Mastering the Presbyopic Surgery Lenses &amp; Phakic IOLs

Garg, Ashok; Rosen, Emanuel; Lin, JT; Goes, Frank; Lovisolo, Carlo; Malyugin, Boris

doi:10.5005/jp/books/10498

Cited by 2 publications

(4 citation statements)

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“…The total system power is given by D=1000n/F (D in diopter, F in mm),which is determined by the corneal power (D') and lens power (D) as follows where nj (j=1, 2, 3, 4) are the refractive index for the aqueous, vitreous, cornea, and lens, respectively, the anterior and posterior radius of curvatures (in the unit of mm) of the cornea and lens are given by (r, r') and (R, R'), respectively, noting that R'<0 for a concave surface. Finally, S is the effective anterior chamber depth, related to the anterior chamber depth (ACD), S 1 , by S=S 1 +P11+0.05 (in mm), where P11 is the distance between the lens anterior surface and its first principal plane, and 0.05 mm is a correction amount to include the effect of corneal thickness (assumed to be 0.55 mm) [17,18]. The thickness terms in Eq.…”

Section: The Effective Eye Modelmentioning

confidence: 99%

“…The increase of S 1 results in a hyperopia shift (HS), whereas S 2 results in a myopia shift (MS), where M6 is about two times of M5, which has two competing terms as shown by Eq.(6). The rather high change rate M6=-2.67 (D/mm) has a significant impact on the onset of emmetropization and myopia, which are governed by the correlation among the growth of axial length (L=S 1 +S 2 +T) and the power decrease of the cornea and lens when an eye grows [18]. The change rate M7 having a lower value than M8 can be analyzed as follows.The competing between the MS (due to the increase of ACD, S 1 ) and the HS (due to the associate decrease of S 2 for a fixed axial length (L=S 1 +S 2 +T) results in a net hyperopic-shift, because the hyperopic component is always the dominant one, since the corneal power (D) is always less than the total system power (D) in Eq.(3.a).…”

Section: Effects Of S 1 and Smentioning

confidence: 99%

“…(5) has not been explored before.The hyperopic shift due to the increase of S 1 is equivalent to a myopic-shift when S 1 decreases, or a forward movement of the lens. This feature is important for presbyopia accommodation which is contributed by two components: the lens curvature decrease and the lens forward movement [18,1]. The lens forward movement is also the main feature in an accommodative IOL, and our formulas, Eq.…”

Section: Effects Of S 1 and Smentioning

confidence: 99%

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Analysis of Accommodation Gain of Presbyopia Eye After Laser Ablation (or Shrinkage) of Sclera Via Lens Reshaping and Lens Anterior Shift

Lin¹

2021

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Purpose: To derive and provide analytic formulas for an accommodative gain of presbyopia eyes. via sclera ablation and/or thermal shrinkage such that the lens is reshaped and/or its position is shifted. New mechanisms are also proposed. Study Design: To increase the accommodation of presbyopia. Place and Duration of Study: New Taipei City, Taiwan, between June 2021 and July 2021. Methodology: Accommodation gain is calculated by a 4-component theory, in which the rate functions are derived by an effective eye model for the change of anterior curvature of the lens and its anterior shift. The measured data of accommodative response of the lens versus the lens curvature change and anterior shift are analyzed. The measured net change of the posterior vitreal zonules (PVZ) length and the space between the ciliary body and lens (CLS) during the accommodation are also analyzed. Results: The accommodative gain (AG) is mainly due to the change of lens anterior curvature and its anterior shift. The AG per diopter change of the reshaped lens is 0.62 to 0.68 by our formulas, comparing to the measured average value M'=0.69.The efficacy of LASA (or AG) is proportional to the amount of scleral tissue removed (or shrinkaged), such that more space is produced for the change of PVZ and CLS from a UCS to AS for accommodation. Conclusion: The AG is proportional to the amount of scleral tissue removed (or shrinkaged), such that more space is produced for the change of PVZ and CLS from a UCS to AS for accommodation.

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Section: The Effective Eye Modelmentioning

confidence: 99%

Section: Effects Of S 1 and Smentioning

confidence: 99%

Section: Effects Of S 1 and Smentioning

confidence: 99%

See 1 more Smart Citation

Analysis of Accommodation Gain of Presbyopia Eye After Laser Ablation (or Shrinkage) of Sclera Via Lens Reshaping and Lens Anterior Shift

Lin¹

2021

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“…The principles of presbyopia were given by the classical hypothesis of von Helmholtz [1][2][3][4] and Schachar [5][6][7] and the modern theory of Lin [8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Efficacy Theory and Proposed Protocol for Presbyopia Correction using Scleral Softening by Non-invasive Infrared Diode Lasers

Lin

2022

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Purpose: To derive and provide analytic formulas and proposed protocol for accommodative gain of presbyopia eyes via laser scleral softening, which causes increased space between ciliary body and lens (SCL) and mobility of the posterior vitreal zonules (PVZ). Study Design: To increase the accommodation of presbyopia by laser scleral heating/softening. Place and Duration of Study: New Taipei City, Taiwan, between April 2022 and June 2022. Purpose: To analyze the safety and efficacy of presbyopia treatment via scleral softening. Methodology: The scleral softening efficacy is calculated based on the rate equation of scleral tissue with a rate coefficient given by an Arrhenius formula, Temperature spatial and temporal profiles are given by the numerical solutions of a heat diffusion equation with a volume heating source. Various effective depths including tissue damage depth, temperature penetration depth and conversion depth, governed by tissue absorption coefficient, light intensity and dose (or irradiation time), and the related threshold values, are introduced in replacing the conventional penetration depth based on a Beer's law. Results: Given the the temperature spatial and temporal profiles, scleral softening efficacy can be calculated. Scleral surface damage can be prevented by cooling window. The suggested protocol for scleral softening treatments include: a diode laser at about 1.45 to 1.5 µm or about 1.86 to1.9 µm, or about 2.0 to 2.15 µm, wavelength (with absorption coefficient about 20 to 100 cm-1); laser power about 0.2 to 0.8 W per spot, having a total of 4 to 16 spots; and irradiation time of 100 to 600 ms. Results of corneal thermal shrinkage are demonstrated by the topography changes of pig eyes, in which the scleral softening does not affect the corneal shapes. The accommodative gain is proportional to the softening efficacy (Seff) of the scleral tissue after a thermal laser leading to the increase of PVZ mobility and SCL. However, the actual relation of Seff and the PVZ and SCL changes require measured data. Conclusion: Safety and efficacy of scleral softening for presbyopia treatment depend upon the laser parameters (intensity, dose, spot size, wavelength) and the effective depths. By choosing the laser treated areas, a dual function treatment using scleral softening for presbyopia, and cornea stromal shrinkage for hyperopia is proposed and demonstrated by topography of pig eyes.

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Mastering the Presbyopic Surgery Lenses & Phakic IOLs

Cited by 2 publications

References 0 publications

Analysis of Accommodation Gain of Presbyopia Eye After Laser Ablation (or Shrinkage) of Sclera Via Lens Reshaping and Lens Anterior Shift

Analysis of Accommodation Gain of Presbyopia Eye After Laser Ablation (or Shrinkage) of Sclera Via Lens Reshaping and Lens Anterior Shift

Efficacy Theory and Proposed Protocol for Presbyopia Correction using Scleral Softening by Non-invasive Infrared Diode Lasers

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