Regular astigmatism by Dr.vinay gadiputi

regular astigmatism signs and symptoms and investigations

1. ASTIGMATISM BY VINAY GADIPUTI

2. OPTICS OF REGULAR ASTIGMATISM STURM’S CONOID: configuration of rays refracted through a toric surface. TORIC LENS: Lens with two different powers in two orientations perpendicular to each other. A toric surface resembles a section of surface of an doughnut where there are two regular radii.

3. A – vertical rays - converging more than horizontal rays so the section –horizontal oval . B – first focus point – here vertical rays are completely converged – horizontal rays are still converging – horizontal line. C – vertical rays are diverging but less than the convergence of horizontal rays – horizontal oval is formed. D – “circle of least diffusion” divergence of vertical rays is exactly equal to convergence of horizontal rays.

4. E – divergence of vertical rays – more than the convergence of horizontal rays – vertical oval. F – second focus – horizontal rays are completely converged and vertical rays are diverging – vertical line. Beyond F – horizontal and vertical rays are diverging – vertical oval. “Focal interval of sturm ”

5. REFRACTIVE TYPES OF REGULAR ASTIGMATISM Simple Astigmatism Simple myopic astigmatism simple hypermetropic astigmatism Compound Astigmatism compound myopic astigmatism compound hypermetropic astigmatism Mixed Astigmatism: circle of least diffusion is formed on the retina.

6. Clinical Features SYMPTOMS: A sthenopia : difficulty in focusing dull ache in eyes frontal headache nausea and drowsiness(astigmatism < 1 D

7. Blurred vision and defective vision – astigmatism >1D

8. Elongation of objects proportionate to degree and type of astigmatism.\ Keeping the reading material close to the eye may be needed.

9. signs Half closure of the lid.

10. Head tilt: develops torticollis in an attempt to bring there axis nearer to the horizontal or vertical meridians.

11. Oval or tilted optic disc- seen on ophthalmoscopy in patients with high degree of astigmatism.

12. INVESTIGATIONS RETINOSCOPY : Reveals different power in two different axis. KERATOMETRY : Reveals different corneal curvature in two different meridians in corneal astigmatism. ASTIGMATIC FAN TEST:

13. JACKSON’S CROSS CYLINDER TEST

14. REFERENCE REFERENCE: comprehensive ophthalmology by A.K .KHURANA 6 th edition.