APPLIED ANATOMY
Sclera forms the posterior five-sixth opaque part of
the external fibrous tunic of the eyeball. Its whole
outer surface is covered by Tenon’s capsule. In the
anterior part it is also covered by bulbar conjunctiva.
Its inner surface lies in contact with choroid with a
potential suprachoroidal space in between. In its
anterior most part near the limbus there is a furrow
which encloses the canal of Schlemm.
Thickness of sclera varies considerably in different
individuals and with the age of the person. It is
generally thinner in children than the adults and in
females than the males. Sclera is thickest posteriorly
(1 mm) and gradually becomes thin when traced
anteriorly. It is thinnest at the insertion of extraocular
muscles (0.3 mm). Lamina cribrosa is a sieve-like
sclera from which fibres of optic nerve pass.
Apertures. Sclera is pierced by three sets of apertures
(Fig. 7.1).
1. Posterior apertures are situated around the optic
nerve and transmit long and short ciliary nerves
and vessels.
2. Middle apertures (four in number) are situated
slightly posterior to the equator; through these
pass the four vortex veins (vena verticosae).
3. Anterior apertures are situated 3 to 4 mm away
from the limbus. Anterior ciliary vessels and
branches from long ciliary nerves pass through
these apertures.
3. Lamina fusca. It is the innermost part of sclera
which blends with suprachoroidal and supraciliary
laminae of the uveal tract. It is brownish in colour
owing to the presence of pigmented cells.
Nerve supply. Sclera is supplied by branches from the
long ciliary nerves which pierce it 2–4 mm from the
limbus to form a plexus.
INFLAMMATIONS OF SCLERA
Episcleritis
Episcleritis is benign recurrent inflammation of the
episclera, involving the overlying Tenon’s capsule but
not the underlying sclera. It typically affects young
adults, being twice as common in women than men.
Etiology
1. Idiopathic. Exact etiology is not known in many
cases.
2. Systemic diseases associated with episcleritis,
include gout, rosacea, psoriasis and connective
tissue diseases.
3. Hypersensitivity reaction to endogenous
tubercular or streptococcal toxins is also reported.
4. Infectious episcleritis may be caused by herpes
zoster virus, syphillis, Lyme disease and
tuberculosis.
Pathology
Histologically, there occurs localised lymphocytic
infiltration of episcleral tissue associated with
oedema and congestion of overlying Tenon’s capsule
and conjunctiva.
Clinical features
Symptoms. Episcleritis is characterised by redness,
mild ocular discomfort described as gritty, burning
or foreign body sensation. Many a time it may not be
accompanied by any discomfort at all. Rarely, mild
photophobia and lacrimation may occur.
Signs. On examination two clinical types of
episcleritis, simple and nodular may be recognised.
Episclera is seen acutely inflamed in the involved
area.
• Simple episcleritis is characterised by sectorial
(occasionally diffuse) inflammation of episclera.
The engorged episcleral vessels are large and run
in radial direction beneath the conjunctiva (Fig.
7.2A).
• Nodular episcleritis is characterised by a pink
or purple flat nodule surrounded by injection,
usually situated 2–3 mm away from the limbus
(Fig. 7.2B). The nodule is firm, tender, can be
moved separately from the sclera and the overlying
conjunctiva also moves freely.
Clinical course. Episcleritis runs a limited course
of 10 days to 3 weeks and resolves spontaneously.
However, recurrences are common and tend to occur
in bouts. Rarely, a fleeting type of disease (episcleritis
periodica) may occur.
Differential diagnosis
• Simple episcleritis may be confused rarely with
conjunctivitis.
• Nodular episcleritis may be confused with inflamed
pinguecula, swelling and congestion due to foreign
body lodged in bulbar conjunctiva and, very rarely
with scleritis.
Treatment
1. Topical NSAIDs, e.g., ketorolac 0.3% may be useful.
2. Topical mild corticosteroid eyedrops e.g.,
fluorometholone or loteprednol instilled 2–3
hourly, render the eye more comfortable and
resolve the episcleritis within a few days.
3. Topical artificial tears e.g., 0.5% carboxy methyl
cellulose have soothing effect.
Cold compresses applied to the closed lids may
offer symptomatic relief from ocular discomfort.
5. Systemic nonsteroidal anti-inflammatory drugs
(NSAIDs) such as flurbiprofen (300 mg OD),
indomethacin (25 mg three times a day), or
oxyphenbutazone may be required in recurrent
cases.
Scleritis
Scleritis refers to a inflammation of the sclera proper.
It is a comparatively serious disease which may cause
visual impairment and even loss of the eye if treated
inadequately. Fortunately, its incidence is much less
than that of episcleritis. It usually occurs in elderly
patients (40-70 years) involving females more than
the males.
Etiology
Overall about 50% cases of scleritis are associated
with some systemic diseases, most common being
connective tissue diseases.
common conditions are as follows:
1. Autoimmune collagen disorders, especially
rheumatoid arthritis, is the most common
association. About 0.5% of patients (1 in 200)
suffering from seropositive rheumatoid arthritis
develop scleritis. Other associated collagen disorders
are Wegener’s granulomatosis, polyarteritis nodosa
(PAN), systemic lupus erythematosus (SLE) and
ankylosing spondylitis.
2. Metabolic disorders like gout and thyrotoxicosis
have also been reported to be associated with
scleritis.
3. Some infections, particularly herpes zoster
ophthalmicus, chronic staphylococcal and
streptococcal infection have also been known to
cause infectious scleritis.
4. Granulomatous diseases like tuberculosis, syphilis,
sarcoidosis, leprosy can also cause scleritis.
5. Miscellaneous conditions like irradiation, chemical
burns, Vogt-Koyanagi-Harada syndrome, Behcet’s
disease and rosacea are also implicated in the
etiology.
6. Surgically induced scleritis (SIS) is a rare complication
of ocular surgery. It occurs within 6 months
postoperatively. Exact mechanism not known, may
be precipitation of underlying systemic cause.
7. Idiopathic. In many cases of scleritis, cause is
unknown.
Pathology
Histopathological changes are that of a chronic
granulomatous disorder characterised by fibrinoid
necrosis, destruction of collagen together with
infiltration by polymorphonuclear cells, lymphocytes,
plasma cells and macrophages. The granuloma is
surrounded by multinucleated epithelioid giant cells
and old and new vessels, some of which may show
evidence of vasculitis.
Classification
Scleritis can be classified as follows:
A. Non-infectious scleritis
I. Anterior scleritis (98%)
a. Non-necrotizing scleritis (85%)
1. Diffuse
2. Nodular
b. Necrotizing scleritis (13%)
1. with inflammation
2. without inflammation (scleromalacia perforans)
II. Posterior scleritis (2%)
B. Infectious scleritis
Clinical features
Symptoms
■Pain: Patients complain of moderate to severe pain
which is deep and boring in character and often
wakes the patient early in the morning. Ocular pain
radiates to the jaw and temple.
■Redness may be localized or diffuse.
■Photophobia and lacrimation may be mild to
moderate.
■Diminution of vision may occur occasionally.
Signs
A. Non-infectious scleritis
Salient features of different clinical types of noninfectious scleritis are as below:
I. Anterior scleritis
a. Non–necrotizing anterior scleritis
1. Non-necrotizing anterior diffuse scleritis. It is the
commonest variety, characterised by widespread
inflammation involving a quadrant or more of the
anterior sclera. The involved area is raised and
salmon pink to purple in colour
2. Non-necrotizing anterior nodular scleritis. It is
characterised by one or two hard, purplish elevated
immovable scleral nodules, usually situated near
the limbus (Fig. 7.4). Sometimes, the nodules are
arranged in a ring around the limbus (annular
scleritis).
b. Necrotizing anterior scleritis
1. Anterior necrotizing scleritis with inflammation.
It is an acute severe form of scleritis characterised by
intense localised inflammation associated with areas
of infarction due to vasculitis (Fig. 7.5). The affected
necrosed area is thinned out and sclera becomes
transparent and ectatic with uveal tissue shining
through it. It is usually associated with anterior uveitis.
2. Anterior necrotizing scleritis without inflammation
(scleromalacia perforans). This specific entity typically
occurs in elderly females usually suffering from longstanding rheumatoid arthritis. It is characterised by
development of yellowish patch of melting sclera
(due to obliteration of arterial supply); which often
together with the overlying episclera and conjunctiva
completely separates from the surrounding normal
sclera. This sequestrum of sclera becomes dead white
in colour, which eventually absorbs leaving behind
it a large punched out area of thin sclera through
which the uveal tissue shines (Fig. 7.6). Spontaneous
perforation is extremely rare.
II. Posterior scleritis.
It is an inflammation involving the sclera behind the
equator. The condition is frequently misdiagnosed.
It is characterised by features of associated
inflammation of adjacent structures, which include:
exudative retinal detachment, macular oedema,
proptosis and limitation of ocular movements.
B. Infectious scleritis
• Infectious scleritis accounts for 5–10% of all cases.
• In the early stage diagnosis becomes difficult as
presentation is similar to as non-infectious scleritis.
• Scleritis with purulent exudates (Fig. 7.7) or
infiltrates should raise the suspicion of an
infectious etiology.
• Formation of fistulae, painful nodules, conjunctival
and scleral ulcers are usually the signs of
infectious scleritis.
Complications
These are quite common with necrotizing scleritis
and include sclerosing keratitis, keratolysis,
complicated cataract and secondary glaucoma.
Investigations
Following laboratory studies may be helpful in
identifying associated systemic diseases or in
establishing the nature of immunologic reaction:
1. TLC, DLC and ESR.
2. Serum levels of complement (C3), immune
complexes, rheumatoid factor, antinuclear
antibodies and L.E cells for an immunological
survey.
3. FTA–ABS, VDRL for syphilis.
4. Serum uric acid for gout.
5. Urine analysis.
6. Mantoux test.
7. X-rays of chest, paranasal sinuses, sacroiliac joint
and orbit (to rule out foreign body especially in
patients with nodular scleritis).
Treatment
A. Non-infectious scleritis
I. Non-necrotizing scleritis. It is treated by:
• Topical steroid eyedrops
• Systemic indomethacin 75 mg twice a day until
inflammation resolves.
II. Necrotizing scleritis. It is treated by:
• Topical steroids
• Oral steroids on heavy doses, tapered slowly.
• Immunosuppressive agents like methotrexate
or cyclophosphamide may be required in nonresponsive cases.
• Subconjunctival steroids are contraindicated
because they may lead to scleral thinning and
perforation.
• Surgical treatment, in the form of scleral patch graft
may be required to preserve integrity of the globe
in extensive scleral melt and thinning.
B. Infectious scleritis
• Most of the time diagnosis is delayed and patients
are put on topical and oral steroids which worsen
the infective scleritis.
• Antimicrobial therapy, both with topical and oral
agents is required in an aggressive manner.
• Surgical debridement is found useful by debulking
the infected scleral tissue and also facilitating the
effect of antibiotics.
Blue Sclera
It is an asymptomatic condition characterised by
marked, generalised blue discoloration of sclera
due to thinning (Fig. 7.8). It is typically associated
with osteogenesis imperfecta. Its other causes are
Marfan’s syndrome, Ehlers-Danlos syndrome,
pseudoxanthoma elasticum, buphthalmos, high
myopia and healed scleritis.
STAPHYLOMAS
Staphyloma refers to a localised bulging of weak and
thin outer tunic of the eyeball (cornea or sclera),
lined by uveal tissue which shines through the
thinned out fibrous coat.
Types
Anatomically, it can be divided into anterior, intercalary,
ciliary, equatorial and posterior staphyloma (Fig. 7.9).
1. Anterior staphyloma (see page 135).
2. Intercalary staphyloma. It is the name given to the
localised bulge in limbal area lined by root of iris
(Figs. 7.9A and 7.10).
• It results due to ectasia of weak scar tissue formed
at the limbus, following healing of a perforating
injury or a peripheral corneal ulcer.
• Secondary angle closure glaucoma, may cause
progression of bulge if not treated.
• Defective vision occurs due to marked corneal
astigmatism.
Treatment consists of localised staphylectomy under
heavy doses of oral steroids.
3. Ciliary staphyloma. As the name implies, it is the
bulge of weak sclera lined by ciliary body. It occurs
about 2–3 mm away from the limbus (Figs. 7.9B
and 7.11). Its common causes are thinning of sclera
following perforating injury, scleritis and absolute
glaucoma.
4. Equatorial staphyloma. It results due to bulge of
sclera lined by the choroid in the equatorial region
(Fig. 7.9C). Its causes are scleritis and degeneration
of sclera in pathological myopia. It occurs more
commonly at the regions of sclera which are
perforated by vortex veins.
5. Posterior staphyloma. It refers to bulge of weak
sclera lined by the choroid behind the equator
(Fig. 7.9D). Here again the common causes
are pathological myopia, posterior scleritis
and perforating injuries. It is diagnosed on
ophthalmoscopy. The area is excavated with retinal
vessels dipping in it (just like marked cupping
of optic disc in glaucoma) (Fig. 7.12). Its floor is
focussed with minus lenses in ophthalmoscope as
compared to its margins
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