Characteristics and associations of keratoconus patients
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.
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