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Optha Pearl

Dimensions of the Eye

• Vertical dimension is 23 mm.
• Antero-posterior dimension is 24 mm.
• Horizontal dimension is 23.5 mm.
• Circumference is 75 mm.
• Vitreous humor volume is 4 CC.
• Volume of the eyeball is 6.5 ml.
• Orbit volume is 30 CC.
• Weight of the eyeball is 7 gms.

Layers of the Eye

• Tympanic Membrane has 3 layers.
• Tear film has 3 layers.
• Cornea has 6 layers.
• Retina has 10 layers.

The Tear

• pH is 7.5.
• Composition: water, sugar, salt (NaCl), urea, and protein.
• Daily secretion ranges from 0.5 to 2.25 ml.
• Immunoglobulins present include IgA, IgG, and IgM, with IgA predominating.
• Antibacterial substances present are lysozyme, beta-lysin, and lactoferrin.
• Obstruction to tear flow is known as epiphora (watering of eyes).
• Lacrimation is an excessive secretion of lacrimal fluid by the lacrimal gland.
• Sjogren's Syndrome involves decreased secretion of tear and salivary glands.
• Mikulicz's Syndrome involves bilateral enlargement of the lacrimal and salivary glands.

Palpebral Aperture

• Is the space between the upper and lower eyelids.
• Vertical diameter is 8-11 mm.
• Horizontal diameter is 27-30 mm.
• Blepharophimosis is a reduction in the space of the palpebral aperture.

Blepheritis

• Chronic inflammation of the lid margin.
• The lid margin can be anterior or posterior.
• O/E = Dandruff on the eyelashes.
• Ulcers below the scales and crusting at the lid margin

Chalazion

• A chronic, non-suppurative, non-infective inflammation of the Meibomian gland.
• Also known as a mebomian cyst.
• Site mainly occurs on the upper eyelid margin
• It is a typically painless condition.

Lacrimal Apparatus

• Consists of the lacrimal gland, lacrimal ducts, conjunctival sac, lacrimal punctum, lacrimal canaliculi, lacrimal sac, nasolacrimal duct, and the inferior meatus of the nose.

Dacryocystitis

• Inflammation of the nasolacrimal sac.
• Rx: DCR (Dacryocystorhinostomy) involves nasal drainage.
• DCT (Dacryocystectomy) involves removal of the sac.

Glands in the Eyelid

• Tarsal/Meibomian glands are modified sebaceous glands.
• Zeis glands are sebaceous glands.
• Glands of Moll's are modified sweat glands.

Accessory Lacrimal Glands

• Glands of Krause
• Glands of Wolfring

Eye Conditions

• Madarosis is the absence of eyelashes/cilia.
• Trichiasis is misdirected eyelashes/cilia.
• Distichaisis is an extra layer of eyelashes.
• Poliosis is graying of the eyelashes.
• Ablepharon is the absence of eyelids.
• Tylosis is hypertrophy of the lid margin.
• Districhiasis is an extra row of eyelashes.
• Entropion is inward rotation of the lid margin.
• Ectropion is outward rotation of the lid margin.
• Coloboma is a full-thickness triangular gap in the tissue of the eyelid.
• Cryptophthalmus is a failure in the development of the eyelid.
• Microblephron is abnormally small eyelids.
• Symblepheron is adhesion between the palpebral and bulbar conjunctiva.
• Ankyloblepharon is adhesion between the margins of the upper and lower eyelids.
• Lagophthalmus is the inability to close the eyelids.
• Blepharospasm refers to involuntary forceful closure of the eyelids.
• Tylosis is the thickening of the lid margin.
• Muller muscles are present in the eyelid.
• Procerus muscle is present in the nose.

Cornea and Limbus

• The upper eyelid covers 1/6th of the part of the eyelid cornea.
• The junction between the cornea and sclera is known as the limbus (LSCs).
• The lower eyelid touches the limbus and does not cover the cornea.

Hordeolum (Stye)

• Most commonly found at or near an eyelash follicle.
• Caused by a bacterial infection either at the root of the eyelash follicle or in the oil gland of the lids
• Tenderness and swelling
• Spontaneous drainage, warm compresses
• Suppurative inflammation of the meimobian gland

Chalazion

• Most commonly found above the eyelashes on the upper lid.
• Caused by a blocked oil grand meibomian
• Firm, painless lump
• Warm Compressess, Steroid injection, surgery

Internal Hordeolum

• Is a suppurative inflammation of the meibomian gland and is painful.

Chalazion

• Chronic non-suppurative inflammation of meibomian gland (pain).

External Hordelum(stye)

• There is an acute suppurative inflammation of the eyelash follicle and associated glands, i.e., the Zeis and Moll's glands

Ptosis

• Drooping of the upper eyelid, also known as third nerve palsy
• Nerve damage (oculomotor)
• Muscle damage (LPS)

Trachoma

• Also known as Egyptian ophthalmia/Chronic kerato-conjunctivitis (CKV).
• Causative organism is Chlamydia trachomatis.
• Primarily affects individuals between 1-9 years of age
• Affects epithelial cells of the cornea and conjunctiva, producing Halberstaedter Prowazek inclusion bodies (H.P. bodies).

Mc Callan Trachoma Stages in 1908

• Stage I (Incipient trachoma or stage of infiltration)
• Stage II (Established trachoma)
• Stage III (Cicatrising trachoma or stage of scarring)
• Stage IV (Healed trachoma or stage of sequelae)

1987 - Follicles, Inflammation, Scaring Trichiasis, Opacity Symptoms

• =5 follicles in the upper palpebral

• Inflammation
• Scarring
• Trichiasis
• Opacity

Trachoma Treatment

• SAFE Strategy
• Environmental cleanliness.
• Surgery (for trichiasis and entropion).
• Azithromycin (20mg/kg in children and 1g/kg in adults), tetracycline(1% ointment)
• Facial hygiene

Vision 2020

• Launched in 1999.
• Objective is a global initiative to reduce preventive and curable blindness by the year 2020.
• Theme is ‘The Right to Sight'.
• The WHO program is to control cataract, trachoma, refractive errors, childhood blindness and onchocerciasis.

Conditions that Vision 2020 in India eradicates

• Cataract.
• Trachoma.
• Refractive errors.
• Childhood blindness.
• Glaucoma.
• Corneal blindness.
• Diabetic retinopathy.

Sclera

• Outer sclera is covered by the tenon capsule.
• Anterior sclera is covered by the Bulbar Conjunctiva.
• Inflammation of the episclera along with the tenon capsule that occurs in episcleritis.
• Scleritis (Painful) is more severe than episcleritis and may cause vision loss.

Scleritis Associations

• Rheumatoid arthritis.

Pinguecula

• Yellow spot on the bulbar conjunctiva.
• Originates from the inner canthus.
• Precursor of pterygium.

Pterygium

• Abnormal growth of the conjunctiva on the cornea.

Vitamin A Deficiency (Xerophthalmia)

• Spectrum of ocular diseases
• Child more than one year: 100,000 IU of inj vitamin A on 0 , 1 and 14 day.
• Vit A prophylaxis program start – 1970

Corneal Anatomy

• The cornea is aspherical and avascular.
• Diameter ranges from 11.5 to 12 mm.
• Refractive index is 1.37
• Power ranges from 43D to 45D
• Thickness: 500-600 microns or 0.5 to 0.6 mm
• Thickness at the limbus is 1 mm.
• Average thickness is 540 microns

Megacornea

• More than 13mm (horizontal diameter)

Microcornea

• Less than 10mm (horizontal diameter)

Layers of the Cornea

• Epithelium can regenerate.
• Bowman's membrane is non-regenerative.
• Substantia Propria/Stroma
  • Thickest layer (90% of the cornea).
• Dua's layer is acellular, strongest, and toughest layer.
• Kaiser-fleischer ring (Wilson's Disease)
• Descemet's membrane
  • Has deposits of copper
  • Can form fleischer ring.
• Can show "Schwalbe's Line" on Gonioscopy

Endothelium

• Metabolically most active layer of the cornea
• Non-regenerative

Cornea Investigation

• Keratometry - Measures Curvature of cornea both horizontal and vertical.
• Keratoscopy or placido's disc - Assesses the Overal surface of the cornea
• Esthesiometer measures Corneal sensations
• Pachymetry is used To measure the thickness of cornea

Keratitis - Bacterial Risk Factors

• Contact lens use, dry eyes, and abrasion.

Keratitis - Bacterial Clinical Findings

• Round or oval white lesion, AC activity.

Keratitis - Viral Risk Factors

• History of cold sores.

Keratitis - Viral Clinical Factors

• Branching epithelial defect.

Keratitis - Fungal Risk Factors

• Trauma, vegetative/outdoor exposure.

Keratitis - Fungal Clinical Factors

• Infiltrate with feathery edges.

Keratitis - Protozoal Risk Factors

• Contact lens use with poor hygiene.

Keratitis - Protozoal Clinical Features

Ring-shaped infiltrate

Bacterial Keratitis

• Caused by inflammation of cornea to lead to ulcer formation.
• M/C cause of bacterial corneal ulcer
  • Staphylococcus aureus (in world )
• M/C cause of bacterial corneal ulcer
  • Staphylococcus epidermidis (in india )
• Cause of creeping corneal ulcer
  • Streptococcus pneumoniae (pneumococcus)
• Creeping corneal is known as ulcus Serpens.
• Ground glass appearance of cornea is due to pseudomanas aeruginosa
• Nocardia (Bacteria) causing corneal ulcer that looks like fungal ulcer.

Viral Keratitis

• M/C virus in ocular infection - Herpes Simplex

HSV-I

• Infection above the waist.
• Minimal cornea involvement.
• Leads to blepharoconjunctivitis.

HSV-II

• Infection below the waist.
• Leads to Neonatal conjunctivitis.

Corneal Opacity

• Types:
  • Nebula - Very faint, cloud-like opacity
  • Macula - Grey colour
  • Leucoma - Very dense, White clour opacity

Conjunctiva

• Translucent mucous membrane lining the posterior surface of the eyelids and anterior aspect of the eyeball
• Thinnest membrane in the body - Conjuctiva
• Largest membrane of the body - Peritoneum
• Plica semilunaris - Fold of conjunctiva near middle canthus

Parts of conjunctiva

• 03 - Palparbral + Bulbar + Fornix

Layers of conjunctiva

• 03 - Epithelial + Adenoid/lymphoid + Fibrous

Conjunctiva

• Contains Conjunctiva Glands, Accessory Lacrimal glands, and Mucing Secretory Glands

Conjunctivitis

• Inflammation of conjunctiva - inflammation more near the fornix than at the limbus.

Conjunctivitis Discharge

• Watery/serous discharge (Viral)
• Mucoid discharge (Allergic)
• Stringy, ropy discharge (Vernal)
• Mucopurulent discharge (Bacterial)
• Purulent discharge (Gonococcal)
• Bloody discharge (Gonococcal)

Conjunctivitis Types:

• Bacterial
• Acute (Mcc: staph)
• Hyperacute (Mcc: Gonococcus)
• Chronic (Leads to blepharitis), Mcc: staph
• Viral
• Mcc: Adenovirus
• Allergic
• Simplex allergic conjunctivitis, Hay fever conjunctivitis, Seasonal allergic conjunctivitis (SAC) & Perennial allergic conjunctivitis (PAC)
• Vernal, Atopic & Giant papillary

Vernal keratoconjunctivitis

• (VKC): "summer's conjunctivitis".
• Spring catarrh
• Type I hypersensitivity
• Seasonal & recurs & "warm weather”
• Spontaneous @ puberty

Ocular Signs of VKC:

• Intense itching, vigorous eye rubbing, ropy/stringy discharge
• Bulbar = Tranta dots (gelatinous nodules @ limbus + eosinophils)
• Palpebral - cobblestone appearance.
  • In eyelid margin
  • Discharge (coagulated Maxwell-Lyon sign)
• Corneal - eosinophils infiltrate corea, can leads to subepithelial scarring (Pseudogerontoxon/ cupid’s bow)

Blindness

• According to WHO, blindness: VA in better eye ≤3/60 (visual acuity) or visual field <10°
• Most common cause of blindness in India is Glaucoma
• Most common cause of preventable blindness in both places is Cataract
• India/child Vitamin A deficiency (most cause)
• Second most cause In India is Refractive
• Most cause in developed country is Glaucoma

Lens

• Transparent biconvex. Crystalline structure.
• Located: Patellar Fossa (saucer shaped depression).
• Nourishment: Aqueous humour (cuz avascular)
• Growth: Throughout life
• Power: +15 to +18 D
• Surface of lens - Post has patella fossa, is connected to circular area via Wiegert's

Layers + What Eye Parts Formed From:

• Surface ectoderm - from Lens & retina
• Mesoderm - from Cornea
• Neural endoderm

Cataract

• Opacification of lens and or capsule

Cataract causes

• Most cause worldwide is Age/Senile
• Most congenital cause is Dot/PUNCTATE type
• India blindness common case is cataract = most 2nd common blindness for glaucomic reasons
• Visually TOC important Cataract cause is Phacoemulsification with intraocular lens (IOL) Implantation

Cataract complications/symptoms

• Most common surgery complication is capsular opacification
• First symptom & easiest visual symptom is glare/ difficulty driving @ night.
• Without lenses, = Aphakia - condition
• May have Second side effects (Nuclear sclerosis shift/Myopic shifting)
• Causes: blunt trauma (for rosette shapes)

Diabetes association cataract = Snowflake

• Downe syndrome association cataract = Christmas tree cataract
• Prolonged steroids = Posteriorsubcapsular Cataract
• Myotonic Dystrophy association cataract = Christmas tree cataract
• Fabrys Disease association cataract= Propelle /Spoke cataract
• Wilson's Disease association cataract= Sunflower cataract
• Galactosemia association cataract= Oil drop cataract

Glaucoma

A group of conditions characterized by optic damage/ High interocular pressure (IOP) Normal IOPS = 10 to 21 mmhm + World Glaucoma day on march 06

• Symptoms (Head pain/ Eye redness/Blurred vision)
• Common type = primary open angle glaucoma (POAG)
• Hallmark = Optic disc cupping
• cupping increase = increase in Gl
• Contraindicated drug = Atropine
• Best Initial Drug is - Prostaglandin analogs (Latanoprost)

Nyctalopia + Hemeralopia

• Scotopic vision functions visibility with dim Rod-shaped lights
• Photopic cones allow visibility in bright Cones

Miscellaneous Notes

• Nyc is night blindness
• Hem is day blindness.
• Vit A deficiency causes night blind.
• Decrease in the Number of rods cases blindness in the night time. -Number/absent cones is when blindness is caused. Day time
• Ogudi disease -Stationary night blind at birth time.

Long Sightedness + Other Conditions

• Hypermetropia
• Short Sightening == Myopia
• Muller muscles present within eyelid
• Cherry-red spot found when central retinol artery is blocked
• The cotten is due Diabetic retinopathy
• Conditions
  • Atropine =Mydriatic drug/Cycloplegic
  • Photophobia = vitin B2
  • Epilation - Mechanical removel eyelashes
  • drug choice can vary from (fungals 5% or virals - at 3%