Skip to main content

Posts

Showing posts with the label Ophthalmology

What are the causes of retinal arterial occlusion ?

What are the causes of retinal arterial occlusion ?

The commonest cause is emboli arising from the major arteries supplying the head or'rom the left side of the heart. Embolic particles consist of platelet clumps, cholesterol crystals or Hollenhorst plaques and others (mixed thrombus, calcific or septic material from cardiac valves, fat, myxoma, talc in intravenous drug abusers or silicone in those who receive injections for cosmetic purposes).

Other causes include:
• Temporal arteritis.
• Collagen vascular diseases.
• Increased orbital pressure, e.g. retrobulbar haemorrhage, Graves' exophthalmos.
• Sickle cell disease.
• Acute arteriolar spasm due to intranasal cocaine.
• Syphilis.

How would you manage an acute occlusion of the retinal artery ?

How would you manage an acute occlusion of the retinal artery ?

• Lie the patient in a supine position to ensure adequate circulation.

• Apply intermittent ocular massage for 15 minutes to dislodge the emboli, lower intraocular pressure and improve circulation.

• Intravenous acetazolamide to lower intraocular pressure.

• Inhalation of a mixture of 5% carbon dioxide and 95% oxygen.

• Anterior chamber paracentesis.

If the investigation of a patient with amaurosis fugax provides no evidence of carotid artery disease, embolism or other recognized causes of the disorder, then the diag-nosis by exclusion should be vasospasm. In such cases a calcium channel blocker should be tried.

What are the causes of vitreous opacities ?

What are the causes of vitreous opacities ?

 • Blood: diabetes, retinal vein occlusion, trauma, subarachnoid haemorrhage, sickle cell retinopathy. 

• Cholesterolosis bulbi, where free-floating, highly refractile crystals are seen in liquified vitreous and in patients with severe intraocular disease. 

• Asteroid hyalitis (Benson's disease), where whitish yellow solid bodies, con-taining calcium palmitate and stearate, are suspended in normal vitreous. Prognosis for vision is good. 

• Synchysis scintillans: gold or yellowish-white particles made up of cholesterol are located in the vitreous; they settle to the bottom of the eye due to gravity. Associated with previous trauma or surgery to the eye.

 • Other, e.g. retinoblastoma, primary amyloidosis.

How would you treat the lesions of CMV retinitis ?

How would you treat the lesions of CMV retinitis ?

• Therapy with intravenous ganciclovir or foscarnet is given lifelong to protect unaffected areas but does not restore functional areas already affected. The optimal treatment for patients with AIDS, normal renal function and CMV retinitis is foscarnet plus an antiretroviral nucleoside such as zidovudine. For similar patients with impaired renal function, ganciclovir would be the drug of choice, perhaps with an antiretroviral agent such as didanosine that has few over-lapping side-effects. Late retinal detachment occurs despite therapy in one fifth of these patients.

• Sustained release ganciclovir implant in the pars plana of the eye. Oral ganciclovir in conjunction with an implant reduces the incidence of new cytomegalovirus disease and delays the progression of retinitis (N Engl J Med 1999; 340: 1063-70).

• Intravitreal injections of ganciclovir or foscarnet.

What are the other retinal manifestations in patients with AIDS ?

What are the other retinal manifestations in patients with AIDS ?

· Toxoplasmosis retinochoroiditis - usually nasal to the disc, characterized by extensive whitish infarction and inflammation, with minimal associated intra-retinal haemorrhage (outer retinal involvement may show 'brush-fire' advancement of infection).

· Pneumocystis carinii choroiditis - characterized by scattered nodular yellowish-orange lesions deep in the retina, usually throughout the posterior pole.

· Acute retinal necrosis syndrome - with severe peripheral retinal infarction and retinal vasculitis. Atrophic retinal holes appear later in these areas.

· Progressive outer retinal necrosis syndrome - characterized by diffuse whitish opacification of the retina beneath the retinal vessels and a cherry-red spot in the fovea. It is associated with herpes zoster and the prognosis for visual acuity is dismal.

· Ocular presentations of syphilis include anterior and posterior uveitis, retinitis, retinal vasculitis a…

What diagnostic tests would you perform to detect retinal manifestations of AIDS ?

What diagnostic tests would you perform to detect retinal manifestations of AIDS ?

· Careful clinical observations.

· Serology: CD4 count (usually <50 in untreated cases of CMV retinitis).

· Culture.

· Retinal biopsy by pars plana vitrectomy.

· Fluorescein angiography: helpful in differentiating retinal lesions.

· Sequential fundus photographs: for diagnosis and monitoring of lesions.

· Testing of

ocular fluid by polymerase chain reaction.

What are the types of retinal detachment ?

What are the types of retinal detachment ?

Rhegmatogenous retinal detachment

This is defined as the presence of a hole or break in the retina that allows fluid from the vitreous capacity to enter the subretinal space. It usually occurs spontaneously in those who have a predisposition to it following trauma to the eye or after intra-ocular surgery. Most of these patients develop symptoms. A break in the peripheral retina is associated with a sudden burst of flashing lights or sparks that may be followed by small floaters or spots in the field of vision. When the retina detaches, the patient perceives a dark curtain progressing across the visual field, and when the fovea detaches central vision is abruptly diminished.It is treated surgically with a scleral buckling procedure (where all retinal breaks are localized and adhesions between the choroid and retina are performed around the break with diathermy or a cryoprobe). After draining the subretinal fluid, the detached portion of the ret…

What are drusen ?

What are drusen ? 

Drusen are pale yellow spots that occur individually or in clusters throughout the macula. Nearly all individuals over the age of 50 years of age have at least one small drusen (?< 63 lam) in one or both eyes .

They con-sist of amorphous material accumulated between Bruch's membrane and the pig-ment epithelium. Although the exact origin is not known, it is believed that driJsen occur due to the accumulation of lipofuscin and other cellular debris derived from cells of the retinal pigment epithelium that are compromised by age and other fac-tots.

Only eyes with large dr0sen (>63 lam) are at increased risk for senile macular degeneration.

What are the types of senile macular degeneration ?

What are the types of senile macular degeneration ? 

There are two types: 

1. Atrophic or 'dry' type: involving the choriocapillaries, retinal pigment epithelium and the rods and cones. There is no leakage of blood or serum. 

2. Neovascular exudative or 'wet' type: there is haemorrhagic or serous detachment of the retinal pigment epithelium and choroidal neovascularization resulting in leakage and fibrovascular scarring.

What is the difference between krypton and argon laser photocoagulation ?

What is the difference between krypton and argon laser photocoagulation ? 


The krypton red photocoagulator is useful in treatment when the neovascularization is closer than 200 pm but not under the fovea, because of its ability to spare the inner retina by its virtual lack of absorption by haemoglobin (unlike the argon laser). The conventional argon laser has blue and green wavelengths. The green wave-length is absorbed by haemoglobin and thus may damage the retina, whilst the blue wavelength is absorbed by the macular xanthophyll and results in foveal damage.

Postimet e fundit






Related Posts Plugin for WordPress, Blogger...

Labels

Show more