Different aberrations related to ophthalmic lens

Importance in Visual Quality in aberrations:
Higher-order aberrations particularly affect contrast sensitivity, night vision, and overall visual quality. For patients, this means difficulty with tasks like reading, driving at night, or recognizing faces, even if they have standard corrective lenses.

1. Different Aberrations Related To Ophthalmic Lens Jyoti Pandit Pediatric Optometrist

2. INTRODUCTION Our eyes turn behind the lens to view through the off-axis. It is then the lens aberrations assume importance: Primary direction, Secondary direction, Tertiary direction

3. TYPES OF ABERRATIONS:

4. CHROMATIC ABERRATION Fig: Axial chromatic aberration Peripheral colour fringes around the object which is more pronounced off-axis. The higher the power of the lens—the greater is the chromatic aberration.

5. SPHERICAL ABERRATION Peripheral rays bend more than the paraxial rays. “ Night Myopia ”- The typical amount of night myopia is about 0.5D, but it can be as large as 1.25D. Effect on retinal image: symmetrical blur like defocus which is reduced by the size of pupil.

6. MARGINAL ASTIGMATISM A small angle aberration. When a narrow beam of light enters obliquely to lens axis of a spherical lens, the refracted rays become astigmatic. The emerging rays, instead of uniting in a single image point, form two foci at right angles to one – another with a disk of least confusion .

7. COMA It is applied to oblique rays coming from points not lying on the principal axis. Oblique rays passing through the periphery of the lens are deviated more than the central rays and come to focus near the principal axis. The result is unequal magnification of the image formed by the different zones of the lens. The composite image is not circular , but elongated like a comet and coma

8. CURVATURE OF FIELD Curvature of field affects peripheral vision. A phenomenon which causes the image formation of a plane to become curved like the inside of a shallow bowl, preventing the lens from producing a flat image of a flat object. In the human eye the curvature of the retina compensates for the effect of curvature of field. So this is an advantageous aberration in the human eye.

9. DISTORTION Aberration of thick lenses. Object is sharply imaged but does not retain its shape.

10. REFERENCE Ajay Kumar Bhootra , Jaypee Publication, Ophthalmic lenses. Vagge A, Ferro Desideri L, Del Noce C, Di Mola I, Sindaco D, Traverso CE. Blue light filtering ophthalmic lenses: A systematic review. Semin Ophthalmol . 2021 Oct 3;36(7):541-548. doi : 10.1080/08820538.2021.1900283. Epub 2021 Mar 18. PMID: 33734926. Eyewiki

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