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Optics of Contact Lenses PowerPoint Presentation

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Description : Check out this medical PowerPoint presentation titled "Optics of Contact lenses” by Dr.C.R.Thirumalachar.

This medical PowerPoint presentation is about contact lenses, thin, curved lenses that are placed directly on the surface of the eye to correct refractive errors and provide clear vision. They are typically made of soft or rigid materials and come in various sizes, shapes, and designs to fit different eye shapes and vision needs.

The optics of contact lenses refer to how they alter the way light enters and focuses on the eye. Like eyeglasses, contact lenses work by correcting refractive errors, such as myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia.

When light enters the eye, it is refracted (bent) by the cornea and the lens to focus onto the retina, where images are formed and transmitted to the brain. Refractive errors occur when the cornea and/or lens cannot refract light properly, causing images to appear blurry or distorted.

Contact lenses correct refractive errors by altering the path of light as it enters the eye. They do this by changing the shape and curvature of the cornea, and in the case of multifocal contact lenses, by providing different powers of correction for different distances.

Soft contact lenses are typically made of hydrogel or silicone hydrogel materials that are designed to conform to the shape of the eye and provide a smooth optical surface for light to pass through. Rigid gas permeable (RGP) lenses, on the other hand, are made of a hard, oxygen-permeable material that allows more oxygen to reach the eye and provides a sharper, crisper vision than soft lenses.

In addition to correcting refractive errors, contact lenses can also be designed to correct other visual anomalies, such as higher-order aberrations, that cannot be corrected with eyeglasses. This can provide even sharper, clearer vision for people with more complex visual needs.

Overall, the optics of contact lenses are complex and depend on various factors, such as the lens material, design, power, and fit. It is important to have a comprehensive eye exam and contact lens fitting by a qualified eye care professional to ensure that the contact lenses provide optimal visual acuity and comfort.

Tags : contact lenses, clear vision, refractive errors, myopia, nearsightedness, hyperopia, farsightedness, astigmatism, presbyopia, Ophthalmology, Ophthalmology PowerPoint presentation

Published on : Jun 20, 2023 | Views : 2250 | Downloads : 0

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Transcript

Slide 1-

Optics of Contact lenses Dr.C.R.Thirumalachar
Slide 2-

Introduction Major refraction of eye occurs at AIR/CORNEA INTERFACE. Spectacle lenses- most common method of correcting ref. errors Disadv of spectacles- too many, though advantages are considerable Development of contact lenses – quest for better looks and better vision
Slide 3-

Idea of contact lenses- Leonardo Da Vinci Herschel & Fick evolved its practical use Blown, Ground, moulded lenses Lathe cutting, injection moulding & spin moulding Evolved better materials , polymer chemistry –Hard, soft, semisoft & gas permeable .
Slide 4-

Optics Contact lens placed in contact with cornea with a thin fluid film in between It eliminates cornea as ref. surface Afocal contact lens: ant & post curvatures of CL same as cornea No optical power Surface irregularities of cornea are taken care of
Slide 5-

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Fluid lens Curvature of posterior surface of CL derives the power of CL Glass lens Post surface of CL same curvature as cornea CL power derived by curvature of ant surface of CL
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Combined lens Curvature of both surfaces contribute Both glass lens & fluid lens give dioptric power.
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Slide 10-

Physical factors of CL Overall diameter of Hard lenses- 8mm, about 1.5-2mm less than corneal diameter GP & soft lenses allow larger diameters Larger lenses are more stable Larger lenses – vaulting effect Optical zone- central zone of 5-6mm Average of maximum & minimum pupil size
Slide 11-

3. Curvatures Ant. Curvatures: C.A.C (Cental ant.Curvature)- ant surface of optical zone P.A.C. (Peripheral ant curvature): slope on the periphery of ant surface I.A.C. (Intermediate anterior curvature) for high power plus & minus lenses in between CAC & PAC
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Posterior curvatures: CPC (central post curve )– Base curve to fit the front surface of cornea I.P.C.(Intermediate)- flatter than CPC P.P.C.(Peripheral)- flatter than IPC These are meant to serve as tear fluid reservoir. These form ski for contact lens movement. CL can have bicurve, tricurve or even multi curve contour design.
Slide 14-

4. Blend Smooth area of transition of radius of curvature from one curve to other 5. Edge-Polished & blended union of ant & post surfaces Too sharp- may dig into corneal epithelium Too thick- may irritate the lids Edge lift or Z factor- comfort & stability
Slide 15-

Power of CL determined by central ant & post surfaces at O.Z. determined by the ammetropic correction required Tint- to reduce the glare for cosmesis Ref. error determined by retinoscopy Curvature determined by keratometry Fit can be assessed by fluorescein pattern- flat , steep, ideal
Slide 16-

Special situations Keratoconus, Aphakia, Pseudophakia, Post keratoplasty
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Thank you