is not crisp
Irregular astigmatism related to keratoconus makes vision correction difficult with glasses. Further investigate poor quality of vision to rule out ocular disease.
Visual Quality
Complaints
From the Case Files of
iDetective Gloria “Gadget” Chiu
OD, FAAO, FSLS
iDetective’s Notes:
Retinoscopy and
Ophthalmoscopy Signals
Scissor reflex with retinoscopy
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
Charleaux “oil droplet” sign with direct ophthalmoscopy
If a patient has keratoconus, a total internal reflection of light due to the conical cornea may produce the oil droplet reflex.
Reference
- Al-Mahrouqi H, Oraba SB, Al-Habsi S, et al. Retinoscopy as a screening tool for keratoconus. Cornea. 2019;(4):442-445.
Retinoscopy and
Ophthalmoscopy Signals
From the Case Files of
iDetective Bobby “Eye Spy KC” Saenz
OD, MS, FAAO
iDetective’s Notes:
Topographic
Irregularities
Asymmetry on topography
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.
Skewed radial axis (SRAX) or irregular astigmatism on topography
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.
Increase in steepest K or Kmax
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.
Topographic
Irregularities
From the Case Files of
iDetective Bill “Bond” Tullo
OD, FAAO
iDetective’s Notes:
Down Syndrome
Higher predisposition to keratoconus
Studies have shown that the risk of keratoconus is at least 10 times greater in the Down syndrome population.1
Patients who rub their eyes aggressively
You may observe that patients with Down syndrome who also have keratoconus frequently rub their eyes.
Objective tests
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.
Reference
- Alio JL, Vega-Estrada A, Sanz P, et al. Corneal morphologic characteristics in patients with Down Syndrome. JAMA Ophthalmol. 2018;136(9)971-978.
Down Syndrome
From the Case Files of
iDetective Mitch “Private Eye” Ibach
OD, FAAO
iDetective’s Notes:
Connective Tissue Disorders
Collagen disorders
Because the cornea is composed of collagen, keratoconus may be a manifestation of an underling systemic condition.1
Ehlers-Danlos syndromes (EDS)
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
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
References
- 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.
- 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.
- 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.
Connective Tissue Disorders
From the Case Files of
iDetective Tracy “Tracker” Swartz
OD, MS, FAAO
iDetective’s Notes:
Contact Lens
Considerations
Instability with toric soft lenses
Corneal ectasia causes irregular astigmatism, which makes correction in toric soft contact lenses difficult. If fit and vision are unstable, consider keratoconus screening.
Improved clarity with rigid contact lenses
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.
Corneal molding effect
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.
Contact Lens
Considerations
From the Case Files of
iDetective Gloria “Gadget” Chiu
OD, FAAO, FSLS
iDetective’s Notes:
Abnormal Slit
Lamp Examination
Fleischer ring
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.
Vogt striae
If you suspect keratoconus, look for vertical lines within
the posterior stroma or Descemet membrane.
Stromal thinning
Stromal thinning is often present in the cone. It may initially be subtle, but it can become more pronounced over time.
Abnormal Slit
Lamp Examination
From the Case Files of
iDetective Susan “Super Sleuth” Gromacki
OD, MS, FAAO, FSLS
iDetective’s Notes:
Discover the first and only FDA-approved cross-linking procedure for progressive keratoconus
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