IN THE NAME OF GOD

SELECTION OF APPROPRIATE IOL IN CATARACT SURGERY

HISTORY The history of the modern intraocular lens (lOL) began in 1949 when Harold Ridley implanted a polymethylmethacrylate (PMMA) I0L following an extracapsular cataract extraction. Although early IOLs were associated with a high rate of complications, including uveitis, glaucoma, and dislocation, more recent improvements in lens design and surgical techniques have greatly reduced the incidence of postoperative problems. I0Ls are now used in 98% of cataract extractions in the United States.

Types of IOLs In the 1990s, most I0Ls were made with PMMA optics and polypropylene or PMMA supporting haptics. Removal of a cataractous lens through incisions as small as 3 mm, have led to the development of foldable I0Ls manufactured from newer materials such as silicone, acrylic,and hydrogels. Although the role of ultraviolet light in contributing to retinal damage is still unclear, ultraviolet filters may be included in I0Ls. Although the role of ultraviolet light in contributing to retinal damage is still unclear, ultraviolet filters may be included in I0Ls.

Larger optics (6mm+) are:  Less centeration dependent  Have fewer dysphotopic symptoms in patients with large pupils or under mydriatic conditions  Lower rates of posterior capsule opacification (PCO)

Haptic size  Haptic size needs to be appropriate for bag fixation without causing posterior capsular folds as these can cause symptoms from scattering of light or PCO.  An appropriate IOL with a larger haptic is required for sulcus fixation.

IOL materials & designs  Hydrophilic IOL have a better uveal biocompatibility (lower inflammatory cell attachment).  Hydrophobic IOL have a better performance in preventing PCO.  Square edge optic has been shown to be an important factor in preventing PCO but increases dysphotopic symptoms.

Two basic lens designs are currently in use,differentiated by the plane in which the lens is placed and the tissue supporting the lens. Anterior Chamber Lenses Anterior Chamber Lenses Posterior Chamber Lenses Iris plane lenses Iris plane lenses attached or sutured to the iris. attached or sutured to the iris.

Techniques of "piggyback" lenses, in which two IOLs are inserted in an eye either at the same time or sequentially. These may be useful in two situations: when the actual postoperative refraction These may be useful in two situations: when the actual postoperative refraction is very different from what was desired and expected and when the required IOL power is higher than what is commercially available.

Minus-power IOLs are available for extreme myopes. Toric IOLs may be useful to partially correct high degrees of astigmatism. Toric IOLs may be useful to partially correct high degrees of astigmatism.

Anterior Chamber Lenses AC IOL may be inserted following intracapsular or extracapsular cataract extraction. A particular problem associated A particular problem associated with the use of rigid anterior chamber lenses is inaccurate estimation of the size of the lens required to traverse the anterior chamber. The lens support elements must rest lightly in the chamber angle without trauma to the angle Such unstable fixation can lead to persistent uveitis, hyphema, iris atrophy, corneal decompensation, and glaucoma (UGH syndrome).

Artisan iris-fixation IOL  Since it is fixated to the mid-peripheral iris, not the angle or sulcus, it has the advantage of being a one-size-fits-all length.  It is 8.5 mm in length with a 5.0 or 6.0 mm PMMA optic.  A 12 o'clock incision will require side port incisions at 10 and 2 o'clock.

Artisan iris-fixation IOL  The "claw“ haptics are fixated to the iris by a process called enclavation.  The long axis is ultimately oriented perpendicular to the axis of the incision.

Artisan iris-fixation IOL

Posterior Chamber Lenses The lens is supported by loops placed either in the capsular bag or in the ciliary sulcus. PC IOL may be used with a torn posterior capsule in front of an intact anterior capsule. It may be used with no remaining capsule by suturing the haptics into the ciliary sulcus with nonabsorbable suture material.

Toric IOL (STAAR)  In Corneal astigmatism of > 1.5 D that is present in 15% to 29% of patients.  FDA-approved, single-piece, plate-haptic, foldable silicone.  The 2.0 D I0L corrects 1.4 D of corneal astigmatism and the 3.5 D I0L corrects 2.3 D.

Patient Selection  1.5 to 3.5 D of regular corneal astigmatism.  Not be appropriate for diabetic patients who require an acrylic IOL optic, such as patients with a history of iritis,or patients who may require silicone oil for retinal detachment repair.

Outcomes  Uncorrected visual acuity of >20/40 in 48% to 84% of patients.  Postoperative astigmatism was <0.50 D in 48% of patients and < 1.00 D in 75% to 81% of patients.

Complications  10° off-axis rotation reduces the correction by approximately 1/3  20° off-axis rotation reduces the correction by 2/3  Off-axis correction of> 30° can actually increase the cylindrical refractive error

Multifocal lOLs Conventional IOLs focus on distance only. Patient want to see with acceptable clarity over a range of distances. This ability may be further augmented if the patient is left with a residual refractive cylinder such as a myopic astigmatism. An alternative approach to this problem is to correct one eye for distance and the other for near vision, so-called monovision.

Depending on the type of multifocal IOL and the viewing situation, both near and far foci may be presented to the eye at one time.

Factors that need particular consideration with multifocal IOLs are: Lens centeration ( intact posterior capsule) Pupil size Accuracy of IOL power calculation Low preoperative and postoperative astigmatism

Array (AMO) multifocal silicone IOL  The optical design is distance-dominant with a functional add power +2.5 D at the corneal plane.  The focusing of the incoming light is divided 50% for distance, 30% for near, and 20% for intermediate.

Array (AMO) multifocal lOL. Note circular zones of correction shown in lens optic.

Patient Selection  Adaptable,relatively easy-going people  Good potential vision  Less than 1.0 D of residual astigmatism.  Pupil should be at least 4.0 mm diameter

Outcomes  4 times more likely to never wear glasses(32% vs 8%).  At 3 months binocular uncorrected distance acuity of 20/40 or better and near acuity of at least J3 in 96% vs 65%.

Side Effects and Complications  More glare (11 % vs 1%)  More haloes (15% vs 6%) (over several months subside)  Some reduction in contrast sensitivity  1% of patients have insisted on exchange for a monofocal lOL.

Accommodating IOLs  Investigations found that during ciliary muscle contraction there was a forward displacement of the IOL.  Two IOLs that use this accommodative approach are the CrystaLens and the Akkommodative ICU.  Regression does not seem to be a problem after more than 2 years of follow- up.

CrystaLens (Eyeonics)  Approved by the FDA for improvement of near, intermediate, and distance vision  Posterior chamber pressure on the back surface of the IOL  Pressure of the ciliary body on the IOL haptics  Forward movement of the entire ciliary body

Flexible hinge in the haptic at the proximal end and a polyamide foot plate at the distal end

CrystaLens (Eyeonics)  1 D of power generated at near  Not indicated for secondary IOL placement  Only 57% of patients could read a newspaper without spectacles  Contrast sensitivity was better than standard posterior chamber IOLs

Akkommodative ICU IOL (HumanOptics AG)  Undergoing clinical trials  Foldable acrylic IOL with four haptics with flexible transition zones  Anterior shift of approximately 0.60 mm  Myopic shift of 1.3 to 1.7 D

Akkommodative ICU

Light-Adjustable IOL LAL (Calhoun Vision)  Three-piece silicone-optic IOL  Silicone matrix has been embedded with silicone subunits called macromers  When the IOL is irradiated with ultraviolet light, the macromers polymerize and are depleted.  Macromers from the nonirradiated part of the IOL optic are in higher concentration and, diffuse toward the area of irradiation, causing the IOL to swell in this region.

Light-Adjustable IOL

 For myopia,irradiation of the I0L periphery  For hyperopia,irradiation of the I0L center  Correction of astigmatism through a toric exposure pattern  Over a 5.0 D range  Once the desired power has been achieved, the I0L optic is diffusely irradiated in a subsequent session within 1 to 2 weeks postoperatively (locking in)

Light-Adjustable IOL  Can be used to induce a reversible monovision state that could be adjusted if the patient failed to adapt to it.  Multifocal patterns can be placed in the IOL optic for specific pupil diameters.  Can Induce a wavefront correction on the IOL that could correct higher-order aberrations.

Aspheric Intraocular Lens Selection Based on Corneal Wavefront Journal of Refractive Surgery Vol. 25 No. 1 January 2009  Corneal topographic spherical aberration Z4,0 was measured at the 6-mm optical zone.  One of three aspheric IOLs was chosen so the arithmetic sum of the corneal spherical aberration and pseudophakic spherical aberration came closest to zero.

RESULTS  Thirty eyes of 18 patients were available for analysis.  The SofPort Advanced Optics (Bausch & Lomb) lens was implanted in 1 eye  The AcrySof IQ (Alcon Laboratories Inc) in 11 eyes  The Tecnis Z9000 or Z9002 (Advanced Medical Optics [AMO]) in 18 eyes

 Total postoperative ocular spherical aberration for the entire population measured –0.013±0.072 µm  SofPort: µm  AcrySof IQ: ±0.053 µm  Tecnis: –0.015±0.052 µm

CONCLUSIONS  They reduced whole eye spherical aberration from a mean preoperative corneal spherical aberration of to a mean postoperative spherical aberration of

Horizon  Thermoplastic acrylic gel that can be customized to any size, shape, or power specified by the physician  Restore accommodation by increasing its surface curvature in response to zonule- induced changes in the lens capsule  Flexible polymers for injection into a nearly intact capsular bag, after extraction of the crystalline lens through a tiny laterally capsulorrhexis

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