The use of Cycloplegia in retinoscopy
In retinoscopy a common source of error is
accommodation which is most active in young patients. When patient accommodates
the refractive power of the eye increases resulting in a variable shift towards
myopia. A simple solution would be to relax the accommodation by the use of a
cycloplegic but cycloplegia leads to abolition of basal tone of the ciliary body
muscles resulting in manifestation of latent hypermetropia. So if the patient
accommodates there is a shift towards myopia, and if we use cycloplegia there is
a shift towards hypermetropia; however, the latter situation is preferable as
the amount of shift towards hypermetropia caused by a given cycloplegic is known
and the same amount can be reduced from the retinoscopy value to get the
Age Group of patient
Amount to be reduced
Duration of action
1. Atropine sulfate 1 % oint.
|TDS ΄ 3 days
||0 to 5 years
||1.0 to 1.5 D
||2 to 3 weeks
||Allergy, Fever, Flushing of
2. Homatropine hydrobromide 2 % drops
|every 15 min. ΄ 4
||5 to 7 years
||0.5 to 1.0 D
||24 to 48 hr.
||Dry mouth, Urine retention in
3. Cyclopentolate HCl 1% drops
|every 15 min. ΄ 4
||7 to 20 years
||0.5 to 1.0 D
||12 to 24 hr.
||Transient psychotic reaction
4. Tropicamide 0.5-1 % drops
|every 15 min. ΄ 4
||0.25 to 0.5 D
||2 to 4 hr.
5. Phenylepherine HCl 5-10 % drops
|every 15 min. ΄ 4
||where only mydriasis is
||Nil (it has no cycloplegic
||6 to 8 hr.
||Increase in BP in
NB- For patients of 20 to 30 years of age
cycloplegia is used if needed in a particular case, and after the age of 30
years cycloplegia is not required.
When retinoscopy is done under cycloplegia,
patient is not prescribed glasses at the same time but patient is examined again
after the effect of the cycloplegic has worn off i.e. usually after 1 week, for
subjective verification (post cycloplegic test). However, patients acceptance
of the refractive correction is determined the same day. Therefore, the sequence
of steps of refraction are:
- Retinoscopy under cycloplegia.
- Get the acceptance by adding -1Έ distance (m). If the
distance is 1 m then add -1Έ 1 i.e. -1.0
- Prescibe after cycloplegia is worn off by reducing from
above value the amount for given cycloplegic used.
Note that the amount for cycloplegia is
reduced only form the spherical component of the refractive correction.
II. Distant Direct Ophthalmoscopy (DDO) at 22
cm using plane mirror
After preliminary examination at 1 m examiner
moves closer to the patient to a comfortable near vision distance of 22 cm (or
25 cm and concave mirror according to some authors). In a normal eye with clear
media one can see red fundal glow in the pupil. The abnormalities that can be
observed by this method are as follows:
Opacity in the media (cornea, aqueous,
lens and vitreous) will appear black against the background of red fundal
glow. The opacity appears black because no light goes in the eye or comes
out of it from the area of opacity.
Depth of opacity (Parallactic
Displacement) can be estimated qualitatively by the method of parallactic
displacement. While observing the pupil patient is asked to move the eye up,
down, right and left. An opacity located in the pupillary plane does not
seem to move relative to the pupil whereas any opacity anterior to the pupil
seems to move in the same direction and an opacity posterior to the pupil
seems to move in opposite direction. The further away an opacity is from the
pupillary plane the more does it move in relation to the pupil. This can be
easily understood by studying the diagram above. If we take a rod which is
hinged at point 3, and turn it up. The points 1 and 2 which are in front of
the hinge move in the same direction and points 4 and 5 behind the hinge
move in the opposite direction, whereas the point 3 which is in the plane of
the hinge does not seem to move. When looked at end-on it appears like the
figures on the right with the circles representing the pupil. The pupil acts
a frame to which all the movements are referred. Contrary to expectation the
reference plane in the eye is not the center of rotation because the
movement of any opacity can be appreciated only in relation to the pupil.
Opacity in fluid or solid part of the
media can be differentiated by observing the after-movement of the opacity
i.e. movement of the opacity after the eye has halted. Presence of
after-movement denotes opacity in the fluid part of the media (aqueous or
Keratoconus gives rise to a ring-shadow
corresponding to the base of the cone of the keratoconus. It occurs despite
the fact that the cornea is transparent, because of total internal
reflection of light occurring at the base of the cone. This reflects the
light back into the eye and, thus, the base of the cone appears as a dark
ring. Similar ring shadow may also be seen in lenticonus and the two can be
differentiated by parallactic displacement.
Iris nevus and coloboma, both of which
appear as black patch on the iris, can be differentiated by DDO. Coloboma
being a defect in the iris permits light to pass through it making fundal
glow visible. However, glow cannot be seen across the nevus.
Cataract can be easily differentiated from
nuclear sclerosis which also appears gray with torch light examination.
Cataract appears as dark opacity against fundal glow but in nuclear
sclerosis the media are clear. Moreover, as long as some clear cortex is
present in cataract some fundal glow is visible, thus differentiating
immature from mature cataract. In mature cataract no glow is seen, rather
pupil appears gray even with DDO due to light reflected from the cataract.
Subluxation of clear lens is not obvious
on examination with torch light as the pupil appears dark. With the DDO the
edge of the lens crossing the pupil stand out as a dark crescent against
fundal glow. Though the lens is clear yet the edge appears dark because of
total internal reflection of light at lens edge.
Lens Coloboma, a notch like defect in lens
edge can be readily seen with DDO.
Vitreous hemorrhage in its milder form
gives rise to darkening of the red fundal glow which then appears deep red
or maroon. In severe vitreous hemorrhage no glow can be seen and pupil
appears dark as whatever light gets reflected from fundus is absorbed by the
Retinal Detachment (RD) is separation of
the neural layer of retina from the retinal pigment layer leading to loss of
nutrition of the former from the choroidal vasculature. As a result of this
the retina becomes grayish opaque and lies much anteriorly (closer to the
lens). This gives rise to grayish glow in the area of RD and makes that part
of the retina visible by DDO (detached retina becomes highly hypermetropic).
Retinal folds may be seen moving with the movement of the eye and retinal
vessels running over the folds as dark bands.
Retinal Tumors are also visible on DDO as
gray glow and sometimes the mass itself can be seen with a bunch of abnormal
vessels on it. Unlike RD no folds are seen and there is no after-movement in
Gray glow on DDO; other causes are:
III. Indirect Ophthalmoscopy
Ophthalmoscopy means visualization of the
fundus oculi. In principle, indirect ophthalmoscopy involves making the eye
highly myopic by placing a high power convex lens (+13, +20 or +28 D) in front
of the eye so that a real inverted image is formed in front of the lens.
Classically indirect ophthalmoscopy was done
using concave mirror of the Priestly-Smith retinoscope but now it is done using
a head mounted binocular indirect ophthalmoscope. Patient lies on a couch with
the pupils fully dilated. The examiner stands at the head end of the bed and
directs the light of the ophthalmoscope onto the patients eye and while
looking at the pupil interposes the convex lens in front of the eye, then moving
the lens away form the eye till the retina is seen clearly. A real inverted
image which is 3 to 5 times magnified is formed in between the lens and the
observer. The magnification depends on the power of the lens used and the
refraction of the eye and is given by the refraction of the eye divided by the
power of the lens used e.g. 60 D Έ 13 D = 5 approx.
This article is part 2 of the three article series. For rest of the parts please see the ophthalmology section of this site.
1. Stereopsis: the greatest advantage is the 3
dimensional view possible with this method which lets the depth or the
solid nature of a lesion to be appreciated.
2. Large field of view enables a wide area of the
retina to be seen at a given time (about 30° ). Thus a large lesion
e.g. retinal-detachment, tumors, etc. can be observed in its entirety.
3. Periphery of the retina can be seen, even up to
ora serrata (combined with indentation of the sclera) by this method.
So the peripheral retinal lesions e.g. retinal degenerations, breaks
or holes etc. may be visualized.
4. Vitreous can be easily examined and various
vitreous abnormalities diagnosed.
5. In hazy media this method is useful because the
illumination is very bright and the method does not make use of the
refractive system of the eye, thus being of immense benefit in corneal
haze, cataract, vitreous hemorrhage, etc.
6. This can be used intra-operatively as there is
reasonable distance between the patient and the examiner so various
maneuvers can be done on the eye, and also the lens used for the
purpose can be sterilized.
1. The technique is difficult to learn as the image
is inverted; the orientation being achieved with lot of practice.
Although by examining the patient from the head end of the bed the
retina is inverted thus resulting in an erect image yet
coordinating the indentation of the sclera with the observed image
2. It is very difficult to use this method in an
3. The instrument is bulky and therefore not easily
4. Magnification is less, therefore
the small lesions e.g. macular pathology, cannot be examined in all