Significance of Intraocular Pressure Measurements in the Early Diagnosis of Glaucoma and Clinical Studies of Its Impact Factors
|School||Dalian Medical University|
|Keywords||non-contact tonometer cornea curvature central corneal thickness glaucoma Goldmann applanation tonometer|
Objective: To investigate the difference between the intraocular pressure (IOP)measurements by the Goldmann applanation tonometer (GAT) and the non-contacttonometer (NCT), and the effects of central corneal thickness (CCT) and cornealcurvature (CC) on them. The measured value of NCT can be converted to the measuredvalue of GAT by a regression equation, which can be applied accurate diagnosis toglaucoma early diagnosis, the treatment plan of other eye diseases.Methods: Comparative study.201ophthalmology outpatient patients wererecruited from the clinic of The second affiliated Hospital of Dalian Medical Unversity.All volunteers are subject to the consent, without fluorescein sodium allergy history andserious systemic disease, can tolerate all inspection items. Visual acuity, anteriorsegment examination of slit lamp microscope, direct ophthalmoscope fundusexamination were given. All tests were taken by doctors with professional training at13:00-15:00, special examination room, the normal state of pupil. The CCT wasmeasured by TOMEY SP-3000ultrasound pachymetry, the corneal curvature by usingTopcon KR8800auto refractometer(K1、K2), The IOP of each eye was measured byboth Switzerland Haag-Streit AT900M/Q GAT and Topcon CT-80A type NCT.Make intraocular pressure correction(IOPc)=IOPGAT+[(520-CCT)/70]×5, differencein corrected intraocular pressure(IOP△)=IOPc-IOPNCT, difference in cornealcurvature(K_△)=K1-K2, mean corneal curvature(Ka)=(K1+K2)/2. SPSS17.0softwarefor data processing, measurement data were expressed as mean±standard deviation(), paired t-test was used to compare the measurement results of two tonometer,multi regression was used to analyze the relationships between CCT, CC and themeasurements of GAT and NCT. P <0.05for the statistically significant difference, and draw a scatter plot.Results:(1) IOPNCTis9～29mmHg, the mean and standard deviation is14.65±2.72mmHg; IOPGATis8～26mmHg, the mean and standard deviation is16.53±2.51mmHg; IOPc7.79～23mmHg, the mean and standard deviation is15.42±2.78mmHg.; IOP_△is (-12.79)～9.50mmHg, the mean and standard deviation is0.77±2.91mmHg.;(2) CCT is452～616μm, the mean and standard deviation was535.52±30.84μm; Ka is39.50～48.88D, the mean and standard deviation was44.05±1.51D;K_△is0～6D, the mean and standard deviation was0.91±0.791D;(3) IOPNCTwaslower than IOPc, statistically significant difference (P<0.05);(4)NCT=0.036*CCT-0.210*K_△+0.016*Ka-3.606.The regression equation shows a statistically significantdifference,IOPNCTbecomes higher with the central corneal thickness increases, higherwith the average corneal curvature increases, decreases with the curvature of the corneadifference;(5) IOP correction=NCT-0.082*CCT+0.167*K_△-0.119*Ka+39.116.Conclusions:(1) IOP measured by NCT associated with after correction GAT,but there are differences, can be converted after substituted for each other;(2) IOPmeasured by NCT is a linear relationship with central corneal thickness, cornealcurvature, the difference of corneal curvature;(3) CCT increased by an average of12μm, NCT is on the high side of1mm Hg; the Ka increases8.4D, NCT is on the highside of1mmHg; the K_△increase6.0D, NCT is on the low side of1mmHg. Multiplelinear regression drawn: IOP correction=NCT-0.082*CCT+0.167*K_△-0.119*Ka+39.116.