Ophthalmology / Eye Surgery

Eye surgery

Ocular surgery is a complex number of surgical procedures performed on the eye and/or its adjoining parts. These procedures require extreme care of the eye before, during and after performing them. There are some conditions that can be treated by using eye drops, ointments and other drugs, while others can be treated only by surgery.

Cataract surgery

A cataract is the clouding of the internal natural crystalline lens of the eye. The condition is more common with old people due to aging, but can also be the resulting cause of an eye trauma or radiation exposure. It could be present at birth (congenital cataract) or occur after an eye surgery. The condition causes blurry vision, faded colors, trouble with bright light and trouble with night vision, which, if not treated, can slowly lead to blindness.
Cataract surgery (CS) may be required if the vision loss cannot be corrected with glasses or contact lenses. The surgery involves removing the opacified natural lens of the eye and replacing it with a transparent artificial one. There are two main types of surgery procedures:

• Phacoemulsification (phaco) - a tiny incision is made in the eye, and with the help of ultrasound waves the lens is broken and then absorbed. After that the lens is taken out completely, and an intraocular lens (IOL) is inserted / implanted. 
• Extracapsular cataract extraction (ECCE) - the procedure requires a larger incision, and extracting the cloudy lens intact (in one piece), followed by implanting an IOL.

Glaucoma surgery

Glaucoma is a group of diseases, often associated with elevated intraocular pressure (IOP) that causes optic nerve (major vision nerve that receives light generated nerve impulses and transmits them to the brain where the image/vision is formed) damage with loss of peripheral vision, which may eventually lead to permanent blindness. 
Types of glaucoma:

• Open-angle glaucoma - blocked eye’s drainage canals that control the outflow of the aqueous humor (watery fluid produced continuously in the eye). The buildup of fluid elevates the IOP and eventually leads to optic nerve damage. Usually it develops slowly, showing no symptoms at the beginning.
• Closed-angle glaucoma (narrow-angle glaucoma) - the iris (circular colored eye structure responsible for controlling pupil size and diameter) blocks the drainage canals by bending over the drainage angle, resulting in acute increase in IOP and severe eye pain associated usually with migraine, nausea, vomiting and red eye.
• Normal-tension glaucoma - the same damage of the optic nerve as in other types of glaucoma, except the IOP is normal.

Treating glaucoma involves eye drops that lower IOP, but if the medication is ineffective, it requires laser treatment or glaucoma surgery:

• Laser trabeculoplasty (LTP) - procedure that uses a laser to create tiny burns on the trabecular meshwork (the drainage canals), increasing fluid outflow. It is used to treat open-angle glaucoma. The types of trabeculoplasty are argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT).
• Laser iridotomy (LI) - procedure that uses the laser to create a small, puncture-like hole in the iris, decreasing IOP in patients with closed-angle glaucoma.
• Iridectomy - procedure that involves removing of a small piece of the iris, resulting in decreased IOP.
• Filtering procedures: 
  • Penetrating: Trabeculectomy - a microsurgery procedure that involves the removal of a small piece of the trabecular meshwork in order to create a drainage channel from the anterior chamber of the eye to the conjunctiva (the white outer coating of the eye), creating a filtering bleb (reservoir) from conjunctival tissue, allowing the aqueous to collect into it, and eventually being absorbed. This procedure facilitates the drainage and decreases IOP. Sclerectomy -  involves completely excising an area of the sclera instead of creating the bleb.
  • Non-penetrating: Bleb-forming - major ocular procedure that involves cutting from outside the eye to reach the Schlemm’s canal (circular vessel of the eye that collects the aqueous from the anterior chamber and delivers it to the blood vessels), exposing it and excising its inner wall, allowing the filtration of the aqueous without entering the chamber. Viscocanalostomy - also a major ocular procedure, in which the Schlemm’s canal is exposed, cannulated and then a viscoelastic substance is injected that dilates the canal.
• Tube-shunt surgery or drainage implant surgery - small medical devices that are surgically implanted into the eye during a trabeculectomy to increase the outflow of the aqueous, creating an alternative passageway and bypassing the damaged drainage canals, resulting in decreased IOP.
• Canaloplasty - a non-invasive procedure that uses a microcatheter to enter the canal around the iris, enlarging the drainage channels through the injection of a gel-like material - viscoelastic, which reduces the IOP.
• Procedures that decrease production of aqueous humor - the aim is to destroy the cells that produce the aqueous humor.

Refractive surgery

RS is used to correct refractive errors in the eye, limiting or eliminating the need for corrective lenses. RS can reduce or cure vision disorders such as myopia, hypermetropia, astigmatism and keratoconus.

• Flap procedures:
  • Automated Lamellar Keratoplasty (ALK) - a surgical procedure that uses an instrument known as microkeratome to cut a thin flap of the corneal tissue, lifting it up and remove a thin disc of corneal stroma, then placing back the flap. The thickness of the removed disc determines the change in the refractive error.
  • Laser-Assisted in situ Keratomileusis (LASIK) - a surgical procedure that uses the same instrument or a femtosecond laser to cut a flap of the cornea, lifting it and removing a thin layer of the stroma with an excimer laser, in contrast to ALK. The procedure improves visual acuity (sharpness of vision)
  • Refractive Lenticule Extraction (ReLEX): ReLEX FLEx (Femtosecond Lenticule Extraction) - a femtosecond laser cuts a lenticule within the corneal tissue, afterwards cutting a flap and removing the piece. ReLEX SMILE (Small Incision Lenticule Extraction) - a technique without the flap. A femtosecond laser is used to cut a lenticule within the corneal tissue and then, using the same laser, a small incision is made at the edge of the lenticule removing it.

• Surface procedures

  • Photorefractive Keratectomy (PRK) - a procedure that uses excimer laser to remove microscopic amounts of corneal tissue, with the top layer of the corneal epithelium being removed and a bandage contact lens is placed on top, in addition to creating a flap.
  • Transepithelial Photorefractive Keratectomy (TransPRK) - to correct eye optical power, an excimer laser removes the outer layer of the cornea, epithelium, its connective tissue and stroma.
  • Laser Assisted Sub-Epithelium Keratomileusis (LASEK) - a procedure that uses the excimer laser to cut the tissue from corneal stroma, leaving the corneal epithelium intact and using it as a “natural bandage”.
  • EPI-LASEK - a similar technique as LASEK that uses an epi-keratome to remove the top layer of the corneal epithelium.
• Corneal incision procedures:
  • Radial Keratotomy (RK) - the procedure alters the shape of the cornea by making spoke-shaped incisions with a diamond knife.
  • Mini Asymmetric Radial Keratotomy (MARK) - diamond knife that performs micro incisions to cause controlled scarring the cornea and change its thickness and shape. The procedure can cure astigmatism and the first two stages of keratoconus, avoiding corneal transplant.
  • Limbal Relaxing Incisions (LRI) - incisions made on the outer edge of the iris to correct astigmatism.

Corneal surgery

• Corneal transplantation (corneal grafting) - a surgical procedure that replaces a damaged or ill cornea with a donated corneal tissue (graft). The cornea can be entirely replaced - penetrating keratoplasty; or only partially replaced - lamellar keratoplasty. 
• Keratoprosthesis - a surgical procedure that replaces a damaged or diseased cornea with an artificial one. It is usually recommended after one or more failed corneal donor transplants.
• Pterygium excision. A pterygium is a wing-like membrane growing on the cornea. The surgery involves removing the pterygium and, using a graft of conjunctiva from under the eyelid, covering the remaining defect.
• Corneal tattooing - the procedure is used to improve cosmetic appearance and sight. The methods are different, but they all consist of injecting the dyeing agent directly into the cornea.
• Osteo-Odonto-keratoprosthesis (“tooth in eye” surgery) - the procedure involves removal of a tooth and extracting a lamina of tissue from it. After that, a hole is drilled and the tissue is fitted with optics. For a few months, the lamina is grown in the patient’s cheek, and then implanted on the eye. The procedure is used to restore vision to patients that suffer from most severe corneal and ocular surface problems.

Vitreo-retinal surgery

Vitrectomy - a surgical procedure that removes some or all vitreous humor (the transparent gel that fills the space between the lens and the retina of the eyeball) from the eye.
Retinal detachment repair - procedures used to repair the retina (the inner coat of the eye which is light-sensitive, and where the image is created and transmitted to the brain through the optic nerve) after its detachment.

Eye muscle surgery

A surgical procedure is performed to correct strabismus. This is a condition that prevents the patient from directing both eyes simultaneously towards the same fixation point. The surgery is performed on the extraocular muscles to correct the misalignment of the eyes.

Eyelid surgery: A series of plastic surgeries performed to correct different types of eyelid damages.

Orbital surgery: Usually referred to ocular prosthesis (artificial eye) that replaces an absent natural eye.

Eye removal

Enucleation - removal of the eye, with the eye muscles and orbital contents remaining intact;
Evisceration - removal of the eye’s contents, with the scleral shell remaining intact. A procedure used mostly to reduce eye pain in a blind eye;
Exenteration - removal of the orbital contents that includes the eye, extraocular muscles, fat and connective tissue. A procedure used for patients with malignant orbital tumors.