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Keratoconus

Keratoconus is a disorder of the eye, characterized by thinning of the cornea, causing it to bulge outwards. Such a condition can cause gradual distortion of vision, making reading and driving difficult for affected individuals.


Presentation

Keratoconus presents with the following signs and symptoms:

  • Distorted vision, individuals with keratconus suffer from blurred vision.
  • Development of problems with vision during night time.
  • Eyes become sensitive to light and glare.
  • Frequent changes in eye glass and contact lens prescriptions.

Symptoms of keratoconus usually differ with disease progression. In more severe cases, the cornea may rupture, and get accumulated with fluid. In such conditions, the already distorted vision worsens, indicating immediate medical intervention [6].

Unable to Stand
  • The weakened cornea is unable to stand the intraocular pressure and protrudes in a conical shape ( Ertan 2008a ).[doi.org]
Hunting
  • Iowa: Kendall/Hunt; 1995. p. 101-22. 10. Perry HD, Buxton JN, Fine BS. Round and oval cones in keratoconus. Ophthalmology 1980;87:905-9. [ PUBMED ] 11. Barr JT, Zadnik K, Wilson BS, Edrington TB, Everett DF, Fink BA, et al.[doi.org]
Pupillary Abnormality
  • In all, IOP was elevated on postoperative day 1 or after re-bubbling for graft dislocation, and the high IOP may have led to iris ischemia. [7] Excess surgical manipulation may increase the risk of damaging the iris vasculature and cause pupillary abnormalities[eyewiki.aao.org]
Corneal Infiltrate
  • Although silicone-hydrogel lenses almost eliminate hypoxia in patients due to their very high levels of oxygen transmissibility, [97] they also seem to provide a more efficient platform for bacterial contamination and corneal infiltration than other conventional[en.wikipedia.org]

Workup

A preliminary, thorough examination of the eye will be carried out. Thereafter, the following tests are conducted to diagnose the condition [7]:

  • Eye refraction test: This is the standard vision test, to check for conditions such as astigmatism and vision disorders. Along with this test, an automatic refractor may be used to measure the amount of light reflected by the eyes.
  • Slit lamp test: Such a type of examination is done, after the pupils are dilated with help of eye drops. Following this, the shape of the cornea is studied, and other problems within the eye are also determined.
  • Keratometry: This is a test used for measuring the curve of the cornea.
  • Corneal mapping: With such a kind of examination, the corneal thickness is studied, using corneal topography and optical coherence tomography [8].
Chlamydia
  • He was born at 38 weeks gestation by spontaneous, unassisted vaginal delivery, and at the time of delivery the mother had a yeast infection and chlamydia, which were being treated.[ncbi.nlm.nih.gov]
Gliosis
  • She was diagnosed as both eyes keratoconus with RE near total rhegmatogenous retinal detachment (RRD) with sub retinal gliosis. She gave no history of vigorous eye rubbing or atopic dermatitis.[ncbi.nlm.nih.gov]

Treatment

The following methods will be employed for treating keratoconus.

  • Lenses: This is one of the most common, as well as effective method for treating keratoconus. In the preliminary stages, soft contact lenses can help correct the distorted vision. When the disease progresses to more advanced stages, rigid gas permeable lenses are fitted to cornea, for correcting the associated symptoms. Piggyback lenses are recommended for individuals, who are uncomfortable with gas permeable lenses. This type of lens is hard in nature, and not all individuals can tolerate them. In such cases, hybrid lenses which have softer outer ring for more comfortable wear are suggested. For advanced stages contact lenses are recommended.
  • Surgery: In more advanced and severe cases surgery is indicated. When there is corneal scarring, and extreme corneal thinning, then surgical intervention becomes necessary. Surgical procedures, such as keratoplasty, and corneal inserts are required. Depending on the condition of the individual, the type of surgery is decided [9].
  • Collagen cross linking: This is a new form of treatment that employs exposing the individual to ultraviolet rays, to prevent further scarring, and thinning. The efficacy of this method is however being tested, before it is made widely available [10].

Prognosis

Individuals with keratoconus present with mild signs and symptoms during adolescence. However, the condition is diagnosed only during the late teens to early 20s. If younger individuals or children are affected, then the disease progresses at a faster rate and can get severe. The prognosis of the condition is pretty unpredictable; in some, the disease progresses at a faster pace, while in some cases patients remain stable for several years [5].

Etiology

The exact cause of keratoconus is not known. However, several practices or factors can predispose an individual to contract this chronic noninflammatory eye disorder. These include:

In addition, several other factors can also put an individual at risk for contracting this disease condition. Individuals with family history of keratoconus, are at an increased risk for developing the same. Also, certain disease conditions, such as osteogenesis imperfecta, Leber’s congenital amarousis and Ehlers Danlos syndrome, are some of the risk factors for keratoconus.

Epidemiology

In majority of the cases, keratoconus occurs as a singular condition. But there are some incidences, when the condition coexists along with ocular and systemic diseases. It has been estimated that about 50 to 200 cases occur per 100,000 populations. Statistical reports have suggested that about 2000 Americans are affected with this eye disorder. There have been small pieces of evidence suggesting that females are more likely to develop this condition than males [3].

Sex distribution
Age distribution

Pathophysiology

The condition of keratoconus is known to affect all the corneal layers. Structural changes occur in the epithelial membrane, along with scarring, that occurs in the Bowman membrane. Oxidative stress is known to cause such sequence of events to occur [4]. Oxidative stress on the other hand, can stimulate or activate the degradative enzymes, which in turn leads to thinning of the corneal cells. Such a kind of phenomenon causes vision distortion, and the condition normally affects both the eyes.

Prevention

Keratoconus cannot be prevented. However, it is advised that individuals with this condition should treat their eye allergies, and also avoid rubbing their eye often.

Summary

Keratoconus affects both the eyes, and majorly strikes individuals aged 10 to 25 years. This degenerative eye disease is diagnosed during the adolescence, and gradual loss of vision occurs, as the disease progresses to more advanced stages. More advanced stages of the disease may require surgical intervention, which includes corneal transplant [1].

Patient Information

  • Definition: Keratoconus is a condition, characterized by thinning of the cornea, which leads to vision distortion. As the disease progresses, the cornea becomes cone shaped causing the eye to bulge out.
  • Cause: The exact cause of keratoconus is unknown. However, several factors are known to increase the risk of contracting this eye disorder. Factors such as wearing contact lenses for several years, rubbing eye often, other eye disorders and heredity are known to play foul.
  • Symptoms: Symptoms of keratoconus include blurred vision, experiencing difficulty in seeing at night, frequent changes in contact lens prescriptions, sensitivity to light and glare, and sudden worsening of vision.
  • Diagnosis: A preliminary eye examination, using eye refraction test, is conducted to determine presence of conditions, such as astigmatism. In addition, slit lamp examination and corneal topography are also done to diagnose keratoconus.
  • Treatment: Lenses form the most common, and primary basis of the treatment regime. Different types of lenses are suggested, for correcting the distorted vision. When these do not work, then surgical intervention is required. Depending on the condition of the individual, either corneal transplant, or corneal inserts are employed. A new method of treating keratoconus has been designed, known as collagen cross linking. In this method, using riboflavin drops, the individual is exposed to ultraviolet rays.

References

Article

  1. Cristina Kenney M, Brown DJ. The cascade hypothesis of keratoconus. Cont Lens Anterior Eye. Sep 2003;26(3):139-46
  2. Macsai MS, Varley GA, Krachmer JH. Development of keratoconus after contact lens wear. Patient characteristics. Arch Ophthalmol. Apr 1990;108(4):534-8.
  3. Atilano SR, Coskun P, Chwa M, Jordan N, Reddy V, Le K. Accumulation of mitochondrial DNA damage in keratoconus corneas. Invest Ophthalmol Vis Sci. Apr 2005;46(4):1256-63
  4. Kenney MC, Nesburn AB, Burgeson RE, Butkowski RJ, Ljubimov AV. Abnormalities of the extracellular matrix in keratoconus corneas. Cornea. May 1997;16(3):345-51.
  5. Moodaley LC, Woodward EG, Liu CS, Buckley RJ. Life expectancy in keratoconus. Br J Ophthalmol. Oct 1992;76(10):590-1. 
  6. Zadnik K, Barr JT, Edrington TB, et al. Baseline findings in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. Invest Ophthalmol Vis Sci. Dec 1998;39(13):2537-46
  7. Wilson SE, Lin DT, Klyce SD, et al. Topographic changes in contact lens-induced corneal warpage. Ophthalmology 1990; 97:734.
  8. Wagner H, Barr JT, Zadnik K. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study: methods and findings to date. Cont Lens Anterior Eye. Sep 2007;30(4):223-32.
  9. Kelly TL, Williams KA, Coster DJ. Corneal transplantation for keratoconus: a registry study. Arch Ophthalmol. Jun 2011;129(6):691-7
  10. Raiskup-Wolf F, Hoyer A, Spoerl E, Pillunat LE. Collagen crosslinking with riboflavin and ultraviolet-A light in keratoconus: long-term results. J Cataract Refract Surg. May 2008;34(5):796-801.

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Last updated: 2019-07-11 22:29