Comparison between Measurement of Central Corneal Thickness by Non-Contact Clinical Specular Microscope and Ocular Coherence Tomography

Comparison between measurement of Central Corneal Thickness by Clinical Specular Microscopy and OCT. Purpose: To study the difference between central corneal thickness measurements, acquired by Clinical Specular Microscopy and OCT and infer whether one instrument gives consistently higher readings as compared to other. Materials and Methods: An observational, cross-sectional study was carried out in 2000 eyes of 1000 patients coming to the out-patient department. Patients having corneal pathology, pterygium, those wearing contact lenses, those having undergone corneal surgical procedures and those having a history of previous corneal trauma were excluded from the study. Basic ophthalmological and systemic history was recorded followed by a thorough anterior and posterior segment examination done with the help of Slit lamp and Ophthalmoscope. Central Corneal Thickness was calculated by Non-contact Clinical Specular Microscope and AS-OCT, taking three readings of each eye with each instrument. Results: Non-contact Clinical Specular Microscope (NCSM) and Anterior Segment Ocular Coherence Tomography (AS-OCT) showed strong positive correlation in the measurements of Central Corneal Thickness (CCT) (r = 0.97, p& lt; 0.01). NCSM measured the CCT consistently higher than AS-OCT, the mean difference being 6.51& #43; 6.53 m. A mean CCT of 536 m was found in males as compared to 531 m in females when measured by OCT. A mean CCT of 542 m was found in males as compared to 539 m in females when measured by Specular Microscope. A mean CCT of 543 m was found in Diabetics compared to 533 m in non-diabetics when measured by OCT. NCSM showed a mean CCT of 552 m in diabetics as compared to 540 m in non-diabetics. Hypertensive patients showed a mean CCT of 533 m, compared to non-hypertensive showing 532 m by NCSM. With OCT, the means were found to be 526 m in the hypertensive, compared to 527 m in non-hypertensive. Conclusion: NCSM and OCT show a strong positive correlation in their measurements of CCT. But the difference between their readings is statistically significant. Although they cannot be used interchangeably for research purposes, their readings can be compared for clinical assessment since we know that NCSM measures the CCT 6.51& #43; 6.53 m higher than OCT.