Characteristics and associations of keratoconus patients

https://doi.org/10.1016/j.clae.2015.01.008Get rights and content

Highlights

  • Patients have significant higher family history of keratoconus, giving strong evidence of a genetic predisposition.

  • There is a significant association between allergic disease, eye rubbing and keratoconus.

  • Family history of keratoconus, eye rubbing, itchy eyes, and low educational level are independent predictors of keratoconus.

  • Diabetic patients had a significantly less severe keratoconus.

  • Keratoconus patients with a higher frequency of eye rubbing, family history of keratoconus and more keratoconus members in their family had a more severe disease.

Abstract

Purpose

To determine the characteristics and risk factors of keratoconus (KC) patients and the possible associations between these characteristics and the severity of KC.

Methods

A prospective case–control study was performed in a referral eye hospital, recruiting KC patients and comparing their demographic and clinical characteristics with age and sex-matched control subjects to determine factors associated with KC. Mean keratometry (mean K) and central corneal thickness (CCT) of KC patients were recorded and compared. The severity of KC was further compared with the characteristics of KC patients.

Results

A total of 922 KC patients and controls were enrolled in the study. The mean age at the first presentation of KC patients was 21.03 ± 6.17 years. The most frequent presenting symptom was blurred vision. The multivariate analysis revealed that KC in relatives, eye rubbing, itchy eyes, and low educational level are independent predictors of KC. Severity of KC was moderate in 43.8% and severe in 41% of the patients. None of the proposed characteristics were significantly associated with mean K and CCT. KC patients with a higher frequency of eye rubbing, family history of KC and more KC members in their family had a more severe KC, while diabetic patients had a less severe KC.

Conclusion

This study presented an overview of a large population of KC patients in Iran, emphasizing the associated risk factors for this condition. Our findings add weights to the evidences that eye rubbing and positive family history of KC are independent risk factors for developing KC.

Introduction

Keratoconus (KC) is a bilateral chronic and asymmetric eye disease with a usual onset at puberty [1], [2]. It is a condition in which the cornea steepens, protrudes, and takes on a conical shape which is progressive in the majority of cases [2], [3].

KC has been linked to Down syndrome, Ehlers–Danlos syndrome, osteogenesis imperfecta and some other connective tissue disorders, though the underlying etiology has not been sufficiently described [4], [5]. A common belief is that environmental factors may trigger the disease in genetically susceptible patients [6], [7], [8], [9]. Although asymptomatic in the earlier stages, KC patients eventually present with visual impairment in the later stages, along with bio-microscopic signs of KC including marked stromal thinning, Fleischer's ring, Vogt's striae and corneal apical scarring [10], [11].

The treatment of mild KC typically begins with spectacles or even soft contact lenses, whilst cases with more advanced disease usually require rigid gas-permeable (RGP) contact lenses [1], [2], [10], [11], [12]. RGP lenses offer superior visual correction over spectacles and soft contact lenses by providing superior masking of irregular astigmatism and correcting both cylindrical and coma aberrations [13]. Surgical keratoplasty is used for KC patients who do not tolerate RGP lenses or for severe cases with corneal scar who may not benefit from other treatment alternatives [14].

Though detecting of KC can be difficult in the early stages, awareness and consideration of the risk factors may help the diagnosis. A large number of studies have already reported the characteristics and factors associated with KC [6], [7], [8], [9], [15], [16], [17], [18], [19], [20], [21], [22]. Very few studies, however, have compared KC patients with normal subjects [9], [10]. Moreover, epidemiological and geographical studies may provide different factors associated with KC.

For this reason, we aimed to study the demographic, epidemiological and clinical characteristics of KC in our population and determine how the proposed risk factors are related to this condition and its severity.

Section snippets

Study population

A prospective case–control study was conducted at Farabi Eye Hospital, Tehran, Iran, a major tertiary eye care center, recruiting 461 consecutive KC patients aged between 18 and 65 attending the corneal clinic of our hospital between January 2012 and January 2014. The KC diagnosis was made by a certified ophthalmologist based on clinical diagnostic signs of KC found by scanning-slit biomicroscopy such as conical protrusion of the cornea, Fleischer ring, corneal tilting, Vogt's striae, Munson's

Results

A total of 461 KC subjects and 461 controls were included in this study. Demographic characteristics and keratometric and topographic findings of each group are summarized in Table 1. Each group consisted of 282 males (61.17%) and 179 females (38.83%). The mean age was 21.03 ± 6.17 at the first presentation of KC patients (range, 5–49 years) where male patients had a lower mean age compared to females (20.45 ± 5.87 vs. 21.95 ± 6.53 years, p = 0.01). Mean keratometric findings (flat, steep and mean

Discussion

This study was an age and sex-matched case–control study on KC patients in the largest eye hospital in Iran. Consistent with the previous reports from Asian populations, where KC was diagnosed mostly in the second decade of life [6], and other studies conducted on white ethnicity [20], [23], the mean age at first presentation at the clinic of KC patients was 21 years in our study. In contrast to our finding, Olivares Jimenez et al. [24] reported that the age of KC patients in their first

Conflict of interest

There is no conflict of interest in any forms.

Disclosure statement

There is no fund, no grant, and no support received in any form. The article has not been presented at a meeting and has not published or submitted for publication elsewhere. The authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.

References (44)

  • A.M. Bawazeer et al.

    Atopy and keratoconus: a multivariate analysis

    Br J Ophthalmol

    (2000)
  • A. Ertan et al.

    Keratoconus clinical findings according to different age and gender groups

    Cornea

    (2008)
  • C.W. McMonnies et al.

    Keratoconus, allergy, itch, eye-rubbing and hand-dominance

    Clin Exp Optom

    (2003)
  • K.H. Weed et al.

    The Dundee University Scottish Keratoconus study: demographics, corneal signs, associated diseases, and eye rubbing

    Eye (Lond)

    (2008)
  • K.H. Weed et al.

    Referral patterns, treatment management and visual outcome in keratoconus

    Eye (Lond)

    (1998)
  • E. Shneor et al.

    Characteristics of 244 patients with keratoconus seen in an optometric contact lens practice

    Clin Exp Optom

    (2013)
  • A. Jinabhai et al.

    Optical quality and visual performance with customised soft contact lenses for keratoconus

    Ophthalmic Physiol Opt

    (2014)
  • D.C. Han et al.

    Comparison of outcomes of lamellar keratoplasty and penetrating keratoplasty in keratoconus

    Am J Ophthalmol

    (2009)
  • M.A. Abu Ameerh et al.

    Keratoconus patients at Jordan University Hospital: a descriptive study

    Clin Ophthalmol

    (2012)
  • A.A. Assiri et al.

    Incidence and severity of keratoconus in Asir province, Saudi Arabia

    Br J Ophthalmol

    (2005)
  • B.A. Fink et al.

    Differences in keratoconus as a function of gender

    Am J Ophthalmol

    (2005)
  • T. Georgiou et al.

    Influence of ethnic origin on the incidence of keratoconus and associated atopic disease in Asians and white patients

    Eye (Lond)

    (2004)
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