trial set

trial set includes the following : trial frames , lens , occluder , pinhole etc

1. Optical instruments Assignment

2. TRIAL BOX Is a box containing lenses , arranged in pairs , a trial spectacle frame, and other devices in testing vision. It is also called as trial case .

3. Uses of trial case: Objective refraction Subjective refraction Diplopia charting Diagnosis of squint Assess binocular vision

4. TRIAL LENSES A pair of convex lenses ranging from +0.12D to +4D in 0.25 steps. +4.0D to +6.0 in 0.5 steps. +6.0D to +14D in 1 steps . +14 D to +20 D in 2 steps. Same range in concave spherical lenses A pair of concave cylindrical lenses ranging from +0.25 D to +3.50D in 0.25 steps. +4 to +6 in 0.5 steps .

5. TRIAL CASE Consists of : Pair of convex and concave lenses Pin hole Occluder Maddox rod Trial frame Red and green filters Prism Retinoscopic mirror

6. 1.OCCLUDER It is a black coloured opaque disc used for covering one eye while testing the other eye. It is mounted in metal/plastic rim. It is used for uniocular testing and to occlude light reaching the eye .

7. occluder

8. 2.PIN HOLE It is a black opaque disc with central pinhole of 1 to 2 mm. Ideal central pinhole diameter is 1.42 mm. Principle: It allows only one ray of light to pas through along the principle axis of the eye.

9. Uses: To see best corrected visual acuity. Used for macular function test. To analysed opacity of cornea is central or para central.

10. 3 .STENOPIC SLIT It is made of black opaque with slit aperture Slit aperture with 15mm length and 1mm width. It allows rays of light to pass through only 1 meridian. Uses: T o record V/A in 1 meridian . To find axis of cylinder. To find principle meridian.

11. 4 .MADDOX ROD It is a series of high power convex cylinder mounted with their axis parallel to each other. This available in red and green colours . Principle: It convert spot light into the line. Uses: To diagnose & measure phoria . To measure conversion.

12. Maddox rod

13. 5 .GREEN AND RED FILTERS Green and R ed filters: These are red glasses of 640nm & green of 353nm wavelength. Red filter in front of the RE and Green filter for the LE. Usually done after sub refraction. Principle: this dissociate the eye using colour sense.

14. 6.TRIAL FRAME Trial frame is an eyeglass frame designed to permit insertion of different lenses used in correcting refractive errors of vision .

15. Features of trial frame: Light weight Adjustable It should have comfortable nose resting Readily adjustable and allow accurate centering vertically and horizontally for each eye.

16. 7 . RETINOSCOPE MIRROR It consist of plane mirror on one side and concave mirror on the other side. This instrument is used for estimating the error of refraction by the method of neutralisation.

17. 8.PRISMS Prisms are used to correct latent squint and also in the case of diplopia.

18. SUBMITTED BY : NASRIN NAZEER 2 ND year optometry