A Patient's Guide To Retinal Diseases

By Dr Gerard Chuah

Retina of the eye is more than a light-sensitive layer of tissue. A healthy retina is essential for a good vision. Retina controls how the images are displayed by sending electrical impulses to the brain.

Retinal diseases affect this vital tissue, causing poor vision or even blindness in serious cases. This book provides us with insights on patients’ guide to retinal diseases and the treatments involved. “A Patient’s Guide to Retinal Diseases” is written by Dr Gerard Chuah, a leading eye surgeon in Asia and also the Medical Director of the Asian Diabetic and Retinal Disease Center and his team of doctors.

• Language: English
• Publisher: Faris Digital Solutions Pte Ltd
• Release date: Jan 9, 2015
• ISBN: 9789814645041

Book preview

Chapter 1

The Vitreous and the Retina

Dr Gerard Chuah, Dr Lam Wai Ching

Qn 1: What is the Vitreous Gel?

The vitreous is the structure that occupies the space between the lens and the retina. Referring to the cross sectional diagram of the eye, you can see that it is quite a large structure, occupying about 4 cubic centimetres. (Fig 4) It has several unique properties which are important to vision: it is transparent, colourless, it has the consistency of thick, sticky jelly which provides a firm structural framework, and is involved in the supply and transport of nutrients to several important structures of the eyeball. If any of these proper ties are disturbed, for example when bleeding occurs into the vitreous gel in diabetics, the gel loses its transparency and the vision gets blurred.

Qn 2: What is the Retina?

The retina is a transparent, thin layer of light sensitive cells that line the inside back wall of the eye. The retina is very important for good vision.

Referring to the diagram of a camera, the retina is like the film of a camera. (Fig 5) If the film of the camera is damaged, there will not be good quality pictures. Similarly, if the retina is damaged, the images received by the brain will be blurred and the vision will not be clear.

In the colour picture of the normal retina shown, the central part of the retina is called the macula. (Fig 6) The macula is the area of the retina most critical to fine, discriminatory central vision. The rest of the retina outside the macula is important for peripheral (side) vision.

If the peripheral retina is normal and the macula is damaged (for example in age related macula degeneration), the patient will have poor central vision. Conversely, if the peripheral retina is damaged and the macula is normal (for example in retinal detachments that have not involved the macula), the vision will be normal centrally and the patient will likely notice only defective vision in the periphery.

Chapter 2

Retinal Tears and Retinal Detachments

Dr Gerard Chuah, Dr Robert Devenyi, Dr Alan Berger, Dr Lam Wai Ching

Qn 1: What causes retinal tears or retinal holes?

The vitreous is the gel-like structure that occupies the space between the lens and the retina. When the vitreous gel is healthy, it has a firm, uniform consistency and acts as a support to the retina, keeping it in place against the choroid and sclera. It undergoes gradual degeneration and liquefaction with age and in certain ocular conditions (such as high myopia, ocular trauma, intra-ocular inflammation or ocular surgery). Due to increasing liquefaction, it will eventually collapse upon itself and separate from its attachment to the retinal surface in most areas except at the vitreous base (anterior edge of the retina). (Fig 7)

In most individuals, the vitreous separates cleanly from the retinal surface without causing any damage to the retina. In some cases, some part(s) of the vitreous is abnormally adherent to the retina and in the process of detaching, causes a tear(s) to the retina. (Fig 8a, 8b) Liquefied vitreous entering the tear into the subretinal space then causes a retinal detachment. (Fig 9)

Qn 2: Why is a retinal detachment dangerous?

A retinal detachment is dangerous because it can cause blindness. When liquefied vitreous enters through a retinal tear and separates the retina causing a retinal detachment, the photoreceptor cells of the retina that are crucial for vision lose their blood supply and begin to die off. This is especially true if the macula is involved by the retinal detachment. The central part of the vision will be lost and if the retina is not reattached soon, the photoreceptor cells may not recover completely even if the retina is successfully reattached. In such unfortunate patients, even though the surgery is a success, they will not recover their previous level of good vision.

Qn 3: I have been seeing ‘floaters’ and ‘flashing lights’. Is this a sign of a retinal tear?

‘Floaters’ are essentially shadows of opacities in the vitreous cavity cast onto and appreciated by the retina. As the vitreous liquefies and detaches from the retinal surface, there is a prominent opacity in the form of a ring or part of a ring that marks the vitreous attachment to the optic nerve. This manifests as a prominent floater at or around the point of fixation. Other causes of ‘floaters’ include blood or strands in the vitreous that casts a shadow on the retina. ‘Floaters’ have been described by patients in all shapes and sizes, ranging in appearance from ‘flying saucers’, ‘cobwebs’, ‘strings’, ‘showers of black dots’, ‘veils’ etc. ‘Floaters’ are usually more easily observed in areas of bright illumination, especially against a plain light coloured background.

‘Flashing lights’ are another common symptom of vitreoretinal disease. Mechanical stimulation of the retina elicits a visual sensation of bright light ‘flashes’. The mechanical stimulation of the retina may be due to physical traction (‘pulling’) on the retina from the collapsing vitreous gel or to actual physical ‘bumping’ of the retina by the collapsed vitreous gel.

When traction of the retina by the collapsing vitreous gel is severe enough to cause a retinal tear, some patients will complain of ‘flashing lights’ due to the mechanical stimulation of the retina. If a retinal tear has developed, there may be some bleeding due to torn blood vessels and the blood in the vitreous gel will cast shadows on the retina giving rise to the sensation of ‘floaters’. These floaters are usually like a ‘shower of black dots’. Hence, ophthalmologists will warn their patients that if they experience a sudden onset of ‘floaters’ and ‘flashing lights’, they should be screened by their ophthalmologists for a retinal tear.

Qn 4: Do all retinal tears need to be treated? I have been told that I have lattice degeneration. Should I have it treated?

Retinal tears should be treated if there is any significant risk of the retinal tear progressing to a retinal detachment.

This is especially true in the following circumstances:

If the fellow eye had a retinal detachment.

If there is a family history of retinal