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Static Retinoscopy
PURPOSE To objectively determine the distance refractive status of the patient’s eyes．The results of this technique serve as a starting point for the subjective refraction or as the patient’s final prescription if the patient is unable to respond to subjective testing．
EQUIPMENT
·Streak retinoscope．
·Phoropter, lens rack, or loose trial lenses．The technique described here refers to lenses in the phoropter, since that is the usual clinical method of retinoscopy．The same principles can be applied to retinoscopy using loose lenses or a retinoscopy rack instead of the phoropter．
·Fixation target：20/400 E projected through a red/green filter．
SET-UP
·The patient removes his corrective lenses．
·Adjust the height of the examination chair so that the patient’s eyes are at the same level as yours．
·Disinfect patient contact surfaces of the phoropter．
·Place the phoropter in front of the patient with the interpillary distance (PD) set to match the patient’s distance PD．Level the phoropter so the patient’s eyes are centered in the apertures．
·Instruct the patient to keep both eyes open during retinoscopy．Ask the patient to inform you if your head blocks his view of the fixation target．It may be necessary to rotate the phoropter slightly or to move the target off the screen and onto the wall to allow the patient to see the target while you maintain alignment along the patient’s visual axis．
·During retinoscopy，the examiner keeps both of his eyes open and examines the patient’s right eye with his right eye and examines the patient’s left eye with his left eye．
·The examiner holds the retinoscope 20 in(50 cm)or 26 in(67 cm) from the patient’s eye．The retinoscope is held in the examiner’s right hand to examine the patient’s right eye and in the examiner’s left hand to examine the patient’s left eye．
·Retinoscopy is most easily done in dim illumination．An illustration of the performance of static retinoscopy is provided in Figure 3-7．
STEP-BY-STEP PROCEDURE
1．Instruct the patient to look at the fixation target．Examine the patient’s right eye．
2．Determine if the refractive error is spherical or astigmatic by changing the position of the sleeve of the streak retinoscope and the distance between the examiner and the patient until the reflex is enhanced．Then rotate the streak of the retinoscope through 360°，looking for the break phenomenon，the thickness phenomenon，and the skew phenomenon．
a．If the error is spherical，the reflex within the pil will be continuous with the intercept of the streak on the patient’s face (ie, there will be no break phenomenon)．If the error is astigmatic, the reflex within the pil may not be continuous with the intercept on the patient’s face (ie, there will be a break phenomenon)(see Figure 3-8)．
b．As the streak is rotated through 360°, the thickness of the reflex within the pil will be constant in a spherical error and vary in an astigmatic error (thickness phenomenon)(see Figure 3-9)．
c．In an astigmatic error, as the streak is swept across the patient’s pil，the reflex within the pil will move parallel to the movement of the streak on the patient’s face when the streak is aligned with one of the two principal meridians．The reflex will move in a different direction than the streak when the streak is not aligned with one of the principal meridians (skew phenomenon)．There will be no skew phenomenon in a spherical error(see Figure 3-10)．
3．If the error is spherical, observe the reflex for with or against motion and add plus or minus lenses until there is no motion of the reflex．The type of lens needed for neutralization depends on the patient’s refractive error, the position of the sleeve of the retinoscope (plane mirror position or short concave mirror position)，and the type of motion seen(with motion or against motion)(see Table 3-1)．
Note：With motion is easier to observe and to neutralize than against motion．However，if with motion is present, the patient may accommodate, particularly if minus lenses were added．When against motion is initially seen, it can be changed to with motion, without affecting the patient’s accommodation, by changing the sleeve of the retinoscope from the plane mirror position to the short concave mirror position．
4．To neutralize an astigmatic error, first identify the two principal meridians (see step 2)．Then neutralize each meridian separately．When using a phoropter with minus cylinders, one meridian is neutralized with sphere only．The other meridian is neutralized with a combination of sphere and minus-cylinder．The least myopic or most hyperopic meridian is neutralized with sphere．The most myopic or least hyperopic meridian is neutralized with cylinder in addition to the sphere．
Since it may be difficult for a novice retinoscopist to determine which meridian is the least myopic, either meridian can be neutralized first．The other meridian can then be checked and adjustments can be made in the sphere power if necessary．If using a plane mirror retinoscope, when one meridian is neutralized the other meridian must show against motion in order to be neutralize with minus-cylinder power．If the retinoscopist neutralizes the most myopic meridian first, one meridian will show neutrality while the other shows with motion．To correct this, The retinoscopist can add more plus to the sphere power to neutralize the second meridian．This will leave the first meridian showing against motion．The newly created against motion can now be neutralized by adding minus-cylinder power with the cylinder axis aligned with the orientation of the streak．
5．When both principal meridians are neutralized, recheck the meridian neutralized with sphere and adjust the spherical power in necessary．
6．When neutrality is reached, recheck all meridians with the sleeve of the retinoscope in both the plane mirror position and the short concave mirror position．If true neutrality is achieved, all meridians will look neutral regardless of the position of the sleeve of the retinoscope．If neutrality is not reached in all meridians, make necessary adjustments．
7．The lens (or combination of lenses) that produces neutrality is called the gross retinoscopy finding．The gross finding makes the patient’s fundus conjugate with the examiner’s entrance pil．Leave the gross static finding in front of the patient’s right eye and neutralize the patient’s left eye by following steps 2 to 6．When the patient’s left eye is neutralized, recheck the right eye and adjust the sphere or cylinder if necessary．
8．To convert the gross retinoscopy finding to a net finding，algebraically add a spherical minus lens equal to your working distance in diopters to the spherical lens that produced neutrality．For example，-2.00 D for a working distance of 20 in; -1.50 D for a working distance of 26 in．This is the net static retinoscopy finding，or the net static, that makes the patient’s retina conjugate with infinity．
9．Measure the patient’s visual acuity in each eye through the net static retinoscopy finding．
RECORDING
·Record the net static for each eye separately．
·Record the patient’s visual acuity for each eye through the net static retinoscopy finding．
EXAMPLES
·OD +4.75 sphere 20/60
OS +1.50 = -0.50×175 20/20
·OD +1.O0 = -1.25×10 20/15
OS +1.O0 = -0.75×165 20/15 |
