Keratoconus / Conical cornea

KF Ring REF: khurana 4th ed p. 141 Fliescher’s ring is seen in keratoconus and not KF rings

Classical features of Alport’s syndrome:

• Hematuria
• Thinning and splitting of the GBMs
• Mild proteinuria (
• Chronic glomerulosclerosis leading to renal failure
• Sensorineural deafness
• Lenticonus of the anterior lens capsule
• “Dot and fleck” retinopathy

Also know:

• Approximately 85% of patients with Alport’s syndrome have an X-linked inheritance of mutations in the 5(IV) collagen chain on chromosome Xq22–24.
• Early onset of severe deafness, lenticonus, or proteinuria suggests a poorer prognosis.

Ref: Lewis J.B., Neilson E.G. (2012). Chapter 283. Glomerular Diseases. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds),Harrison’s Principles of Internal Medicine, 18e.

Keratoconus is a non inflammatory bilateral ecstatic condition of the cornea in its axial part. Slit lamp examination in this condition shows thinning and ectasia of central cornea, presence of opacity at the apex, fleischers ring at the base of cone, folds in the Descements membrane and Bowmans membrane.

Ref: Comprehensive Ophthalmology By A K Khurana, 4th Edition, Page 11

Placido disc examination is used to diagnose keratoconus. In a case of keratoconus, placido disc examination shows irregularities of the circles.

Placido’s keratoscopic disc: It is a disc painted with alternating black and white circles. It may be used to assess the smoothness and curvature of corneal surface. Normally, on looking through the hole in the center of disc a uniform sharp image of the circle is seen on the cornea. Distortion of the circles occur when irregularities are present on the corneal surface.

Ref: Comprehensive Ophthalmology By AK Khurana, 4th edn, page 119

B i.e. Herpes simplex keratitis

A. i.e. Spectacles; B. i.e. Contact lens; C. i.e. Keratoplasty

A i.e. Munson’s sign; B i.e. Protrusion of anterior cornea

D i.e. Hypermetropic refractory error found

D i.e. Keratoconus 

Corneal Pigmentation

Ans. All of the above

Ans. Keratoconus

Ans. Interstitial keratitis

Ans. Keratoconus

Ans. None

Ans. Paralysis of inferior oblique

Ans. All of the above

Ans. C i.e. Keratoconus

Keratoconus

• Protrusion of central part of cornea with thinning,
• Corneal nerves are visible,
• Associated features:

–         Munsen’s sign,

–         Fleischer sign

Ans. C i.e. Cornea thins near the centre & bulges forwards

Ans. C i.e. Wilson’s disease

Ans. B: It manifests just after birth

Keratoconus is divided into mild, moderate, and advanced.

Mild keratoconus

– External and corneal signs are often absent or minimal.

– A history of multiple inadequate spectacle corrections of one or both eyes may be noted and may include oblique astigmatism on refraction as well as moderate-to-high myopia.

– Irregularly astigmatic keratometry values (egg-shaped), not necessarily on the steep side of normal (approximately 45 diopters (D)), are consistent with diagnosis.

Diagnosis can be confirmed with computer-assisted videokeratography, which may reveal corneal inferior steepening (approximately 80% of keratoconus cases), central corneal astigmatic steepening (approximately 15% of keratoconus cases), or even bilateral temporal steepening (extremely rare).

Diagnosis may also be aided by applying a diagnostic rigid contact lens with its base curve equal to the flat keratometry value. One observes a typical nipple pattern by use of sodium fluorescein dye in the underlying tear film.

Moderate keratoconus

One or more corneal signs of keratoconus are often present.

Enhanced appearance of the corneal nerves is noted.

Approximatel^y 40% of eyes in patients with moderate keratoconus develop Vogt striae (fine-stress lines) in the deep stroma.

Approximately 50% develop the deposition of iron in the basal epithelial cells in a (often partial) ring shape at the base of the conical protrusion called the Fleischer ring.

Approximately 20% develop corneal scarring.

Superficial corneal scarring can be fibular, nebular, or nodular.

Deep stromal scarring may occur, perhaps representing resolved mini-hydrops events.

Some patients show scarring at the level of the Descemet membrane (posterior limiting lamina), consistent in appearance with posterior polymorphous corneal dystrophy.

Paraxial (usually inferior to the pupil) stromal thinning may be appreciated.

Keratometry values typically increase to 45-52 D.

Distortion of the retinoscopy and direct ophthalmoscope red pupillary reflex may allow observation of “scissoring” or an inferior distortion termed the oil drop sign.

The Munson sign is noted when, upon downgaze, a “V” shape is noted in the cornea’s profile against the lower lid margin, an accentuation of the conical shape of the modest to advanced keratoconus cornea.

Advanced keratoconus

This often results in keratometry values greater than 52 D and enhancement of all corneal signs, symptoms, and visual loss/distortion.

Vogt striae are seen in approximately 60% of eyes, and Fleischer ring and/or scarring are seen in approximately 70% of eyes.

Acute corneal hydrops can occur.

Treatment: In the early stages, vision may be improved with spectacles but contact lens are more beneficial as they eliminate the irregular corneal curvature.

If the disease progresses and the cone hydrated, the most satisfactory treatment is corneal transplantation.

Ans. D: Keratoconus

Corneal hydrops is an uncommon complication seen in patients with keratoconus.

It is characterized by significant corneal edema resulting from a spontaneous rupture in Descemet’s membrane.

Clinical findings include dense stromal and epithelial edema with corneal protrusion, possible conjunctival hyperemia and irregular epithelium secondary to microcystic edema.

The location and area of the involved cornea is variable

Ans. A: Corneal dystrophy

Epithelial and subepithelial corneal dystrophies may present with bouts of recurrent corneal erosions Bowman layer corneal dystrophy usually presents with recurrent corneal erosions

Recurrent corneal erosion

• It is characterized by the failure of the cornea’s outermost layer of epithelial cells to attach to the underlying basement membrane (Bowman’s layer).
• The condition is excruciatingly painful because the loss of these cells results in the exposure of sensitive corneal nerves.
• There is often a history of previous corneal injury (corneal abrasion or ulcer), but also may be due to corneal dystrophy or corneal disease.
• In other words, one may suffer from corneal erosions as a result of another disorder, such as map dot fingerprint disease

Presentation

• Symptom include recurring attacks of severe acute ocular pain, foreign-body sensation, photophobia (i.e. sensitivity to bright lights), and tearing often at the time of awakening or during sleep when the eyelids are rubbed or opened.
• Signs of the condition include corneal abrasion or localized roughening of the corneal epithelium, sometimes with map-like lines, epithelial dots or microcyts, or fingerprint patterns

Investigation

• The erosion may be seen by using the magnification of an ophthalmoscope, although usually fluorescein stain must be applied first and a blue-light used.
• Use of slit lamp microscopes allow for more thorough evaluation under the higher magnification.

Management

• With the eye generally profusely watering, the type of tears being produced have little adhesive property.
• Water or saline eye drops tend therefore to be ineffective.
• Rather a ‘better quality’ of tear is required with higher ‘wetting ability’ (i.e. greater amount of glycoproteins) and so artificial tears (e.g. viscotears) are applied frequently.
• Where episodes frequently occur, or there is an underlying disorder, one medical, or three types of surgical curative procedures may be attempted:
• Use of therapeutic contact lens, controlled puncturing of the surface layer of the eye (Anterior Stromal Puncture) and laser phototherapeutic keratectomy (PTK).
• These all essentially try to allow the surface epithelium to reestablish with normal binding to the underlying basement membrane

Medical

• Patients with recalcitrant recurrent corneal erosions often show increased levels of matrix metalloproteinase (MMP) enzymes.
• These enzymes dissolve the basement membrane and fibrils of the hemidesmosomes, which can lead to the separation of the epithelial layer.
• Treatment with oral tetracycline antibiotics (such as doxycycline or oxytetracycline) together with a topical corticosteroid (such as prednisolone), reduce MMP activity and may rapidly resolve and prevent further episodes in cases unresponsive to conventional therapies.

Ans. B: Down syndrome

Ans. is ‘a’ i.e., Keratoconus

Kerotoconus

• Keratoconus is a progressive, noninflammatory, bilateral ectatic corneal disease, characterizedparaxia/stromal thinning and weakening that leads to corneal surface distortion.
• Essential pathological changes are thinning and ectasia which occur as a result of defective synthesis of mucopolysaccharide and collagen tissue.
• It usually starts at puberty and progresses slowly.
• Symptoms usually begins as blurred vision with shadowing around images.
• Vision becomes progressively more blurred and distorted with associated glare, halos around lights, light sensitivity and ocular irritation.
• Visual loss occurs primarily from irregular astigmatism and myopia, and secondarily from corneal scarring. o The hallmark of keratoconus is central or paracentral stromal thinning, apical protrusion of anterior corneaand irregular astigmatism.
• The cornea thins near the centre and progressively bulges forwards, with the apex of cone always being slightly below the centre of the cornea.

Important findings an examination are –

i) Distarted window reflex (Corneal reflex)e.

ii) Fleisher’s rine.

iii) Yawning reflex (Scissor reflex).

iv) Oil drop reflex.

v) Munson’s signs

Treatment includes :‑

1) Spectacles for regular or mild irregular astigmatism.

2) Rigid gas permeable contact lens for higher astigmatism.

3) Epikeratoplasty in patients intolerant to lens and without significant corneal scarring.

4) Keratoplasty penetrating or deep lamellar if there is significant corneal scarring.