Preclin: Normal Values Flashcards
Emmetropia:
-0.25 to +0.75DS
Myopia:
Low:
Medium:
High:
- less than -0.50DS
- low: -2.00DS
- medium: -2 to -4.00DS
- high: less than -6.00DS
Hyperopia:
over +0.75DS
PD:
53-72mm for distance (2-3mm less at near)
minimum best VA to drive:
6/12
Discrimination:
line subtending 0.5sec of arc
Resolution:
30-40 arcsec
Recognition:
1 arcmin
Vernier:
10 arcsec
VA (18-42yrs)
6/4.5 (-0.13 logmar conversion) (SD 0.05)
Abnormal VA:
if decrease of 5 or more letters
Orthophoria H and V:
H: less than 1 prism diopter
V: less than 0.25 prism diopters
Normal H and V:
H: 3 prism diopters V: 1 prism diopter
NPC:
6/8cm break/recovery - for all ages
NPA:
15-1/4(age) min
or 18-1/3(age) avg
Steropsis:
40 arcsec
What if stereopsis worse than 40”?
any ocular misalignment cannot be larger than PFA; 60 is still within normal limits. If worse than 60”, see if bifoveal fixation still present and check for binocular vision problems
Ocular motility:
no pain or DV, no head tilt, no over/underaction/restriction/jerky movements
Pupil size (in light) vs (in dim)
in light: 2-4mm
in dim: 4-8mm
Colour vision Ishihara:
more than 2 errors is a fail
Palpebral fissure aperture (distance between upper and lower eyelid):
9-10mm (less than 9mm is abnormal)
Marginal reflex distances (distance between superior/inferior lid and corneal reflex):
4-5mm
less than 4 = abnormal
less than 2.5 = visually impairing
difference of 1.5mm b/w sup and inf = abnormal
Levator function (distance b/w excursion of upper lid margin from full down gaze to full up gaze without brow movement - how much the upper lid margin moves when looking down – looking up):
more than 10mm = normal
8-10mm = good
5-7 = moderate
less than 4 = poor
Lid crease (distance from upper lid margin to lid crease) for men and women:
women: 10-11mm
men: 8-9mm
If lid crease is higher than normal or if there is a deeper upper lid sulcus = sign of aponeurotic disinsertion
Motolity/pupils/colour vision/vis. fields/lids: what may abnormal results indicate?
neurological disorders – to CN assessment, CT scan, MRI, blood workup – refer to GP, neurologist, neuro-ophthalmologist, determine urgency of referrel
Pelli Robson: for over and under 50yr olds
under 50: 1.80 log units
over 50: 1.65 log units (peak of CSF drops with age)
Melbourne edge test: for over and under 65yr olds
under 65: 19-22dB
over 65: 16-18dB
less than 15dB is abnormal (significant CS loss and needs differential diagnosis)
More than 2dB change between tests = abnormal
less than 10dB = severe impairment (trouble with everyday activities)
severe if can’t do first line. moderate if can’t do second line. mild if can’t do 3rd line
Aus. Vision Chart: for under and over 65yr olds
under 65: 0.21 logmar/2 lines difference
over 65: 0.24 logmar/2.5 lines difference
more than 3 lines difference is abnormal (significant CS loss)
3 or more lines difference between tests is also abnormal
Ishihara tracing plate: When fail?
If fail to trace within 10 seconds
Ishiahara screening: When fail?
If more than 2 errors
Farnsworth F2: how distinguish tritan from RG?
Tritan: if see blur square clearer/only see blue square
congenital RG: if only see green square
Farnsworth D15: When fail?
2 or more diametrical crossings (except a single one aroud cap 7)
orientation of crossings tells you if protan/deutan/tritan
Lanthony H16: when fail?
3 or more diametrical crossings
Medmont C100: what classifies as protan/duetan?
Anything outside of -2 to +2 is protan/deutan
Anomaloscope: when fail?
When can match RG to yellow at multiple points
near retinoscopy (posture of acc):
+0.50DS +/-0.25
Binoc cross cyl:
+0.50DS +/-0.25
NPA:
15 - 1/4age
Acc. Range (PRA and NRA):
+/-2.00 at distance
-2.00 at near
Acc. facility flippers:
8cpm at near with +/-2.00 filipper
record preference for puls or minus with +/-1.00 flipper
AC/A ratio
4+/-2pd/D *pd = prism diopters
Near phoria and distance phoria (verg posture)
near phoria: 3pd exo +/-3
distance phoria: 1pd exo +/-1
Verg. Range. Near: for BI and BO
BI: more than10/16/10, BO: more than 10/16/10
blur/break/recovery
Verg. Range. DIstance: for BI and BO
BI: -/6/4, BO: 10/16/10
Verg. facility flippers: at near
15cpm at near of 3pd BI/12pd BO flipper
Phorial/vergence-range consideration 1:
opposite reserve more than 2x phoria
Phoria/vergence-range consideration 2:
phoria within mid 1/3 of fusional range
Fixation disparity:
curve type 1, fixation disparity 4’exo +/-6’, Assoc, phoria 0 + 2pd
