PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 7667019

Blur due to pupil area when using progressive addition spectacles.

D Burns
View original source ↗Export metadata ↓

Abstract

The progression zone of a progressive addition spectacle lens cannot provide a sharp retinal image as it presents the pupil with a range of powers through which to view an object. The resulting blur is explored mathematically. The nature of this blur is extraordinary but its visual significance is very slight and is less than previously believed. Peripheral astigmatism, found in all such lenses, may lower their visual performance.

Explore related subjects

AstigmatismEyeglassesHumansMathematicsOptics and PhotonicsPupilRetinaJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

D Burns. 1995. Blur due to pupil area when using progressive addition spectacles.. https://pubmed.ncbi.nlm.nih.gov/7667019/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Paraxial optics of astigmatic systems: relations between the wavefront and the ray picture approaches.

PURPOSE: The paraxial propagation of astigmatic wavefronts through astigmatic optical systems can be described by the augmented step-along method (ASAM). Its equivalence to the linear ray optics approach is considered in detail. METHODS: The ASAM is exploited to derive paraxial ray paths through a general coaxial astigmatic system. RESULTS: Starting from the information inherent in the ASAM all 2x2 submatrices rendering the general 4x4 transference of linear optics can be generated. This proves the complete equivalence of both approaches. Additionally, we show that the symplectic relations are automatically obeyed in the ASAM. CONCLUSIONS: The ASAM offers a complete alternative to describe the paraxial optics of astigmatic optical systems. According to the ASAM, an optical system is fully characterized by the back vertex vergence and the angular magnification matrix. Hence, a complete description of the paraxial optics of an eye should not only report the state of refraction but the angular magnification matrix as well, although it is not yet very common. The magnification matrix might be important in cases of anisometropia or the design of progressive addition lenses. Yet, a simple clinical procedure to determine the angular magnification matrix is missing.

Astigmatism↗
PubMed2007

Status of toric intraocular lenses.

PURPOSE OF REVIEW: To provide an update on the status of toric intraocular lenses. These lenses can be used as an alternative or adjunct to corneal astigmatic incisions for correcting preexisting astigmatism in patients with cataracts. They are a particularly attractive option in those cases where limbal-relaxing incisions are not powerful or predictable enough. Other toric lenses may correct astigmatism in addition to spherical refractive errors in phakic patients. RECENT FINDINGS: Toric lenses have continued to gain popularity with the US Food and Drugs Administration (FDA) approval of the Acrysof Toric intraocular lenses. This lens is designed to be implanted in patients undergoing cataract removal and who have significant preexisting corneal astigmatism. In the FDA clinical trial, study patients received one of the three cylindrical powers, and control patients received a standard monofocal intraocular lenses. The study found that the Acrysof Toric intraocular lenses provided excellent visual outcomes and exhibited excellent rotational stability. With the Acrysof Toric intraocular lenses, the average lens rotation was less than 4 degrees from the lens' initial placement at 6 months after surgery. SUMMARY: Toric intraocular lenses provide excellent vision for astigmatic cataract patients, and new designs are significantly improving visual acuity by minimizing the risk of rotation.

Astigmatism↗