Abstract
Purpose:To compare ultrasound pachymetry and Orbscan II for measurement of central corneal thickness (CCT) in normal eyes.Methods:The current study was performed at Labbafinejad Medical Center (LMC), Tehran, Iran. Three hundred eyes from 150 healthy individuals referred for keratorefractive surgery were assessed first by Orbscan II and then by ultrasound pachymetry, and CCT values were recorded and compared.Results:Overall, Orbscan II overestimated CCT as compared to ultrasound pachymetry by about 2.4% (mean values 547.6 ± 34.7 versus 534.8 ± 34.7, respectively, P < 0.001). The difference was more significant when CCT was less than 500 microns (mean values 493.2 ± 16.9 versus 479.9 ± 15.6, mean overestimation: 2.6%, P < 0.001). There was good linear correlation between the two methods (Pearson's correlation r = 0.968, P < 0.0001).Conclusion:Orbscan II has good correlation with ultrasound pachymetry for measurement of CCT in normal eyes; however Orbscan II should not be used to evaluate corneal thickness before keratorefractive surgeries, as it tends to overestimate corneal thickness and may result in undesirable, low residual stromal thickness.
Highlights
Central corneal thickness (CCT) is an important parameter in ophthalmology and optometry.[1]
CCT values of 300 eyes from 150 otherwise healthy people including 94 (63%) women and 56 (37%) men were measured by ultrasound pachymetry and Orbscan II
Ultrasound pachymetry remains the gold standard for measuring corneal thickness; several non‐contact methods are being used for this purpose by many clinicians
Summary
Central corneal thickness (CCT) is an important parameter in ophthalmology and optometry.[1] It has a critical role in determining flap and residual stromal thickness and optical zone in keratorefractive procedures.[2] This matter is of particular importance since the extensive popularity of keratorefractive procedures has resulted in cases of post keratorefractive surgery ectasia.[3,4]. CCT is a valuable parameter in patients with glaucoma. Measurement of intraocular pressure (IOP), especially with applanation tonometry, may be affected by CCT.[5] CCT is an independent risk factor for developing glaucomatous optic nerve damage.[6]
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