External Eye

·         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.

·         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:

1. cover test
2. Krimsky's test
3. Hirschberg light reflex test

·         STRABISMUS SYNDROMES:

1. 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.
2. 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
3. Maubius  Syndrome: congenital 6 & 7^th CN palsy
4. Double elevator palsy: congenital defect, usually isolated, in which one eye can elevate
5. 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.

·         Sometime  eye develops diffuse lamellar keratitis several days after uncomplicated laser in situ keratomileusis having desert sand appearance centrally