Myodisc
Encyclopedia
A myodisc or myopic disk is a corrective lens
with a steep concave curvature that is fitted on the posterior surface of a carrier lens, or a high power single-vision lens specially ordered with slab-off the edge, creating a central prescription disc. These are used for correction of extremely high myopia
often seen in low vision patients. Myodiscs are not a preferred lens type, but are the least expensive option among available lenses fitted for minus powers beyond -12 diopters. They are cheap to produce but cause scotoma
, a ringed blind spot. As a result, most practitioners encourage using other lens styles.
The myodisc, has been categorized as a lenticular lens
. These are rarely prescribed sets of specialty lenses used in cases of extremely poor vision, or near blindness. The lenticular subrogate nomenclature has been extensively used in ophthalmology
, requiring scope of context. Newer lens products can also be found using vague terminology. Low vision clinics in under-privileged cost-reducing centers list the myodisc for correction of high myopia.
Another factor is spectacle frame selection. Large eyesize fashion frames are impractical. Lens box diagrams used in dispensing should consider edge thickness, reduced by smaller eyesizes, and oval/circular shapes. The bridge should be fitted to increase surface contact using rigid nose support if possible. Weight problems associated with these lenses are often not anticipated by untrained dispensaries, and end products are disappointing after inclusion of special instructions to fabricating labs.
In some cases, more aesthetic aspheric lens
designs can be fitted, reducing Scotoma
associated with lenticulars.
Corrective lens
A corrective lens is a lens worn in front of the eye, mainly used to treat myopia, hyperopia, astigmatism, and presbyopia. Glasses or "spectacles" are worn on the face a short distance in front of the eye. Contact lenses are worn directly on the surface of the eye...
with a steep concave curvature that is fitted on the posterior surface of a carrier lens, or a high power single-vision lens specially ordered with slab-off the edge, creating a central prescription disc. These are used for correction of extremely high myopia
Myopia
Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...
often seen in low vision patients. Myodiscs are not a preferred lens type, but are the least expensive option among available lenses fitted for minus powers beyond -12 diopters. They are cheap to produce but cause scotoma
Scotoma
A scotoma is an area of partial alteration in one's field of vision consisting of a partially diminished or entirely degenerated visual acuity which is surrounded by a field of normal - or relatively well-preserved - vision.Every normal mammalian eye has a scotoma in its field of vision, usually...
, a ringed blind spot. As a result, most practitioners encourage using other lens styles.
The myodisc, has been categorized as a lenticular lens
Lenticular lens
A lenticular lens is an array of magnifying lenses, designed so that when viewed from slightly different angles, different images are magnified...
. These are rarely prescribed sets of specialty lenses used in cases of extremely poor vision, or near blindness. The lenticular subrogate nomenclature has been extensively used in ophthalmology
Ophthalmology
Ophthalmology is the branch of medicine that deals with the anatomy, physiology and diseases of the eye. An ophthalmologist is a specialist in medical and surgical eye problems...
, requiring scope of context. Newer lens products can also be found using vague terminology. Low vision clinics in under-privileged cost-reducing centers list the myodisc for correction of high myopia.
Another factor is spectacle frame selection. Large eyesize fashion frames are impractical. Lens box diagrams used in dispensing should consider edge thickness, reduced by smaller eyesizes, and oval/circular shapes. The bridge should be fitted to increase surface contact using rigid nose support if possible. Weight problems associated with these lenses are often not anticipated by untrained dispensaries, and end products are disappointing after inclusion of special instructions to fabricating labs.
In some cases, more aesthetic aspheric lens
Aspheric lens
An aspheric lens or asphere is a lens whose surface profiles are not portions of a sphere or cylinder. In photography, a lens assembly that includes an aspheric element is often called an aspherical lens....
designs can be fitted, reducing Scotoma
Scotoma
A scotoma is an area of partial alteration in one's field of vision consisting of a partially diminished or entirely degenerated visual acuity which is surrounded by a field of normal - or relatively well-preserved - vision.Every normal mammalian eye has a scotoma in its field of vision, usually...
associated with lenticulars.