CA1108448A - Contact lenses - Google Patents
Contact lensesInfo
- Publication number
- CA1108448A CA1108448A CA323,900A CA323900A CA1108448A CA 1108448 A CA1108448 A CA 1108448A CA 323900 A CA323900 A CA 323900A CA 1108448 A CA1108448 A CA 1108448A
- Authority
- CA
- Canada
- Prior art keywords
- lens
- correction
- eye
- sclera
- astigmatism
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
- G02C7/00—Optical parts
- G02C7/02—Lenses; Lens systems ; Methods of designing lenses
- G02C7/04—Contact lenses for the eyes
- G02C7/047—Contact lens fitting; Contact lenses for orthokeratology; Contact lenses for specially shaped corneae
-
- G—PHYSICS
- G02—OPTICS
- G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
- G02C7/00—Optical parts
- G02C7/02—Lenses; Lens systems ; Methods of designing lenses
- G02C7/04—Contact lenses for the eyes
-
- G—PHYSICS
- G02—OPTICS
- G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
- G02C7/00—Optical parts
- G02C7/02—Lenses; Lens systems ; Methods of designing lenses
- G02C7/04—Contact lenses for the eyes
- G02C7/048—Means for stabilising the orientation of lenses in the eye
Abstract
ABSTRACT
There is disclosed a soft, hydrophilic plastic corneal contact lens, comprising a substantially circular optical correction zone which is shaped for the correction of astigmatism. The lens is soft enough to tend to conform to the shape of the cornea when placed on an eye with corneal astigmatism. The lens comprises at least one discrete lug or flange extending from the periphery of the correction zone, the lug having a radial width measured from the periphery of the correction zone which is less than the radius of the correction zone.
The lug is adapted to engage the sclera of the eye, adjacent to the cornea, at one of the depressions on the eyeball formed between the four rectus muscles attached to the sclera of the eye, to thereby prevent rotation of the lens to maintain the required astigmatism correction.
There is disclosed a soft, hydrophilic plastic corneal contact lens, comprising a substantially circular optical correction zone which is shaped for the correction of astigmatism. The lens is soft enough to tend to conform to the shape of the cornea when placed on an eye with corneal astigmatism. The lens comprises at least one discrete lug or flange extending from the periphery of the correction zone, the lug having a radial width measured from the periphery of the correction zone which is less than the radius of the correction zone.
The lug is adapted to engage the sclera of the eye, adjacent to the cornea, at one of the depressions on the eyeball formed between the four rectus muscles attached to the sclera of the eye, to thereby prevent rotation of the lens to maintain the required astigmatism correction.
Description
The invention relates to improvements in contact lenses and more particularly to the improvement of contact lenses made Erom so~t hydrophilic plastics.
The development of soft hydrophilic plastics contact lenses has made it possible for the wearer to wear the lenses for lengthy periods of time without any irritation of the eye. However, a major difficulty has been exper-ienced with such lenses as, owing to the flexibility of the plastic lens, the lens tends to conform to the corneal shape and thereby transmits any corneal astigmatism through the lens to its outer surface. Thus,for example, a circular spherical hydrophilic lens of the correct fitting parameters, when placed on an eye with a corneal astigmat-ism, will tend to conform to this astigmatic shape of the cornea and thus transmits this astigmatism to the anterior surface of the lens resulting in ineffective visual correction.
Various attempts have been made to modify the lens design by providing a lens with a prism ballast or by truncation and by combining therewith an equivalent astigmatic surface which may be on the posterior or anterior surface of the lens.
The prism ballast and/or the truncation, is then located at a required axis so as to locate the axis of the ~ astigmatic surface in such a manner that the resultant cylinderof the cornea is neutralised.
Although optimum visual correction can be achieved in this manner, difficulties arise in keeping the lens located ~ 6. ~ , :
.. .. . . .. . .. ... ... _. _ __ _ . .
4~8 in the proper position. Not only may the action of the lids in blinking rotate the lens off the desired axis, but also ` the lens may fail to remain located in the required position when the head is tilted due to the gravity effect on the base of the locating ballast prism. On the other hand, it is not possible to lock the circular conventional hydrophilic lens in any predetermined axis, whilst maintaining an ade~uate tear flow beneath the lens at all ti~les.
It is an object of this invention to overcome these problems and to assure the position of the lens on the cornea irrespective of movements of the eye lids and movements of the head. To achieve this object, the invention takes advantage of the variation in scleral shape caused by the ocular muscles attached to the external surface of the eye ball.
Four ocular muscles are located in different directions on the eye ball and are generally defined as superior and inferior muscles attached to the eye ball in vertical opposition to each other and nasal and temporal muscles sometimes also - referred to as lateral and medial muscles and attaahed horizontally opposed to each other. These muscles, which are inserted in the sclera of the eye ball, form between them depressions which according to the invention are used to locate the contact lens on the cornea. The object of the invention is therefore achieved by providing a soft hydrophilic plastic corneal - contact lens comprising a substantially circular op-tical correction zone which is shaped for the correction of astigmatism, said lens being soft enough to tend to conform to the shape of the cornea when placed on an eye with corneal astigmatism, at ~ 3 _ ' , .
.. . .
~ 8fl~48 least one discrete lug or flange extending from the periphery of said correction zone, said lug having a radial width measured from the periphery o said correction zone which is less than the radius of said correction zone, said lug being adapted to engage the sclera of the eye adjacent to the cornea at one of the depressions on the eyeball formed between the four rectus muscles attached to the sclera of the eye to thereby prevent rotation of the lens to maintain the re~uired astigmatism correction. The lens itself can then be p.rovided with the required astigmatic anterior and/or posterior surface to correct any residual astigmatism due to corneal and/or optical surfaces posterior to the cornea to provide optimum correction of the ametropia.
By adapting the lug or flange to the depression on the cornea to which the lens is fitted, the position of the lens can be secured without inhibiting the tear flow beneath the lens.
Although the location of the lens can be achieved wi.th one single lug or flange, it may be advantageous to provide the lens with two opposing lugs or four lugs so as to balance the lens and thus avoid any strain on the lens due to movement of the head r and at the same time to engage more than one depression formed between the ocular muscles. It is, however, possible also to provide the lens with three lugs or flanges which may facilitate the proper location of the lens on the cornea.
The particular shape of the lugs or flanges can be determined in each case by the use of clinical trial lenses struc-tured with various radii of curvature for the scleral lugs or flanges.
Several embodiments of the invention will be described _ in detail hereinafker in connection with the drawings in which:
Figure 1 shows schematically an eyeball with muscles attached thereto and the positioning of a lens according to the invention in relation to these muscles.
'' `: :
':
~' '' .
~, - 4a -.i~
.
: . . . ~ . . . .. . .
: : : . . .
. . , .: . . , - . :
: . :
' Fig. 2 shows under A, s, C and D various forms of a corneal lens according to the invention, Fig. 3 shows a cross~section of the lens shown in ig. 2D along line III-III, and In Fig. 1 the eyeball or its sclera is shown schematically supported by its four ocular muscles namely the superior muscle 2, the inferior muscle 3 attached to the eyeball 1 in vertical opposition and the lateral or nasal muscle 4 and the medial or temporal muscle 5 attached to the eyeball 1 in horizontal opposition embedded in the sclera O
~` A corneal lens 6 is positioned on the cornea 7 of the eye and is located by lugs 8 and 9 of the lens which fit into depressions between the muscles 2 and 5 and 3 and 4 respectively. Although generally two lugs will be suffic-ient to locate the corneal lens on the eyeball, any other number of lugs, for example four lugs, can be employed as indicated by the additional lugs 10 and 11 shown in dotted lines in Fig. 1.
In E'ig. 2 various preferred forms of the corneal lens accord1ng to the invention are shown. While Fig. 2A
shows a lens with a central optical correction zone 22 and a single flange 12. Fig. 2B shows a double flanged lens having oppositely arranged flange's 13 and 14.
25 ~ In some cases a triple flanged lens wi-th flanges 15, 16 and 17 may be required as shown in Fig. 2C. To achieve a comple-tely balanced lens arrangement the four- lug arrangement as shown in Fig. 2D can be used whereby the lugs 18, 19, 20 and 21 attached to the optical correction zone 22 fi-t into the depressions in the sclera as shown in Fig. 1 by the lugs 8, 9/ 10 and 11.
A cross-section through the lens arrangement of Fig. 2D is shown in Fig. 3. The central optical correction zone 22 covers the corneal zone 23, while the lugs 18, 20 and 21 (lug 19 not being shown in this cross-section) are adapted to contact the depressions in the sclera as explained a~ove. ~
The dimensions of the central optical correction zone 22 and the ~lange or flanges 12 to 21 are selected according to -the ocular shape of the sclera, corneal curvature/s and corneal diameter.
The power of the central optic zone 22 is determined by accepted professional procedures for power and axis of cylinder.
The parameters of the lens once determ.ined either by calculation or trial lens fitting may be generated by conventional lathing and polishing or moulding of the lens plastic to the required shape and dimensions.
The lens design permits the selection of a range of basic lens parameters which covers the majority of eyes requiring this type of amptropic correction. An example oE a fitting set would be :
25` ABBREVIATIONS
.:
BASE CURVE O~TIC RADIUS BCOR
RADIUS SCLERAL FLANGE RSF
DIAMETER OF OPTIC ZONE DO
FLANGE WIDTHSTANDARD 3 MM.
.
- . . -- : :
- - . ,, : ' , ' ~ " .:
- ' ~, : '. ':
COR _ _ RSF
_, 7.8 13.0 12,0 7.8 13.5 12.0 8.1 13.5 12.0 8.1 14.0 12.5 8.1 14.5 13.0 8.4 13.5 12.0 8.4 14.0 12.5 8.4 14.5 12.5 8.7 14.0 12.5 : 8.7 14.5 13 ~
' .
`The size of the fitting set is limited only by the number of lenses and variatlons in paramaters desire.
The foregoing detailed description of some forms . .i. .
of the invention is not to be considered as limiting the invention to the particular examples. It must be understood that variatlons can be made without departing from the scope of the invention.
~`:
The development of soft hydrophilic plastics contact lenses has made it possible for the wearer to wear the lenses for lengthy periods of time without any irritation of the eye. However, a major difficulty has been exper-ienced with such lenses as, owing to the flexibility of the plastic lens, the lens tends to conform to the corneal shape and thereby transmits any corneal astigmatism through the lens to its outer surface. Thus,for example, a circular spherical hydrophilic lens of the correct fitting parameters, when placed on an eye with a corneal astigmat-ism, will tend to conform to this astigmatic shape of the cornea and thus transmits this astigmatism to the anterior surface of the lens resulting in ineffective visual correction.
Various attempts have been made to modify the lens design by providing a lens with a prism ballast or by truncation and by combining therewith an equivalent astigmatic surface which may be on the posterior or anterior surface of the lens.
The prism ballast and/or the truncation, is then located at a required axis so as to locate the axis of the ~ astigmatic surface in such a manner that the resultant cylinderof the cornea is neutralised.
Although optimum visual correction can be achieved in this manner, difficulties arise in keeping the lens located ~ 6. ~ , :
.. .. . . .. . .. ... ... _. _ __ _ . .
4~8 in the proper position. Not only may the action of the lids in blinking rotate the lens off the desired axis, but also ` the lens may fail to remain located in the required position when the head is tilted due to the gravity effect on the base of the locating ballast prism. On the other hand, it is not possible to lock the circular conventional hydrophilic lens in any predetermined axis, whilst maintaining an ade~uate tear flow beneath the lens at all ti~les.
It is an object of this invention to overcome these problems and to assure the position of the lens on the cornea irrespective of movements of the eye lids and movements of the head. To achieve this object, the invention takes advantage of the variation in scleral shape caused by the ocular muscles attached to the external surface of the eye ball.
Four ocular muscles are located in different directions on the eye ball and are generally defined as superior and inferior muscles attached to the eye ball in vertical opposition to each other and nasal and temporal muscles sometimes also - referred to as lateral and medial muscles and attaahed horizontally opposed to each other. These muscles, which are inserted in the sclera of the eye ball, form between them depressions which according to the invention are used to locate the contact lens on the cornea. The object of the invention is therefore achieved by providing a soft hydrophilic plastic corneal - contact lens comprising a substantially circular op-tical correction zone which is shaped for the correction of astigmatism, said lens being soft enough to tend to conform to the shape of the cornea when placed on an eye with corneal astigmatism, at ~ 3 _ ' , .
.. . .
~ 8fl~48 least one discrete lug or flange extending from the periphery of said correction zone, said lug having a radial width measured from the periphery o said correction zone which is less than the radius of said correction zone, said lug being adapted to engage the sclera of the eye adjacent to the cornea at one of the depressions on the eyeball formed between the four rectus muscles attached to the sclera of the eye to thereby prevent rotation of the lens to maintain the re~uired astigmatism correction. The lens itself can then be p.rovided with the required astigmatic anterior and/or posterior surface to correct any residual astigmatism due to corneal and/or optical surfaces posterior to the cornea to provide optimum correction of the ametropia.
By adapting the lug or flange to the depression on the cornea to which the lens is fitted, the position of the lens can be secured without inhibiting the tear flow beneath the lens.
Although the location of the lens can be achieved wi.th one single lug or flange, it may be advantageous to provide the lens with two opposing lugs or four lugs so as to balance the lens and thus avoid any strain on the lens due to movement of the head r and at the same time to engage more than one depression formed between the ocular muscles. It is, however, possible also to provide the lens with three lugs or flanges which may facilitate the proper location of the lens on the cornea.
The particular shape of the lugs or flanges can be determined in each case by the use of clinical trial lenses struc-tured with various radii of curvature for the scleral lugs or flanges.
Several embodiments of the invention will be described _ in detail hereinafker in connection with the drawings in which:
Figure 1 shows schematically an eyeball with muscles attached thereto and the positioning of a lens according to the invention in relation to these muscles.
'' `: :
':
~' '' .
~, - 4a -.i~
.
: . . . ~ . . . .. . .
: : : . . .
. . , .: . . , - . :
: . :
' Fig. 2 shows under A, s, C and D various forms of a corneal lens according to the invention, Fig. 3 shows a cross~section of the lens shown in ig. 2D along line III-III, and In Fig. 1 the eyeball or its sclera is shown schematically supported by its four ocular muscles namely the superior muscle 2, the inferior muscle 3 attached to the eyeball 1 in vertical opposition and the lateral or nasal muscle 4 and the medial or temporal muscle 5 attached to the eyeball 1 in horizontal opposition embedded in the sclera O
~` A corneal lens 6 is positioned on the cornea 7 of the eye and is located by lugs 8 and 9 of the lens which fit into depressions between the muscles 2 and 5 and 3 and 4 respectively. Although generally two lugs will be suffic-ient to locate the corneal lens on the eyeball, any other number of lugs, for example four lugs, can be employed as indicated by the additional lugs 10 and 11 shown in dotted lines in Fig. 1.
In E'ig. 2 various preferred forms of the corneal lens accord1ng to the invention are shown. While Fig. 2A
shows a lens with a central optical correction zone 22 and a single flange 12. Fig. 2B shows a double flanged lens having oppositely arranged flange's 13 and 14.
25 ~ In some cases a triple flanged lens wi-th flanges 15, 16 and 17 may be required as shown in Fig. 2C. To achieve a comple-tely balanced lens arrangement the four- lug arrangement as shown in Fig. 2D can be used whereby the lugs 18, 19, 20 and 21 attached to the optical correction zone 22 fi-t into the depressions in the sclera as shown in Fig. 1 by the lugs 8, 9/ 10 and 11.
A cross-section through the lens arrangement of Fig. 2D is shown in Fig. 3. The central optical correction zone 22 covers the corneal zone 23, while the lugs 18, 20 and 21 (lug 19 not being shown in this cross-section) are adapted to contact the depressions in the sclera as explained a~ove. ~
The dimensions of the central optical correction zone 22 and the ~lange or flanges 12 to 21 are selected according to -the ocular shape of the sclera, corneal curvature/s and corneal diameter.
The power of the central optic zone 22 is determined by accepted professional procedures for power and axis of cylinder.
The parameters of the lens once determ.ined either by calculation or trial lens fitting may be generated by conventional lathing and polishing or moulding of the lens plastic to the required shape and dimensions.
The lens design permits the selection of a range of basic lens parameters which covers the majority of eyes requiring this type of amptropic correction. An example oE a fitting set would be :
25` ABBREVIATIONS
.:
BASE CURVE O~TIC RADIUS BCOR
RADIUS SCLERAL FLANGE RSF
DIAMETER OF OPTIC ZONE DO
FLANGE WIDTHSTANDARD 3 MM.
.
- . . -- : :
- - . ,, : ' , ' ~ " .:
- ' ~, : '. ':
COR _ _ RSF
_, 7.8 13.0 12,0 7.8 13.5 12.0 8.1 13.5 12.0 8.1 14.0 12.5 8.1 14.5 13.0 8.4 13.5 12.0 8.4 14.0 12.5 8.4 14.5 12.5 8.7 14.0 12.5 : 8.7 14.5 13 ~
' .
`The size of the fitting set is limited only by the number of lenses and variatlons in paramaters desire.
The foregoing detailed description of some forms . .i. .
of the invention is not to be considered as limiting the invention to the particular examples. It must be understood that variatlons can be made without departing from the scope of the invention.
~`:
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A soft hydrophilic plastic corneal contact lens comprising a substantially circular optical correction zone which is shaped for the correction of astigmatism, said lens being soft enough to tend to conform to the shape of the cornea when placed on an eye with corneal astigmatism, at least one discrete lug or flange extending from the periphery of said correction zone, said lug having a radial width measured from the periphery of said correction zone which is less than the radius of said correction zone, said lug being adapted to engage the sclera of the eye adjacent to the cornea at one of the depressions on the eyeball formed between the four rectus muscles attached to the sclera of the eye to thereby prevent rotation of the lens to maintain the required astigmatism correction.
2. A corneal lens according to claim 1 having at least two and no more than four lugs or flanges, at least two of said lugs or flanges being arranged on diametrically opposite sides of the optical correction zone, each of said lugs being adapted to engage the sclera of the eye adjacent to the cornea at one of the depressions on the eyeball formed between the four rectus muscles attached to the sclera of the eye to thereby prevent rotation of the lens to maintain the required astigmatism correction.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPD3762 | 1978-03-21 | ||
| AU376278 | 1978-03-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1108448A true CA1108448A (en) | 1981-09-08 |
Family
ID=3694230
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA323,900A Expired CA1108448A (en) | 1978-03-21 | 1979-03-21 | Contact lenses |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1108448A (en) |
| GB (1) | GB2016736B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4435050A (en) * | 1980-02-26 | 1984-03-06 | Stanley Poler | Contact lens assembly with haptic and method for making the same |
| GB2117130B (en) * | 1982-03-10 | 1985-09-11 | American Optical Corp | Contact lens having lateral carrier |
| DE3817334A1 (en) * | 1988-05-20 | 1989-11-30 | Hecht Gmbh Kontaktlinsen | Contact lens |
| AU2011320709B2 (en) | 2010-10-26 | 2015-12-17 | Alcon Inc. | Ophthalmoscopic surgical contact lens |
-
1979
- 1979-03-20 GB GB7909771A patent/GB2016736B/en not_active Expired
- 1979-03-21 CA CA323,900A patent/CA1108448A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2016736A (en) | 1979-09-26 |
| GB2016736B (en) | 1982-04-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |