Aqueous humor is produced by the ciliary processes of each eye.  Aqueous bathes the anterior chamber eye structures, and then flows to the chamber angle and through the filtering trabecular meshwork, into the canal of Schlemm, and is then absorbed into the blood circulation.  This is a continual process and glaucoma can develop if this flow is interrupted or if there is an overproduction of aqueous.

Glaucoma in children is a difficult and challenging disease.  If the glaucoma is congenital, usually there is a developmental problem with the anterior chamber angle which inhibits the aqueous humor drainage from the eye.  The glaucoma could be in one or both eyes.  Primary congenital glaucoma is a surgical disease.  Additionally, patients who have had cataracts removed may develop a mechanical, or secondary, glaucoma such as from peripheral anterior synechiae ("PAS").  Diseases such as Sturge-Weber with unilateral port wine stain of the face frequently develop glaucoma  on the affected side.  Pediatric eyes with one of the secondary glaucomas, or potential glaucoma, should be watched closely (via serial exams under anesthesia) and are operated if the symptoms of glaucoma persist or worsen when medical management has not been successful. 

Pediatric glaucoma is most often seen as a result of an inadequate drainage pathway at the anterior chamber angle.  Initial symptoms can include epiphora (excessing tearing), photophobia (sensitivity to light), and irritability.  Physical signs of glaucoma in infants and children can include increased intraocular pressure (IOP), excessive growth of the cornea, corneal haze as the epithelial layers of the cornea are affected by the high intraocular pressure, Haab's striae which are tears in the corneal Descemet's membrane, and changes in the optic nerve head ("cupping") which also indicates the effect of chronically high IOP.  With end-stage glaucoma, corneal opacity and buphthalmos ("cow's eye") occurs.

Exam under anesthesia (EUA) in cases with or suspected of having glaucoma in infancy and childhood includes intraocular pressure (IOP) measurement; measurement of the cornea with a caliper; slit lamp exam of the corneal layers;  and exam of the anterior chamber angle using the slit lamp and a magnifying goniolens.  Dilating drops can be administered at this point so the examination can continue with axial length measurement of the globe; inspection of the optic nerve with ophthalmoscopes; and possibly photos of the optic nerve head for historical comparison.

After a surgical procedure is performed, a follow-up exam is done to determine the success of surgery.  Post-op care is very important and recommended administration of eye drops (usually by parents or caregivers) when prescribed is mandatory for successful management of the child's glaucoma.  Serial exams under anesthesia are done to continue to evaluate the child's clinical progress until the child is old enough to have all parameters measured in the clinic setting.

Types of surgical procedures done for glaucoma in children are listed below.  All but cryosurgery are intraocular procedures where an operating microscope and strict sterile technique is used.  Cryosurgery is an extra-ocular procedure and is done with an exam under anesthesia set-up while using clean (versus sterile) technique.  The surgical procedures listed below are in alphabetical order:

Cryo Therapy -  Cryosurgery is used outside the sclera around the eye to freeze ciliary processes.  The cryo probe is attached to the cryo machine which uses tanks of nitrogen to produce a freezing application when the foot pedal is depressed.  Cryo has been shown to be very effective, but it is painful for the patient.  Freezing applications are done for several 'clock hours' around the circumference of the anterior segment.  The cryo probe is defrosted between applications with balanced salt solution via cannula irrigation administered by the assistant.  Remember to let the anesthesia care-giver know that this is a painful procedure.  Retrobulbar injection of local anesthetic can be administered prior to or following cryo therapy.  Antibiotic/steroid eye drops are administered prior to the pediatric patient's emergence from general anesthesia.

Endo-Cyclo-Phototherapy - "ECP" is, basically, laser within the eye to the ciliary processes.  Again, this is done to decrease the aqueous production by the ciliary processes.  A fiberoptic camera/laser probe is used for ECP.  The probe is fairly new technology and has both a tiny fiberoptic camera and also delivers diode laser via the single handpiece.  A 19g. knife incision allows the probe to be inserted into the anterior chamber and the endo-probe is directed to within a few tenths of a millimeter of the ciliary processes at the chamber angle.  Progress is watched on a remote monitor and laser is delivered at a range of power between .25 milliwatts to .40 milliwatts.  As the ciliary processes are ablated, they will turn white and shrivel.  A second incision can be made which allows continuation of the ablation for additional 'clock hours' around the globe.  10-0 absorbable suture closes the incision(s).  Antibiotic/steroid eye drops are administered, the eyelid is closed, and a soft patch is placed prior to the patient's emergence from general anesthesia.

Endo-Goniotomy - This procedure can be used when the cornea is not clear enough to perform a conventional goniotomy.  Again, the fiberoptic camera/laser probe is used for visualization of the anterior chamber angle.  Prior to insertion through a knife incision, a sterile gonioknife is attached to the distal end of the laser probe.  The extension of the 2mm gonioknife blade can be adjusted to allow for focal length.  No laser is used; the camera visualizes the membrane which is blocking the aqueous drainage pathway.  The gonioknife incises the membrane for several 'clock hours'.  Slight bleeding from blood reflux from Schlemm's canal is a good sign.  10-0 absorbable suture closes the corneal incision.  Antibiotic/steroid eye drops are administered, the eyelid is closed, and a soft patch is placed prior to the patient's emergence from general anesthesia.

Goniotomy - Goniotomy can be done only if the cornea is clear enough to allow for good visualization.  A spherical magnifying lens is placed onto the eye and is attached to constant balanced salt solution flow via the attached small-bore tubing.  Holes at the periphery of the worst lens accommodate 4-0 silk sutures which secure the lens tightly against the globe.  Through a small opening in the lens, a small incision is made in the peripheral cornea and an angled gonioknife is introduced into the anterior chamber and directed to the chamber angle.  The blocking membrane is incised for several 'clock hours' and slight bleeding is a positive sign.  The spherical lens is removed from the eye and 10-0 absorbable suture closes the incision.  Antibiotic/steroid eye drops are administered, the eyelid is closed, and a soft patch is placed prior to the patient's emergence from general anesthesia.  Another goniotomy technique uses a smaller gonio lens (Barkan) held in place by a finger or hook.

Trabeculectomy - After making a flap incision through conjunctiva and sclera, a wedge section of trabecular meshwork and underlying iris ('peripheral iridectomy') is excised using a 'punch' instrument which allows retained aqueous humor to bypass the dysfunctioning drainage pathway.  The scleral incision is closed using non-absorbable sutures.   Use of an agent (such as Mitimycin-C or 5-FU) may be used to prevent scarring/healing in the area to which it is applied.  Instrument isolation technique is used when these agents are used to prevent inadvertent exposure of other eye tissues to the drug.  A bleb is created beneath the conjunctival layer which retains draining aqueous thereby helping to lower intraocular pressure.  The conjunctiva is closed with 8-0 absorbable sutures.  Antibiotic/steroid eye drops are administered, the eyelid is closed, and a soft patch is placed prior to the patient's emergence from general anesthesia. 

Trabeculotomy - After making a flap opening in the conjunctiva, very fine radial cuts are made into the sclera with a sharp blade with care, exaggerated to be said proceed  "one cell layer at a time" over the location of Schlemm's canal.  When the canal is entered, aqueous will flow outward and for this reason, the surgical field is kept dry while these minute cuts are being made.  When aqueous is seen, Schlemm's canal is cannulated with butterfly trabeculotomes.  Trabeculotomes are two stainless steel instruments shaped in a right and also left curve which are designed to follow the arc of the canal surrounding the eye at the anterior chamber angle.  The canal is entered both to the right and to the left prior to performing trabeculotomies.  For trabeculotomy, the canal is entered with the trabeculotome and then subsequently 'popped' into the anterior chamber which mechanically opens the blocked angle.  Trabeculotomy is then done on the opposite side.  Slight bleeding may be present and is a good sign.  The chamber may be washed out with balanced salt solution via three milliliter syringe with 30g. irrigating cannula.  The scleral incision is closed with 10-0 non-absorbable suture and the wound is checked for leak; an additional suture may be needed to ensure a 'water-tight' wound.  The conjunctiva is closed with absorbable 8-0 sutures.  Antibiotic/steroid eye drops are administered, the eyelid is closed, and a soft patch is placed prior to the patient's emergence from general anesthesia.

Tube Shunt - A tube shunt is an implanted device that takes aqueous humor through a small tubing placed into the anterior chamber which connects to a reservoir which is placed, generally, superiotemporal in the operated eye.  A small piece of tissue implant covers the extraocular portion of the tube to prevent erosion through the conjunctiva.  Aqueous is shunted from the anterior chamber and the intraocular pressure lowers in a regulated fashion.  Care is taken when placing the tubing in the anterior chamber to not allow it to touch the cornea or the lens.

Gwen Kopecky, BSN, RN, CRNO
Riley Hospital for Children
Indianapolis, Indiana, USA
GKopecky@clarian.org