الفهرس 
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Abstract
Keratoconus is a progressive disorder that affects the corneal collagen, causing structural and biomechanical changes, which leads to thinning and ectasia.
Described as a non-inflammatory disease, the pathophysiology of keratoconus remains enigmatic. It is considered to be a multifactorial corneal ectasia triggered by external factors such as eye-rubbing or contact lens wear and endogenous stimuli through the interplay of inflammatory tear mediators, a dysregulation of oxidative stress and proteolytic enzymes resulting in corneal remodeling and keratocytes apoptosis, as well as the presence of atopic patient history.
The keratoconus prevalence rate in the general population has been reported to be around 54.5 and 86 per 100 000 in the general population in the United States and Northern Europe, respectively.
However, with improvements in diagnostic imaging via the introduction of Scheimpflug technology, and with better clinician and patient awareness, this figure is expected to be much higher. The prevalence of keratoconus has also been shown to be dependent on region and ethnicity.
The presence of a positive family history of keratoconus in patients with the disease ranges between 3% and 21% based on ethnicity and region. This high prevalence rate puts relatives of keratoconus patients in a much higher risk bracket than the general population.
Identifying very early keratoconus in pediatric age group, known to have high progression rate, could lead to better vision preservation.
Aim of the Work to evaluate the tomographic and refractive characteristics of relatives of patients with keratoconus.
This observational cross sectional study was done on both eyes of 248 (496 eyes) relatives of 52 patients diagnosed as Keratoconus. The study was conducted at outpatient clinic of Beni-Suef University hospital & outpatient clinic of Memorial Institute for Ophthalmic Research.
The main results of the study revealed that:
The age of studied cases was ranged from 6 to 65 years with mean ± SD was 30.05 ± 15.98 years and median of 26.5 years. The commonest age group involved was 30- <50 years age group with 77 (31.0%) cases followed by 6- <18 years group with 71 (28.6%) cases. 117 (47.2%) of cases were males and 131 (52.8%) were females with male to female ratio of 0.89:1. Sisters and brothers were the commonest relation studied representing 26.6% and 23.8% respectively.
In the right eye the mean uncorrected visual acuity (UCVA) of the participants was 0.44 ±SD 0.31 in decimal, the mean refractive sphere was -1.16 ±SD 2.05, the mean refractive cylinder of was -1.12 ± SD 1.35 with 10 (4.03%) cases had refractive cylinder more than -4 and the mean best corrected visual acuity (BCVA) was 0.83 ± 0.22.
In the left eye the mean uncorrected visual acuity (UCVA) of the participants was 0.37 ± SD 0.25 in decimal, the mean refractive sphere was -1.24 ± SD 1.93, the mean refractive cylinder of studied cases was -1.14 ± SD 1.39 with 15 (6%) cases had refractive cylinder more than -4 and the mean best corrected visual acuity (BCVA) was 0.80 ± SD 0.25.
The mean thinnest corneal thickness in right eye of studied cases was 524.33± SD 31.14 µm, meanwhile, the mean thinnest corneal thickness in left eye of studied cases was 521.34± SD 39.87µm.
The most common finding is that majority of cases were normal representing 73.8%, the prevalence of Keratoconus in the relative of our studied cases was 19/248 (7.7%), 3.2% cases had forme frost and 15.3% cases were suspected to have Keratoconus.
Based on our results we recommend for further studies on larger patients and longer period of follow up to emphasize our conclusion.