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A simple clinical method to measure the optic disc size in glaucoma
C S Lim1, C O'Brien, N M Bolton
1Princess Alexandra Eye Pavilion, Edinburgh, Scotland.
Journal of Glaucoma
|August 1, 1996
Summary
This study shows that slit-lamp biomicroscopy with lower-power lenses can accurately estimate optic disc size, aiding glaucoma diagnosis. This provides a simple, cost-effective method for assessing optic nerve damage.
Area of Science:
- Ophthalmology
- Optometry
Background:
- The cup-to-disc ratio is crucial for diagnosing glaucoma.
- Accurate optic disc size measurement improves the clinical significance assessment of the cup-to-disc ratio.
Purpose of the Study:
- To evaluate slit-lamp biomicroscopy and confocal scanning laser ophthalmoscopy for measuring vertical optic disc diameter.
- To establish a simple, clinically useful technique for estimating optic disc size in glaucoma management.
Main Methods:
- Vertical optic disc diameter was measured using slit-lamp biomicroscopy with various aspheric lenses (60, 78, 90 D) in 25 normal volunteers.
- Measurements were correlated with magnification-corrected diameters obtained from Heidelberg Retina Tomograph (HRT).
Main Results:
- The mean vertical disc diameter measured by HRT was 1.81 ± 0.18 mm.
- Lower-power lenses (e.g., Volk 60 D) showed better correlation with HRT measurements (r=0.80) compared to higher-power lenses (e.g., Volk 90 D, r=0.59).
- A formula (Y = 0.85X + 0.06) was derived using the Volk 60-D lens for estimating disc diameter.
Conclusions:
- Clinicians can estimate optic disc diameter using slit-lamp biomicroscopy and derived formulae.
- This method offers sufficient accuracy for clinical decisions in glaucoma evaluation without expensive equipment.