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Affecting the central corneal thickness of multi-factor analysis_2809

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Affecting the central corneal thickness of multi-factor analysis_2809

Affecting the central corneal thickness of multi-factor

    analysis

     Author: Wei Bin, with Doherty, Fu Lingling, Wang Xing Jin

     Abstract Objective: To investigate the impact of central corneal thickness of the relevant factors. Methods: 306 cases of 612 myopic corneal thickness with ultrasound, computer Refractometer, non-contact tonometer, A Chao, and corneal

    topography were measured the data. And analysis of their age, gender, ethnicity, occupation, address, family history of

    myopia, history of wearing contact lenses, eye do not, uncorrected visual acuity, corrected visual acuity. Of the results were analyzed statistically. Results: The availability of long-term contact lens wear history of central corneal thickness in myopia that there are significant differences (t = 4.183, P = 0.000). Central corneal thickness and visual acuity, intraocular pressure was positively correlated (r = 0.114, P = 0.005; r = 0.483, P = 0.000); and corneal curvature for the negative correlation (r =- 0.114, P = 0.005). Central

    corneal thickness with age-related (r =- 0.041, P = 0.312),

    according to age group, comparison between groups statistically significant difference (F = 5.490, P = 0.000), central corneal thickness with age seems to be growth in

    thinning trend. Central corneal thickness and myopic refraction was no correlation between (r = 0.027, P = 0.499). The establishment of multiple regression equation: Y = 557.824-7.254X 7 27.989X 9-2.499X 12 5.285X 13 (F = 16.840, P

    = 0.000). Conclusion: The impact of central corneal thickness

    is a major factor in the history of wearing contact lenses, uncorrected visual acuity, corneal curvature and intraocular pressure.

     Key words corneal central thickness factor analysis

     0 Introduction

     In the eye refractive system, the corneal refractive power of about 70% of the total refractive power. Mild corneal refractive power changes, can have significant effects on myopia. However, corneal refractive surgery to achieve the greatest depth of cut the amount of central corneal residual bed thickness of not less than what the value is currently no accurate data and a unified standard. As the central corneal thickness affected by many factors, which affect the current domestic and international scholars, the central corneal thickness of factors, mostly carried out against a sample comparison of a single factor, the lack of multi-factor

    comprehensive analysis of joint involvement. The results vary widely, or even completely at odds. This allows the individual

    clinical situation of patients with accurate measurement of central corneal thickness has become difficult, which is the choice for the surgical method, surgical planning and operation of the design and operation of the success or

    failure has a specific significance. Therefore, we have adopted a multi-factor analysis of epidemiological methods to explore the impact of central corneal thickness of the relevant factors.

     An object and method

     1.1 Object 2005-11/2006-04 myopia in myopia treatment

    centers meet diagnostic criteria for patients, sorted according to patient medical record number, according to random number table, randomly selected subjects (research to meet the sample size is 20 times the number of independent

    variables). Reference to the diagnostic criteria of myopia in Australia, "Blue Mountains eye study" the standard [1]:

    spherical equivalent ?-1.00D. Exclusion criteria: no corneal organic disease, no history of corneal surgery, eye routine examination no abnormalities, visual field defect-free, no

    family history of glaucoma. The study were included 306 cases of 612, 272 men and 136 cases, 170 cases of 340 women; aged 18 to 52 (mean 32.3 ? 5.6) years of age. -1.00 ~ -23.00 Diopters

    of myopia (mean -6.60 ? 3.11) D. Grouped according to diopter of myopia: low to moderate myopia group: diopter ?-3.00D, 119

    eye; moderate myopia group:-3.00D <diopter <-6.00D, 194 eye;

    high myopia group:-6.00D ? diopter "-9.00 D, 200 eye; ultra-

    high myopia group: diopter ? - 9.00D, 99 Yan.

     1.2 Methods The subjects of the history of the situation, routine inspection items credited to a unified epidemiological questionnaire. Topics covered include: age, gender, nationality, occupation, address, family history of myopia, history of wearing contact lenses, eye do not, uncorrected visual acuity, corrected visual acuity, myopia refraction, corneal curvature, intraocular pressure, axial length, central corneal thickness. Study of factors and their assignment (Table 1). To adopt Japanese Tomey SP-3000 ultrasonic corneal

    thickness measurement of central corneal thickness, continuous measurement of all cases three times, whichever is the average. Japan Tomey TMS-4 corneal topography were measured

    corneal curvature photo is three higher-quality images, except

    for tears and eyelid interference, and then select the best quality of an analysis. Japan Tomey AL-100 A ultrasound

    measured axial length, conventional topical anesthesia, continuous measurement three times, whichever is the average.

    Japan Topcon8100 Automatic Refractometer measurements diopter of myopia, using the computer after cycloplegic refraction, with the pupil returned to normal emperor felt optometry to determine the diopter of myopia. Japan Topcon CT-60 type non-

    contact applanation tonometer intraocular pressure

    measurement. Patient was sitting in an appropriate measurement of height and relaxed state, each eye measured three times, whichever is the average. In order to avoid corneal thickness, corneal curvature and intraocular pressure fluctuations at

    different times, the results of impact studies [2,3], the Institute and some examinations are 10 am to 12 points. All research subjects measured by double-blind method, one skilled

    professionals to operate by the same complete.

     Statistical analysis: The SPSS12.0 statistical processing software, will be measured by the number of study factors noted in the number noted in the establishment of library classification. Do affect the central corneal thickness of the relevance of each factor analysis, t test was used to compare between the two groups, multiple groups using analysis of variance and multiple linear stepwise regression analysis, to establish multiple regression equation.

     2 Results

     Central corneal thickness and the history of wearing

    contact lenses, uncorrected visual acuity, corneal curvature and intraocular pressure related (P <0.01, Table 2,3). Pairwise comparison shows that moderate myopia and high myopia group and central corneal thickness on the group there are

    differences (P <0.05), the other was no significant difference among the three groups (P> 0.05). According to Table 1 of the assignment of age (X 1), gender (X 2) ... axial length (X 14) as independent variables, central corneal thickness (Y) as the

    dependent variable, multiple linear stepwise regression analysis, the establishment of multi - The regression

    equation: Y = 557.824-7.254X 7 27.989X 9-2.499X 12 5.285X 13,

    F = 16.840, P = 0.000, results showed that the four independent variables from the above constitutes a regression equation was statistically significant.

     3 Discussion

     With the wide range of corneal refractive surgery carried out, an accurate evaluation of preoperative corneal thickness and corneal shape to a large extent directly related to the

    refractive surgical correction of safety and predictability. As myopia in patients with large individual differences in central corneal thickness, which makes clinicians more concerned about how a specific patient's thin flap as much as

    possible to preserve the corneal stroma bed is thick enough. This issue in need of laser-cutting deeper high myopia is

    especially important. Otherwise, there is cause corneal

    expansion and the risk of iatrogenic keratoconus. Therefore, we selected patients with myopia as a research object, and to explore the influence of central corneal thickness of its relevant factors.

     With regard to central corneal thickness and myopic eyes do not, gender, address, with or without a family history of

    myopia, nationality, occupation, age, myopic refraction, corrected visual acuity and axial length relationship. The results of this study show that: central corneal thickness and the above factors, no association. Although there are scholars believe that the central corneal thickness in gender [4], address [5], ethnic [6] that there are differences. However, we think this may be related to the cases studied composition, sample size and use of devices different from the corneal thickness. Age and myopia in the study of the relationship

    between central corneal thickness. We found that different age groups on the central corneal thickness in myopia significant difference (F = 5.490, P = 0.000). At the same time, this set of data also showed that central corneal thickness of the

    trend of thinning with age (Table 2). We believe that this may be related to the study of corneal hydration status related to increasing age and the role of water, weakening the cornea, resulting in ultrasound rate increased, the ultrasonic pulse

    more rapid return to holding head, manifested as reduced central corneal thickness. In addition, changes with age, corneal stroma in the density of collagen matrix changes will also affect ultrasound rate, the measurement results to meaningful change. For this study, 40 subjects over the age of corneal thickness fluctuations, we consider this age group may be relatively few number of samples, data related to sampling error. With regard to central corneal thickness of myopia and myopic refraction of the relationship between the results of domestic research at present there is a positive correlation [7], a negative correlation [8], not related to [9,10] three kinds of conclusions, more controversial. The results of this study is the diopter of myopia and central corneal thickness

    was no correlation (r = 0.027, P = 0.499). Diopters of myopia will be grouped according to the study, the statistical difference between the different groups (F = 4.555, P = 0.004). However, pairwise comparison found that: only moderate

    myopia and high myopia group and central corneal thickness on the group there are differences (P <0.05), remaining there was

    no significant difference between the two groups (P> 0.05). Thinner corneal thickness in high myopia in the low to moderate myopia. On these results, we believe that a high degree of myopia may be related to axial stretching, eye-wall

    expansion and blood supply to varying degrees disorders. But can not come to central corneal thickness increased with the myopia of the thinning of the conclusions. Reposted elsewhere in the paper for free download http://

     Affecting the central corneal thickness is a major factor in the history of wearing contact lenses, uncorrected visual acuity, corneal curvature and intraocular pressure [11-13].

    Whether the long-term wear contact lenses in which the history of the relationship between central corneal thickness in myopia. We have found two significant differences exist between the (t = 4.183, P = 0.000). Derived from multiple regression equations showed a long-term thinning of the cornea

    can wear contact lenses. This result, we believe that there may be three mechanisms: corneal stroma, chronic edema and corneal matrix components and biochemical changes have taken place; tear osmolarity This has led to corneal thickness

    thinning; chronic hypoxia and chronic minor injuries result in corneal cell apoptosis increase caused. Uncorrected visual acuity and central corneal thickness showed a positive correlation (r = 0.114, P = 0.005). Multiple linear stepwise

    regression equation (P = 0.000) shows that with the reduction of uncorrected visual acuity, central corneal thickness of a decreasing trend. For these results, I believe that multi-axis

    nature of myopia myopia, axial length increase is the main

    reason for increased myopia, especially in the high degree of myopia, the axial length plays a decisive role in the higher degrees, the longer axial length. As the axial length of the extension of corresponding changes in the eye, such as the thinning of the sclera, choroid, retinal atrophy and degeneration, which are on the visual impact, resulting in a decline in visual acuity, in the posterior sclera, while thinning of the cornea by the surrounding pull Rally role can be a corresponding flattened, thin. This is Chang et al [14]

    viewpoint. However, Shimmyo et al [15] that, in myopia axial extension, the involvement should be to weak sclera, thinning of corneal thickness is not followed. Of these disputes, has yet to be our further observation and study. For the corneal

    curvature and the relationship between central corneal

    thickness in myopia. More controversial at home and abroad, Srivannaboon [16] and domestic, Liu Yuan, etc. [17] that the central corneal thickness and corneal curvature were positively correlated. However, there are studies [18] confirmed that the central corneal thickness and corneal curvature has nothing to do. The results of this study show that: corneal curvature and corneal thickness is a negative correlation between the central (r =- 0.114, P = 0.005). This

    result, we believe that the increase in corneal curvature may cause the tear film in the peripheral cornea, resulting in a stronger capillary suction effect, and thus make the cornea resulting flattened effect. Our results with Chang et al [14]

    the same, but the domestic Luan Chunsheng et al [19] the use of rabbit eyes has proved central corneal thickness and corneal curvature a negative correlation, further supporting the results of this study. Intraocular pressure and myopia on

    the relationship between central corneal thickness. Shildkrot, etc. [20] that the intraocular pressure and central corneal thickness is not related to results of this study showed that central corneal thickness and intraocular pressure were positively correlated (r = 0.483, P = 0.000). In this regard, we believe that due to changes in intraocular pressure has led to changes in the nature of corneal biomechanical changes such as flexible, thus affecting the measurement of central corneal thickness. In addition, the intraocular pressure changes may affect the hydration status of the cornea, which can lead to changes in hydration status of anti-compression capacity of

    matrix and collagen fiber elastic modulus changes thereby affecting the elastic modulus of the cornea affecting the

    central corneal thickness measurements. In addition, the intraocular pressure can lead to anterior segment abnormalities on the anatomy and physiology, this change had a significant effect on the anterior chamber volume will also

    affect the central corneal thickness measurements.

     These results indicate that, in many studies the factors that eventually through the multiple linear stepwise regression analysis, into the multiple regression equation and has a significant influence of central corneal thickness

    factors are: the history of wearing contact lenses, uncorrected visual acuity, corneal curvature and intraocular pressure. Therefore, emphasis should focus on corneal refractive surgery for more than four factors. As the current

    lack of central corneal thickness on the impact of multiple factors of practical conclusions. Therefore, the results still need to be supported by further similar studies. With a view to the precise effect of central corneal thickness of this important ocular parameters related factors, clinical factors, Colonel reason caused by differences in central corneal thickness to provide a frame of reference.

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