Multiple fundus images of our 47-year-old patient's left eye. What do you notice, and how should it be managed?
A 47-year-old white female presented with a chief complaint of a floater in her left eye that had persisted for four weeks. The patient explained that she first noticed the moving spot after being accidently hit near the eye by another person while out dancing. Her systemic and ocular histories were unremarkable. She reported no known allergies of any kind.
Her best-corrected entering visual acuity measured 20/20 OU at distance and near. Her external examination was normal, with no sign of afferent pupillary defect. The biomicroscopic examination of the anterior segment was normal. She exhibited no evidence of iris neovascularization. Her intraocular pressure measured 15mm Hg OU. We documented peripheral pathologies in both eyes. The pertinent clinical findings are illustrated in the photograph.
How would you approach this case? Does the patient require any additional tests? What is your diagnosis? How would you manage this patient? What is the likely prognosis?
Additional diagnostic testing included indirect stereo-biomicroscopic examination of the fundus, color and brightness testing to rule out optic nerve involvement, photdocumentation and optical coherence tomography (OCT). The diagnosis in this case is uncomplicated posterior vitreous detachment OS. The vitreous is an extracellular matrix that forms a transparent hydrophilic gel.1-5
It is principally composed of water (98% to 99.7%).1-3 The vitreous serves as a conduit for nutrients to reach the lens and retina; offers structural support that stabilizes the volume of the globe; and may regulate eye growth and shape during fetal development.1-4
To maintain transparency, the vitreous functions as a barrier to cellular invasion and diffusion of macromolecules from surrounding intraocular tissues.3 In the gel state, the vitreous lowers oxygen tension in the retina and lens.3,5
The vitreous can be divided into two parts: the central nucleus and the peripheral cortex.1,2,6 The nucleus has a lower collagen fibril density than the cortex.2 Collagen fibrils in this region generally run in an anterior-to-posterior direction. Anteriorly, the fibrils blend with those of the basal vitreous; posteriorly, they insert into the surrounding vitreous cortex shell (cortical vitreous).2
The cortical vitreous is a thin layer (100µm to 300µm ) that lies adjacent to the lens, ciliary body and zonules anteriorly, and adjacent to the retina posteriorly.1-3 The cortical vitreous encircles the nuclear vitreous. The posterior vitreous cortex consists of densely packed, type II collagen fibrils and contains the highest vitreal concentration of hyaluronic acid (HA).7 It is absent over the optic nerve head and thins over the macular region.2
Here, the collagen fibrils run parallel to the retina and do not insert directly into the internal limiting membrane (ILM).3 The condensation of peripheral cortical collagen fibrils forms a false anatomic membrane. Anteriorly, it is termed the anterior hyaloid membrane (AHM). This structure runs adjacent to the lens zonules and the posterior surface of the lens, and anterior to the ora serrata. The false anatomic membrane posterior to the ora serrata is termed the posterior hyaloid membrane. It runs adjacent to the retina.2,6
The AHM is in direct contact with the aqueous humor and thus behaves like a membrane, separating these two ocular compartments.3,6 Cloquet’s canal (or the hyaloid canal) is a remnant of the embryonic hyaloid system. It runs from the posterior pole of the lens to the optic nerve head.2,6 This canal widens anteriorly to form the patellar fossa and posteriorly to form the Area of Martegiani over the optic disc.6
The void formed between the lens and the patellar fossa is known as Berger’s space.6 The primary vitreous is the innermost segment, and is derived from surface ectoderm. It provides support for the developing eye and serves as the primordial vascular supply. It reaches its most vascular stage near the ninth week of gestation. Shortly after this time, these vessels begin to atrophy and are replaced by the clear, avascular, secondary adult vitreous that originates from neuroectoderm and mesoderm. Lastly, the tertiary vitreous forms the lens zonules. It is primarily derived from neuroectoderm.6 Attachments between the vitreous and retina typically occur in areas where the ILM is the thinnest. Attachment locations include the vitreous base, the margins of the optic disc (when this area detaches, it produces the classic circular Weiss or Vogt ring observed in our patient), the back of the crystalline lens in contact with the hyloidocapsular ligament of Wieger, the 500µm-diameter foveola, along large retinal vessels, and at sites of abnormal vitreoretinal adhesion such as lattice margins.1,2,6-8
The strongest attachment occurs at the vitreous base, which is located 3mm to 4mm across the ora serrata and pars plana.2 Here, there is a high concentration of collagen fibrils orientated perpendicular to the base that insert into the pars plana and the anterior retina via defects in the ILM, where they merge with a network of collagen fibrils on the cellular side of the membrane.3 A false ligament, the hyaloideocapsular ligament of Wieger, is a circular attachment between the margin of the patellar fossa and the posterior surface of the lens.1,2
It was previously believed that the posterior vitreous collagen fibrils directly inserted into the ILM, but recent findings suggest that an extracellular matrix composed of laminin, fibronectin and sulfated proteoglycans interface and act as a “molecular glue.”7,9 Postmortem studies of vitreous structure confirm two major degenerations of the vitreous: liquefaction (synchysis) and collagen fibril aggregation (syneresis).9
• Synchysis refers to liquefaction of the vitreous, and typically is a senile process accelerated by myopia, inflammation, trauma, hereditary vitreoretinal syndromes (e.g., Stickler and Marfan syndromes), retinal vascular diseases, aphakia and vitreous hemorrhage.2,8,10-14
Synchysis is the most common degenerative change in the vitreous, and may present as early as age four.2,3 Senile synchysis may be caused by aggregation and redistribution of the collagen fibrils. This phenomenon leaves pockets of liquefaction known as lacunae that are devoid of collagen fibrils.3,10,15,16 These lacunae initially develop centrally; however, they often enlarge and coalesce.2 Lacunae are evident on slit-lamp biomicroscopy as pockets of optically empty space, with an absence of the characteristic fine fibrillar structure.2
• Syneresis, or a collapse of the vitreous secondary to collagen fiber aggregation, is the other major vitreous degeneration.2,9,12 When both synchysis and syneresis are present, collagen aggregates can be seen moving freely in the vitreous with ocular movement.2 The consequent shadows cast on the retina create the symptoms of floaters. Posterior vitreous detachment (PVD) refers to the separation of the cortical vitreous from the ILM anywhere posterior to vitreous base.2,17
The detachment may be localized, partial or complete.3 A complete PVD occurs when the posterior cortical vitreous is detached from the entire retina, including its adhesion to the optic nerve up to the posterior border of the vitreous base.3 At 50 years of age, the incidence of PVD in phakic eyes is grater than 50%––increasing to approximately 75% by age 65.18 Additionally, there is an increased risk for PVD in aphakic or pseudophakic eyes, myopes, and those with a history of trauma or intraocular inflammation.18
It is worth noting that women are prone to PVD at a younger age than men. This is likely because females experience reduced HA synthesis secondary to decreased postmenopausal estrogen levels.8,17 In our patient, biomicroscopic examination revealed an optically clear space filled with liquefied vitreous located between the detached posterior hyaloid and the retina.2 The pathognomic sign of a PVD is the presence of a clinically observable Weiss or Vogt ring overlying the optic disc.18 This ring represents circular attachment remnants of the posterior cortical vitreous to the site encircling the nerve (Area of Martegiani).18 A patient with an acute PVD may complain of newly visible floating spots that follow eye movement and continue to travel even after termination of the ocular movement.18
Another common symptom is photopsia, which is perceived as peripheral arcs or flashes of light secondary to mechanical retinal stimulation as the vitreous articulates with the retina at the attachment site.18 The process of PVD begins with synchysis of the vitreous and weakening of the posterior vitreoretinal adhesion.9 Enlargement of formed lucunae cause the posterior vitreal cortical wall overlying the involved area to thin.8,19 In general, as the vitreoretinal adhesion dissolves, it forms discontinuities within the posterior hyaloid––either via fissure evolution or a microbreak in the thin cortical vitreous layer.8,9,17 This allows synchytic vitreous to enter the subhyaloid space dissecting the posterior hyaloid from the ILM.9
Posterior vitreal detachments typically begin in a single quadrant of the perifovea (most often superior). Persistent attachments to the ILM remain at the fovea and optic nerve head.20 Over time, the perifoveal detachment enlarges to completely surround the persistent attachment at the fovea.20 Finally, detachment of the vitreous from the remaining foveal region produces a funnel-shaped configuration, with attachments at the optic disc and vitreous base. When the PVD releases from the optic nerve, the process is complete.18,20 One study outlined a grading system for age-related PVD:20
• Stage 1: Incomplete perifoveal PVD in up to three quadrants.
• Stage 2: Incomplete perifoveal PVD in all quadrants, with residual attachment to the fovea and optic disc.
• Stage 3: Incomplete PVD over the posterior pole, with residual attachment to the optic disc.
• Stage 4: Complete PVD. The researchers showed that even young, healthy eyes might exhibit incomplete or partial PVDs beginning as early as the fourth decade of life. Often, such partial detachments progress slowly for years before becoming complete.8,20 An anomalous PVD results when synchysis occurs without sufficient detachment from the ILM. This results in tractional effects at the interface.9 Those with genetic collagen diseases, such Marfan’s, Ehlers-Danlos and Stickler’s syndromes, have a higher incidence of anomalous PVD. These maladies also increase the risk of retinal complications at an early age.9,14,21
Anomalous PVD may result in vitreoschisis––a splitting of the posterior vitreous cortex and forward displacement of the vitreous body, leaving remnants of the outer layer firmly attached to the retina.22,23 Vitreoschisis is thought to play a role in the pathogenesis of macular pucker, macular holes and proliferative diabetic retinopathy.22-24 A common consequence of anomalous PVD is the development of vitreoretinal traction. On OCT, vitreoretinal traction––as opposed to vitreoretinal adherence without traction––presents as an attachment to the retina with associated tissue elevation, thickening and deformity.25 Deflection of the posterior hyaloid or vitreous strands often can be observed at that site.25 Complications of anomalous PVD result from anteriorly directed tension induced by the vitreous degeneration itself and/or dynamic traction associated with ocular movements.8 Ocular movements localize traction to areas of firm vitreoretinal adhesion.7
Most early-stage, anomalous PVD complications occur insidiously and are located in the posterior pole. Late-stage complications of complete anomalous PVD commonly develop in the periphery with acute symptoms, including retinal or optic disc hemorrhage, vitreous hemorrhage, retinal break or tear, and rhegmatogenous retinal detachment.8 Clearly, our patient exhibited a stage IV PVD without complications of maculopathy. We educated the patient that the floater would be less evident when her visual attention was occupied.
On the other hand––we informed her that, for at least for the next six months, the spot would be more noticeable when she was outside in bright sunlight or in rooms with white fluorescent lighting and/or lightly colored pastel walls. Again, we reiterated that this phenomenon would fade over time. We provided the patient with an Amsler grid for home monitoring and instructed her to inform us of any visual changes. We also asked her to return in three weeks for a dilated retinal examination to rule out additional complications. Further, we advised the patient to avoid contact sports and strenuous exercise until her follow-up appointment. Fortunately, she exhibited no complications at the three-week follow-up.
Thanks to Carolyn Majcher, OD, of San Antonio, and Julie Hutchinson, OD, of St. Loius, for their contributions to this case.
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