Download perception, and partly because a later operating

perception, and partly because a later operating age implies diminishing ability to
adapt to the optical errors inherent in the use of an optical aid in front of the eye.
; The critical patient's point of view has been advanced by two ophthal1 mologists who have themselves undergone bilateral cataract extraction:
! a. briefly by MCLEMORE (1965), who says: 'an ophthalmologist giving his paI
' tients cataract spectacles, is creating visual invalids1.
1>. at length, by WOODS in 'The adjustment to aphakia' (WOODS, 1952). The
most important disadvantages mentioned by WOODS;, are:
; 1. the astonishing increase in the size of familiar objects;
: 2. diplopia in monocular aphakia, rendering binocular vision impossible until
the second eye has been operated upon;
3. lack of co-ordination between eye and hand due to the new visual imagery
created by false spatial orientation which is even present in bilateral aphakia.
Eveiything seems much closer than before. This can be overcome after several
weeks of constant exercise and adjustment. During this period tumblers are
overturned, ink is spilled and similar minor domestic tragedies occur;
4. all straight lines are transformed into curves: the world becomes parabolic,
and ocular movement causes this parabolic world to squirm like a writhing
snake. This can be overcome by the simple trick of holding the eyes still, the
gaze fixed through the optical centres of the correcting lenses, while moving
the head slowly to look at a new object;
5. a portion of the peripheral visual field, from about 35 to 55 degrees, depending on the size of the spectacle lens, is blotted out (area b in Fig. 1);
in addition, objects observed in the peripheral field may disappear if the gaze
is moved towards them. This is particularly tiresome at distances between 0.5
and 3 m: 'faces and objects pop in and out of the blind area with the annoying
insolence of a jack-in-the-box, leading to constant collision with chairs or
individuals. This social handicap cannot be cured, it must be endured.'
The optical causes of these complaints are:
re 1, 2, 3 image magnification: about 25%.
spherical aberration giving rise to blurring of the periphery of the
re 4
image, and pincushion distortion. Moreover, this distortion is asymmetrical if
the eye is not looking through the optical centre of the correcting lens. Both
can be partially rectified by an aspherical spectacle lens,
ring scotoma inherent in high dioptre convex lenses and causing the
re 5 a
Jack-in-the-box phenomenon of moving objects (area b in Fig. 1).
roving ring scotoma (WELSH phenomenon), i.e. an aperture scotoma
re 5 b
elicited by the movement of the eye, especially of the nodal point, behind an
aperture of absolute limits, resulting in the apparent jumping of an object from
one edge of the scotoma to the other which is caused by the retraction of rays
passing through the edge of a powerful convex lens. This is the Jack-in-the-box
phenomenon caused by the moving of the eye (WELSH, 1961b). See Fig. 1. 'It is
obviously the eye rather than the scotoma which does the roving' (LINKSZ, 1964).
Thus it seems that adjustment to aphakia is not as easy as ophthalmologists
often think. That may be the reason why patients with unilateral aphakia
frequently prefer to use the fellow-eye, especially for distance vision, eypn if
this eye has a less visual acuity (RIDLEY, 1951, 1952abc, 1953b, 1954; SLOANE,
1962), or even is actually amblyopic (see case F 1 on page 136).
According to COLENBRANDER the best solution in case of anisometropia of
x dioptres is the full correction of the one eye and a modification of the correction of the fellow-eye by 4(x - 1) dioptres (COLENBRANDER. 1971).
Ophthalmologists who wish to obtain some insight into spectacle-corrected
aphakic vision might like to try WELSH'S suggestion and simulate aphakia by
jneans of a combination of a contact lens ot -14 D and a spectacle lens of +12 D
(WELSH71965) The unadjusted omocular experience of this author during a longlasting hour remains ineffable in his memory.
Fig. 1 (After R. c. WELSH, 1961b)
The roving ring scotoma with its Jack-in-the-box phenomenon of high positive spectacle lenses (spheric or aspheric). Area b is the ring scotoma of a spectacle corrected
aphakic eye fixing centrally: Jack is observed with peripheral vision. If the eye turns
towards Jack he is hidden in the area a: the ring scotoma has moved towards the centre.