Clinical skills

• Barret method


  1. px fixates on red dot on retinoscope (if target is too small=accommodation)

  2. Ensure there is sufficient light to illuminate the fixation target. Use wall test chart for light

  3. Ensure there is against movement in left eye normally

  4. Neutralise right eye normally then left eye (sph,cyl power,axis)

  5. Be aware of pupil size during retinoscopy. If constricts= accommodation so wait minute until it dilates

  6. Swing beam from eye to eye to check sphere balance is ok

  7. Ask subject to look at the spot light on the chart at 6m. The spherical portion of refraction will now change by an equal amount in both eyes
• IOP normal range- 15.7mmHg (mm of mercury) anything over 21 then check using Goldman's
• Advantages of non-contact tonometry over contact tonometry

  • No physical contact with cornea
  • No anaesthetic required
  • Can be performed by non optometric staff
• When should you refer for primary open angle glaucoma according to NICE guidelines


  • If there is optic nerve head damage on the stereoscopic slit biomicroscopicy
  • If there is a visual field defect consistent with glaucoma
  • If the IOP is 24mmHg or more using Goldman's
  • CD ratio more than 0.6
  • Unhealthy neuro retinal rim
• Lidocaine 4%


  Local anaesthetic drop used in cases of previous toxic reaction to ester anaesthetics
• Thick central cornea


  Overestimates the IOP in goldmans
• Flat cornea


  Underestimates the IOP
• Steep cornea


  Overestimates the IOP
• Adjustments for patient with -6.00 cyls

  Rotate the axis of the tonohead 43 degrees to the meridian of the lower power to ensure a more flattened area (change axis of lower power to 43 degrees)
• Patients who would benefit from binocular refraction

  • Amblyopic
  • Anisometropic
  • Latent hyperopia
  • Px with unequal VA due to pathology
  • Nystagmus px
• Cognitive behaviour


  • Puts patient at ease
  • More likely to give practitioner more info
  • Can give them information to patient in a way they can understand
• PERRLA


  Pupil equal round responsive light and accommodation
• RAPD

  Relative afferent pupillary distance
• Pathology for flashes+floaters, 40 years old, reduced VA, RE:-8.00/-1.50x90, LE:-8.25/-1.25x90 is retinal detachment
• Important tests to diagnose these pathologies

  • IOPS
  • OCT
  • Dilated volk
  • Visual fields
  • Slit lamp
• Binocular balancing


  Performed after subjective to make sure the eyes are accommodating by the same amount
• Binocular balancing techniques


  • HIC comfort method
  • HIC clarity method
  • HIC duochrome
• Patients not suitable for binocular balancing


  • Presbyopes
  • Amblyopic px
  • Patients with no stereopsis
• Tropicamide


  Anti muscarinic which relaxes the sphincter muscle and prevents it from constricting, therefore keeping the eye dilated, causes cycloplegia which prevents accommodation
• Phenylphrine


  Sympathomemtic drug which stimulates dilator muscles of the iris causing mydriasis (dilation of pupil)
• Disadvantages of phenylphrine: doesn't cause cycloplegia, incomplete mydriasis so would need to mix with tropicamide
• Contraindications of phenylphrine


  • Px with cardiac disease
  • Hypertension
  • Aneurysms
  • If they use beta blockers
  • Any diabetic
• Features of the disc in ophthalmoscopy for glaucoma patient

  • More than 0.6 CD ratio
  • Neural retinal rim- ISNT rule not followed, pale, notch
  • Asymmetry between of the disc more than 0.2
  • Disc haemorrhage
  • Larger disc, larger cup, larger CD ratio
• Blind spot


  • The spot px is expected not to see at
  • Temporal projection of the optic nerve located 15 degrees from fixation and 1.5 below horizontal midline
  • 5.5 degrees wide, 7.5 degrees high
  • Threshold sensitivity= 0
• Patient you would use Amsler chart

  • AMD
• Other clinical tests to diagnose AMD

  • Ophthalmoscopy
  • OCT
• Snellen


  Method for measuring vision
• Measuring vision using Snellen


  1. Record smallest line that can be read

  2. Deduct 1 from score for each letter not read correctly

  3. One mistake made on 6/6 line record as 6/6-1

  4. 3 mistakes on 6/9 line 6/9 -3 or is it 6/12 +3?

  5. What about the patient who makes 2 mistakes on 6/12 line, 3 on the 6/9 line and 4 on the 6/6 line?
• Snellen Chart


  • Some letters are easier to read than others
  • Irregular spacing between letters and lines
  • Lines have different numbers of letters: 6/60 line has only one letter and 6/6 line has 10 letters
  • Non-linear progression of letter sizes
  • Inadequate scoring method – ceiling effect - Some letter charts only go down to 6/6 - You don't know they can read more up 6/5 and 6/4 or 6/3
• Recording vision - Unaided

  1. Up to 6/60

  2. If less than 6/60, use a hand held letter 'E' which gives four choices (up, down, left or right)

  3. DO NOT GET PX OUT OF CHAIR

  4. 3/60, 2/60, 1/60, 0.5/60

  5. Counting fingers (CF) at 1m

  6. Hand movements (HM)

  7. Perception of light (PL)

  8. No perception of light (NPL)
• Recording vision - LogMAR Unaided


  1. 6/6 = 0.0

  2. 6/60 = 1.0

  3. For every incorrectly read letter, ADD 0.02 i.e. if the Px reads all of the 6/6 (0.0) line but gets two letters wrong then their score is 0.04

  4. For every additional letter read on the next line, SUBTRACT 0.02 e.g. if the Px reads all of the 6/6 (0.0) line and one more letter on the next line, then their score is -0.02

  5. If <6/60 (1.0), at 3m, add on 0.3 to their final score e.g. if they read 6/60 (1.0) at 3m then the final vision is 1.3

  6. If <6/60 (1.0), at 1m, add on 0.8 to their final score e.g. if they read 6/60 (1.0) at 1m then the final vision is 1.8
• Hyperope


  Can see 6/5
• Emmetrope


  Can see 6/5
• 6/9


  Approx -0.50DS
• 6/12


  Approx -0.75DS
• 6/18


  Approx -1.00DS
• Top of Snellen chart

  Approx -2.50DS
• Myope


  Can see close up but cannot see far away
• Measuring myopia


  1. If cannot see top of chart then test u/a NV

  2. A myope will always see N5 at their far point – Bring in the chart closer when they can just read N5 , measure this distance in cm and then divide into 100

  3. i.e. can read N5 at 33cm so must have MS of 100/33 = -3.00DS

  4. i.e. can read N5 at 10cm so must have MS of -10.00DS
• Read lab book pages 21-27