adv 1 Flashcards
Fully Accommodative Esotropia
- secondary to hypermetropia
- accommodation convergence and miosis (pupil constriction) linked so excess accommodation causes extra convergence which causes Esotropia. For Near and Distance.
-Hypermetropic refractive correction alleviate the need to accommodate so much, therefore eyes will converge less with gls on, and no manifest dev with gls on (for D and nr)
-Normal BSV, ARC with and AC:A ratio with glasses on.
-onset usually 2-5 yrs old when start to focus on objects at near (toys, books, drawing e.c.t.)
-Usually no or slight amblyopia unless Esotropia present for long time.
-May have microtropia if anisohypermetropic (reduced BSV, 10^ less pct, negative PRT 4^, eccentric fixation)
Management-
-full cycloplegic refraction (more plus = less accom = less convergence = less deviation) + refractive hypermetropic rx for FULL TIME wear (nr + dis)
-Review in 6-8 wks, check compliance (usually good) check no more latent hyperopia has become manifest and alter rx if big diff.
-check if have BSV and if microtropia present.
-Full refraction adaptive period is 16-18 weeks to settle in to glasses.
-If amblyopia worse than 0.3, part time occlusion if less than 7 years old, if microtropia present VA will never be equal.
ARC
-abnormal retinal correspondence is where a parafoveal point (approx 5 degrees off fovea) on the retina corresponds with another retinal point in other eye.
-this only develops if the person has good VA, small deviation (>20^ Eso) or microtropia but not common in exos, and deviation is stable (not variabe)
-This is opposed to normal retinal correspondence where the two foveal points match on the right eye retina and the left eye retina.
-This allows some BSV in a manifest deviation but not great e.g. 300”
-in boh Unharmonious and Harmonious ARC, the subjecttive angle < objective angle but in harmonious arc the subjective angle is 0 and in unharmonious, the subjective angle is >0.
-Harmonious ARC = think their eye is straight, Unharmonious ARC = knows eye is off axis.
-On the synoptopher, in harmonious ARC the patient would move the arm so that the lion is in the cage but in unharmonious arc they would move the arm slightly but not as much as we would.
-Dont get ARC in phorias
-draw projection digram (pic 1)
Convergence Insufficiency 5
-Most commonly occurs in the mid-teens when reduced convergence &/or increased myopia which breaks down the BV ( px often myopic)
- can be in adults c Presbyopia with increasing near add
* Typically XOP at distance XOT at near
* Pxs present with symptoms (diplopia, asthenopia)
* Usually equal VAs, poor or no convergence, NRC and normal sensory fusion with poor positive fusional amplitude
management…
-If strabismus is constantly manifest for near and angle >25∆ refer to HES
* For smaller angles and inconsistently manifest:
– Correct any myopia (this may be enough to make deviation latent, exo + myopic = the more - rx they have, induce accom + convergence more = alleviate symptomd)
– Orthoptics – exercise base out prism vergences and importantly need to improve Near Point covergence if reduced
– Prisms fresnel or incorperated onto glasses = base In just sufficient to enable BSV for near (Usually tolerated for distance) then gradually reduce the strength of the prism and combine with orthoptic excercises
– If no improvement = refer for surgery.
Emmetropization
- emmatropisaion is the process by which the refractive state of the eye changes and is mostly complete by 3 years old, from birth.
-Its the reduction in mostly hypermetropia and astigmatism and can eradicate around +3.00 DS and +1.50 DC (asigmatism)
-Passive emmetropization refers to normal eye growth as eye size increases, power of optical components decreases and proportionally refractive error decreases.
-Active emmatropisation decribes the visual feedback mechanism in the control of eye growth (feedback from eye which is blur and stimulates cortex to keep/stop growing the eye)
-The eye axial legnth elongates, the lens becomes thinner and the cornea becomes thinner. The cone cells elongate and migrate towards the centre of the retina to form the foveal pit and bunch closer together so theres less space for light to fall inbetween and the signal getting lost.
-The Critical period is where vision and BV connections are being rapidly formed and this period lasts until roughly 2 y/o. Any disruption during this time can have a severe effect on the overall visual outcome.
-The sensitive period is when the visual system is still developing therefore disruptions can still have an effect on the overall visual outcome but are not as severe, and lasts up to 8-10 y/o.
-The earlier the deprivation, the more severe the visual loss.
-Amblyopia exists when the process of emmetropization has failed and one eye (or rarely both) have not developed the neural connections from the eye to the brain due to disruption to the visual system such as
-stimulus deprivation amblyopia: where something e.g. tumor, ptosis, corneal opacity, deprives the retina of any stimulus, therefore, the brain doesn’t receive any signals to emmetropise.
-Strabismic amblyopia: the result of manifest strabismus which causes the brain to suppress one eye and therefore doesn’t emmetropise.
-Anisometropic amblyopia: the result of a difference in refractive error between two eyes where one eye will have the visual advantage at all distances.
-ametropic amblyopia: the reult of a high degree of uncorrected bilateral refractive error
-Meridional ambylopia: the result of uncorreced astigmatism therefore the retina did not recieve a clear image.
-can draw a little emmatropisation diagram
Dynamic retinoscopy 5
-The presence of accommodative lag or lead can be detected and measured using dynamic retinoscopy.
Typically the accommodative response to a near target does not match exactly with the accommodative stimulus. If the accommodation response is less than the stimuli, this is termed a “lag of accommodation” e.g. target at 40cm (2.50D) may elicit a
response of only 2.00D. A “lead of accommodation” is when the response exceeds the stimulus. Accommodative lags of 1.00D or greater may indicate presbyopia, uncorrected (or under-correction of) hypermetropia, or reduced amplitude of accommodation. Lack of a lag, or presence of an accommodative lead may indicate an accommodative spasm or pseudomyopia.
> Two distinct methods:
Monocular Estimation Method (MEM):
- Ensure the patient has the optimal distance correction
placed before each eye. Attach a near chart to the front of the retinoscope. Measure the patients habitual near working distance. Dim the room lights but ensure the near chart is illuminated. Ask the patient to fixate letters of a suitable size on the near chart (Slightly larger than binocular near VA). Perform retinoscopy on the RE at the habitual working distance with the streak vertical. Assess whether relfex is with (add +) or minus (add -) add lenses until neutral is achieved. Hold lenses in front of the eye for as short a time as possible (~ 500ms) (Ensures that accommodation response does not change). Repeat for LE. Record the power of the neutralizing lens for each eye. Positive lenses indicate a lag of accommodation, negative lenses indicate a lead (<1D = normal, >1D = needs + lens near add or spasm (need to relax)
Nott method:
-Begin with the optimal distance correction. Measure the Px habitual near working distance. Position the near chart at the working distance (25cm on RAF rule) and ask the patient to fixate on letters of a suitable size. Dim the room lights but ensure the near chart is illuminated. Perform retinoscopy on the RE from ~10cm behind the near chart with the streak vertical (Get as close to visual axis as possible). If the reflex is not neutral change your position. Move further away if reflex is WITH and move closer if AGAINST. Measure the distance of your retinoscope, relative to the patient, when the reflex appears neutral. Repeat for the LE. If the neutral point is behind the target then there is a lag. If the neutral point is in front of the target there is a lead. The dioptric distance between the near chart and the neutral point is a measure of the lag or lead. Near chart position = 40cm (2.50D). Neutral position = 50cm (2.00D). Accommodative lag = 2.50 - 2.00 = 0.50D.
sensory Fusion 5
Sensory fusion is the ability to perceive 2 similar images, one formed on each retina, and interpret them as one. Images must be located on corresponding retinal areas and be similar in size, brightness, and sharpness.
sensory fusion can be tested with Worths lights, bagollini glasses and on the synoptopher.
Motor fusion is the ability to maintain sensory fusion through a range of vergence movements.
Bagolini lenses are placed in front of the pateints eyes or refractive correction and the lights are turned off. The pateint is instructed to fixate on the spotlight at 33cm and 6m. Examiner notes the directions of the striations and if theres any gaps in the lines. For younger children, they can draw their response. The right eye should see a line at 135 degree angle and left eye line at 45 degree angle, so with both eyes open a cross should be seen but if suppressing only one line will be seen.
Worths light consists of 4 lights arranged in a diamond shame, two green lights horizontally, one red light and one white light. Ptient wears corrective error and wears red and green goggles (red on the right eye), the red and white lights are only seen through the red filter and green + white is only seen through the green filter. The white light is visible to both eyes and therefore a stimulus for fusion. Patient looks at worths light at 6m and 33cm. Patient asked how many lights seen, what colour and where are they in relation to each other. 4 lights indicate BSV, 5 lights = diplopia, two or 3 lights = suppression.
-both tests are subjective and partially dissociative.
Distance Exotropia 5
Manifest for distance fixation only, usually intermittently but may be constant
* Most apparent during inattention, ill health and fatigue, and in bright light
* Mostly females
* Little refractive error
* VA usually good and equal
* Usually no symptoms as the sensory adaptations are good
* Px may not have known about strabismus until told by others
* AC/A may be high in simulated type or they have increased fusional control
* True type is unaffected by AC/A or fusion
* Diagnosis of True or Simulated 1st
True = no change to angle after diagnostic occlusion after 30 mins, or to accom. Simulated: Fusion- near angle increases after occlusion, normla AC:A. Accom: NEar angle increases with accom high AC:A
* Correction of myopia or anisometropia
* Low degrees of hyperopia best left uncorrected- unless surgery is going to be planned or amblyopia potential
* Most require referral for surgery
* Orthoptist will use Newcastle Control Score to decide when Sx is required, as squint will always be in distance
* Where angle is <15∆ and BSV maintained most of the time, optical &/or orthoptic treatment may be of benefit – but usually only in the short term to delay surgery
- Optical:negative lenses can be successful in the short term, where accommodation is good
* Prisms (full base in – then gradually reduce) – short term
* Tinted spectacles – useful in countries with high light intensity - again only short-term- high illumination has a dissociation effect
* True – Bilat Lateral Rectus Recession
* Simulated MR Resection with LR Recession in one eye
PROBABLY BEST TO REFER FOR SURGERY FROM
OUTSET
Bagolini Glasses 5
Bagolini lenses are placed in front of the pateints eyes or refractive correction and the lights are turned off. The pateint is instructed to fixate on the spotlight at 33cm and 6m. Examiner notes the directions of the striations and if theres any gaps in the lines. For younger children, they can draw their response. The right eye should see a line at 135 degree angle and left eye line at 45 degree angle, so with both eyes open a cross should be seen but if suppressing only one line will be seen.
AC/A ratio 5
-accommodative convergence/accommodation ratio represents the amount of accommodative convergence exerted in response to one dioptre of accommodation. Use it to determine the change in accommodative convergence that occurs when the patient accommodates or relaxes accommodation a given amount.
-Significant in diagnosis of accomodative esotropia with convegrence excess and intemrittent distance exotropia. and for treatement.
remains mostly unchanges from birth to prebyopia.
-normal ac/a is 3-5:1 (for every 1 DS of accom, 3-5 prism D of vergence occurs .
Gradient method: use concave lenses for 6m or convex lenses for nr.
px wears refractive error, PCT at 6m using detailed target or synoptophore. Concave lenses are then introduced in trail frames (from +1 to +3). Allow time for accom to occur and clarity of vision.
AC/A = (PCT with concave lenses - PCT without lenses) / strength of lens used e.g. +30 - +6(with +3D) / 3 = 24/3 = 8:1
Deviation measured using accom target at near, convex lenses inserted into trail frames upto 3D, PCT then repeated.
e.g. 45-25/3 = 20/3 = 6.66/7:1
Dissociated Vertical Deviation (DVD) 5
Convergence Excess Esotropia 5
Suppression 5
Consecutive Exotropia 5
Near Esotropia 6
Sensory Fusion 5
Abnormal Retinal Correspondence 5
Classify the different types of Amblyopia. (5)
Discuss the treatment options for a 4 yr old with Visual Acuity of R 0.6 and
L 0.2 Crowded Logmar. Wearing R +4.50/+1.75 90 and L +2.0/+1.0 90 (15)
Compare and contrast the symptoms associated with reading as a result of visual stress and or binocular vision anomalies.
You may use a table to highlight your answers. 10
