There is no substitute to examining pathology slides under the microscope. Most teaching centres have histopathology slides for trainee ophthalmologists. It is recommended that you examine the slides (especially those mentioned in the main section) regularly before the examination to understand the characteristic features for each condition.

When handed a slide, it is tempting to place it straight on the microscope for detailed examination. However, in so doing some vital clues which are visible to the naked eye may be missed.

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A piece of skin containing basal cell carcinoma.

The following steps are recommended to derive the maximum information from the slide:

• Check the name and date of birth (sometimes the date the specimen was obtained is written on the slide giving you clue to the patient's age)

 
• Hold the slide against the light and decide on:


1. the type of tissue being examined (skin, cornea or the whole eye. Avoid 
    guessing; ask the examiner for history if you were not certain about its nature).

2. the type of stains used (this is especially useful in corneal dystrophy as it 
    provides clue to the type of dystrophy being given).

3. the site and size of the lesion; intraocular tumour is always visible on naked
    eye (it is time-consuming to examine the entire eye section under the 
    microscope, locating the site of  the lesion allows you to focus your 
    examination).

The history and the preliminary survey should have given you the diagnosis or at least a differential diagnosis before you place the slide under the microscope. The microscopic examination and findings will depend on the pathology involved (details in relevant sections):

• Skin tumours (decide if it is a benign or malignant tumour)

 
• Other skin lesions (presence of giant cells or empty spaces as in chalazion cells, fat cells in xanthelasma)

 
• Choroidal melanoma (size and location, the cell types, any extraocular invasion for example through the sclera or vascular invasion)

A naked eye examination shows the presence of a raised intraocular lesion and overlying retinal detachment  (a choroidal melanoma)

• Retinoblastoma (size and location, differentiation, optic nerve invasion)

 
• Cornea (bullae, pannus or intraepithelial basement membrane in the epithelium, abnormal deposits, vessels, scarring or microbes in the stroma; break or thickening of the Descemet's membrane; numbers of and pigmentation on the endothelium)