|Vitreoretinal Disease Unit|
The Vitreoretinal Disease Unit is responsible for tackling all diseases concerning the retina and the vitreous membrane. Our centre is endowed with the latest technological equipment for diagnosis and medical/surgical treatment of retinal pathologies, the most outstanding techniques being retinography and ultrawide-field angiography, multispot argon laser and late generation vitrectomy.
This enables us to safely deal with the most common retinal diseases affecting our patients, whereas the most complex ones (uveitis, intraocular tumours) are treated in conjunction with the IVO(I nstituto Valenciano de Oncología)'s Oncology and Radiotherapy Unit and the Rheumatology units of our regional hospitals.
Over the last few years, OCT has revolutionized our habits in the diagnosis of posterior pole pathologies; thanks to it, we can visualize histological cuts off the retina in vivo. At the same time, it is possible to examine different structures like the macula, the nerve, the nerve fibers as well as their interaction with neighbouring structures, vitreous membrane and choroid.
OCT measurement is based on a physical process called interferometry: Light is emitted into the eye, whereupon we can measure reflected echoes, time delay, scattered intensity and reflection from the different structures of the eye.
The device incorporates a high-resolution camera to examine the retina in real time and so obtain the images in which we are interested, with a high quality in vivo histological equivalence.
It is widely used to take a close look at certain retinal diseases (including hypertensive or diabetic retinopathy) or to confirm the presence, location, size and type of choroidal neovascular membranes in the context of an age-related macular degeneration or a myopic choroidal neovascular membrane.
Examination of these images provides some additional information about the state of the eye. The procedure is non-painful and rarely causes side-effects, We only need to consider allergic reactions to contrast, especially fluor.
Nowadays, digital retinography systems (IMAGINET TOPCON, RETINA CAMARATRC 50IX) are used to obtain such images.
Commoly used in conjunction with fluorescein angiography, this technique enables observation of the deepest retinal layers. Side-effects are rare, even though it's necessary to verify the patient's allergic reactions. We resort to it if fluorescein angiography fails to demonstrate the presence of the subretinal neovascular membrane. It has a pattern of absorption and emission of light in an infrared wavelenght, which allows us to see through hemorrhages and the retinal pigment epithelum.
Indocyanine-green videoangiography (IGVA) is a relatively new diagnostic technique. Visualization of choroidal circulation is better than that of fluorescein angiography, for indocyanine green is bound to plasma proteins in a 98% rate, spreading scarcely from choroidal vessels; at the same time, absorption and emission of fluorescence will border on a near-infrared wavelenght, which enables penetration through the retinal pigment epithelum, opaque areas and blood.
Interpretation of angiograms is complex; however, their properties justify the use of the IGVA in the study and guided treatment of subretinal neovascularization (SRNV) associated with age-related macular degeneration (ARMD).
Clinical use currently encompasses:
- Ganzfeld electroretinogram
- Flash electroretinogram
- Pattern electroretinogram
- Multifocal electroretinogram
Similarly performed, Flash ERG is only stimulated with a flash and it is employed when collaboration becomes more difficult.
Pattern ERG is useful to assess the functional integrity of the central retina; and especially the ganglion cells. Optical accuracy is necessary for on-screen fixation.
Multifocal ERG is an innovative technique in which we use an on-screen stimulus, which is made up of multiple hexagons arrayed in concentric annular segments. Specifically, it innervates peripheral (nasal retinal fibers, superior and inferior temporals) or central retinal areas (maculae).
Computer resources and computational tools can stimulate distinct retinal areas, register and average local responses and so obtain electroretinographic traces of precise areas, which provide information about the functional state of each retina.
Furthermore, it is an indirect measurement of the retinal pigment epithelum.
Pattern VEP requires a stimulus from a screen displaying a checkerboard pattern so the patient may gaze at some of its central points. We can identify any visual system dysfunction by checking any possible predominance of demyelinating disorders with delayed potentials (increased latency) or a prevalence of an axonal defect in the eye (reduced visual range).
Ensuing monitoring makes it possible to assess treatment effectiveness or examine progression of a speficic disease. Anomalies in one eye are indicative of a prechiasmatic pathology on that side; if they are bilateral, we cannot pinpoint the exact location of the injury since nasal retinal fibers decussate across the chiasm to the contralateral side.
Flash PEV is intended for uncooperative patients or patients unable to see the already-mentioned checkerboard pattern. Flashes work as a stimulus, whose evoked responses present a wide interindividual variability; consequently, they only help confirm that the luminous stimulus has reached the brain cortex and compare the responses in both eyes in search of possible asymmetries.
LASER is an English acronym that stands for Light Amplification by Stimulated Emission of Radiation. As a result of the luminous energy that passes through different gases, it emmits a single, concentrated, monochromatic beam of light. Thus, the kind of gas will determine the name Opthalmology uses to denominate each type of laser:
Neodyminum YAG (Ytrium Aluminium Garnet) laser
Prior to application, we will resort to mydriatic drops to dilate eye pupils and to contact lenses to enlarge the retinal surface that the laser will incise. We will provoke a painless, size and intensity controlled retinal burn (according to the laser parameters).
On most occasions, the patient will not appreciate eyesight improvement (as laser is normally applied to avoid worse consequences). Above all, this technique aims to maintain the current eyesight. Results will also depend on the pathology itself.
This is an ambulatory procedure. We start by instilling a small anesthetic drop into the affected eye, then we put a contact lens. Treatment concluded, patient can go back home and return to normalcy with no need to take precautions. Should photodynamic therapy be contraindicated (or not possible to use on certain patients) we can use Transpupillary Thermotherapy.
Nevertheless, it has not proven effective when dealing with age-related macular degeneration.
Re-treatments may be necessary every three months.
Treatment comprises two phases: 1) Intravenous injection of photosensitive drug, which will be activated by a specific wavelenght light using thermal diode laser during 83 seconds. It is normally well tolerated.
Most adverse drug reactions are mild-to-moderate and have transitory effects (backache being the most common one due to verteprofin infusion). As the drug is photosensitive, post treatment ought to suggest:
-Avoiding direct exposure to sunlight or bright artificial light.
-Wearing dark sunglasses in the next 48 hours.
-Re-schedule elective or hospital-based dental surgery so as to avoid exposure to powerful surgical lighting.
Simplicity and quickness of this technique will allow the patient to rejoin daily life the day after if no complications are observed. Though little frequent, the most important ones are vitreous hemorrhage, detachment of retina, serious infection in the eye, cataract and non-infectious ocular inflammation. There can also be an increase in intraocular pressure, which can be offset and controlled with drugs.
Routes of administraton and dosage will vary. Topical use (drops) is common in anterior uveitis: instillation frequency may range from a single drop a day to a few drops per hour. When inflammation is intense and external use is not sufficient, medication can be injected around the eye. At times, oral administration with systemic corticoids can be necessary; or, in the most unmanageable cases, inmunosupressive drugs like cyclosporine or mycophelonate mofetil.
Understanding what it is and why it appears is a key factor to find out treatment, which will usually be a surgical procedure. There exist two chief techniques: in the first one (extrascleral surgery) we act outside the globe by indenting the wall of the eye (sclera) inward. In the second one (intraocular; that is, “within the eye”) we act inside the globe of the eye.
Combination of both techniques (in the same surgery, or in two consecutive operations) may not be rare. In this case, extrascleral surgery will precede intraocular surgery.
Therefore, injected air will have exert a two-way pressure: inwards (due to the explant) and outwards. The air bubble will push the retina towards the sclera and, ultimately, put it back in place.
Unless otherwise specified, surgery will demand local anesthesia and no hospitalization. After this, patient will be allowed to go home and expected to stay in a certain position for the next few days (till retina heals and intraocular gas disappears).
As this technique can change the shape (mainly an elongation) of the eye and can alter refraction, correction of myopia will be usually required.
Other possible complications are alterations in muscles responsible for eye movement, bleeding, choroidal detachment, increase in ocular tension, etc. In this case, patients' response is good with the suitable medical or surgical treatment.
Prior to application, it's necessary to dilate the pupils with mydriatic drops to be able to observe -with the help of magnifying lenses- the retinal image on which the probe tip will be applied.
Apart from serving as a complement to heal retinal breaks, it is also used to treat other retinal disorders (diabetic retinopathy) and destroy certain tumours.
Argon laser is a thermal laser, whose radiated light turns into heat when touching ocular tissues. Wherever it may be applied, it will result in cicatrization and tear closure. Prior to its application, we will need mydriatic drops (for pupillary dilation) and contact lenses (to magnify the retinal area that laser will incise). In doing so, we will cause a painless, size and intensity-controlled retinal burn (according to the laser parameters).
Application of laser within the eye will provoke a scar to reattach the retina. We may combine it with extrascleral surgery through an explant (in the same surgical procedure).
Possible complications can be: bleeding, cataract formation, increased intraocular pressure, etc. Unless otherwise specified, this surgery can be performed with local anesthesia, requires no hospitalization and the patient can be discharged shortly after operation. In some cases air/gas left over in the eye will force them to rest in the same position for a few days.
Vitrectomy is the only procedure to treat several retinal diseases, namely complicated detachments, membranes on the surface, macular holes, subretinal membranes, venous thromboses or diabetic retinopathy, among others.
Prognosis. The retina is a nervous tissue, and nerve cells can be irreversibly damaged. Reattachment may give way to recovery of visual acuity; nonetheless, such an improvement may not be as expected.
Prognosis will differ according to the type of damage (magnitude, location of detachment and evolution period) that precedes surgery. In addition, recurrence (a formerly detached retina is more liable to peeling back away) may demand more than an operation. At all events though, success depends on the patient's readiness to rest the head according to a specialist's advice prior to -and in the aftermath of- surgery on the basis of two factors: tear location and type of operation.
Prognosis for untreated rhegmatogenous or tractional detachments is very bad, since it tends to affect the entire retina and does not only cause vision loss, but also inflammatory changes concerning the eye as a whole.
In spite of being a delicate surgery involving a troublesome postoperative recovery process, with no guaranteed success and possible side-effects, refusal to operate entails more risks than operation itself. Surgery will be the most advisable alternative unless the specialist (who can determine more exceptional cases) suggests otherwise.
a) Macular translocation with 360 degree retinotomy:
It consists in a thorough vitrectomy, which will require crystalline lens extraction by means of a phacoemulsification or a pars plana lensectomy. An all-transretinal infusion of balanced salt solution (BSS) will allow us to detach the retina starting from the middle periphery till the obtention of 2-3 retinal detachment bags. At this point we proceed to a liquid-air exchange causing bags to unite, whereupon the posterior retina peels away.
When the retina is detached, we perform a 360 degree retinotomy at the ora serrata, go on to extract the neovascular membrane and rotate the retina till the fovea is relocated in contact with an area of healthy pigment epithelum, preferably towards the upper part (Fig.1)
The posterior pole repositioned, the rest of the retina is flattened with perfluorocarbon liquid and, later on, replaced with some silicone oil. In the same procedure or, in a second stage, we act on the extraocular muscles rotating the eyeball in the opposite direction (opposite to the one we applied in the macula (Fig.2)
It is a complex technique that requires an important learning curve. That is why published results have improved over the last years. As a surgery, possible complications cannot be discarded: retinal detachment, proliferative vitreoretinopathy, cystoid macular edema, hemorrhages, macular epiretinal membrane, retention of subretinal perfluorocarbon, relapse of neovascularization, etc.
Explanatory figures for Macular Translocation with 360 degree Retinotomy (Fundación Oftalmológica del Mediterráneo).
Figure 1. When the retina detaches, it is rotated towards the upper part leaving the macula on a healthy area.
Figure 2. The eyeball is rotated in an opposite direction -different from the one the retina has been turned to- and so we work on the extraocular muscles.
b) Macular translocation and scleral shortening:
Procedure starts with a conjuctival opening so as to expose the upper and lower temporal quadrants. Scleral sutures give way to scleral shortening, which in turn enables macular translocation. A complete vitrectomy is succeeded by 2/3 retinotomies, right in the area where liquid injection is performed in order to cause retinal detachment. When total detachment is achieved, we undertake a liquid-air exchange, then we tie scleral sutures.
At the end of the surgery we leave half the vitreous cavity with some air inside and half the retina detached. Patients will spend the first few hours in a semi-stitting position, and the next 45 days in a prone position. After surgery we may apply laser photocoagulation, photodynamic therapy or other treatments.
Most frequent complications might be macular hole formation, retinal rupture during surgery, subretinal hemorrhage, choroidal hemorrhage, macular folds, recurrence of neovascularization, etc.
This technique aims to eliminate central scotoma by relocating the fovea on a healthy area. As such, this technique is difficult and requires an extremely skilled surgeon. There are no studies providing a comparison with photodynamic therapy; nonetheless, translocation can be used in conjunction with other treatments like transpupillary thermotherapy, thermal photocoagulation and photodynamic therapy itself.
On exerting such pressure, we get to displace the liquid towards the centre of the eye and not below the retina, which would continue to detach it. In addition, when we push the sclera against the vitreous membrane we succeed in relaxing the traction force that the latter exerts on the retina.