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A pinhole test
allows only paraxial parallel light rays through and improves visual acuity if
refractory errors are present (most commonly myopia). The slit-lamp examination is a direct
visualization of the eye and its components. The pseudochromatic plate test detects color blindness, and Schiotz tonometry measures
intraocular pressure. Visual field testing determines if the patient has any
blind spots. The Amsler grid test screens for macular degeneration. Fluorescein staining is used to detect abrasions of the
cornea. A cobalt blue light is used to detect foreign bodies after the fluorescein is instilled into the affected eye.
·
Sometime eye develops diffuse lamellar keratitis
several days after uncomplicated laser in situ keratomileusis
having desert sand appearance centrally
·
The common abbreviations used to discuss visual
acuity are as follows: VA = Visual acuity
OD = Oculus dexter
or right eye OS = Oculus sinister or left
eye OU = Oculus uterque
or both eyes
·
Unlike the
attachment of Bowman’s membrane and corneal stroma, Descemet’s membrane is comparatively weakly attached to corneal stroma and this surface is sharply defined. Descemet’s membrane is a tough layer which is resistant to
enzymatic degradation by phagocytes and toxins.
In corneal ulcer, Descemet’s
membrane remains intact and often herniates out as a
result of increased intraocular pressure, which known as Descematocele.
·
The gene whose mutation causes gyrate atrophy
is found on chromosome 10, and encodes an enzyme called ornithine
ketoacid aminotransferase
(OAT). Different inherited mutations in OAT cause differences in the severity
of symptoms of the disease. OAT converts the amino acid ornithine
from the urea cycle ultimately into glutamate.
·
Rheumatoid
arthritis is associated with dry eyes. Tear-film integrity on the corneal surface is required both for comfort
and to provide an optically smooth surface for refraction. Therefore in dry
eye, when the tear film cannot provide adequate wetting of the corneal surface
between blinks, grittiness and intermittent blur occurs. A reflex response to
irritation of the corneal surface is epiphora, or
watering. Symptoms will be worse when tear-film evaporation is greater, for
example in windy or in warm dry (air-conditioned air) environments, or when the
blink rate declines as is likely when concentrating on computer work.
·
Acne rosacea is a facial
dermatosis that appears in middle age and causes
facial flushing in response to alcohol. Later on the flushing becomes permanent
and the vessels of the face become telangiectatic. Seborrhoeic gland hypertrophy causes rhinophyma.
The ocular features are blepharitis,
recurrent chalazia, conjunctival
hyperaemia and a characteristic keratitis with
peripheral vascularisation of the cornea.
·
Band keratopathy is due to
calcium deposition in Bowman’s
layer of the cornea. It can be due to the degenerative phase of chronic eye
diseases or due to hypercalcaemia; the level of serum
angiotensin-converting enzyme (ACE) is raised in hypercalcaemia due to sarcoidosis.
Kayser–Fleischer
rings are due to copper deposition in Descemet’s membrane of the cornea.
Corneal arcus is idiopathic or due to hyperlipidaemia.
Cornea verticillata
(vortex keratopathy) is commonly a side-effect of amiodarone (and rarely due to chloroquine,
hydroxychloroquine, indometacin,
tamoxifen, chlorpromazine or Fabry’s
disease).
Hudson–Stahli lines are due to iron deposition with normal ageing.
·
KERATOCONUS:
C3R (Corneal Collagen Crosslinking
with Riboflavin) causes the collagen fibrils to thicken, stiffen,
and crosslink & reattach to each other, making the cornea stronger and more
stable & halting
the progression of the disease.
RGP
Contact Lenses
Intacs: It is insertion of intrastromal
corneal ring segments.
·
STRABISMUS Tests:
- cover test
- Krimsky's test
- Hirschberg light reflex test
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STRABISMUS SYNDROMES:
- Brown's syndrome is a condition in which the affected eye cannot look up and in normally in the position of gaze that is the primary field of the inferior oblique muscle.
- Duane's Syndrome: Congenital, Inability to abduct the involved eye, Slight limitation of adduction of the involved eye as manifested by Small exotropia in the field of adduction Remote near point of convergence Narrowing of the fissure in the involved eye with adduction Retraction of the globe of the involved eye with adduction
- Maubius Syndrome: congenital 6 & 7th CN palsy
- Double elevator palsy: congenital defect, usually isolated, in which one eye can elevate
- Congenital fibrosis syndrome has defects of elevation of both eyes and both lids.
·
The Descemet's breaks or Haab's
striae from birth trauma tend to be vertical, while the Descemet's
tears associated with congenital glaucoma tend to be horizontal or curvilinear.
·
Cystinosis: Cystinosis occurs in three forms, all of which
have the characteristic corneal crystals. The infantile
form is associated with growth retardation, renal
failure, decreased pigmentation, and early death.
The adult form has no systemic manifestations. The adolescent form
has only the renal complications. The
crystals in the cornea are mainly in the anterior stroma.
·
RIDERs are seen in Zonular Cataract.
·
Telecanthus is a soft tissue
abnormality defined as an abnormally widened separation of the medial canthi. As an isolated condition the interpupillary
distance remains normal. It is most often seen as a result of severe nasoorbital-ethmoid trauma in adults, but can occur congenitally,
generally in conjunction with other ocular and facial anomalies.
Teleorbitism (hypertelorism, or hyperteleorbitism) is a bony abnormality
of the orbit wherein the medial walls are too widely separated. In this
condition, the interpupillary
distance is abnormally widened. Soft tissue telecanthus
is a secondary finding. The condition is almost invariably associated with
other maldevelopments and is most often encountered
in craniofacial dysmorphisms.
·
Lateral coloboma of the lower lid is a frequent finding in mandibulofacial dysostoses such
as the Treacher Collins syndrome.
·
Blepharochalasis is
characterized by recurrent bouts of bilateral angioneurotic
edema, which secondarily distends the overlying skin tissues. The lid becomes
thinned and takes on a crenulated or “cigarette-paper”
texture.
·
Marcus-Gunn
jaw-winking phenomenon
is thought to result from an abnormal synkinetic
connection between cranial nerves V and III.
Branches from the motor root of cranial nerve V destined for the ipsilateral lateral pterygoid
muscle (or less commonly, the inner pterygoid)
innervate the ipsilateral levator
muscle such that jaw movements, especially those to the opposite side, cause
elevation of the lid.
The condition can be
confused with aberrant
regeneration of cranial nerve VII
(i.e., winking jaw of Wartenberg). In this
latter, acquired condition, motor fibers originally innervating the orofacial musculature are redirected abnormally to the orbicularis fibers, causing synkinetic
closure of the lid with ipsilateral facial movements.
It is common after trauma to cranial nerve VII.
·
The hallmark of ocular cicatricial
pemphigoid (OCP)
is inferior forniceal
foreshortening.
·
Cornea verticillata, characterized by brownish,
whorl-like patterns in the epithelium, is seen in patients who have or are
carriers of Fabry's
disease (i.e., sphingolipidosis).Cornea verticillata can also be seen in patients using systemic
medications such as chloroquine, hydroxychloroquine, indomethacin, and amiodarone.
·
Thygeson's superficial punctate keratopathy is a bilateral inflammatory
condition of the cornea. Its cause is unknown, and it undergoes remissions and
exacerbations. Symptoms include mild-to-moderate light sensitivity and foreign
body sensation, with or without mildly decreased vision.
Terrien's
marginal degeneration is a slowly progressive, unilateral or
bilateral, essentially noninflammatory, peripheral
corneal thinning disorder seen more commonly in men.
Mooren's
ulcer is a unilateral or bilateral, chronic, progressive, painful
thinning and ulceration of the peripheral cornea. The underlying cause is
unknown.
A peripheral corneal ulceration to
the level of Descemet's membrane superiorly is found in rheumatoid
arthritis and is known as a rheumatoid melt.
Kerectasia is a rare, severe ectasia of the cornea. It is probably not a developmental
abnormality but is instead a result of an intrauterine
corneal infection with corneal ulceration and often perforation
·
Axenfeld's anomaly is posterior
embryotoxon with adherent iris stands. Axenfeld's syndrome is Axenfeld's
anomaly and glaucoma, which occurs in one
half of the patients with Axenfeld's anomaly. Both
conditions are autosomal dominant.
Rieger's
anomaly is the Axenfeld's anomaly plus iris stromal
atrophy. One half of these eyes develop glaucoma. Rieger's
syndrome is the Rieger's anomaly plus skeletal,
dental, and other abnormalities. Both conditions are autosomal
dominant.
Peters'
anomaly is a spectrum of disorders that all include a central corneal scar with defects of the posterior
cornea. One half of these eyes have glaucoma. Peters' anomaly is typically
sporadic but can be inherited.
·
Pellucid
marginal degeneration is a
variation of keratoconus in which there is
marked corneal steepening and anterior protrusion of the inferior cornea near the 6-o'clock limbus. It
is considerably rarer than keratoconus. Unlike keratoconus, in which the corneal steepening appears in the
paracentral cornea, this ectasia
occurs close to the limbus but not directly at the limbus. The central cornea remains normal until later in
the disease course, and visual acuity is good. A fine inferior pannus can occur, and the cornea can protrude
significantly, making contact lens wear difficult or impossible.
·
The limbal
girdle of Vogt consists of fine radial white lines at the temporal or nasal limbus
and represents elastotic and hyaline changes. Most
patients older than 60 years of age have some form of limbal
girdle, and almost all patients who are very elderly have some limbal girdle of Vogt. This is a normal
finding, and it does not grow farther onto the cornea as does band keratopathy.
·
Coats' ring is an oval deposit
of iron that is a small remnant of a previous
corneal injury, as from a foreign body. Coats' ring is usually located
in the region of Bowman's layer and consists
of discrete white dots, located for the most part in the inferior cornea where
the trauma has occurred. The white dots consist of iron deposits and are
probably remnants of the previous injury.
·
Whorl keratopathy in a patient who had a corneal transplant
has the hurricane-like appearance of
this defect, which diffusely stains with fluorescein.
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