holes, pseudoholes or pseudocysts between January 2004 and July 2007. The mean age of the patients was 67.7 (SD 9.4) years (range 39–87 years). The study was conducted in accordance with the tenets of the Declaration of Helsinki and the requirements of the Queensland University of Technology Human Research Ethics Committee. Informed verbal consent was obtained from all patients after explanation of the nature of the study. A complete ocular examination was performed including best corrected visual acuity (VA) measurement, slit-lamp biomicroscopy and fundus photography. VA was measured on a Snellen chart and converted to the logMAR notation for statistical analysis. All eyes with macular defects were evaluated with OCT 3 (Carl Zeiss Meditec, Dublin, CA). OCT is based on an optical technique known as Michelson low-coherence interferometry, which measures the echo delay and intensity of back-reflected or backscattered infrared light (,800 nm) to produce high-resolution, cross-sectional tomo- graphy of ocular strucutres.19 OCT 3 provides a maximum of 512 (transverse)61024 (axial) data points per image, acquired in 1.92 s, and has an axial resolution of approximately 10 mm. All images were captured using the Macular Thickness Map protocol where six radial scans of 6 mm length, at equally spaced angular orientations centred on the macula, were performed. Images were then processed using the Retinal Thickness/Volume protocol, and the software caliper was used to obtain parameters on lamellar macular defects (see below). Subtypes of lamellar macular defects Lamellar macular defects were categorised into three different subtypes based on their OCT appearance: macular pseudoholes (MPH), lamellar macular holes (LMH) and foveal pseudocysts (FP). Lamellar macular defects which had a sharply punched out, well-delineated, steepened foveal contour were classified as MPH. OCT profiles corresponding to LMH had a thin and irregular foveal floor overlying the plane of the retinal pigment epithelium. In many cases of LMH, the central defect also extended laterally, resulting in a split between the inner and outer retinal layers. FP appeared as a cystoid space occupying mostly the inner part of the fovea, with a perifoveal detachment of the posterior hyaloid. In some cases of FP, there was an elevation of the foveal floor, which suggests vitreomacular traction from adherence of the partially detached posterior hyaloid to the roof of the FP.11 OCT measurements of base diameter, depth and retinal thickness Measurements of base diameters and depth of lamellar macular defects were obtained using the software calipers. As lamellar macular defects were frequently asymmetrical and irregular, macular profiles of the lamellar defects varied depending on the orientation of the scan. All six radial scans were examined to find the scan which revealed the deepest and widest defect from which all measurements were obtained. Figure 1 shows examples of parameter measurements for the three types of lamellar macular defect on OCT scans. Measurements of base diameters and depths were made to the most lateral extent of the intraretinal split and the thinnest part of the foveal base respectively. Both the base diameter and the opening (mini- mum) diameter were measured for LMH. While FP defects were not open macular defects and had a roof over the cystic area, the measured depth here referred to depth of the cystic space. Br J Ophthalmol 2008;92:1342–1346. doi:10.1136/bjo.2007.133041 Clinical science Figure 1 Optical coherence tomography scans of lamellar macular defect measurements showing placement of calipers for base diameter, depth, central foveal and perifoveal retinal thickness measurement for the three types of defects: macular pseudohole (MPH), lamellar macular hole (LMH) and foveal pseudocyst (FP). For LMH, the opening (minimum) diameter of the lamellar hole was also measured. The blue arrows indicate the base diameter of the defects, while the yellow arrow indicates the opening diameter. The purple bar indicates the depth of the lamellar defect; the red bar indicates the central foveal thickness; and the white arrows indicate retinal thickness at points 750 mm either side of the foveal centre. The perifoveal retinal thickness was calculated as the average of the two measurements on either side from the foveal centre. Retinal thickness was measured at the foveal centre (central foveal thickness) and at points 750 mm from either side of the foveal centre. The two measurements from both sides of the foveal centre were averaged and referred to as the perifoveal retinal thickness. The presence of epiretinal membrane was also noted for each lamellar macular defect. Statistical analysis Statistical analysis of the data was conducted using the Statistical Packages for the Social Sciences (SPSS 14.0.1). One- way analysis of variance (ANOVA) was used to determine if there were any differences in OCT parameters for MPH, LMH and FP. In all cases where comparisons between MPH, LMH and FP were made, a Bonferroni-corrected post hoc test was used, adjusting the observed significance level for multiple compar- isons. Correlations were also performed to establish if there was any relationship between OCT parameters and VA. 1343