Anterior Segment

In some instances, cataract surgery can be particularly challenging and requires surgical expertise to safely remove the cataract and implant an Intraocular Lens Implant (IOL), in order to avoid any serious sight threatening complications and achieve the best visual outcome for the patient.

Such cases include cataract surgery in the context of Pseudoexfoliative Disease, previous eye trauma, previous intraocular inflammation, high myopia, short axial length (Nanophthalmos) or previous angle closure glaucoma. There is a variety of reasons that the aforementioned cases can be challenging to deal with and these include a possible instability of the cataract (phacodoneis), the presence of a small pupil and/or very shallow anterior chamber, the possibility of intraoperative malignant glaucoma or the presence of vitreous in the anterior chamber.

The surgeon should identify these signs at the pre-operative assessment and be able to address any potential issues during the surgery using appropriate techniques. For instance, the surgical technique should be as friendly as possible to the zonules that hold the crystalline lens/cataract in place, pupil expansion devices like iris hooks might need to be used, a Capsular Tension Ring - CTR or Capsular Tension Segment might need to be implanted or sutured within the eye and special IOL implantation techniques (like the Yamane technique) or special IOLs (like the Artisan® IOL) might need to be used.

The Intraocular Lens implant (IOL) that is implanted in the eye during cataract surgery can move out of its position under certain circumstances. The most common cause of a subluxated or dislocated IOL is the presence of Pseudoexfoliation.

Pseudoexfoliation is a systemic syndrome with a possible genetic background and is characterised by the deposition of abnormal material that is produced within the body in the tissues inside the eye as well as other in organs of the body like the liver, the heart and the lungs. It is usually seen in people over the age of 50. Pseudoexfoliation is also associated with a significant increase in the development of glaucoma, complications during cataract surgery and progressive weakening of the zonules that hold the lens in place.

Other causes of IOL subluxations and dislocations are history of eye trauma, complicated cataract surgery, Marfan’s syndrome, high axial myopia and previous episodes of uveitis.

Depending on the degree of IOL subluxation, the problem can be rectified with surgery either with repositioning of the IOL in its original position using sutures or by removing the old IOL and putting a new IOL in the Anterior Chamber (standard ACIOL or Artisan iris claw IOL) or placing a 3 piece IOL in the eye and fixating it with intrascleral haptic fixation (Yamane technique).

If the IOL has dislocated completely in the vitreous cavity, then special surgery is needed and a pars plana vitrectomy is performed. The IOL is removed out of the eye and an IOL exchange takes place. Surgeries for dislocated IOLs are done together with a vitreoretinal surgeon.

Finally, in cases where there is concurrent uncontrolled glaucoma, the surgeon might recommend combined surgery -  IOL repositioning or exchange together with glaucoma surgery usually in the form of a Glaucoma Drainage Device using an Ahmed or Baerveldt tube.

The term aphakia is used to describe the absence of the natural crystalline lens from the eye. Most times, it arises following the removal of congenital cataracts in infants or children or after complicated cataract surgery in adults.

Other causes of aphakia include a penetrating trauma to the eye with subsequent primary repair of it and removal of the crystalline lens. Rarely, the aphakia can be congenital. 

When there is no lens inside the eye, the eye is unable to focus the light on the retina, it has a high hyperopic refractive error and the vision is very blurry.

In general, aphakia can be corrected with glasses, contact lenses or surgery. If the patient opts for surgery, the type of intraocular lens (IOL) that will be used depends on whether there is adequate capsular support and options include placing a 3-piece IOL in the sulcus, suturing a 3-piece IOL on the iris or fixating it within the sclera or placing an anterior chamber IOL/ iris claw IOL (Artisan).

It is worth noting that in cases of aphakia due to cataract surgery for congenital cataracts, the presence of amblyopia might limit the final outcome. 

In certain circumstances, an intraocular lens implant (IOL) exchange might be warranted.

Indications for IOL exchange include:

- Refractive surprises that cannot be tolerated by the patient.
Even though the biometry measurements and IOL formulas have improved considerably over the last years, there are some cases where a refractive surprise can occur. This is usually due to an error in the IOL selection and rarely due to inaccurate biometry measurements. It can be more common in patients with history of corneal refractive surgery. If the residual refractive error is significant enough and troublesome for the patient, an IOL exchange can be done.

- Extensive calcification of the lens implant

- The Uveitis Glaucoma, Hyphema Syndrome (UGH) where the IOL irritates the iris and causes recurrent episodes of intraocular inflammation

- Dysphotopsias in monodical or multifocal IOLs (that can be divided in positive and negative dysphotopsias depending on the exact symptoms).

- Intolerance to multifocal or Extended Depth of Focus (EDOF) lens implants due to glare, haloes or reduced contrast sensitivity.

-A subluxated or dislocated IOL.

IOL exchanges are complex procedures that require specialist input and a meticulous surgical technique as there is a high risk for damaging surrounding tissues like the cornea, iris or lens capsule. There is also increased risk of vitreous loss and for this reason IOL exchanges are done in conjunction with anterior vitrectomy.

Another important thing to consider in such cases is that it might not be possible to place the new lens implant within the capsular bag which is the physiological position of the lens in the eye. In that case, alternative IOL designs might have to be used such as 3-piece IOLs that are fixated on the iris or within the sclera or anterior chamber lenses such as the Artisan iris claw lens implant. 

Certain iris diseases such as iris defects, iris deformities or permanent mydriasis of the iris can be addressed surgically with iridoplasty techniques.

Iris defects can be cause by blunt or penetrating eye injuries or after complicated intraocular surgery (Iatrogenic). Less often, they can be congenital like ectopic lentils et pupillae or iris coloboma. Complete or partial iris absence can be seen in congenital aniridia. As far as cases of permanent mydriasis are concerned where the pupil is in a permanent dilated state, these are usually due to trauma to the eye or related with neurological conditions such as a 3rd nerve palsy or following an angle closure attack and less commonly after intraocular surgery such as corneal transplantation (Urrets-Zavalia syndrome).

All the aforementioned iris diseases can cause significant problems in the day to day life of patients as they are associated with glare, blurred vision, sensitivity to light and cosmetic issues. Depending on the extent of the defect, some of the above conditions can be surgically repaired with special microsurgery called iridoplasty in order to provide a good cosmetic and functional outcome. 

In cases of extensive iris defects, it is not possible to do iridoplasty and iris implants have to be used. The most widely used iris implants are the Morcher iris implants (67F or 96F) that are placed either within the capsular bag or sutured on the sclera and the ARTIFICIALIRIS from Human Optics. The latter, is a the most accurate representation of the human iris and is tailor made for each patient. The Human Optics iris implants are available for use in Europe. The Morcher implants are not available any more in Europe.