Moti, Farah Razack2014-03-312014-03-312014-03-31http://hdl.handle.net10539/14422There is large variability between individuals on many measurable parameters of the optic disc. The retinal fundus is most commonly measured indirectly via slit-lamp biomicroscopic examination with a fundus spherical lens. Three optical methods of measuring the vertical disc height were compared: – Optical Coherence Tomographic (OCT) method – Calculation using a modified Littman’s equation: t = pqs – Measurement using five different double aspheric Volk fundus lenses on two different slit lamps (Haag-Streit and CSO) The aims of the study were: – To calculate a conversion equation of optic disc height measurement by clinical assessment using any one of five double aspheric fundus lenses at the slit-lamp – To compare the control mechanism of optic disc height measurement on OCT versus calculation using a modified Littman’s equation – To compare measurements between the Haag-Streit BM900 and CSO SL990 slit lamps – To compare accuracy and agreement of Volk conversion factors based on manufacturer magnification values to the control mechanism DESIGN & METHOD: A cross-sectional study was performed on patients presenting to the St John Eye Hospital from August ’11 to July ‘12. 100 eyes were measured for: – The optic nerve head vertical disc height on OCT – Vertical disc height (VDH) on Haag-Streit and CSO slit lamps with Volk super 66D, 78D, Superfield, Digital Wide Field, Digital High Magnification lenses – Axial length – Refraction Subsequently, 44 new eyes were measured and used to test agreement of the formulated equations. RESULTS: – Axial length was not found to have a correlation with VDH (p=0.64). – The modified Littman’s equation: t=pqs where p varies for each lens and q = 0.01306(axial length – 1.82), had very low correlation and poor agreement – Comparing formulated equations to the OCT VDH, the formulated Digital High Magnification and super 66D lenses were found to have the most accuracy – Measurements with the Volk Digital Wide Field lens were highly inaccurate and are therefore not recommended for vertical disc height measurement in future – Comparison of the fundus lens measurements using the two slit lamps showed alarmingly different results. There was no agreement between slit lamp measurements using four of the lenses CONCLUSIONS: – The use of axial length and other quantitative factors attained by measures of a schematic eye cannot be used accurately in clinical practice to determine fundus object sizes. – The slit lamp technique of measuring optic disc size with application of a simple equation yields useful results in close agreement to those yielded by expensive technology. It cannot replace accurate analysis using an OCT but is sufficient in aiding clinical decisions – Two important factors need to be taken into account when applying slit lamp fundus measurements: the type of lens used, and the slit lamp being used – as measurement standards are inconsistent between slip lampsenThesis