hello and welcome to Insight of filmology this is Dr Amrit welcoming you to another important lecture in this Quinn Series today we are studying the pseudostrabismus so what is meant by true strabismus true strabismus is as I told you in the introductory video is the true deviation of the visual axis however anything which is not true strabismus is pseudostropismus or false trabismus can also be defined as an apparent deviation of the eye so it can be an inward deviation so that is an apparent or pseudo-isotropia and outward deviation which is an apparent or pseudo exotropia an upward deviation that is apparent or pseudo hypertropia or a downward deviation which is pseudo-hypotropia so what are the causes of pseudostropismus now the most important cause of pseudostropismus is the presence of an epicanthus so what is an epicanthus an epicanthus is basically a semilunar that is a crescent-like fold of skin which runs downwards from the side of the nose and it runs this fold runs in such a way that it actually covers your inner canthus now as it obscures or hides the inner canthus the part of sclera or the inner sclera of the eye basically gets obscured and it gives an appearance as if the eyes are deviated inwards therefore an epicanthus or a presence of epicanthus basically leads to an appearance of esotropia and is a common cause of pseudo-isotropia right now this epicanthus basically disappears as the bridge of the nose starts developing so basically it's uh because of the immature or we can say a party develop Bridge of the nose and as a bridge of nose develops the epicanthus will disappear in most of the children however it can persist in a few and which it can cause pseudoesotropia a very common test that is basically employed to differentiate between true esotropia and pseudo-isotropia is a pinch test so what is done in a pinch test is we try to pinch the skin present at the nasal Bridge as seen in this third picture so if we are dealing with a true esotropia the esotropia is still very very apparent however if you are dealing with a pseudoesotropia as we lift the skin from the bridge of the nose the epicanthus also gets stretched and therefore the epicanthus is also that fold is also lifted off the inner canthus and the sclera is visible now and now the the eyes will look straight ahead so this is test that helps you differentiate between pseudoesotropia and true esotropia another cause of pseudostrabismus is the presence of Earth symmetry in the palpable fissure width now if you have very narrow palpable fissures as seen in the first picture it creates an impression as if the eyes are deviated inwards right so narrow palpable fissure gives an impression that we are dealing with a pseudoesotropia similarly enough thalmos which is a recession of the globe inside the orbit that gives an appearance as if again we are dealing with an esotropia on the contrary if you have very large palpable fissures or if the eyeballs are protruding outwards which is called proptosis or exothalmers then it gives an appearance as if we are dealing with an exorbation that is an outward deviation the third important cause of pseudostrabismus is the interpupillary distance abnormalities now the ipd or the interpupillary distance is basically the distance between the two popular pupillary centers normally the normal interpuple distance is about 63 millimeters now if you have a very narrow ipd okay that means the two pupils are set very close together it gives an appearance as if you are dealing with an esotropia so it would not be wrong to say that narrow ipd basically causes pseudoesotropia on the contrary if you have wider ipd that is called a wider interpupillary distance it basically simulates an exorbiation and causes a pseudo exotropia as you can see in this picture basically the pupils are set too far apart and it gives an impression as if we are dealing with an exor deviation however this is only an apparent exotication or a false exhibition that means we are dealing with a pseudo EXO deviation another cause of pseudoster business is displacement of the orbits of facial asymmetry now many a times the orbits might not be present straight together there might be some displacement of the orbit either because of a consular condition like in hypertherism hypertellorism is a condition where the orbits are basically placed far apart from each other or we can have displacement of orbits which could be acquired because of a trauma now when we have such displace orbit what happens is the eyeballs will not be present at the same level and it might actually stimulate a presence of a squid and therefore this is also a cause of pseudostropismus now what you should remember is that in pseudoster business there will not be any disruption of the bsv that is binocular single measure another important cause which is commonly asked is the angle Kappa anomalies so they're any kind of anomalies in the angle Kappa can also lead to simulation of squint a positive angle copper causes pseudo-exotropia and negative angle copper causes pseudo esotropia right so these are very important high yield points now whenever the angle Kappa is involved it is basically involved symmetrically in both the eyes so it is not always it does not always leads to development of a pseudostropismus however if you have angle copper anomalies particularly in one eye then the squinting appearance is much more accentuated now I already in the first video the introductory video in which I talk about the hershberg's corneal reflex test I have explained to you in detail about the angle copper and the angle copper anomalies and we also have a video on angle Kappa on the channel so I would advise you to visit that video if you do not really understand what is a positive angle copper or a negative angle copper now to summarize what are the causes of pseudoesotropia a negative angle Kappa can lead to a pseudoesotropia an epicanthus can lead to a pseudoesotropia and how do you know whether we are dealing with a true or a pseudo isotropia in epicanthus by doing a pinch test a narrow ipd can cause flu isotropia small palpable fissures and enough thalmers basically causes pseudo-isotropia now what are the other causes of pseudo exotropia so a positive angle Kappa causes pseudo exotropia narrow lateral palpable fissure so here in epicanthus what was happening the medial part of the sclera was obscured by this fold of skin which was called an epicanthus now what if you have a condition where the lateral Parable fissure is a smaller obscuring the obscuring your view of the lateral sclera so in that condition you might feel as if the cornea is present more laterally and will give you an appearance of pseudo exotropia similarly a wider interpupillary distance will lead to pseudo exotropia a wide palpable fissure height and exophthalmers or proptosis will lead to pseudo exotropia what are the causes of pseudo hyper or hypertropia that means pseudo vertical deviations lid positions now suppose you have an eye and the eye actually has ptosis ptosis is nothing but it is a drooping of the eyelid now if you have an eye in which there is ptosis or drooping of the eyelid what happens is that because the lid will be covering more amount of superior cornea you might feel as if the eye is deviated upwards so so tosses also can give you an appearance of a hyper deviation and therefore is a common cause of pseudo-hypertropia what if the lower eyelid was placed above the normal position then that is called inverse doses so inverse doses however gives you a different appearance of a hypo deviation okay as if the eyeball is deviated downwards right so inverse doses can cause a pseudo hypotropia and of course facial asymmetry can cause any sort of pseudostropism now as we know now that what are the causes of pseudos to dismiss now the question is are there other ways to confirm Are there specific tests to confirm that are we dealing with pseudostropismus or true strabismus the answer is yes we do have tests and these are the tests that through whether by fovial binocular single vision is present or not now the first test that we do is the hershberg's corneal reflex test so in the first video of the sequencies I told you in detail about the hcrt then we have a cover test cover test also I mentioned in the second video and whenever there's a movement on the cover test it tells you that there is going present so as you can guess in pseudostropismus there will be no movement on a cover test what about stereoopsis stereopsis usually a person who has squint who has a true deviation or true stabismus will have a deteriorating stereopsis okay and the most common test that we do is a random DOT test a person with a pseudostropismus will usually have normal random DOT test or normal stereopsis test another test that we do is a testing of the motor Fusion which is done using a 15 or a 20 prism diopter test and something which is not such a hard and fast tool however in in case of solar establishment is usually the visual Equity will be normal in both the eyes it will be normal or equal in both the eyes but for this you have to assume that the rest of the uh I is normal so the first test that we do is the hcrt test this test basically uh is a test to estimate the relative position of the eye the patient will fixate on the pen light this is done at a near vision and also at distance so basically you look at the reflection of the light at the center of the corneas if the reflected images are appearing at the center of the cornea you you basically know that the visual direction of both the eyes are straight and there is no squint however if the reflexes are altered if the reflexes are deviated or displaced we know that we are dealing with a true strabismus now in the first picture you can see that although it looks as if we are dealing with squint we know that here is an epicanthus as well and if you carefully observe the corneal reflexes the corner reflexes seem to be present right at the center of the pupil in the right eye and also in the left eye it is present at the center of the pupil that means we are dealing with a pseudostropismus and the cause of surestavismus and in this case is pseudoesotropia the cause is the epicanthus in the second picture however again you have an esotropia however just observe the reflexes The Reflex here in the left eye seems to be displaced too temporally and as I explained you in the first video on hcrt whenever the reflex is displaced temporarily it means that we are dealing with an ISO deviation so the second picture is a true deviation and the first picture is a pseudo or a false deviation now what about the base art prism test so as I told you that you can actually carry out this test of motor Fusion so it tells you whether motor Fusion is present or not so if the motor Fusion is present it means that the visual directions and the visual Axis or the patient is normal and what we are dealing with is basically a pseudoster business okay however intruster business also you might have problems or you might have a negative base out prism test okay but in pseudostrabismus you will always have a normal base out prism test so that you must remember so let us see how do we do it now it can be demonstrated in children who are aged from four to six months onwards and as a name suggests you're going to use a prism that is placed in a base out Direction a base out means that you are going to place this base okay towards the temporal side of the eye okay now what is the amount of prism that you're going to use here we use a 15 prism day after or a 20 present day after prison and that's going to be hold that's going to be held base out in front of each eye okay so you're going to test one eye at a time if the binocular single vision is present what happens is let us see now normally first of all we'll give a fixation Target to the patient now if both the eyes are normal what happens the right eye is fixing on this Target and so is the left eye right so both the eyes are actually nicely fixating on this object now if you are going to put a base out prism in front of the right eye suppose right so this is how a base or prism is put now you should know that whenever we put a prism in this way that means in a base out fashion the image is going to be always shifted towards the apex of the prism right so if the image was initially here now it's going to get shifted towards this Apex right so it will be shifted more towards the left side right so how does the right eye compensate for that add the right eye to in order to fixate on that image now we'll also have to move towards the left side and in order to move towards the left side the right eye actually has to adapt that is add that is end up okay and which is the muscle it is going to use it is going to use the medial rectus muscle right so using the medial rectus muscle the right eye is going to adapt in order to look at the displaced image right now as the medial rectus is going to get innervation the left die lateral rectus is also going to get innervation and this is because of your headings law now as the left uh isolator vectors is going to get innervation what will happen to the left eye the left eye is going to move outwards and this is called abduction that is a b induction right so as the right type adapts the left eye will abduct right now the right I did adduction and therefore achieved fixation of the displaced image but what about the left eye the left eye realizes that it has not it is not really fixing fixating on the Target and therefore now it's going to come back towards the center and therefore it is again going to show this adapting movement okay whereas the right eye will remain adapted right so this movement of the right eye the right eye is initially showing adduction and the left eye is showing abduction and later it realizes that oops it's not at the correct spot so it's going to come back it's going to do adduction again right so this entire process of uh movement first and then correcting movement is your base out prism test and it actually tells you that the patient has a normal motor Fusion right now as you're going to remove the prism in front of the right eye what will happen the right eye is going to come back to its original position okay so therefore now it is going to add up and because of the headings law what will happen to the left eye the left eye will also follow the lead and therefore the left eye will actually end up however the right eye is now now normally fixating on the target but what about the left eye the left eye realizes that it's not at the correct spot it's not fixating at the correct spot and therefore it is going to come back towards the center by showing an abduction movement right so basically both the eyes are working together so that they can fixate on that Target regardless of whether you put a prism or not right so this is what is called motor Fusion right so using the movement of the eyeball the eyes are basically trying to fuse the image which is fuse the image of the object which is placed in front of them so this is your 15 prism diopters or 20 prism diopters base out test so I hope that is clear now after all this an important clinical nugget is that pseudostrabismus although a separate entity sometimes can be present along with a true squint as well and it can mask or it can accentuate the presence of the true squid so therefore before you rule out squint there are certain specific uh clinical scenarios where even when the squint is not present you have to observe the child for some time okay and what are the clinical scenarios one when a family history of refractive error ostrobismus is present second when a significant amount of heterophoria even a small amount of esophoria is very very significant so be on your guard in such children and third when the child has a tendency to close one eye in sunlight because that indicates a possible intermittent exotropia so I hope by now you know what is the difference between true deviation and pseudoor deviation or pseudoster business so that's all for today thank you and have a nice day