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Keratoconus 1(KTCN1)

MedGen UID:
372103
Concept ID:
C1835677
Disease or Syndrome
Synonym: KTCN1
 
Gene (location): VSX1 (20p11.21)
 
Monarch Initiative: MONDO:0007851
OMIM®: 148300

Definition

Keratoconus, the most common corneal dystrophy, is a bilateral, noninflammatory progressive corneal ectasia. Clinically, the cornea becomes progressively thin and conical, resulting in myopia, irregular astigmatism, and corneal scarring. The disease usually arises in the teenage years, eventually stabilizing in the third and fourth decades. The incidence of keratoconus is 1 in 2,000 in the general population; it occurs with no ethnic or gender preponderance, and causes significant visual impairment in young adults. No specific treatment exists except to replace the corneal tissue by surgery (corneal transplantation) when visual acuity can no longer be corrected by contact lenses (summary by Dash et al., 2006). Ihalainen (1986) reviewed various conditions with which keratoconus is at times associated. Keratoconus is frequent in cases of amaurosis congenita of Leber (204000). Genetic Heterogeneity of Keratoconus Also see KTCN2 (608932), mapped to 16q22.3-q23.1; KTCN3 (608586), mapped to 3p14-q13; KTCN4 (609271), mapped to 2p24; KTCN5 (614622), mapped to 5q14.1-q21.3; KTCN6 (614623), mapped to 9q34; KTCN7 (614629), mapped to 13q32; KTCN8 (614628), mapped to 14q24; and KTCN9 (617928), caused by mutation in the TUBA3D gene (617878) on 2q21. [from OMIM]

Additional description

From MedlinePlus Genetics
Keratoconus is an eye condition that affects the shape of the cornea, which is the clear outer covering of the eye. In this condition, the cornea thins and bulges outward, eventually resembling a cone shape. These corneal abnormalities, which worsen over time, can lead to nearsightedness (myopia), blurred vision that cannot be improved with corrective lenses (irregular astigmatism), and vision loss.

Other corneal changes typical of keratoconus that can be seen during an eye exam include iron deposits in the cornea that form a yellow-to-brownish ring, called the Fleischer ring, surrounding the colored part of the eye (iris). Affected individuals may also develop Vogt's striae, which are thin, vertical, white lines in the tissue at the back of the cornea.

Keratoconus may affect only one eye at first, but eventually the corneas of both eyes become misshapen, although they might not be affected with the same severity. As keratoconus worsens, people with this condition can develop corneal scarring, often caused by exposure of the abnormally thin cornea to prolonged contact lens use or excessive eye rubbing.

The eye changes characteristic of keratoconus typically begin in adolescence and slowly worsen until mid-adulthood at which point the shape of the cornea remains stable.  https://medlineplus.gov/genetics/condition/keratoconus

Clinical features

From HPO
Astigmatism
MedGen UID:
2473
Concept ID:
C0004106
Disease or Syndrome
Astigmatism (from the Greek 'a' meaning absence and 'stigma' meaning point) is a condition in which the parallel rays of light entering the eye through the refractive media are not focused on a single point. Both corneal and noncorneal factors contribute to refractive astigmatism. Corneal astigmatism is mainly the result of an aspheric anterior surface of the cornea, which can be measured readily by means of a keratometer; in a small fraction of cases (approximately 1 in 10) the effect is neutralized by the back surface. The curvature of the back surface of the cornea is not considered in most studies, because it is more difficult to measure; moreover, in the case of severe corneal astigmatism, there is evidence that both surfaces have the same configuration. Noncorneal factors are errors in the curvature of the 2 surfaces of the crystalline lens, irregularity in the refractive index of the lens, and an eccentric lens position. Since the cornea is the dominant component of the eye's refracting system, a highly astigmatic cornea is likely to result in a similarly astigmatic ocular refraction (summary by Clementi et al., 1998).
Keratoconus
MedGen UID:
44015
Concept ID:
C0022578
Disease or Syndrome
A cone-shaped deformity of the cornea characterized by the presence of corneal distortion secondary to thinning of the apex.

Professional guidelines

PubMed

Iqbal M, Elmassry A, Tawfik A, Elgharieb M, Nagy K, Soliman A, Saad H, Tawfik T, Ali O, Gad A, El Saman I, Radwan A, Elzembely H, Abou Ali A, Fawzy O
Acta Ophthalmol 2019 Jun;97(4):e623-e631. Epub 2018 Nov 29 doi: 10.1111/aos.13986. PMID: 30499232Free PMC Article

Recent clinical studies

Etiology

Gil JQ, Rosa AM, Costa E, Quadrado MJ, Murta JN
J Cataract Refract Surg 2023 Jun 1;49(6):602-607. doi: 10.1097/j.jcrs.0000000000001166. PMID: 36779807
Salouti R, Nowroozzadeh MH, Azizi A, Salouti K, Ghoreyshi M, Oboodi R, Tajbakhsh Z
J Cataract Refract Surg 2022 Oct 1;48(10):1148-1154. doi: 10.1097/j.jcrs.0000000000000953. PMID: 35404317
Tian M, Jian W, Zhang X, Sun L, Shen Y, Zhou X
BMC Ophthalmol 2022 Jan 3;22(1):7. doi: 10.1186/s12886-021-02235-4. PMID: 34980018Free PMC Article
Kang MJ, Hwang J, Chung SH
J Cataract Refract Surg 2021 May 1;47(5):641-648. doi: 10.1097/j.jcrs.0000000000000488. PMID: 33196569
Nordström M, Schiller M, Fredriksson A, Behndig A
Br J Ophthalmol 2017 Jul;101(7):920-925. Epub 2016 Nov 29 doi: 10.1136/bjophthalmol-2016-309210. PMID: 27899371

Diagnosis

Benca Kapitánová K, Javorka M
Cesk Slov Oftalmol 2022 Spring;78(3):122-127. doi: 10.31348/2022/14. PMID: 35760583
Salouti R, Nowroozzadeh MH, Azizi A, Salouti K, Ghoreyshi M, Oboodi R, Tajbakhsh Z
J Cataract Refract Surg 2022 Oct 1;48(10):1148-1154. doi: 10.1097/j.jcrs.0000000000000953. PMID: 35404317
Kang MJ, Hwang J, Chung SH
J Cataract Refract Surg 2021 May 1;47(5):641-648. doi: 10.1097/j.jcrs.0000000000000488. PMID: 33196569
Alió JL, Alió Del Barrio JL, El Zarif M, Azaar A, Makdissy N, Khalil C, Harb W, El Achkar I, Jawad ZA, De Miguel MP
Am J Ophthalmol 2019 Jul;203:53-68. Epub 2019 Feb 15 doi: 10.1016/j.ajo.2019.02.009. PMID: 30772348
Tréchot F, Angioi K, Latarche C, Conroy G, Beaujeux P, Andrianjafy C, Portier M, Batta B, Conart JB, Cloché V, Peyrin-Biroulet L
J Crohns Colitis 2015 Dec;9(12):1108-12. Epub 2015 Sep 7 doi: 10.1093/ecco-jcc/jjv151. PMID: 26351387

Therapy

Gil JQ, Rosa AM, Costa E, Quadrado MJ, Murta JN
J Cataract Refract Surg 2023 Jun 1;49(6):602-607. doi: 10.1097/j.jcrs.0000000000001166. PMID: 36779807
Tian M, Jian W, Zhang X, Sun L, Shen Y, Zhou X
BMC Ophthalmol 2022 Jan 3;22(1):7. doi: 10.1186/s12886-021-02235-4. PMID: 34980018Free PMC Article
Matthys A, Cassagne M, Galiacy SD, El Hout S, Fournié P, Malecaze F
J Refract Surg 2021 Jan 1;37(1):42-48. doi: 10.3928/1081597X-20201111-01. PMID: 33432994
Kang MJ, Hwang J, Chung SH
J Cataract Refract Surg 2021 May 1;47(5):641-648. doi: 10.1097/j.jcrs.0000000000000488. PMID: 33196569
Nordström M, Schiller M, Fredriksson A, Behndig A
Br J Ophthalmol 2017 Jul;101(7):920-925. Epub 2016 Nov 29 doi: 10.1136/bjophthalmol-2016-309210. PMID: 27899371

Prognosis

Cronin B, Gunn D, Chang CY
J Cataract Refract Surg 2024 Mar 1;50(3):209-216. doi: 10.1097/j.jcrs.0000000000001339. PMID: 38381615Free PMC Article
Tian M, Jian W, Zhang X, Sun L, Shen Y, Zhou X
BMC Ophthalmol 2022 Jan 3;22(1):7. doi: 10.1186/s12886-021-02235-4. PMID: 34980018Free PMC Article
Kandel H, Nguyen V, Ferdi AC, Gupta A, Abbondanza M, Sullivan L, Apel A, Watson SL
Cornea 2021 Dec 1;40(12):1581-1589. doi: 10.1097/ICO.0000000000002747. PMID: 33935236
Alió JL, Alió Del Barrio JL, El Zarif M, Azaar A, Makdissy N, Khalil C, Harb W, El Achkar I, Jawad ZA, De Miguel MP
Am J Ophthalmol 2019 Jul;203:53-68. Epub 2019 Feb 15 doi: 10.1016/j.ajo.2019.02.009. PMID: 30772348
Nordström M, Schiller M, Fredriksson A, Behndig A
Br J Ophthalmol 2017 Jul;101(7):920-925. Epub 2016 Nov 29 doi: 10.1136/bjophthalmol-2016-309210. PMID: 27899371

Clinical prediction guides

Benca Kapitánová K, Javorka M
Cesk Slov Oftalmol 2022 Spring;78(3):122-127. doi: 10.31348/2022/14. PMID: 35760583
Salouti R, Nowroozzadeh MH, Azizi A, Salouti K, Ghoreyshi M, Oboodi R, Tajbakhsh Z
J Cataract Refract Surg 2022 Oct 1;48(10):1148-1154. doi: 10.1097/j.jcrs.0000000000000953. PMID: 35404317
Tian M, Jian W, Zhang X, Sun L, Shen Y, Zhou X
BMC Ophthalmol 2022 Jan 3;22(1):7. doi: 10.1186/s12886-021-02235-4. PMID: 34980018Free PMC Article
Kang MJ, Hwang J, Chung SH
J Cataract Refract Surg 2021 May 1;47(5):641-648. doi: 10.1097/j.jcrs.0000000000000488. PMID: 33196569
Alió JL, Alió Del Barrio JL, El Zarif M, Azaar A, Makdissy N, Khalil C, Harb W, El Achkar I, Jawad ZA, De Miguel MP
Am J Ophthalmol 2019 Jul;203:53-68. Epub 2019 Feb 15 doi: 10.1016/j.ajo.2019.02.009. PMID: 30772348

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