The PHOROPTER or Refractor
- First phoropter was introduced in 1917 by Nathan Shigon.
- Phoropter is a common name for an ophthalmic testing device.
- It used to manually determine refraction.
- This device fit the patient and it looks like strange alien mask or a mechanical butterfly.
- Commonly Used to examination refractive errors and determine eyeglass prescription.
- This device contains different type of lenses use for refraction of the eye during sight testing.
- During the examination, each eye to used individual lenses.
- Nearsightedness, farsightedness and astigmatism like vision problem discover by using phoropters.
- This machine special in used switch multiple lenses in front the eye to correct vision.
- These lenses switching used correct vision impairment, patient look an image or big E latter in Snellen chart though phoropter.
- This device used manually determine refection.
- This measurement like as shaped and curved of lens used to form correcting vision by eyeglass.
Two types of phoropter are
- Manual phoropter
- Automated phoropter
Automated phoropter
- This machine is divided into main body and keyboard
- Same principal of operation like manual phoropter and it easier to operate
- Contains memory system for store all testing process.
- Simple and convenient
- Also used to measure patients phorias and ductions which are feature of BSV
- Can measure IPD, convergence, stereopsis, myopia, hyperopia, astigmatism
Parts are
- near vision chart holder
- knob to adjust the vertex distance
- refraction viewer
- vertex distance viewer.
Instrumental and patient adjustment
- Turn the phoropter head on
- Phoropter head needs to be aligned with patient before any measurements
- Backside of phoropter head needs to be placed in front of patient and centered in front of patient eyes.
- Illuminated bubble present in phoropter should be used to make sure forehead level is alright
- After phoropter alignment phoropter head should be adjusted physically by examiner to line up with patient’s eye.
- IPD should be adjusted by pressing PD and using multifunction knob
- Then the corneal vertex distance should be adjusted so that refractor lenses are at a proper distance from patients’ eyes (default vortex distance is 16mm)
- The operating monitor screen can be either placed on left or right sides of patient
- Then data can be inputted on the box placed in keyboard as according spherical, cylindrical powers and their axis can be adjusted by rotating knob CW or ACW direction
- Near add can also be obtained by data input a/c to response of patient
- Finally, data can save and print out easily
Advantages
- More comfortable for patient
- Lenses don’t become a dirty or starched
- Axis of any cylindrical correction can be read of from the refractor
- Additive errors can be reduced
Disadvantages
- Examiner depends upon subjective response
- Refracting unit hides the patient face
- Corrector only lower aberrations
- If head is tiled during refraction the cylindrical axis will be prescribed off axis
- Expensive
- Not portable
- Restriction field of vision
Manual vs automated phoropter
- Data processing of LM and AR
- Link of the chart and auxiliary lens
- Near vision test
- Near chart illumination
- Data comparison
- Data transfer to PC
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Instruments