Glaucoma and Neurophthalmology Unit
     
     
   
     
     
This department studies all pathologies affecting the optic nerve and the eyesight. Many diseases of this kind are chronic and can develop over time, which requires evolutive control. In this section, activity is structured in order to ensure appropriate monitoring over time and incorporates technology to document it: nerve fiber analyzers, optic disc topography, visual field campimetry and electrophysiology testing. If necessary,  clinical trials are complemented with the most innovative implants and surgical techniques, which provide an extra effectiveness with higher safety and precision.

DIAGNOSTIC TECHNIQUES

1. Ocular tonometry (Measurement of Intraocular Pressure):

Goldmann Tonometer. Widely used to determine the level of intraocular pressure. Its measurement is influenced by corneal features, mainly corneal thickness.

Dynamic contour tonometer: It measures intraocular pressure and it's highly reliable among patients whose corneal features are different from those of the average population (operated on with refractive laser eye surgery, uncommon corneal thickness) as their measurements are less influenced by the cornea.

Ocular Response Analyzer: An air-puff tonometer providing information about biomechanical properties of he cornea, which seem to be associated with development and progression of glaucoma.

2. Morphological analysis of the cornea:
 
Corneal pachimetry: measurement of corneal thickness. Corneal pachimeters measure the thickness of the cornea, a datum we have to know for two reasons:
a) Measurement of intraocular pressure depends on corneal thickness: According to each individual,  corneal thickness may vary between 420 and 680 microns, although average corneal thickness is 520 microns.  The most used tonometer (Goldmann tonometer) is calibrated to reliably check intraocular pressure in eyes with a corneal thickness between 500 and 520 microns. Thus, patients with a thicker-than-average cornea show overestimated measurements, which might explain why some are wrongly diagnosed with ocular hypertension  and are given a treatment that they don't need.
Conversely, patients with lower-than-average thickness indicate underestimated measurements and make believe that they show intraocular pressure within a normal range; still, they may be sufffering from ocular hypertension and require a treatment. To make sure intraocular pressure is being accurately measured, we need to determine corneal thickness.

b) Clinical studies reveal that development and progression of glaucoma is more common among patients with a lower-than-average corneal thickness, and such an increased risk deserves closer monitoring.

Study of corneal biomechanics: O.R.A (Ocular Response Analyzer). See tonometry.
 
3. Morphological analysis of the anterior pole of the eyeball:

Optical Coherence Tomography (O.C.T) of the anterior pole. It makes it possible to study the structures of the camerular angle -which, in turn, allow drainage of aqueous humour-  so as to examine the reasons for a rise in intraocular pressure.  

Ultrasound Biomicrospic examination (B.M.U): Like the OCT, it enables study of the camerular angle as well as the structures that produce aqueous humour (ciliary body).  

Ocular photography.

4. Morphological analysis of optic nerve and nerve fiber layer:
This combination of tests is aimed to measure the amount of optic nerve fibers. When glaucoma progresses, nerve fibers become more and more damaged till they cease to function. This loss is irreversible. Several studies hold that, by the time visual field defects are detectable, a great quantity of nerve fibers has been lost. At an early stage, these tests would reveal such a loss. In case of being necessary, treatment could be started as soon as possible in order to halt the advance of the disease.

These tests are very straightforward.  Patient rests their chin on a support to steady the head and repeatedly made to stare into a single point. In order to optimize the test,  it's important for the patientto remain motionless. All measurements can be taken in a matter of few seconds; hence it's a quick, convienient and painless procedure. Eventually, a database in the device will enable a comparison determining whether the amount of fibers are suggestive of normalcy or, on the contrary, indicative of glaucoma. The test takes longer and sheds less reliable results among the short-sighted or people unable to maintain visual fixation.  

Tests:
Optical Coherence Tompgraphy (O.C.T) for anterior pole of eyeball
Scanning Laser Polarimetry
GDX-scans.
Heidelberg Retina Tomography  for  papilla (H.R.T)
Full-colour photography of optic nerve head.
Red-free imaging on retinal nerve fiber layers.


5. Functional analysis of the optic nerve:
Computerized Visual Campimetry: Campimetry is a technique for assessing the central part of the visual field with the aid of luminous stimuli. In the test, lights of different intensity are projected on a background and they go progressively dim till patient can't see them. These lights appear in all positions of visual space. A person suffering from glaucoma will be incapable of seeing all the regions in the visual space; or, at least, some of them will require more intense stimuli to be appreciated.  

In this way, this method gives us a chance to verify glaucoma-related injuries or -among already-diagnosed patients-  the extent to which these injuries are serious, might affect the visual field or can be succeeded by other injuries.  This justifies the need to undertake serially arranged campimetries to study the disease's progression.  

In this study, Humphrey perimetry is specially effective:

The Humphrey Field Analyzer (H.F.A) is a campimeter that shortens test duration for the patient's convenience and obtains more refined and reliable results.  Moreover, it has an extensive database  to allow ophthalmologists to distinguish routine from pathology tests. It's endowed with advanced software to detect a  worsening of the disease and orientate the ophthalmologist's decision as to whether change treatment or resort to surgery.

ocular electrophisiology: Visual evoked potential. This technique enables visual examination with the help of electrodes on the head, which register transmission of visual stimuli to the cerebral cortex.

Colour tests. Enables detection of impairments in the perception of some longitudinal waves.

TREATMENTS:

1. Laser.

Iridotomy
Mainly used to treat narrow-angle glaucoma. In this type there isn't  a drainage system failure, but the iris hinders outflow of intraocular fluid.
At times, angle-narrowness turns into angle closure, which may block drainage, build up intraocular fluid and lead to a dramatic iincrease in pressure, succeeded by pain and vision loss. This phenomenon is more common among the  long-sighted with a high gradation.  To solve it, it's possible to use a YAG laser to open windows in the iris and so allow intraocular fluid to flow freely.

Iridoplasty
This technique aims to change configuration of the peripheral iris. In some cases, the peripheral iris might block the outflow  of aqueous humour through the camerular sinus for being too  close to -or in contact with- them.
 
Trabeculoplasty
Trabeculoplasty uses laser photocoagulation surgery to treat glaucoma. This technique can be used when intraocular fluid's drainage system clogs up: Laser energy can be applied on the obturated zone and create an opening to let fluid drain out of the eye.

Goniopuncture
Most glaucoma surgeries seek to create an alternative way out for the intraocular fluid drainage and so diminish intraocular pressure. All in all, it resembles a permanently open wound. However, wound healing plays a significant role in a human being's ability to survive and the body often tends to block the new exit, whereupon surgery fails.  One possibility is the utilization of laser to reopen the wound without needing another operation.

2. Surgical
Techniques that increase aqueous humour drainage:

Trabeculectomy
Glaucoma occurs when the eye's drainage system doesn't work, intraocular fluid builds up and pressure rises. The drainage system is called trabecula. This operation involves removing part of the eye's meshwork creating an opening so the fluid can drain out freely.

This way we facilitate fluid outflow and reduce eye pressure. The snag with this technique is that it dramatically decreases pressure in the early postoperative period, raising the risk of side-effects. In the long term, our body tends to heal the already-mentioned opening and the technique ceases to be effective.  

Non-perforating deep sclerectomy:
The basic rule in this techinique is  the same as that of trabeculectomy; and yet, it doesn't partly interrupt the drainage system. We attempt to make the opening walls thinner so that fluid drains out in a slower more controlled way.  Thus, there are fewer side effects, although propensity to scar -and fail to achieve the pursued goal- is higher.    

Drainage devices:
There is a multitude of  devices or valves for regulating intraocular pressure, They are placed in the eye, eliminating -in a controlled way- the excess  fluid so as to normalize pressure levels.
 They are:
Subconjunctival drainage devices: Express, Ahmed.
Drainage implants.
Suprachoroidal
Trabecular implants
iStent
 
Techniques reducing aqueous humour production:
 
Laser cyclodestruction: Occasionally, if pressure can't be controlled in any other way, it becomes necessary to apply heat or cold to destroy ciliary processes, the spot where intraocular fluid -which fills up the anterior chamber of eyeball- is produced.  There are two types: endoscopic and transscleral.