Retina
Retina is very fine, thin part of the eye, comprised of neural elements, which function is reception of light stimuli and sending information toward centers of sight in the brain.
Illustratively, retina is compared with film of photo camera for easier explanation of its role and place in the eye. If “the film is damaged”, the image will be bad, regardless of perfect optics of that camera (analogue to optics are cornea, anterior chamber, pupil-aperture, lens and vitreous body). Through these elements travels the light ray-signal toward its receptors on retina.
Retina is a part of “nervous system” of the eye and it is consisting of intricate tangles of nerve cells-photoreceptors, and their fibers, which collect visual information and send it by means of optic nerve toward “processing center”, which is located at occipital part of the brain. All these segments are important in forming of good quality image and its recognition.
Is separation of nervous part of retina with photoreceptors (cones and rods), from its base-retinal pigment epithelium with accumulation of fluid underneath retina. Pigment epithelium has important metabolic and protective role, so in case of separation of retina from it, photoreceptors will perish and loss of sight will occur. The condition is ACUTE and requires IMMEDIATE SURGICAL treatment.
SYMPTOMS – flashes, bolts, “curtain” in a part of visual field, loss of vision
Disturbances to patient preceding to retinal detachment usually are sudden phenomena such as “flashes” or “thunderbolts” in visual field. They signify that strong traction of vitreous body occurred, and not seldom even appearance one or more defects on retina, so called ruptures, preceding detachment. If the patient, at that moment, calls ophthalmologist, by examination it is possible to detect occurrence and location of rupture and by in-office application of laser barrage around rupture, prevent further development of retinal detachment. Sometimes the blurriness of vision will happen, because of breaking of blood vessel, in which case, certainly must be checked whether besides bleeding retinal detachment is present.
If the detachment has already occurred, the surgery is required.
Patient notices smaller or larger “curtain” or “shadow” in for the most part lower part of visual field, considering the fact that rupture will predominantly occur in upper part of retina, which is projected in inverted image. Some patients do not pay close attention to first disturbances thinking they would “go away by itself” particularly if the vision on the other eye is good. Yet, if detachment occurs on better eye, patients very soon become conscious of gravity of changes and timely ask for help. If retinal detachment is not operated at once it encompasses the yellow spot as well, which results in sudden loss of vision, reducing it with time only to light and movement recognition. Yellow spot is most sensitive and susceptible to fast functional deterioration, because that such small field of 5mm2 consists of greatest concentration of photoreceptors- cones, and retinal, actually yellow spot nourishment ceases after its detachment. Full visual acuity can be preserved only if it the yellow spot detachment had not yet occurred therefore at first signs of detachment- “curtains” it is imperative to perform URGENT SURGICAL TREATMENT, during first several days. Until surgery the patient must rest strictly laying on back, to prevent further spreading of detachment toward yellow spot, surgery must be performed in the first week.
In case of longer lasting retinal detachment, irreversible degenerative changes in retina occur, primarily in the yellow spot, resulting in poorer visual acuity, regardless of technical success of the surgery.
By criterion of inception mechanism, the largest group are retinal detachments occurred as consequence of specific process developments in retina, primarily rupture. Retinal rupture begins because of vitreous body detachment and consequential retinal tractions at places with strong attachments to peripheral retina. That happens because of vitreous body collapse i.e. patients with high myopia or aging processes, also sudden shock of vitreous during eye trauma, or its increased movement and greater physical activity (jumping, lifting weights, scooter…)
Vitreous fluid is pulled through rupture by strength of osmotic pressure in choroid and progressively builds up underneath retina bringing about fast expansion of detachment. On the other hand, numerous eyes with retinal ruptures do not develop detachment, because when strong attachments of vitreous to retina are absent, lone physiological processes in choroid and pigment epithelium are enough to keep retina in place. Retinal ruptures in these cases are detected accidently at eye exams, because patients do not experience typical disturbances like “flashes” or “thunderbolts”.
The other group are retinal detachment occurred as a resultant of slower retinal recession in presence of retinal membranes (tractional detachments). This is a description of diabetic changes in the eye-proliferative diabetic retinopathy (PDR), but also in longer lasting untreated detachments – PVR proliferative vitreoretinopathy. This type of “plucking out” can exist in macular zone and lead to symptom of central vision (VMT – vitreomacular traction).
Third, rare group are detachments with fluid spilling under retina, without rupture or traction, as in case of tumor inside the eye, choroid inflammation and congenital anomalies, and some “stress conditions”- which have not been completely explained.
Retinal detachment is solely treated surgically. The aim of surgery is closing of the rupture, performed by inducing adhesions between retina and choroid, by cryo-treatment at the locus of rupture or by means of laser. To achieve that, rupture must be in close proximity with choroidal tissue either from outside of the bulbus utilizing cerclage with scleral buckle with puncture of scleral tissue and evacuation of subretinal liquid (old style surgery), or from within by application of expansive gas. Prior to instillation of expansive gas vitreous body must be removed. This procedure is called VITRECTOMY and is more and more often applied in comparison with conservative surgery with buckle and puncture. The reason for this is that by removing the vitreous body the chances for genesis of new ruptures are eliminated, as well as new detachments, and that is not the case with application of cerclage and buckle.
In case of shallow detachments and in case of younger patients, usually the classic method is used. In 30% of cases there will be need to operate again, by method of vitrectomy. Vitrectomy is, nevertheless, number one choice in cases of detachments generated by presence of membranes on retina, cases of longer lasting retinal detachments, diabetes mellitus, detachments resulted from trauma, or resultant of high myopia. During the surgery those masses are completely removed, which enables permanent adhesion of retina.
In place of vitreous body expansive gas is instilled as tamponade, or silicone oil.
Gas will remain in the eye for some time, 2 – 4 weeks, then it is resorbed. Patient must know that because of gas, he will not be able to see for several days, after receding of gas bubble, the vision is coming back. First two to three weeks after the surgery one should avoid altitudes higher than 1000m and airplane flights until resorption of gas, because there is possibility of sudden increase of intraocular pressure resulting from gas expansion.
In cases of more complicated and longer lasting detachments, it is practice to use silicone oil as tamponade. Its advantage over gas is that patient seas immediately after the surgery and is always used in case of only one functional eye, multiple ruptures, highly myopic eye, but it demands additional surgery, evacuation of silicone oil, approximately two-three months after the first surgery.
In cases of complicated retinal detachments the scarring processes occur, i.e genesis of new membranes, even after complete removal, requiring one or more additional surgeries. This is a case with advanced, longlasting, nontreated processes, proliferative diabetic changes, traumatic retinal detachments.
Special hospital SVETI VID is rearing high quality, new age retinal and vitreous surgery, in cooperation with European universities. Here was for the first time in the country initiated vitreoretinal surgery with gas tamponade. Among first in the world, here was applied surgery of minimal incision, 25 gauge and 23 gauge, meaning that the surgery of posterior segment became micro-incisional and without suture, like surgery of the anterior segment. With perfect visualization during the surgery it is possible to reach the utmost periphery of the back of the eye, which creates conditions for precise and sophisticated surgery thereby solving the retinal problems completely with long lasting effect. In this institution particular care is given to macular surgery. Very few world centers have developed fine techniques of treating macular problems, especially macular hole and membranes (macular pucker) in macular regions, processes which elevate and change macular structure resulting in fall of visual acuity and distortion of images. Great possibilities are given by new diagnostic procedures, as is optical coherent tomography (OCT) with possibility of viewing fine, almost histological structures of macula.
In SVETI VID, limits of operability are furthered toward higher possibilities employing precision of surgical techniques, extraordinary surgical equipment and apparatus of the latest technology.