Incidentally discovered keratoconus in patients seeking vision correction by LASIK

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Introduction
Keratoconus (KC) is described as a progressive bilateral degenerative noninflammatory ectatic corneal disease manifested by corneal axial protrusion and thinning of the stroma that subsequently causes the cornea to take the shape of the cone, which is responsible for variable astigmatism and myopia [1].
There are numerous genetic and environmental risk factors associated with KC, but the exact cause is unknown.It is unknown how much each component contributes to the development of KC.However, in people with genetic predispositions, the environment may act as a stimulus for the disease.Even though the standard definition is known as a degenerative disease in which any mechanical damage produced by trauma accelerates its progression, a significant body of evidence shows that inflammation is fundamental to the pathogenesis of KC [2].Numerous studies have connected KC with different inflammatory mediators (cytokines) [3].
There are several variables that increase the incidence of keratoconus, including family history, rubbing your eyes, eczema, asthma, and allergies [4].It is linked to decreased visual acuity, especially in connection with progressive corneal irregularity, and typically manifests asymmetrically in the same patient's two eyes.
On rare occasions, the patient may exhibit photophobia, glare, and monocular diplopia symptoms [5].
Keratoconus frequently begins to appear in the second and third decades of life, and it is only in the fourth decade that it becomes fully developed.The keratoconic process often begins around the time of adolescence.The process continues for the next 10 to 20 years until the progression eventually comes to an end.When the disorder's growth ends, its severity can range from barely perceptible irregular astigmatism to severe thinning, protrusion, and scarring that needs keratoplasty [6].
People of all sexes and races have been impacted by the disease.The average incidence rates stated in various research studies range from 0.00002 to 3.33%, or 0.02 to 3333 cases per individual.However, refractive surgery clinics experienced a higher proportion of undiagnosed keratoconus cases than this [7].
The wide disparity in prevalence rates can be related to variations in place of birth, race, associated conditions, disparity in type of selected sample, and keratoconus diagnostic requirements [8].

Subjects
The current study was performed in a private center for cataract and refractive surgery at Zagazig, Egypt within a year.188 individuals selected from those who are about to undergo LASIK surgery.
The Pentacam HR system (Oculus, GmbH, Wetzlar, Germany) was used for the usual ophthalmologic examination and corneal tomographic evaluation of each individual.
Additionally, people who wear contacts had not worn them for at least three weeks before the assessment.

Inclusion criteria
Total sample of study: 188 participants (376 eyes) separated into 2 groups according to screening by Pentacam

Exclusion criteria
• Non-helpful cases.
• Participants younger than 18 years old.
• Cases had opacity of cornea.
• Prior experience with corneal surgery or trauma.

Study design
A cross-sectional retrospective study.

Data Collection
Data on the patient's demographics, the topography of their cornea, and their health

Analytical statistics
using SPSS version 26, all data were gathered, tabulated, and statistically examined.
Categories qualitative data were represented as definite frequencies (number) and relative frequencies (%), while continuous quantitative data were expressed as the mean SD & (range).
The Shapiro-Wilk test was used to determine whether continuous data were normal.unbiased samples.To compare two sets of normally distributed data, the student's t-test was utilized.
Chi-square test (2test) was used to compare categorical data.As shown in Table 4, a statistically significant difference was found among the studied cases concerning the mean anterior K values measured by PENTACAM.In comparison to the control group, the KC group was found to have high values (47.16 vs. 43.61,respectively).The anterior mean K measures identified by OCT also showed a high statistically significant difference between the study groups, with the keratoconus group showing higher values than the control group (52.94 vs. 48.19,respectively).

A
As shown in Table 5, the positive family history of KC was significant risk factor for keratoconus.

Discussion
The epidemiology of keratoconus differs from one place to another in accordance with numerous variables, including the amount of UV rays, altitude, and frequency of consanguinity.10 Geographic variations entirely affected the overall prevalence of Keratoconus.
It is frequently linked to a hot temperature and a population with low socioeconomic status.
Additionally, keratoconus growth is significantly influenced by the frequency of incidents of ocular allergies, which are followed by subsequent eye rubbing [11].
Prior This notwithstanding, our study had many drawbacks, largely due to its retrospective research methodology and small sample size.
One of the most effective is a single-centre study, as we concentrated on looking at keratoconus patients who came to our clinic.
The chance of selection bias is higher, and the results are less generalizable.

Conclusion
In conclusion, patients seeking LVC had a high incidence of keratoconus.An essential method for determining the prevalence of keratoconus in the Egyptian community is the screening of LVC candidates for keratoconus.

Ethical approval and consent to participate:
The committee of Ethics in Fayoum university hospital & Faculty of Medicine approved this study.
Funding: No sources of funding for this study.

Conflicts of Interest: the authors declare no conflict of interest
were gathered during routine exams to assess whether they were eligible for refractive surgery.The existence or absence of keratoconus was emphasized specifically when identifying the reasons why refractive surgery was not performed.Those who met at least two of the following requirements-21° corneal thickness, a posterior elevation greater than 20 m, and an inferior-superior (I-S) asymmetry greater than 1.4 D-were deemed to have keratoconus.If one of the following conditions was met in a subject, keratoconus suspect status was assigned: corneal thickness of 25 m or I-S asymmetry of greater than 1.6 D (Figures 1, 2).

Figure 3 :
Figure 3: Frequency distribution of keratoconus among patients seeking for LASIK.

Table 1 :
Basic characteristics of the studied groups.

Table 2 :
Risk factors among the studied groups.

Table 3 :
Comparison of CCT between the study groups using PENTACAM and OCT.

Table 4 :
Comparison of K anterior measurements between the study groups using PENTACAM and OCT.

Table 5 :
Logistic regression analysis of risk factors for keratoconus.