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Techniques Of Vision Examination

 

Vision Examination

A major proportion of the vital sensory input required for flying an aircraft is visually acquired & therefore, a healthy and focused visual apparatus is an essential requirement.

Distant Vision Testing

  • Distant vision should be tested using a chart of Snellen letters, situated at an optical distance of 6 meters using either an eye lane or an approved vision testing instrument.

  • The examination room should be darkened with the exception of the chart. The uncorrected vision should be tested initially in each eye separately, and then in both eyes. After the uncorrected vision is tested the corrected vision should be tested in the same manner.

Near Vision

  • Near vision should be tested with the ‘N’ charts or equivalent. Vision in each eye separately should be tested without and then with correction.

  • Use good “over the shoulder” illumination of the card and avoid reflections and glare.

The visual standards recommended are:

Class I

Distant Visual Acuity (with or without correction)

  • 6/9 or better – Each eye separately

  • 6/6 or better – Both eyes together (Binocular Visual Acuity)

Near Visual Acuity (with or without correction)

  • N 5 – At 30 – 50 cms

  • N 14 – At 100 cms

Class II

Distant Visual Acuity (with or without correction)

  • 6/12 or better – Each eye separately

  • 6/9 or better – Both eyes together (Binocular Visual Acuity)

Near Visual Acuity (with or without correction)

  • N 5 – At 30 – 50 cms

  • N 14 – At 100 cms

  • This should include examination of the external eye and direct or indirect ophthalmoscopy. Particular attention should be directed to the cornea to detect contact lenses and / or the scars of surgical procedures to correct refractive errors such as PRK and LASIK. Even though there are no limits to correction lenses, high myopes should have a fundoscopy done to ensure absence of retinal pathology (lattice degeneration).

  • Individuals who have undergone surgery affecting refractive status of the eye may be considered on case –to – case basis. A minimum period of six months must have lapsed after the procedure and eyes must be free from any related complications, as under.

                             (i)      Over- or under-treatment of the condition may occur, requiring additional surgery, contact lens, or glasses.

                           (ii)      Problems with a decrease in contrast sensitivity, and even with 6/6 vision, objects may appear fuzzy or gray.

                         (iii)      Corneal scarring, permanent warping of the cornea and an inability to wear contact lenses.

                         (iv)      Flap complications.

                           (v)      Dryness.

Assessment of Visual Fields

By confrontation is adequate. In case of doubt (congenital or acquired ptosis, corneal opacities, suspected glaucoma, retinal pathology etc), Humphrey’s Automated Perimetry may be done under supervision of ophthalmologist.

 General Points to note

           The function of the eyes and adnexa shall be normal. No active pathological condition, acute or chronic, nor any sequelae of surgery or trauma of eyes or adnexa likely to reduce proper visual function. Some examples are as follows:

Ø  Eyelids:  Blepharoptosis interfering with vision is a cause for unfitness.

Ø  Conjunctiva: Progressive Pterygium.

Ø  Cornea: Opacities affecting vision.

Ø  Keratoconus

Ø  Lens: Lenticular opacities interfering with vision

Ø  Pupil:  Gross pupillary abnormalities e.g. mydriasis, anisocoria or irregularity.

Ø  Glaucoma / Uveitis.

Ø  Macular scarring, maculopathy, Retinal detachment, Retinal pigmentary dystrophy (Retinitis pigmentosa), Optic disc oedema / atrophy, Peripheral retinal degenerations, Vasculopathies, haemorrhage and exudates

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