Clinical Care Tips

The foundation of clinical refraction lies in the mastery of optics, information about the epidemiology and physical considerations with models of myopia, hypermetropia and astigmatism, knowledge about the use of tools of refraction such as keratometer, retinoscope, autorefractometer and subjective refraction procedure. The complete process, if done sequentially, looks like an art and as for any other art, refraction also needs to be practiced to master. Another important aspect about the procedure is that measuring refraction is one thing and prescribing the correction is another thing. 




The examiner needs to judge the effectivity of those results together with following factors in his mind:
1. Patient’s expectations
2. Patient’s past experience
3. State of adaptation
4. Previous correction
5. Patient’s visual system.

The aim is not to treat the eyes, but to treat the patient as a whole. This implies that a proactive approach is essential.
1. Analyze previous correction and current visual status with previous correction.
2. Analyze the patient and his lifestyle, profession, working distance, clarity of vision necessary.

3. Avoid large change in prescription, do not change spherical by more than 0.75D, cylinder by 0.50D and axis by 10°. Excess changes call for counseling for probable problems. Whenever, you get a major changes in cylinder or the axis, do not forget to check for aniseikonic effect.

4. One of the simplest ways to check over correction – lift away the trial frame and increase the vertex distance.
5. Verify high astigmatic correction with the help of slit.
6. If the distance visual acuity in two eyes is significantly different, determine the near addition for each eye separately and reverify it binocularly.
7. Do not forget to ask patient’s habitual near working distance while checking the near addition. Be careful while prescribing near addition to a patient below the age of 38–40 years just because it makes the text clearer. Rule out the possibility of latent hypermetropia or esophoria.
8. Remember the importance of room lights. For example full room lights while correcting on visual acuity test chart and for pinhole acuity, dim light condition for Duochrome Test and for Fan and Block Test.
9. Do not prescribe large cylinders to a patient who has never worn before. Break them gradually. The effect of uncorrected cylinder varies from one patient to another. Oblique axis, changes in axis and cylinder powers may likely to cause spatial distortion.
10. Always advise the patient for next check up due date.
11. Explore the need for specific purpose correction.
12. Measure the vertex distance in high refractive error above         –5.00D for myopes and above +4.00 D in hyperopes as the effect of prescribed minus power will reduce if vertex distance increases and it will increase with plus lens. When you measure, write in the prescription.
13. Follow the philosophy of professional practice as under:
• Develop a strict routine series of tests
• Listen, look and feel
• Apply suitable tests and develop strong observation ability
• Educate the patient
• Refer to appropriate professional
• Monitor the condition.





Patient who does not respond to the normal refraction procedures can be puzzling. Some patient may need large changes of powers before they notice any difference. There are others who insist on commenting upon colors being introduced as you change the lens, usually in connection with Fan and Block techniques – one way to remedy this difficulty is to add a yellow filter. Permitting the patient to rotate a cylinder trial lens himself suggests failure on the part of the examiner, but often works wonders. Sometimes the lens in the trial frame moves helplessly – possibly because the patient shakes his head excessively.
The most common mistake that an examiner makes while doing refraction is giving the person more minus power. This is because adding a small amount of extra minus power may not make the vision worse. They may say that their vision looks the same or sometimes better. In such cases the patient may complain asthenopia after wearing them for longer hours of time. Sometimes symptoms may be so bad that the person will not be able to wear the spectacles. Some avid computer users most often complain that their distance vision does not clear immediately. It takes a little more time. This may be because of accommodative spasm, i.e. their accommodation locks at near and takes little more time to relax.
The following additional steps in the procedure may help such patients:
1. Complete the routine procedure with near addition determination, if the patient is presbyopic.
2. Keep the best distance correction in trial frame, if the patient is nonpresbyopic. If the patient is presbyopic, also put the tentative near addition in front of distance correction.
3. Ask the patient to hold the near test chart at a distance of 40 cm under bright light and ask him to keep both eyes open.
4. Direct the patient’s attention to letters one or two line larger than his near visual acuity on the near test chart.
5. Make sure that the letters are clearer at the beginning of the test. If not, add plus spherical power at the step of +0.25D at a time in front of both eyes until patient reports that the letters are clear. This becomes the tentative near prescription.
6. Now add plus lenses binocularly at the step of +0.25Dsph until the patient reports the first sustained blur and the patient notices that letters are not as clear as they were initially, even if the patient can read.
7. Note the total plus added so. Keeping the plus lenses in the trial frame, divert patient’s attention to the distance chart.
8. Isolate the line of letters to the patient’s best distance acuity, but not smaller than 20/20. The patient should report that it is blurry.
9. Reduce the plus binocularly at the step of 0.25D until letters are clear.
10. You may confirm the endpoint using duochrome test.
11. The additional plus so derived may help such patient.