Basil H. Bloom BSc(Hons) FCOptom

Optometrist

Orthokeratologist.

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The eye examination is divided into two parts.

Refraction, which determines what prescription you need and Health which investigates if you have anything wrong with your eyes.

1. Refraction

This is usually undertaking in two ways,objective and subjective.

A.    The objective method, where the practitioner establishes what prescription you need, is done using either a traditional hand-held instrument, a retinoscope, or automated equipment.  I use. the Retinomax handheld autorefractor.

                    This gives an accurate estimation of your prescription in under 10 seconds

                     and  all the patient has to do is to look at a picture in the machine.

B.  The subjective method involves the use of trial lenses and a sight  test chart with the patient replying to questions put to them by the practitioner. For very young children or patients who are unable to read, we use a number of different charts with either pictures or figures on them.

2. Health

I have a number of sophisticated pieces of equipment to investigate specific eye conditions.

Glaucoma is a leading cause of blindness in the world and whilst its detection in the later stages is relatively easy, early diagnosis can be difficult.
Glaucoma is a disease characterized by breakdown of the optic disc, a structure at the back of the eye which leads to vision problems and potential blindness.  In traditional glaucoma evaluations, a doctor will conduct a pressure test and a visual field test, which investigates any decreases in the area visible to one eye without movement.  Various tools to examine the structures at the back of the eye, such as an ophthalmoscope or retinal photography, are also used.  One concern among glaucoma experts is that breakdown to the structures at the back of the eye, specifically the optic disk and the retina, frequently occur to a significant extent before any abnormalities can be detected by visual field tests, ophthalmoscopy, or retinal photography.

The tests at my disposal are

Tonometry.          This is a test to measure the pressure inside your eye. it is done either with a Pulsair non-contact tonometer, air-puff, or a Tonopen which gently touches the front surface of the eye.
Obviously, if the pressure is very high then glaucoma must be suspected but some patients can have normal pressures and still have nerve damage.

Visual Fields.       This measures how well you see to the side and if your vision is good in all areas.  I use a Dikon Automated Perimeter.
Visual field results are very variable and quite often inconclusive in the early stages.

Heidelberg Retinal Tomography HRT3.

The HRT3 uses a confocal scanning system to acquire 3-dimensional images of the optic nerve and retina.
This data is used for retinal thickness measurements as well as topographic optic nerve head analysis.

I am awaiting delivery of this system which can show changes in the optic disc up to 4 years before other tests.

Individuals at high risk of Glaucoma include any of the following:

• Ethnic Africans over 40 years old
• Asymmetric optic disk cupping
• Caucasians over 65 years old
• Family history of glaucoma
• Diabetes
• Ocular hypertension
• Severe myopia
• Visual field loss without elevated intraocular pressure

Diabetes.

I have a Topcon Non Mydriatic Digital camera system which takes a picture of the back of the eye, the Retina. This can show damage caused by the disease.

 The HRT3 can, for the first time , give a quantitative measurement of the retinal function. This means that we can measure any damage caused by the disease.

Some of these tests incur an extra charge.

Copyright © 1999 Basil H. Bloom Optometrist                                    
Last modified: June 26, 2005