21 VT Purpose Flashcards
- relaxation and reduction of accommodation below the normal demand for given binocular fixation distance.
- to determine the amount of accommodation that can be relaxed without change in convergence
- changes in accommodation that can be elicited when convergence is held constant.
- finding the reserve or range of accommodation
NRA
- determine the amount of accommodation that can be stimulated
without the change in convergence. - interaction between accommodation and convergence (negative relative convergence)
- changes in accommodation that can be elicited when convergence is held constant
- finding the reserve or range of accommodation
PRA
- measures the protection of accommodation pattern brought about by senility or advancing age.
- determination of the ADD
AOA
Measure the strength of SE and IR muscle (strength of the muscle is greater than the amount of prism reflected on the phoropter head. The strength of the muscle is not the break value).
VERTICAL DUCTION AT NEAR
- determine the muscular imbalance and binocular vision problem (present or absent)
- determine the relative vertical position of the visual axis of the eye at near when fusion has been broken
VERTICAL PHORIA AT NEAR
To determine the amount of tolerable, where eyes can still maintain single binocular vision (SBV).
NFR
To determine the limit of fusional convergence at near.
NRC
Additional fusional movement to maintain SBV, to keep movement on corresponding retinal points.
PFR
- to determine the effect of positive relative convergence upon refractive condition of patient.
- compensating duction at near in case VT 13b is higher than 6 exophoria
- measures the ability of MR contraction (amt. Of prism less than the actual amt. of contraction of the MR)
PRC
- measures the magnitude of the deviation present with new correction
in place - by suspending convergence, it allows the examiner to see the presence of muscular imbalance
INDUCED PHORIA AT NEAR
- measures the magnitude of the deviation present with the correction
or without any correction in place (objective angle of deviation) - determine the status of accommodation and convergence as they should be equal. (magnitude of phoria present – 6 prism is normal)
HABITUAL PHORIA AT NEAR
Measure the strength of SR and IR muscle, the strength of the muscle is greater than the amount of the prism reflected on the phoropter head. The strength of the muscle is not the break value.
VERTICAL DUCTION AT FAR
Determine the muscular imbalance and binocular vision problem (present or absent)
- determine the relative vertical position of the visual axis of the eye at distance when fusion has been broken.
- to measure vertical phoria were convergence is suspended and no accommodation is present.
VERTICAL PHORIA AT FAR
Compensating duction for esophoria at far
- measures the limit of negative vergence
- to know if the visual pattern is organized to compensate phoria
ABDUCTION AT FAR
It is the compensating duction for exophoria at far.
-measure the amount of convergence at far with the influence of accommodation
- measures the patient’s fusion amplitude/vergence amplitude.
CONVERGENCE AT FAR
Measures the amount of available convergence at far without
the influence of accommodation.
- compensating duction for exophoria at far
TRUE ADDUCTION AT FAR
Measures the magnitude of the deviation present with the
new correction in place.
INDUCED PHORIA AT FAR
To determine the refractive status of the eye by subjective criteria usually in the form of responses from the patient to the changes in the lens power relative to appearance of the letters in the test charts.
SUBJECTIVE REFRACTION
To get the INTERMEDIATE distance.
DYNAMIC RETINOSCOPY AT 40”
To get the ADD correction.
DYNAMIC RETINOSCOPY AT 20”
To determine the error of refraction objectively.
- used for infants, illiterate and uncooperative patients - confirming subjective findings
STATIC RETINOSCOPY
An objective method of determining the corneal curvature, the amount and the direction of regular corneal astigmatism.
- Determining the nature of the corneal refracting surface and the presence of any irregular astigmatism in patients who have corneal abnormalities/injuries
- measures the base curve of the contact lens.
KERATOMETRY
To determine the presence or absence of pathological or structural conditions which either prevent the attainment of or indicate the potential loss of normal vision.
OPHTHALMOSCOPY
