Evaluation Of Keratoconus Progression And Analysis Of Its Influencing Factors

Part I Evaluate the repeatability of keratoconus topographic map parametersBackground: Keratoconus(KC)is a blinding eye disease characterized by corneal dilation,thinning of the corneal stroma,and tapered protrusions,resulting in decreased vision and highly irregular astigmatism.The disease usually occur on puberty and is progressive.At present,the definition of KC progress is not clear,and there is a lack of quantitative values for specific parameters to define precisely.The prerequisite for determining the quantitative value of the parameter requires an understanding of the repeatability of the instrument,which must be consistent over time and higher than the error measured by the instrument.Proper quantification of the variability in relevant corneal parameter measurements is critical to assess progression in patients with KC and the efficacy of cross-linking surgery.Purpose: To explore the repeatability of topographic map parameters measured by Pentacam HR in KC patients(mild,moderate,severe),so as to provide more accurate parameter indicators for the assessment of KC progress.Methods: Ninety eyes of 82 KC patients came to our hospital from January 2019 to March 2022 were included.Steep keratometry(K2)grading index and Rabinowitz YS diagnostic criteria were presented.There were 30 eyes in mild KC(K2<48D)group,30 eyes in moderate KC(48D≤K2<55D)group and 30 eyes in severe KC(K2≥55D)group.Thirty eyes of 29 patients with myopia under refractive surgery without other eye diseases were selected as the control group.Each eye receives Pentacam HR measurments three times by the same physician,and a total of 23 parameters were recorded,including corneal curvature parameters,corneal height parameters,corneal thickness parameters and corneal combine index parameters.By calculating within-subject standard deviation(Sw),repeatability limit(r)and tolerance index(TI)to compare the repeatability of topographic map parameters between KC(mild,moderate,severe)groups and control group.When TI>0.25(n1=30,n2=90)and TI>0.31(n1=30,n2=30),it means P<0.05,and the difference in repeatability is statistically significant.Results: Compared to control group,the KC group had TI>0.25 for 87%(20/23)parameters.The Kmax Zonal Mean 3~5mm(Z-Kmax 3~5mm)was not different between the KC group and the control group(TI<0.25).Compared with the control group,56.52%(13/23)of parameters in the mild KC group,87%(20/23)of parameters in the moderate KC group,and 91.3%(21/23)of parameters in the severe KC group had TI > 0.31.K2,Mean keratometry(Km),Maximal keratometry(Kmax),Z-Kmax 3~5mm,Anterior radius of curvature(ARC),Posterior radius of curvature(PRC),Thinnest corneal thickness(TCT)and Central keratoconus index(CKI),there was no difference in the repeatability of in the mild KC group(TI<0.31);ZKmax 3~5mm and CKI in the moderate KC group did not differ between the control group(TI<0.31);severe KC was only in Z-Kmax 4~5 mm and no difference between control groups(TI< 0.31).Conclusions: For mild KC,Z-Kmax 3~5mm,PRC and TCT are recommended in this study to monitor disease progression.For moderate and severe KC,Z-Kmax 3~5mm can be detected to monitor the progression of the disease.Part II Assessment of keratoconus progressionBackground: As the disease progresses,patients develop mild to severe irreversible visual impairment,and if the progression of the disease is not slowed or stopped in time,about 20% of patients with KC will require corneal transplantation due to severe visual impairment,so it is important to evaluate the progression of KC.Purpose: Parameters with good repeatability of corneal topography were used to assess the progression of KC patients.Methods: This study included KC patients who visited our hospital from January 2019 to December2022,and collected baseline and last follow-up examination results,including corrected visual acuity,intraocular pressure,corneal endothelial cell density,ocular axis and corneal topography parameters.The Wilcoxon rank sum test analysis was used to statistically analyze the relevant parameters at baseline and last follow-up,and P<0.05 represented a statistically significant difference.The progression cut-off value was defined according to the repeatability limit of Pentacam HR measurement KC topographic map parameters in the first part of this study(For non-grouped KC patients,it was considered that the following three parameters Z-Kmax 3mm>1.12 D,Z-Kmax 4mm>1.06 D,Z-Kmax 5mm>0.95 D changes were considered progression.For patients with mild KC,progression is defined as one of the following criteria: Z-Kmax3mm>0.80 D,Z-Kmax 4mm>0.76 D,Z-Kmax 5mm>0.70 D.For patients with moderate KC,it is believed that the following three parameters Z-Kmax 3mm>0.98 D,Z-Kmax 4mm>0.92 D,Z-Kmax 5mm>0.83 D are considered to be progression.For patients with severe KC,it is believed that the following two parameters Z-Kmax 4mm>1.39 D,Z-Kmax 5mm>1.24 D change is progress,calculate its progression rate.Results: This study included 155 patients with 200 eyes(57 eyes of 42 women and 143 eyes of 113men),with a mean age of 22(18,28)years and a mean follow-up time of 8.53(3.83,15.60)months.Compared to baseline examination,the last examination of flat keratometry(K1),K2,Km,Posterior elevation(PE),average pachymetry progression index(PPI Avg),CKI,and Belin/ Ambrósio enhanced ectasia display final D value(BADD)was higher,and the last examination of the PRC was lower(P<0.05).At the last follow-up,patients with KC were found to have a progressive rate of 15.0%.According to the disease severity,the progression rate was 11.8% in patients with mild KC,15.6% in patients with moderate KC,and 35.3% in patients with severe KC,with statistically significant differences among the three groups(P<0.05).Conclusions: Patients with KC have a certain risk of progression during routine follow-up observation,and the more severe the disease,the greater the probability of progression.Part Ⅲ Analysis of influencing factors of keratoconus progressionBackground: The etiology and pathological mechanism of keratoconus are still unclear.Some studies have shown that age,sex,eye rubbing,allergic conjunctivitis,and disease severity may be influencing factors of KC progression.Therefore,studying the influencing factors of KC progression can provide a basis for early intervention in KC patients.Purpose: The influencing factors of KC progression were studied to provide reference for early intervention and improvement of prognosis.Methods: This study included KC patients who visited our hospital from January 2019 to December2022,and a face-to-face questionnaire was used to collect factors related to the progression of KC: gender,age,history of eye rubbing,history of atopic disease,baseline K2,etc..KC progression is defined accorrding to one of the following criteria: Z-Kmax 3mm>1.12 D,Z-Kmax 4mm>1.06 D,Z-Kmax 5mm>0.95 D.Independent sample t-test was used for continuous variables with normal distribution in the factors influencing KC progression,Kruskal-Wallis test for continuous variables with skewed distribution,and chisquare test for categorical variables in qualitative data.Logistic regression were analyzed for the correlation between sex,age,history of eye rubbing,history of atopic disease,baseline K2 and KC progression.Results: A total of 200 KC eyes of 155 patients were enrolled,which were divided into KC progression group(30 eyes)and KC non-progression group(170 eyes).There were no significant significances in gender,age,eye rubbing history,and history of atopic disease in the two groups(P>0.05).The baseline K2(50.80(46.90,63.98)in the KC progression group was larger than that in the KC non-progression group(47.55(44.88,51.25)),and the difference was statistically significant(P<0.05).Logistic regression analysis found only baseline K2 as a risk factor for KC progression(OR=1.07,95% CI: 1.03-1.12,P=0.001)Conclusions: The severity of the disease is a risk factor in the progression of KC,and clinicians should carry out interventions as soon as possible to delay or stop the progression of patients with more severe KC at the beginning of diagnosis,and closely follow up and observe.