المحتويات إخفاء
Hints of Subjective refraction
- After finishing Retinoscopy Remove working distance lenses
- ROOM LIGHTS ON
- Occlude eye not being tested
- Check VA
Verify sphere in Subjective refraction
- Ask patient to look at the smallest line that they can see clearly.
- Verify sphere by offering ± DS (usually ± 0.25DS to fine-tune but may need ± 0.5DS if poor VA).
- Ask patient (Is the line clearer and easier to read with lens 1 or 2) ….!!???
- Do not make the prescription more minus if the lens does not improve the number of letters than can be read and just makes the already read letter to look ‘darker.
- always Put higher power lenses at back of trial frame.
- measure and document back vertex distance (BVD) especially if > ± 4.00 DS.
Verify cylinder axis in subjective refraction
- Ask patient to look at a rounded target/easily readable such as ‘O’ or dots.
- Use cross-cylinder (± 0.25D cross-cylinder, or ± 0.50 or ± 1.00 D if VA poor).
- Align handle with axis of trial cylinder.
- Ask patient (Is the circle rounder and clearer with lens 1 or 2)….!??
- Rotate trial cylinder towards the preferred cross-cylinder position respecting its sign(plus trial cylinder is rotated towards the plus sign of the cross-cylinder).
- Try not to remove the cross-cylinder from in front of the eyes as you rotate the axis and explain to the patient it will be clearer without this lens.
Verify cylinder power in subjective refraction:
- Once there is no difference between the two positions with the cross-cylinder handle along the axis of the cross-cylinder, repeat the procedure but with the handle at 45° to axis of trial cylinder. This will offer ± 0.25D cylinder.
- Add the sign of the cylinder preferred in 0.25D steps until there is a reversal.
- Add 0.25 DS for every 0.50 DC lost.
Refine best sphere in subjective refraction:
- Plus 1.00 blur test (should reduce a VA of 6/5 or 6/6 to about 6/12……..if not, add more plus).
- Duochrome test (monocular and binocular; aim for no preference/ slight red preference in myopia and green preference in hyperopia ).
Measure and record BVD in subjective refraction
- most important if > ± 4DS.
- Check near requirement at usual reading/working distance according to patient preference and occupational requirements.
- If presbyopic (typically over age 45y), add a near addition suitable for the patient’s age and refine for the patient’s preferred working distance and working range.
Estimated near corrections in subjective refraction:
Age 45–50y +1.00 DS
Age 50–55y +1.50 DS
Age 55–60y +2.00 DS
Age >60y or pseudophake +2.50 DS
Causes of spectacle intolerance
- Significant change in axis or size of cylinder.
- Change of lens form.
- Overcorrection, especially of myopes who will end up permanently accommodating.
- excessive near correction resulting in an uncomfortably near and narrow reading distance.
- Unsuitable bifocal or progressive lenses( not fit for occupation,patient visual requirement
Hints of Subjective refraction PowerPoint presentation:
Hints of Subjective refraction videos:
Subjective Refraction : Jackson Cross Cylinder – YouTube
Hints of Subjective refraction
