About phoria and tropia

If a patient has phoria, the eyes will straight before and after test.
If a patient has tropia, one of eye will be deviated before the test and ends up with deviation in the same eye after the test.
If a patient has intermittent deviation, the eyes will be straight before test but get deviated for sometime after the test.

Pre requisites for performing cover test

The essential things that requires for performing cover test are :
Good central fixation and patient should not miss the target as he have shown by observer.
Patient should be good cooperative.
No ocular motility restrictions.

Cover Test

Cover test is helpful to discover visual misalignment. It ought to be accomplished for both separation and close with obsession with an accommodative target.The test ought to be performed with and without remedy.

Visual Acuity Assessment in Children

Testing neonates (new conceived): 

Obsession , support and inclination (burn light). 

1 year old: 

Optokinetic Nystagmus Drum 

Outwardly Evoked Potentials 

2 years of age: 

Teller keenness cards and Lea gratings graphs. 

3 years of age: 

Beacon streak card test 

4 years of age: 

Broken wheel sharpness test 

Sjogren hand test and HOTV test 

5 years of age: 

Snellen graph, Logmar diagram, Allen picture outline, Lea image graph, Tumbling "E" graph and Landolt "C" graph.

Vision Charts

Vision outlines are communicated in different documentations in light of the sort of graph utilized. These incorporates M documentation, P documentation, N documentation, and Reduced Snellen division. Decreased Snellen portion documentation is likewise used to survey close vision particularly where the patient is not educated.

Near Vision

Close vision is measure at separation of 30 to 40 cms. It is communicated in different documentations in light of the sort of graph utilized. Close vision can likewise be surveyed as a point measure at a predefined testing separation. 

Close vision recorded as N taken after by a number alongside the test remove. The N shows the extent of the Times New Roman text style. For instance, N6 at 40cms implies that the littlest print estimate that the patient read was 6 point Times New Roman text style tried at 40cm.

Why vision chart is kept at 6 mtrs.

Vision graph is kept at 6 meters on the grounds that more often than not 6 meters is thought to be sufficiently close to optical infinity.The beams of light from a separation question are for all intents and purposes parallel and little settlement is required.

Factors influencing visual acuity

Visual Acuity relies on upon various components are: 

Refractive mistakes, size of the student, enlightenment, time of presentation of the objective, range of retina empowers, eye developments.

Vision and Visual Acuity

The capacity of the unaided (without glasses) eye to separate fine points of interest is called vision. 

The capacity of a refractively remedial eye to separate the fine points of interest is called visual keenness.

Advantages and disadvantages of logmar chart

Preferences: 

Similarly quantities of letters per line. 

Consistently separating amongst lines and letters. 

Uniform movement in letter estimate. 

Inconveniences: 

Time taking 

Challenges for scoring

Advantages and disadvantages of snellens chart

Advantages:
The chart is familiar
Inexpensive, quick and easy to use and interpret
Disadvantages:
Snellen chart has only one 6/60 letter and an increasing number of letters increase as we go down the lines.
Patients with poor acuity are required to read less number of letters than those with good visual acuity .
The letters are lower lines are more crowded than those on the top on the chart.
There is no standard relationships between the width or height of the letters and spacing between each letters.

Interpretation of Snellen's Fraction

The numerator in the Snellen part demonstrates the separation at which outline is kept from the patient or a separation at which the patient can read the letters, the denominator means the separation at which this letter can be perused by a man having ordinary visual sharpness. 

In the event that visual sharpness is 6/9 

6 signifies the separation at which the graph is kept and 9 means the separation at which an ordinary individual would read this letter.

Visual Acuity and pinhole

Pinhole is utilized while introducing visual sharpness is under 6/6. Pinhole will build the depfth of center of the eye and increment the visual sharpness if there should be an occurrence of the uncorrected refractive mistakes upto - 5D to +5D. 

Ideal pinhole size is 1.0 to 1.5 mm distance across. In the event that visual keenness enhances with pinhole it shows uncorrected refractive blunder and if visual sharpness unaltered with pinhole it demonstrates not optical cause (illness).

Importance of visual acuity (VA)

It gives a thought regarding the respectability of the visual framework. 

Helps in determination and observing of eye maladies. 

Visual sharpness criteria are utilized by certain permitting experts and bosses as qualification criteria for specific occupations (e.g. carrier pilot, cops) and exercises e.g. driving.

Tear Break-Up Time

Fluorescein shading is associated with the tear film and the patient is asked for that not squint rapidly, and a short time later the time taken for dry spots to occur on the corneal surface is noted. This between time of the time is known as the TBUT., and the break is lessened in patients with dry eyes.

Schirmer Test

Schirmers strips is placed inside the lower fornix for a given period of time (usually 5 minutes) with or without topical anesthesia. The strip is then removed and the length of strip that is wet is measured and compared to standard. Patients with dry eye will have less wetting of the strip than normal individuals.Schirmers strips is set inside the lower fornix for a given timeframe (for the most part 5 minutes) with or without topical anesthesia. The strip is then evacuated and the length of strip that is wet is measured and contrasted with standard. Patients with dry eye will have less wetting of the strip than ordinary people

Cyclophotocoagulation

Trans-scleral cyclophotocoagulation is a methodology for glaucoma in which the ciliary body which secretes watery silliness is treated with laser to lessening creation of fluid. This will decrease the Intra Ocular Pressure. Cyclophotocoagulatio is utilized as a treatment when different methods for glaucoma treatment have neglected to legitimately control high weights.

Corneal Topography

Corneal geography is a strategy for measuring corneal ebb and flow helped by PC investigation. This technique is basic for patients before any refrective surgical methodology like LASIK, Corneal geology is likewise be utilized as a part of fitting RGP contact focal points..

Palpebral and bulber conjunctiva

Palpebral conjunctiva is begins from back top edge to the sulcus and contains more veins while bulber conjunctiva is a free mucous layer covering the sclera anteriorly.

Chlamydial conjunctivitis

It is the most common type of neonatal conjunctivitis, occurring 7-14 days after birth. The presentation of chlamydial conjunctivitis may range from mild congestion with mucous discharge, eyelids swelling. Most cases are mild and self limited. It occasionally may lead to corneal involvement and scarring.
Treatment is using erythromycin ointment.

Gonococcal conjunctivitis

Gonococcal conjunctivitis is the most serious condition, usually occuring 24-48 hours following the birth. The child is presented with bilateral accute conjunctivitis, associated with lid edema, chemosis and purulent discharge. Corneal ulcer and perforation may occur, if treatment is delayed.

Neonatal conjunctivitis

Neonatal conjunctivitis occurs during the first month after birth. It is caused by Bacteria, Chlamydia or virus. Infants acquire the infection as they passes through the birth canal during the birth process.
Treatment is 2.5% povidone-iodine solution is useful in preventing neonatal conjunctivitis.

Bacterial conjunctivitis

Bacterial conjunctivitis happens in those patients who have complained of mucopurelent discharge, diffuse congestion, watering, irritation and usually effect one eye first but may spread easily to the fellow eye.
Treatment is only antibiotic eye drops.

Allergic Conjunctivitis

The causes of allergic conjunctivitis can be diagnosed clinically based on signs and symptoms.
Signs and symptoms are :
Ropy discharge
Diffuse congestion
Itching
Watering
Lid edema
Papillae may be present on palpebral conjunctiva.
Treatment :
Cool compresses and artificial tears. Non-steriodal anti-inflammatory medication, steroids and antihistamines are advised in severe condition.

Contrast sensitivity

Contrast sensitivity is the ability of eye to see a given object against a background. The closer the levels of target illumination and background illumination, the more difficult it becomes to resolve the target. The reduction in contrast sensitivity occurs in corneal disease, cataract and retinal degenerations.

Color vision

Color vision is a function of cones of the retina. The most common test of color vision is the Ishihara pseudo-isochromatic color plate exam. It consists of a series of test plates with colored dots forming a number. The numbers are visible to individuals with normal color vision but appear differently or invisible to the individuals who are red green color deficient.

Amsler Grid Test

The Amsler Grid is a test is used to evaluate a patient for macular edema, Age related macular degeneration (ARMD) or central serous retinopathy. The patient is asked to look at the center of the grid where a dot is present and to mark any distortion or disappearance or wavy appearance of lines on the grid.(Metamorphosis).

Retinal Angiography

Fluorescein/Indocyanine green dye (ICG) is injected into a vein in the arm of the patient. The dye then circulates throughout the body, including the eye and the fundus camera is used for taking pictures of the circulation of the eye.

Visual Acuity

Visual acuity is the measure of vision. It can be defined as the resolving power of the eye. It indicates the smallest detail that can be seen. Visual acuity is a function of the dioptric apparatus, the retina, visual pathway and the central nervous system.

Optical Power

The optical power of a lens is measured diopters. Diopter is defined as the reciprocal of the focal length in meters. The greater the optical power, the shorter the focal length. The focal length of a plus lens will be the same as focal length of a minus lens with the same power.

Accommodation

It's a process by which the refractive power of the eye is changed by the shape of its crystalline lens to ensure a clear retinal image or the lens changes its shape and power to adjust for near and distance vision.

Ammetropia

It is a refractive condition where the parallel beams originating from endlessness after the refraction through the eyes won't frames a point concentrate on the retina when settlement is very still.

Emmetropia

It is a refractive condition where the parallel rays coming from infinity after the refraction through the eyes forms a point focus on the retina when accommodation is at rest.