Hetrerophoria

Question 1

what is heterophoria

Answer 1

heterophoria - both visual axies are directed towards the fixation point but deviate on dissociation

Question 2

what will you see on the cover test for someone that has heterophoria

Answer 2

no manifest deviation on cover uncover

latent deviaiton on a alternate cover test

Question 3

what are the different types of heterophoria

Answer 3

• dissociation refers to the eyes not being used binocularly

esophoria (inward deviaiton on disscociation)

exophoria ( outward deviaiton on disscociation)

hyperphoria ( upward deviaiton on disscociation)

hypophoria ( downward devaition on dissociation)

Question 4

what is orthophoria

Answer 4

orthophoria = where both visual axies are directed towards the fixation point and do not deviate on dissociation

Question 5

how is esophoria classified

Answer 5

divergence weakness esophoria - distance angle is greater than the near angle

convergence excess esophoria = near angle is greater than the distance angle

non specific esophoria = nr angle = to distance angle

Question 6

how is exophoria classified

Answer 6

divergence excess exophoria - distance angle is greater than the near angle

convergence weakness exophoria - near angle is greater than the distance angle

non specific exophoria - the near angle is the same as the distance angle

Question 7

do you have bsv with a heterophoriua

Answer 7

in the presence of heterophoria , binocular vision is present and maintained - the heterophoria is often desacribed as compensated or well compensated when the motor fusion amplitude is sufficent to maitain comfortable motor fusion and the patient is sympton free

Question 8

what is a decompensating heterophoria

Answer 8

if the fusion amplitude is insufficent then the heterophoria becomes decompensated or decompensates this will cause visual symptons or manifest strabismus

Question 9

what is the aim of the investigation of heterophoria

Answer 9

investigation focuses on the detection and measurment of hetereophoria and asessing weather the patients symptons ‘fit’ with the findings about heterophoria

Question 10

what would you ask in the case history

Answer 10

their symptons - e.g. headache , blurred vision , diplopia

when do they occur , example morning , night time when tired

when did they start

have they remained the same or worsened since onset

did the patient link the symptoms to anything

• e.g. does any activity make the symptoms better or worse?
• can the patient do anything to make the symptoms better or worse e.g. covering one eye

general health

changes on gh and medication
previous gh problems
symptomatic near exophoria may be associated with neurological problems

previous ocular history
ask about previous ocular diagnoses, previous treatment and previous symptoms

did the patient have strabismus as a child - did they have eye patching or eye exercises

Question 11

what test would you do to detect heterophoria

Answer 11

cover test to detect heterophoria

cover uncover to ensure no manifest deviation
alternate cover test to detect the heterophoria
important to observe the eyes when you remove the cover to observe the recovery
performed at a 1/3m of a m and 6m - may perform at far distance (more than 6m) - if distance deviation is much larger than near fixation

e.g. in divergence excess exophoria to find out if an exotropia is present when you increase the fixation distance beyond 6m

Question 12

what do you need to describe on the cover test

Answer 12

direction of the deviation when the eyes are disscociated

size of the deviation when the eyes are dissociated

recovery on removal of cover

weather the patient describes any symptons i.e. diplopia removal of cover prior to recovery

Question 13

how would you measure a heterophoria

Answer 13

method used must fully dissociate the eyed to measure the maximum angle of deviation

measure at near , 6m and far distance if necessary

PCT- using the alternating cover test and either a prism bar or loose prisms in free space

synoptophore - when testing objective;y by extinguishing the lit tubes in turn

maddox rod - can be useful if deviation is very small and difficult to detect by observation only

Question 14

how would you test convergence

Answer 14

either use a target in free space or using the raf rule to asess their near point of covergence

important to observe the eyes as the patient convergence

note
quality and ease of convergence

near point of convergence

what happens at a break of convergence - i.e. does the patient appreciate diplopoa or suppression at the break of convergence

e.g. free space convergence binocular to 9cm then re diverges c diplopia

example raf rule 8cm, 10cm, 15cm at break point le converges c diplopia. pt needs encouragement to converge as finds it difficult from 20cm

Question 15

How would you asess horizontal fusional amplitude

Answer 15

using the horizontal prism bar asess the base in and base out range for 1/3m and 6m fixation

use a detailed accomodative target suitable for a patients level of acutiy in poorer eye

obserrve the eyes during the pdf (objecively) are they overcoming the prism

record the last prism strength were fusion was maintained - prior to the break point

record what happens at the break point - diplopia or suppression

can record the recovery point (strength of prism where fusion is regained)

example - pfr 1/3m 30bo- 14bi subjectivley diplopia at break point

pfr 1/3m 25 bo- 4bi objectlvely , re diverges under prism at break point and pt unaware of diplopia

Question 16

what prism fusion range is important to control in each type of deviaiton

Answer 16

exophoria it is the base out range (+ve fusion amplitude that is important)

esophoria it is the base in range (-ve) fusion range that is important

Question 17

how would you asess accomodation

Answer 17

heterophphoria and anomilies of accomodation can be linked , therefore it is important to measure the near point of accomodation

using raf rule with a detailed target , measure the near point of accomodation unicocularly and binocualry

repeat testing and observe the pupils during accomodation

Question 18

what is a well compensated vs decompnesated heterophoria

Answer 18

• compensated or well compensated heterophoria when the motor fusion amplitude is sifficent to maintain comfortable motor fusion and the patient is sympton free - if the fusion amplitude is insufficent then the heterophoria becomes decompensated or decompensates this wll cause visual symptons or a manifest strabismus

Question 19

how would you asess the compensation of heterophoria

Answer 19

asessed by the speed of recovery of bsv after dissociation i.e. during ct

near point of convergence

extent of fusional amplitude

Question 20

how would a well compensated heterophoria be described

Answer 20

well compensated , compensation of the heterophphoria is described as good if the patient has

rapid recovery of bsv
well maintained near point of convergence
norma fusional amplitude

Question 21

how would a poorly compensated heterophoria be described

Answer 21

• slow or delayed recovery to bsv

a remote near point of convergence or the patient struggles to maintain convergence

a poor fusional amplitude

example a reduce positive fusion amplitue in exophoria

a reduced - ve fusion amplitude in a esophoria

Question 22

what are symptons of heterophoria

Answer 22

symptons in hetrophoria may be due to effort to maintain bsv or failure to maintain bsv

the effort to maintain bsv may cause headaches , often a frontal headache and eye strain and asthenopia

typically the symptons can be related to a particular ocular activity i.e. closework and often absent on waking but develop during the day

failure to maintain bsc can cause diplopia blurred vision or jumbling of print when reading

the dipolpia may be intermittent, occuring mainly when the patient is tired and unwell- it may also be controlled to by blinking or changing fixation distance

blurred vision may be caused by patient manipulating their accomdoation to try and control their deviation by accomdative vergence

to prevent these symptons pateitns may admit they close or cover one eye i.e. when reading or at night when watching tv