Diplopia is characteristic feature of -
Ans. is 'c' i.e., Paralytic squint o Diplopia is characteristic feature of paralytic squint (Incomitant squint).MANFEST SQUINT fHETEROTROPIA)o In manifest squint the deviation of eye is present as such and cannot be compensated by fusion. Two main types of manifest squint are concomitant squint and paralytic squint.Concomitant squinto In concomitant squint the eyes are not in alignment and the degree of malalignment remains constant in all the directions of gaze and there is no limitation of ocular movements. Concomitant squint may be of following types:Esotropia (Convergent squint) It denotes inward deviation of eye. It can be unilateral or uniocular (the same eye always deviates inwards) or alternating (either of the eyes deviates inwards and the other eye takes up fixation, alternately). Concomitant esotropia is the most common type of squint in children. Following types of esotropia are thereCongenital esotropia (infantile esotropia)True congenital (infantile) esotropia usually appears between the age of 2 and 4 months. However, rarely it may be present from birth. The inward turn of the eye is constant of large amount, i.e., deviation is > 35 prism diopters (17-5deg).Binocular vision (both eyes fixing simultaneously) does not develop. There is alternate fixation in primary gaze, i.e, when the infant looks straight, he fixes the gaze with one eye at a time alternately. On lateral gaze there is cross fixation, i.e, use right eye to fix across the nose to view the objects to the left and vice versa. Amblyopia develops in 25- 40% of cases.Latent horizontal nystagmus (common) and many rotatoiy nystagmus may occur. Inferior oblique overaction may be present initially or develop later and dissociated vertical deviation develop in 80% by age of 3 years.It is more difficult to help this type of strabismus with nonsurgical methods, thus, surgery is the treatment of choice. Surgical procedure to make both medial recti weak by recession. Surgery should be done as early as possible to avoid development of amblyopia and for the development of proper binocular vision. The usually recommended time is between 6 month - 2 years of age (and preferably before 1 year of age}. It is important to treat the amblyopia before performing surgery by patching of normal eye.Accommodative esotropiay Accommodative esotropia occurs due to overaction of convergence associated with accommodation reflex. Accommodative esotropia is the most common type of squint in children (Previously it was believed that congenital esotropia is the most common type squint in children. However now it is very much clear that accommodative esotropia is the most common one). It esotropia is noted around 2-3 years of age, it is most likely accommodative esotropia. On the bases of AG'A (accommodative convergence'accomodation) ratio, accommodative esotropia is divided into two types : (a) Refractive (Normal AC/A ratio); (b) Non - refractive (abnormal AC/A ratio). AC/A ratio gives the relationship between the amount of convergence that is goverened by a given amount of accommodation.Normal AC/A ratio accommodative esotropia This occurs in children with hypermetropia.Esotropia is a physiological response to excessive hypermetropia. Patients with high hypermetropia generate large amount of accommodation to see clearly at near fixation. This excessive accommodation may cause esotropia as accommodation is associated with convergence. AC/A ratio is normal.Large AC/A ratio accommodative esotropia Children have large amounts of focusing power and sometimes the increase of accommodation is accompanied by a disproportionately large increase of convergence. This occurs in patient with hypermetropia but may occur in myopia and without any refractive error. AC/A ratio is high,y Usually, there are no symptoms except for cosmetic embarrassment to the patient. There is no diplopia as the image in the squinting eye is automatically suppressed, i.e., amblyopia develops in squinting eye. The main feature is the failure of binocular vision.Exotropia (divergent squint)It is characterized by outward deviation of eye. This is very- less common than esotropia.Hvpertropia (Vertical squint) It is characterized by vertical deviation of eye. It is also rare.Incomitant squinto Incomitant squint is a squint in which the angle of deviation differs depending upon the direction of gaze i.e, amount of deviation varies in different directions of gaze. There are many type of incomitant squints (paralytic. restrictive, 'A' & 'V' pattern), however the most common type is Paralytic squint and the word incomitan? squint is usually used for paralytic squint. Therefore, I will explain paralytic squint here,o Paralytic squint is the most common type of squint in adults. Paralytic squint is the strabismus resulting from complete or incomplete paralysis of one or more extraocular muscles. There are many causes like neurogenic (e.g. meningitis, cranial nerve palsy etc.), myogenic (myopathies), or neuromuscular junction lesions,o Symptoms of paralytic squint are :-Diplopia : It is the main symptom. It is most marked in the direction of action of paralysed muscle. For example in left rectus palsy, the maximum diplopia occurs when patient tries to see horizontally on left side and in left superior oblique palsy (causes Dextrodepression) diplopia is maximum when patient tries to look downward and right. It is worth noting here that in diplopia, if the images are separated horizontally it is probable that either a lateral or a medial recuts is affected; when the images are separated vertically or the image is tilted (torsion) it is likely that one or more of the vertical recti or the obliques are affected.Other symptoms : Confusion, nausea & vertigo, ocular deviation, loss of stereopsis.o Signs of paralytic squint are :-Secondary deviation is more than primary deviation:- Primary deviation is the deviation in the affected eye and is away from the action of paralysed muscle. Secondary deviation is the deviation of normal eye seen under cover, yvhen the patient is made to fix with the squinting eye.Restriction of ocular movementsCompensatory head posture Patients with a paralytic squint move their head such that the eyes occupy a position in the orbit where the angle of squint is minimal and this can avoid confusion and diplopia. Head is turned towards the action of paralysed muscle. When the horizontal recti (medial or lateral) are affected, the characteristic posture is a turn of the face to right or left, e.g. in left lateral rectus palsy the head is turned to the left and in left medial recuts palsy the head is turned to the right. When a vertical rectus (superior or inferior) or an oblique muscle is affected, a tilt of the head to the right or left with depression or elevation of the chin is adopted to reduce both the vertical deviation and rotation, e.g in superior oblique palsy (dextrodepression of left eye is affected) the head is tilted to left so that the left eye can see down and medially.There is false projection or orientationThere is no amblyopia and visual acuity is normal as paralytic squint develops in adults when visual acuity has already developed.FeaturesParalytic squintNon-paralytic squint1. OnsetUsually suddenUsually slow2. DiplopiaUsually presentUsually absent3. Ocular movementsLimited in the direction of action of paralysed muscle.Full4. False projectionIt is positive i.e., patient cannot correctly locate the object in space when asked to see in the direction of paralysed muscle in early stages.False projection is negative5. Head postureA particular head posture depending upon the muscle paralysed may be present.Nonna!6. Nausea and vertigoPresentAbsent7. Secondary deviationMore than the primary' deviationEqual to primary deviation8. In old eases patho- logical sequelae in the musclesPresentAbsent
Concomitant squint
Non-paralytic squint
Paralytic squint
Latent squint
Strabismus - Definition and Evaluation