Intra ocular lens Opacification
Intraocular lens (IOL ) Opacification is an uncommon but serious complication of cataract surgery. It can cause significant deterioration of visual performance and may necessitate IOL explantation and exchange 1. Clinical identification and evaluation of this condition is important as a misdiagnosis may prompt surgeons to perform unnecessary interventional procedures such as Nd YAG capsulotomy or vitrectomy resulting in complications 2. A better understanding of the risk factors can also help in avoidance of opacification.
IOL opacification is usually unilateral and may be seen on the surfaces or in the substance of the optic, haptics, or whole lens3. Different patterns of opacification are observed in different IOL biomaterials such as Snowflake opacification in Polymethylmethacrylate (PMMA) IOLs, Discoloration in Silicone IOLs, Calcification in Hydrophilic acrylic IOLs and Glistenings in Hydrophobic acrylic IOLs1,4.
Time of presentation
Early postoperative (hours or days after surgery)
Late postoperative (several months or years after surgery).
|Local ocular factors:||Systemic associations||IOL Related Factors:|
|Breakdown of Blood Aqueous Barrier(BAB):
Prolonged or complex surgery,
Severe post-operative inflammation
Preservatives in glaucoma topical medications
Pseudoexfoliation- spoke like opacification on anterior IOL surface
Posterior Lamellar Keratoplasty procedures (DSEK, DSAEK, DMEK) with intra cameral injection of gas or air
There is a recent increase in the incidence
PPV with endotamponade
Vitreoretinal surgeries- adherence of silicone oil to the IOL optic more commonly seen in silicone IOLs
Nd:YAG Capsulotomy -direct contact between lens and vitreous following Nd:YAG capsulotomy
|Diabetes Mellitus due to breakdown of BAB
Systemic medications -Long term use of Amiodarone and Rifabutin are associated with Silicon IOL Opacification/Discoloration.
|IOL biomaterial impurities
Higher refractive power of the IOL and the use of bigger diameter cartridge during phacoemulsification were significantly related to the higher severity of glistening
Etiology and Patho physiology
Based on many literature reports, it has been noted that opacification can occur in different ways depending on the time period and the IOL materials
Intra Operative opacification
Usually caused by precipitation of crystalline deposits on the IOL's surface, which can be related to the viscoelastic substance or the balanced saline solution11,12 used in the procedure. There are recent reports of acute intra operative clouding of hydrophilic and hydrophobic IOLs which could be caused by sudden changes in temperature13. The acute clouding was transient and resolved in a few hours after the procedure.
Opacification in Immediate postoperative period
There are reports of silicone IOL opacification due to hydration (brown haze) and also due to the interaction of hydrogel material with dyes or the viscoelastic used during surgery14.
Glistenings are fluid-filled microvacuoles( 1- 20 µm) that form within the intraocular lens (IOL) optic when the IOL is in an aqueous environment. It is more commonly seen in hydrophobic IOLs and forms as a result of thermal changes rather than structural changes4,15.
Calcification is due to precipitation of calcium and phosphate on and/or within the IOL and is more frequently seen with hydrophilic IOLs.
Neuhann et al. suggested three main groups of calcifications16: primary—related to IOL itself (properties of the polymer, it’s surface or IOL packaging), the secondary calcification can occur as a result of diseases or pathologies that causes the disruption of BAB and pseudocalcification when false positive staining of calcium occurs. However, usually, calcification is a multifactorial problem.
Werner et al. proposed possible causes of calcification after surgeries that require exogenous gas or other substances injection into the eye17 . In these cases, calcification is confined to the central area of optic. Injected gas, air, tissue plasminogen activator, silicone oil can have direct contact to IOL surface. Secondly, it can be related to a metabolic change in the anterior chamber due to the presence of the exogenous substance and lastly—exacerbated inflammatory reaction with the breakdown of BAB caused by the surgical procedure itself.
Calcification in silicone IOLs is associated with the coexistence of asteroid hyalosis, as more than 85% of patients with calcification had clinically detectable ipsilateral asteroid hyalosis
Snow flake Degeneration
Snowflake degeneration is a slowly progressive opacification of PMMA IOLs due to prolonged exposure to ultraviolet radiation. It affects the central region of IOL and leaves the periphery relatively free of the deposits due to its protection by the iris18,19.
History of cataract extraction with IOL implantation.
Opacifications of the IOL optic may cause reduced visual acuity, decreased contrast sensitivity and glare. Glistenings specifically do not appear to cause a significant decrease in visual acuity but could degrade vision by inducing glare symptoms.
The key to diagnosis is careful slit lamp examination in high magnification paying special attention to the IOL optic surfaces for signs of granularity or opacification. Slit lamp photography helps to monitor progression. Visual acuity and contrast sensitivity are reduced in IOL opacification cases.
AS-OCT(Anterior segment-Optical Tomography) helps in detection of presence, location and density of calcification20,21.Very superficial changes are more difficult to detect in this way.
Posterior capsular opacification
Vitreous haze or haemorrhage22
Anterior lens epithelial cell proliferation
Inter lenticular Opacification in piggy back IOL
IOL exchange is the only therapeutic option in symptomatic patients with opacified IOL.
[Video credit- Uday Devgan MD - CataractCoach.com]
IOL Exchange can be associated with zonular dehiscence(ZD), posterior capsular rupture(PCR) or corneal decompensation25.The adherence of most deposits is extremely strong and Nd:YAG laser treatment is often proven to be ineffective in the cleaning of the lenses' surfaces and unnecessary laser capsulotomy in eyes with opacified IOLs may also increase the complication rate during the IOL exchange procedure26. It was reported that 33% of IOL exchanges require an anterior vitrectomy, this can increase to 48% with a previously performed Nd:YAG capsulotomy27 and even jeopardize ‘in the bag’ implantation of IOL2 . Cases of postoperative recurrent cystoid macular edema, retinal detatchment and choroidal haemorrage following IOL exchange have been reported in patients with IOL opacification, misdiagnosed as PCO and treated initially with Nd:YAG Capsulotomy. Errogenous diagnosis as vitreous haemorrage or haze can lead to unnecessary vitrectomy . In such a case, IOL exchange complicated by post operative endophthalmitis has been reported.
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