IU, especially pars planitis, affects both eyes in most of the patients. However, an asymmetric involvement with few vitreous cells in the less affected eye may be seen (Ozdal et al. 2015; Tugal-Tutkun 2011). High rates of bilaterality, ranging between 70% and 90%, have been reported in the Western literature (Babu and Rathinam 2010).
The eye is usually quiet with mild to moderate anterior segment inflammation associated with keratic precipitates (KP) distributed mostly in the inferior part of the cornea. Peripheral corneal endotheliopathy characterized by inferior stromal edema and linearly arranged KPs on the border of edematous and normal cornea has also been reported. Posterior synechiae particularly involving the inferior iris (Fig. 10.2) may be observed especially in childhood pars planitis and usually do not occur in adulthood. In children with long-standing inflammation, a band keratopathy may develop (Bonfioli et al. 2005; Donaldson et al. 2007; Tugal-Tutkun 2011). Compared to adults, anterior segment inflammation, band keratopathy (Fig. 10.2), peripheral corneal endotheliopathy, and posterior synechiae are more frequent in children (Tugal-Tutkun 2011). The characteristic finding of IU is vitritis (Fig. 10.3) which may or may not cause vitreous haze. Vitreous inflammation may be severe and can be visible in the pupillary area at biomicroscopic examination (Fig. 10.4). Yellow-white inflammatory aggregates called as snowballs are usually found in the mid-vitreous and inferior peripheral vitreous (Fig. 10.5). A snowball may rarely be located on the surface of the macula. With progression, these aggregates coalesce (Fig. 10.6a, b) forming a plaque of exudates usually located inferiorly and called as snowbank (Fig. 10.7a, b). Snowballs and snowbank are diagnostic findings of pars planitis. Vitreous bands and vitreous condensations at the inferior peripheral retina are findings suggesting pars planitis (Fig. 10.8). Sheathing of peripheral retinal venules due to retinal vasculitis is another common clinical finding of IU (Fig. 10.9). Optic disc edema can be observed in around 70% of the cases when fluorescein angiography (FA) is performed (Arellanes-Garcia et al. 2008) (Fig. 10.10a, b).
Fig. 10.2
Slit lamp photograph shows posterior synechiae particularly involving the inferior iris and a band keratopathy in a child with pars planitis
Fig. 10.3
Fundus photograph shows severe vitreous haze associated with intermediate uveitis
Fig. 10.4
Slit lamp photograph shows severe vitritis and condensation of the anterior vitreous which is visible in the pupillary area
Fig. 10.5
(a–d) Fundus photographs show variable location of snowballs in patients with pars planitis
Fig. 10.6
(a, b) Fundus photographs show snowballs coalescing and making a plaque located on the inferior retina
Fig. 10.7
Fundus photograph demonstrates snowbank exudates with a distinct border located inferiorly (shown with white arrows, a) and with irregular border located inferiorly (b)
Fig. 10.8
Fundus photograph shows vitreous bands, condensations, and snowballs at the inferior retina
Fig. 10.9
Fundus photograph shows snowballs and vascular sheathing at the inferior retina
Fig. 10.10
(a, b) Fundus photographs showing optic disc edema in patients with pars planitis
Ocular Complications
Cystoid macular edema (CME) is the most common complication of IU and the leading cause of visual morbidity (Fig. 10.11). Chronic edema can lead to further macular complications such as scarring, epiretinal membranes, and macular hole formation (Fig. 10.12) (Bonfioli et al. 2005).
Fig. 10.11
Fundus photograph (a), fluorescein angiography (b), and optical coherence tomography (c) of a patient with intermediate uveitis complicated with cystoid macular edema
Fig. 10.12
Fundus photograph and optical coherence tomography of a patient with pars planitis complicated with the development of a macular hole
Because of the chronic and asymptomatic course, presentation with ocular complications is a prevalent condition especially among pediatric patients. The most frequent complications of pars planitis include CME, cataract, and severe vitreous opacities. Band keratopathy (Figs. 10.2 and 10.13), seclusion pupillae (Fig. 10.13), glaucoma, epiretinal membrane formation (Fig. 10.14a–d), vitreous condensation, retinal neovascularizations (Fig. 10.15a, b), vitreous hemorrhage (Fig. 10.16), retinal detachment, peripheral retinoschisis, cyclitic membranes, and amblyopia are also well-known consequences of chronic pars planitis in children (Arellanes-Garcia et al. 2008; Ness et al. 2017; Ozdal et al. 2015).
Fig. 10.13
Slit lamp photograph shows band keratopathy, seclusio pupillae, and secondary cataract associated in the more severely affected eye of a 5-year-old girl with bilateral pars planitis
Fig. 10.14
(a–d) Fundus photographs showing various epiretinal membrane in intermediate uveitis
Fig. 10.15
Fundus photographs showing exudates, periphlebitis, snowballs, and neovascularization at the inferior peripheral retina (a) and vitreous bands and retinal hemorrhages from the neovascularizations (b) in pars planitis
Fig. 10.16
Fundus photograph shows vitreous hemorrhage from the optic disc neovascularization
Occasionally, dense vitreous condensation appearing as leukocoria may be misdiagnosed as cataract particularly in young children. Pars planitis is the leading cause of vitreous hemorrhage in children which may be associated with neovascularization of the optic disc or the peripheral retina (Tugal-Tutkun 2011). Optic disc neovascularization is mostly due to severe intraocular inflammation. Retinal neovascularization, elsewhere or in the snowbank, and rarely peripapillary subretinal neovascularization have also been reported in pars planitis (Arellanes-Garcia et al. 2008). Peripheral retinal traction and retinal tear may occur occasionally (Fig. 10.17a, b). Retinal detachment (tractional, rhegmatogenous, or exudative) is also a rare complication of pars planitis (Donaldson et al. 2007; Paroli et al. 2011) (Fig. 10.18). Inferior peripheral retinoschisis, however, is a more frequent complication which occurs almost exclusively in children (Tugal-Tutkun 2011) (Fig. 10.19a–d). Retinoschisis has been reported in 19% of eyes in a recent study from a tertiary referral center. It has been found to be bilateral, inferior, and adjacent to a snowbank (Malalis et al. 2017). Young children with pars planitis are at high risk of amblyopia as a consequence of band keratopathy, vitreous opacities and cataracts obscuring the visual axis, or persistent macular edema. Delayed diagnosis and treatment may result in permanent visual loss.
Fig. 10.17
(a, b) Fundus photographs showing retinal tear due to peripheral retinal traction and minimal subretinal fluid around the tear
Fig. 10.18
Fundus photograph shows inferior exudative retinal detachment involving the macula. Optical coherence tomography confirms the macular detachment
Fig. 10.19
(a–d) Fundus photographs show peripheral retinoschisis in different patients with pars planitis
Diagnosis
The diagnosis of IU is based on clinical findings. Decreased and/or blurred vision, floaters in the absence of pain, redness, and photophobia are suggestive symptoms. Clinical diagnosis is based on the presence of vitreous cells, snowballs, and pars plana exudation. When ophthalmoscopy with scleral depression is not performed, inferior snowballs or snowbanks can be missed and especially pars planitis may be underdiagnosed. There is no specific diagnostic laboratory test for IU. For a diagnosis of an idiopathic IU or pars planitis, however, systemic associations and mainly infectious causes of IU need to be ruled out with a careful history, systemic evaluation, and laboratory tests.
Systemic investigations include complete blood count, serological tests for syphilis, Lyme and cat-scratch disease, serum angiotensin-converting enzyme (ACE) and lysozyme levels, chest x-ray, purified protein derivative skin test, and brain magnetic resonance imaging (MRI). Because of the significant association with MS, neuroimaging should be performed especially in adult patients, in whom systemic associations are more common. Imaging modalities such as FA, optical coherence tomography (OCT), ultrasound biomicroscopy (UBM), and ultrasonography are also helpful in confirming the diagnosis and/or showing the disease-related complications.
Fluorescein angiography is usually performed to assess the presence of CME, retinal vasculitis, neovascularizations, and retinal ischemia. Retinal vascular leakage, diffuse capillary leakage, and CME are common FA findings (Fig. 10.20a). Peripheral retinal ischemia, however, may be observed as a less frequent FA finding of the disease (Fig. 10.20b). Fluorescein angiography is also valuable in documenting the response to treatment, especially in eyes with CME and peripheral vasculitis. The OCT imaging shows disease-related macular and retinal changes and provides information regarding the reversibility of lesions. It is valuable in detecting macular edema and its sequelae such as cystoid changes, epiretinal membranes, macular hole, and atrophy. As in FA, it is beneficial in monitoring the treatment response. Ultrasonography and UBM are valuable methods providing additional information regarding the ciliary body, pars plana, and retina when visualization of the fundus is obscured due to band keratopathy, cataract, synechiae, vitreous inflammation, or hemorrhage (Babu and Rathinam 2010; Ozdal et al. 2015).
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