Clinical and Epidemiological Characterization of Keratoconus
Clinical and Epidemiological Characterization of Keratoconus
Clinical and Epidemiological Characterization of Keratoconus
RESEARCH
SUMMARY
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Revista Cubana de Oftalmología 2014;27(4):598-609
ABSTRACT
INTRODUCTION
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Moderate and severe stages of the disease pose no diagnostic difficulty, which is
due to the presence of typical signs. However, the diagnosis of subclinical or mild
forms of keratoconus represents a challenge due to the absence of clinical signs or
the minimal presence of these.
Studies carried out in relation to the biomechanics of the cornea raise the
existence of structural changes (tissue destruction and scarring) of a tissue with
its altered capacity in response to oxidative damage that generates an
architectural weakness from which the structure yields to factors such as
intraocular pressure.3,4
METHODS
Each patient was previously advised to stop wearing contact lenses one month
before the consultation. Biomicroscopy was performed with slit lamp, schiascopy,
refraction, pachymetry, keratometry, corneal topography (Atlas, Zeiss) and
confocal microscopy (Confoscam4, NIDEK). The following variables were studied:
age, sex, associated systemic diseases, associated ophthalmological diseases,
time of use of contact lenses, symptoms, signs, type of astigmatism, central
corneal keratometric power, pachymetry, crystal-free visual acuity (CVA), crystal-
visual acuity (CVA), topographic pattern and histological alterations.
The data were obtained directly from the patient and collected in the model
created for this purpose. A database was created in SPSS version 11.5.1,
where information was processed and analyzed using descriptive and
inferential techniques.
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RESULTS
59.7% of the patients were female; The mean age was 35 years, while by age
group the 30 to 39 years interval was the most represented percentage, with age
averages by more or less similar sex (Table 1). Finally, it is shown that ages differ
significantly (p= 0.0000).
The association of general diseases was analyzed and it was found that 26.4%
had some disease, in correspondence mainly with bronchial asthma and
allergies (13.9% and 12.5% respectively). The absence of systemic diseases
associated with keratoconus was statistically significant in our study. The
absence of an association of diseases and keratoconus occurred in 71.9%.
Allergic keratoconjunctivitis (21.9%) was the most common ophthalmological
condition (Table 2).
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Half of the patients reported a slow and progressive decrease in vision, while 25
patients (34.7%) frequently changed their optical correction (Table 3). Symptoms
such as itching and contact lens intolerance were described by 18.1% of patients.
The presence of any ophthalmic sign was observed in 85.9% of the eyes, and the
most frequent were the conical cornea (38.3%), Munson’s sign (33.6%),
prominent corneal nerves (25.8%) and the scissor sign from schiascopia (65.6%).
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When analyzing the visual acuity, it was observed that the mean of the CVA was
0.1 while in the CVA it was 0.6 0.3 lines (Table 4), where a significant increase
of the CVA was observed (p= 0.000).
Compound myoal astigmatism was significant (p= 0.000) in 85.2% of the eyes, while
the remaining forms of astigmatism were uncommon, below 10% (Table 5).
Regarding the keratometric power of the central cornea, we found that the three
keratometric groups follow the same distribution (p= 0.211). The mean thickness of
the central cornea was 493.2 µm dispersed in 43.4, contained between 485.6 and
500.8 µm with 95% certainty. When comparing the average in microns of the
thickness of the central zone of the cornea with the standardized value (538.09 µm)
it is observed that it is significantly less (p= 0,000) both the estimated value on time
and per confidence interval.
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When evaluating the correction used, we found that 67% of the patients wore
contact lenses for a time greater than or equal to 12 years. The prolonged use
of contact lenses was significant in relation to the diagnosis of keratoconus (p=
0.000).
In confocal microscopy we find in the epithelium fine nerves that penetrate the
basal epithelium (96.1%) and abnormal reflectivity (62.5%). In the Bowman
membrane the most frequent alterations were hyperreflectivity (93.8%) and
invasion of keratocytes (92.2%).
In all the eyes studied, there was a decrease in the density of keratocytes and in the
transparency of the background, deep stromal hyperreflectivity and a decrease in the
cross-linking of collagen fibers. In addition, the
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In the subepithelial nerve plexus (Fig.), the most frequent findings were the
decrease in nerve density (93.7%), nerve fibers that adopt oblique and
horizontal orientation (96.1%) and curvilinear form (86.7%).
ARGUING
The origin of keratoconus is not clearly defined, but there are several theories
that try to explain its presentation. Its incidence varies in several countries,
however, in Cuba there are no epidemiological studies that allow us to know the
true dimension of this condition. In this research keratoconus was more frequent
in the female sex and in the ages between 30-39 years.
Revised research found that the diagnosis of keratoconus was obtained around 24
age of 30, while in men it was a little more early
years of age each and mostly before the
diagnosis and faster evolution.7
Race is not reported as a determinant.
In relation to sex, literature is controversial; Some authors consider that it has the
same distribution in both sexes.7
However, in recent years it has been found that in some
series it would be more frequent in men in a percentage of around 60%.8,9
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Se concluye que los pacientes con diagnóstico de queratocono poseen una edad
media de 35 años de edad, con predominio del sexo femenino, antecedentes de
queratoconjuntivitis alérgica y agudeza visual corregida con lentes de contacto de
0,6, que clínicamente se clasifican en la etapa I y II del Sistema de Krumeich. La
queratoconjuntivitis alérgica es la enfermedad ocular más frecuentemente
asociada al queratocono. Posee un patrón topográfico de astigmatismo irregular
con cono central y agudeza visual con corrección, con lentes de contacto de 0,6.
La microscopia confocal constituye una herramienta valiosa en el diagnóstico del
queratocono.
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