Page 112 - The Indian Optician Digital Edition March-April 2021

̶PART 2

Dr Prof Mo Jalie, SMSA, FBDO (Hons), Hon FCGI Hon FCOptom,
MCMI, is a Visiting Professor of Optometry at the University of Ulster in
Coleraine, and at the post-graduate facility at Varilux University. He served
for nine years as Head of Department of Applied Optics at City & Islington
College, where he taught optics, ophthalmic lenses and dispensing. He
is a recognised international authority on spectacle lens design and has
written several books including Principles of Ophthalmic Lenses. His most
recent book, Ophthalmic Lenses & Dispensing was translated into Russian.
He has authored over 200 papers on ophthalmic, contact and intra-ocular
lenses, and on dispensing; and is a consultant editor to The Optician (UK)
and technical editor to The Indian Optician journal. He holds patents for
aspheric spectacle and intra-ocular lenses. Jalie is a past-chairman of the
Academic Committee of the Association of British Dispensing Opticians,
and was the first Chairman of the Faculty of Dispensing Opticians. He is
the ABDO representative on the BSI committees on ophthalmic lenses
and spectacle frames and a past member of the Education Committee
of the General Optical Council. In 1998 Jalie was thrice honoured: he was
made Honorary Fellow of the British College of Optometrists, a Life Fellow
of the Association of British Dispensing Opticians, and in December of
that year he was granted the Max Wiseman Memorial Research Medal.
Dr Prof Mo Jalie

S
M
ALLVAREZ-LOHMANN LENSES
An adaptive lens which can provide both variable
spherical and cylindrical power was described by Luis W.
Alvarez in 1967. Three years later an adaptive lens of similar
1
2
construction was described by A Lohmann and lenses of
this type are often referred to as Alvarez-Lohmann lenses.
Here, they will be called simply, Alvarez lenses, for brevity.
IN DESIGNING
Consider the parallel-sided block of optical material, say a
A CURVED
block of CR 39, illustrated in Figure 1(a). Clearly, there would
INTERFACE, be no movement of objects under the transverse test when
SUFFICIENT SPACE applied to the block depicted in Figure 1(a).
MUST BE ALLOWED On careful inspection of the block, it is seen that the block
BETWEEN THE is actually made from two separate components which have
TWO SLIDING been put together as shown in Figure 1(b). A cross sectional
COMPONENTS TO view of the two separated components is shown in Figure
ENABLE THEM TO 1(c). Like the plano-convex and plano-concave cylinders
which make up the Stokes’ lens, the absence of material
SLIDE WITHOUT from one component is entirely replaced by the presence of
MAKING CONTACT material from the second component.
WITH ONE Figure 2(a) shows that provided that the two components
ANOTHER are sufficiently thin, despite its peculiar shape, the Alvarez

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