The effect of central corneal thickness on estimates of the anterior chamber depth.
BACKGROUND
The slitlamp can be used to estimate the anterior chamber depth (ACD). The length of a slit object is increased until the corneal and iris/lens images appear to just touch. Multiplying the just-touching-slit-length (JTSL) by a conversion factor gives an estimate of the ACD as measured by ultrasonography. The purpose of this study was to determine if central corneal thickness (CCT) affects the accuracy of this technique.


METHODS
The ACD of 50 subjects was measured by A-scan ultrasonography and estimated by the slitlamp technique. CCT was measured by ultrasonic pachometry. The refractive error was determined subjectively.


RESULTS
The average ultrasonographic ACD for all subjects was 3.32 +/- 0.65 mm. The average JTSL was 2.46 +/- 0.38 mm. The conversion ratio between the ultrasonographic ACD and the average JTSL was 1.35. The predicted ACD using the regression equation of JTSL on the ultrasound anterior chamber depth (USACD) was 3.32 +/- 0.54 mm. The corresponding value using the regression equation of JTSL and CCT on USACD was exactly the same, that is, 3.32 +/- 0.54 mm.


CONCLUSIONS
Incorporation of CCT into a regression equation does not improve the accuracy of the Smith technique.
Osuobeni
Ebi P
EP
Department of Optometry and Ophthalmic Dispensing, Anglia Polytechnic University, East Road, Cambridge CB1 1PT, United Kingdom.
Hegarty
Claire
C
Gunvant
Pinakin
P
D000328:Adult; D000867:Anterior Chamber / Q000000981:diagnostic imaging*; D016022:Case-Control Studies; D003315:Cornea / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000000981:diagnostic imaging* / Q000473:pathology*; D008297:Male; D008962:Models, Theoretical; D009216:Myopia / Q000000981:diagnostic imaging* / Q000473:pathology*; D012044:Regression Analysis; D014463:Ultrasonography