A basic and useful parameter, especially for imaging systems, is the Modulation Transfer Function, or MTF. Over the past few decades technological advances, ...

The 10QM20HM.15 is a 25.4 mm diameter, 6.35 mm thick High Energy Nd:YAG Laser Mirror coated for the fundamental 1064 nm wavelengths. Its reflectivity at this wavelength is greater than 99% for both s- and p-polarization, and it is optimized for 45° AOI. The back surface is polished.

Spherical aberrationimage

Fused Silica is synthetic amorphous silicon dioxide of extremely high purity. This non-crystalline, colorless silica glass combines a low content of inclusions with high refractive index homogeneity, a very low thermal expansion coefficient, and excellent transmittance in the wavelength regime from UV to NIR. As a result, these mirrors will perform better with temperature fluctuations and is ideal for high-energy laser applications due to its high energy damage threshold.

In this issue of JOVR, a double-blind randomized controlled trial conducted by Jafarinasab et al16 compares spherical aberration and contrast sensitivity among 3 different types of aspheric IOLs (Tecnis, Akreos AO, and Acrysof IQ) and one spherical IOL (Sensar). Significantly higher spherical aberration was reported with the spherical IOL and the zero-aberration aspheric IOL as compered to the negative aberration aspheric IOLs, however this advantage was pupil-size dependent. With increased pupil size from 4 to 6 mm, an increase in spherical aberration was observed for all four types of IOLs, however significantly more with the spherical IOL. Contrast sensitivity function under mesopic conditions and at low spatial frequencies (1.5 to 3 cpd) was significantly higher in the Tecnis group as compared to the others. At higher spatial frequencies (12 to 18 cpd), Acrysof IQ worked significantly better. The authors concluded that the performance of aspheric IOLs is pupil dependent and that their function deteriorates to some extent under mesopic conditions, as there was no significant difference between spherical and aspheric IOLs in mesopic contrast sensitivity at 6 cpd.

Spherical aberrationin a lens

Conventional spherical IOLs increase the positive spherical aberration in the eye following cataract extraction.13,14 In 2002, an aspheric IOL design was introduced to compensate for the positive spherical aberration of the cornea.15 Aspheric IOLs have been designed with an anterior prolate suface (Tecnis, Advanced Medical Optics), a posterior prolate surface (Acrysof IQ, Alcon Laboratories), or with both anterior and posterior prolate surfaces (Akreos AO, SofPort AO and L161 AO, Bausch & Lomb) and compensate for corneal spherical aberration to varying degrees.

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Spherical aberrationexample

A diffraction grating is an optical element, which separates (disperses) polychromatic light into its constituent wavelengths (colors).

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Natural sunlight and almost every other form of artificial illumination transmits light waves whose electric field vectors vibrate in all perpendicular ...

Apr 21, 2010 — ISO 12233 Test Chart. The ISO standard for measuring resolution of electronic still imaging" cameras is 12233, available only from the ...

There are several studies comparing different types of spherical and aspheric IOLs under various conditions and with varying protocols. The readers should be careful about applying the results and accepting them as general rules.

Spherical aberrationphotography

Spherical aberrationand chromaticaberration

Advancements in cataract surgery and intraocular lens (IOL) design have optimized the postoperative optical performance of the pseudophakic eye. One of the recent spotlights of IOL design has been formulating optical properties similar to a clear, young lens and addressing spherical aberration.

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Stage Micrometers, Calibration Scales and Grids, PS8 Stage Micrometer 1mm/0.01mm.

Spherical aberrationcause

Spherical aberrationin mirrors

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Spherical aberrationcorrection

Surface Roughness Standards used in optics and photonics applications are available at Edmund Optics.

Spherical aberration in the human eye is a combination of the positive spherical aberration of the cornea,1–3 and the negative spherical aberration of the crystalline lens.4,5 In young eyes, the positive spherical aberration of the cornea is compensated by the negative spherical aberration of the lens; as a result, overall spherical aberration in the young eye is low.2,3,6 As the eye ages, the optical properties of the crystalline lens change,4,7 resulting in overall positive spherical aberration2,8,9 and decreased optical performance. Spherical aberrations generally reduce the contrast of the retinal image10,11 and affect visual performance, especially under mesopic conditions.12

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Although this study is a well-designed clinical trial with interesting results, the readers should keep in mind that the best way to compare two groups with analysis of variance (ANOVA) is using post hoc tests such as Bonferroni adjustment of type one error. This is one of the reasons for discrepancies in the results among different studies. Another explanation could be different measurement protocols.

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