Posterior Scleritis

Posterior scleritis is a relatively uncommon disorder and often misdiagnosed owing to its variable presentations. We describe two cases of posterior scleritis. Both the cases underwent a complete ophthalmic examination, fluorescein angiography, B-scan ultrasonography, systemic evaluation including physical examination and laboratory investigations. We did not find any associated systemic disease in our cases inspite of extensive investigations. Both the cases showed a good response to oral steroid in tapering dose. To detect the underlying disease, for proper treatment and assessment of prognosis, diagnostic work-up is needed. B-scan ultrasonography is the most useful diagnostic tool in such patients. Early diagnosis of posterior scleritis is important due to its excellent response to anti-inflammatory medication, particularly with systemic steroid and most common etiology being idiopathic.


Introduction
Scleritis can be identified as anterior scleritis, posterior scleritis or episcleritis depending on the site of the inflammatory process within the scleral or episcleral tissue. Diagnosing anterior scleritis and episcleritis is much easier than diagnosing posterior scleritis because lesions can be more easily observed in the first two conditions. Posterior scleritis is probably one of the most underdiagnosed conditions in ophthalmology. 1 It has diverse manifestations and can be easily overlooked. This diagnosis must be considered in all inflammatory and painful ocular disorders with no obvious etiology. 2 We report two cases of posterior scleritis that were treated successfully with systemic steroid.

Case 1
A-20 years old female presented on 20.11.2010 with complaints of pain, redness, watering and swelling of the left eye since two weeks. She was diagnosed as a case of acute viral conjunctivitis elsewhere and was prescribed topical antibiotics but the condition worsened. Incidentally an outbreak of epidemic viral conjunctivitis occurred in the city during the previous one month. Examination of left eye showed best corrected visual acuity (BCVA) 6/12, restricted ocular motility, conjunctival and episcleral congestion ( Figure 1) and relative afferent pupillary defect (RAPD). Fundoscopy revealed disc oedema with multiple choroidal folds and a dull foveal reflex (Figure 2) , right eye was within normal limit. USG B-scan of left eye She was diagnosed as a case of left anterior and posterior scleritis and started on oral steroid (60mg OD) therapy which was tapered over 6 weeks, along with topical nonsteroidal anti-inflammatory drugs. Marked improvement was found at 1 week follow up.
USG B-scan of left eye showed complete resolution at 1 month follow up. She developed similar attack in RE in January 2011 and in LE in April 2011 for which oral steroid was given for 6 weeks each time and the condition recovered. Patient was treated with alternate day 10mg prednisolone for one year and there is no recurrence till date.

Case 2
A middle age male presented with the complaints of mild swelling, pain and dimness of vision in RE for 2 weeks, and a history of backache for the same duration. His BCVA was 6/12 (RE) and 6/6 (LE).Anterior segment of the RE was within normal limit except mild conjunctival chemosis and RAPD. Fundus examination of the right eye revealed choroidal folds, blurring of the disc margin, disc hyperemia and a dull foveal reflex ( Figure 6).

Posterior Scleritis
No abnormality was detected in the left eye. Fasting and postprandial blood sugar, routine blood investigations were normal. Mx test was positive (18mm x 18mm). CRP and RA factor were within normal level. X-ray of chest and sacroiliac joint showed no abnormality. USG B-Scan of the left eye showed characteristic 'T-sign'. FFA revealed disc oedema, no leakage . On referral to Chest medicine tuberculosis was ruled out. He was treated as in like Case 1. Oral steroid was continued in tapering doses for 6 weeks. There has been no recurrence till date.

Discussion
Scleritis is a severe inflammatory condition showing microangiopathy in most of the specimens suggesting an underlying immune complex reaction. The antigen is usually the aberrant expression of the HLA-DR on scleral fibroblasts, induced by interferon gamma. 3 Associated systemic diseases are Rheumatoid arthritis ,Wegener's granulomatosis, SLE, JRA, PAN, Relapsing polychondritis, psoriasis, gout, atopy, rosacea, TB, syphilis, HSV, HZV. 4,5 The average age in the largest series of posterior scleritis was 49.3 years with a female preponderance. 6 Occurrence of posterior scleritis at a young age like in Case 1,though uncommon, has been reported in literature. Commonest presenting complaint among these patients is variable decrease of vision associated with moderate to severe ocular pain. 7 As posterior scleritis patient may present with proptosis, lid swelling, limitation of ocular movements, one should consider orbital tumor, inflammatory pseudotumor or thyroid ophthalmopathy in the differential diagnosis. In case of subretinal mass findings, choroidal melanoma, metastatic uveal carcinoma, or choroidal hemangioma should be excluded. In cases with serous detachment of choroid, ciliary body or retina, conditions like uveal effusion syndrome, Vogt-Koyanagi-Harada disease or central serous retinopathy should be kept in mind. 3,4 In one study idiopathic posterior scleritis was seen in 24 cases (75%), and there was an associated systemic disease in 8 patients (25%). In Case 1, both anterior and posterior sclera was involved. In earlier reports also the presence of anterior scleral involvement to variable extent has been seen commonly associated with posterior scleritis. Restriction of ocular movements can be seen with intense periscleral inflammation spreading to orbit and extraocular muscles. 8 Disc oedema, choroidal folds, retinal detachments, subretinal mass lesions and elevated IOP are the commonest associations found in some studies. 6,7 Low grade uveitis is uncommon in posterior scleritis. 7 The condition may be associated with internal ophthalmoplegia caused by inflammatory damage to the cilliary ganglion and short ciliary nerves located around the optic nerve. 9 Diagnostic tests like RA factor, ANA, ANCA, Eosinophil count, IgE, Uric acid, ESR ,Serological tests, Purified-protein derivative (PPD) skin test or Quantiferon gold assay, anergy skin test along with imaging studies of chest, sinus and sacroiliac joint may be considered as and when required. Ultrasonography (A-and B-scan) is the key investigation necessary to make the diagnosis of posterior scleritis. CT and MRI scans are especially important in differential diagnosis of posterior scleritis or the diagnosis of the underlying disease. 10 FFA show circumscribed fundus mass, choroidal folds, retinal striae, disc edema, annular choroidal detachment, exudative macular detachment, cystoid macular edema and localized peripheral retinal detachment. 11 Corticosteroid should be the first line of therapy in this entity. Non-steroidal agents, oral steroids, and periocular steroids have been used successfully in the management of posterior scleritis. The disease usually shows a good response to systemic anti-inflammatory therapy. Complete resolution of inflammation often takes several weeks. Patients with loss of vision, evidence of optic nerve involvement, systemic disease needs aggressive anti inflammatory therapy with systemic immunosuppressive agents. 6 Ophthalmologists must remain aware of the protean manifestations of this rare entity. Early diagnosis of posterior scleritis is important due to its excellent response to antiinflammatory medication, particularly with systemic steroid.