CNV can create a sudden deterioration of central vision, noticeable within a few weeks. Other symptoms which can occur include colour disturbances, and metamorphopsia (distortions in which straight lines appears wavy). Hemorrhaging of the new blood vessels can accelerate the onset of symptoms of CNV. CNV may also include the feeling of pressure behind your eye.

Signs and symptoms of macular degeneration include:

- Visual symptoms

- Distorted vision in the form of metamorphopsia, in which a grid of straight lines appears wavy and parts of the grid may appear blank: Patients often first notice this when looking at things like miniblinds in their home or telephone poles while driving. There may also be central scotomas, shadows or missing areas of vision

- Slow recovery of visual function after exposure to bright light (photostress test)

- Visual acuity drastically decreasing (two levels or more), e.g.: 20/20 to 20/80

- Blurred vision: Those with nonexudative macular degeneration may be asymptomatic or notice a gradual loss of central vision, whereas those with exudative macular degeneration often notice a rapid onset of vision loss (often caused by leakage and bleeding of abnormal blood vessels).

- Trouble discerning colors, specifically dark ones from dark ones and light ones from light ones

- A loss in contrast sensitivity

Macular degeneration by itself will not lead to total blindness. For that matter, only a very small number of people with visual impairment are totally blind. In almost all cases, some vision remains, mainly peripheral. Other complicating conditions may possibly lead to such an acute condition (severe stroke or trauma, untreated glaucoma, etc.), but few macular degeneration patients experience total visual loss.

The area of the macula comprises only about 2.1% of the retina, and the remaining 97.9% (the peripheral field) remains unaffected by the disease. Even though the macula provides such a small fraction of the visual field, almost half of the visual cortex is devoted to processing macular information.

The loss of central vision profoundly affects visual functioning. It is quite difficult, for example, to read without central vision. Pictures that attempt to depict the central visual loss of macular degeneration with a black spot do not really do justice to the devastating nature of the visual loss. This can be demonstrated by printing letters six inches high on a piece of paper and attempting to identify them while looking straight ahead and holding the paper slightly to the side. Most people find this difficult to do.

Patients with idiopathic macular telangiectasia type 1 are typically 40 years of age or older. They may have a coincident history of ischemic vascular diseases such as diabetes or hypertension, but these do not appear to be causative factors.

Macular telangiectasia type 2 usually present first between the ages of 50 and 60 years, with a mean age of 55–59 years. They may present with a wide range of visual impact, from totally asymptomatic to substantially impaired; in most cases however, patients retain functional acuity of 20/200 or better. Metamorphopsia may be a subjective complaint. Due to the development of paracentral scotomota (blind spots), reading ability is impaired early in the disease course. It might be even the first symptom of the disease.

The condition may remain stable for extended periods, sometimes interspersed with sudden decreases in vision. Patients’ loss of visual function is disproportionately worse than the impairment of their visual acuity, which is only mildly affected in many cases. In patients with MacTel, as compared with a reference population, there is a significantly higher prevalence of systemic conditions associated with vascular disease, including history of hypertension, history of diabetes, and history of coronary disease. MacTel does not cause total blindness, yet it commonly causes gradual loss of the central vision required for reading and driving.

Intermediate AMD is diagnosed by large drusen and/or any retinal pigment abnormalities. Intermediate AMD may cause some vision loss, however, like Early AMD, it is usually asymptomatic.

CNV can occur rapidly in individuals with defects in Bruch's membrane, the innermost layer of the choroid. It is also associated with excessive amounts of Vascular endothelial growth factor (VEGF). As well as in wet macular degeneration, CNV can also occur frequently with the rare genetic disease pseudoxanthoma elasticum and rarely with the more common optic disc drusen. CNV has also been associated with extreme myopia or malignant myopic degeneration, where in choroidal neovascularization occurs primarily in the presence of cracks within the retinal (specifically) macular tissue known as lacquer cracks.

Macular telangiectasia describes two distinct retinal diseases affecting the macula of the eye, macular telangiectasia type 1 and macular telangiectasia type 2.

Macular telangiectasia (MacTel) type 1 is a very rare disease, typically unilateral and usually affecting male patients. MacTel type 2 is more frequent than type 1 and generally affects both eyes (bilateral). It usually affects both sexes equally. Both types of MacTel should not be confused with Age-related macular degeneration (AMD), from which it can be distinguished by symptoms, clinical features, pathogenesis, and disease management. However, both AMD and MacTel eventually lead to (photoreceptor) atrophy and thus loss of central vision.

The etiology of both types of MacTel is still unknown and no treatment has been found to be effective to prevent further progression. Because lost photoreceptors cannot be recovered, early diagnosis and treatment appear to be essential to prevent loss of visual function. Several centers are currently trying to find new diagnostics and treatments to understand the causes and biochemical reactions in order to halt or counteract the adverse effects.

Contemporary research has shown that MacTel type 2 is likely a neurodegenerative disease with secondary changes of the blood vessels of the macula. Although MacTel type 2 has been previously regarded as a rare disease, it is in fact probably much more common than previously thought. The very subtle nature of the early findings in MacTel mean the diagnoses are often missed by optometrists and general ophthalmologists. Due to increased research activity since 2005, many new insights have been gained into this condition since its first description by Dr. J. Donald Gass in 1982.

The diagnosis of POHS is based on the clinical triad of multiple white, atrophic choroidal

scars, peripapillary pigment changes (dark spots around optic disc of the eye), and a maculopathy caused by choroidal neovascularization.

Completely distinct from POHS, acute ocular histoplasmosis may rarely occur in immunodeficiency.

Presumed ocular histoplasmosis syndrome (POHS) is a syndrome affecting the eye, which is characterized by peripheral atrophic chorioretinal scars, atrophy or scarring adjacent to the optic disc and maculopathy.

The loss of vision in POHS is caused by choroidal neovascularization.

Diabetic retinopathy often has no early warning signs. Even macular edema, which can cause rapid vision loss, may not have any warning signs for some time. In general, however, a person with macular edema is likely to have blurred vision, making it hard to do things like read or drive. In some cases, the vision will get better or worse during the day.

In the first stage which is called non-proliferative diabetic retinopathy (NPDR) there are no symptoms, the signs are not visible to the eye and patients will have 20/20 vision. The only way to detect NPDR is by fundus photography, in which microaneurysms (microscopic blood-filled bulges in the artery walls) can be seen. If there is reduced vision, fluorescein angiography can be done to see the back of the eye. Narrowing or blocked retinal blood vessels can be seen clearly and this is called retinal ischemia (lack of blood flow).

Macular edema in which blood vessels leak their contents into the macular region can occur at any stage of NPDR. The symptoms of macular edema are blurred vision and darkened or distorted images that are not the same in both eyes. Ten percent (10%) of diabetic patients will have vision loss related to macular edema. Optical Coherence Tomography can show the areas of

retinal thickening (due to fluid accumulation) of macular edema.

In the second stage, abnormal new blood vessels (neovascularisation) form at the back of the eye as part of "proliferative diabetic retinopathy" (PDR); these can burst and bleed (vitreous hemorrhage) and blur the vision, because these new blood vessels are fragile. The first time this bleeding occurs, it may not be very severe. In most cases, it will leave just a few specks of blood, or spots floating in a person's visual field, though the spots often go away after a few hours.

These spots are often followed within a few days or weeks by a much greater leakage of blood, which blurs the vision. In extreme cases, a person may only be able to tell light from dark in that eye. It may take the blood anywhere from a few days to months or even years to clear from the inside of the eye, and in some cases the blood will not clear. These types of large hemorrhages tend to happen more than once, often during sleep.

On funduscopic exam, a doctor will see cotton wool spots, flame hemorrhages (similar lesions are also caused by the alpha-toxin of "Clostridium novyi"), and dot-blot hemorrhages.

Diabetic retinopathy, also known as diabetic eye disease, is a medical condition in which damage occurs to the retina due to diabetes and is a leading cause of blindness.

It affects up to 80 percent of people who have had diabetes for 20 years or more. At least 90% of new cases could be reduced if there were proper treatment and monitoring of the eyes. The longer a person has diabetes, the higher his or her chances of developing diabetic retinopathy. Each year in the United States, diabetic retinopathy accounts for 12% of all new cases of blindness. It is also the leading cause of blindness for people aged 20 to 64 years.

The risk of toxicity is low for individuals without complicating conditions during the first 5 years of treatment using less than 6.5 mg/kg/day of hydroxychloroquine or 3 mg/kg/day of chloroquine, and/or cumulative doses of less than 1000 gram and 460 gram (total dose), respectively. Some physicians suggest that lean body weight is more accurate when calculating daily dosage.

Most patients are routinely given 400 mg of hydroxychloroquine daily (or 250 mg chloroquine). This dose is considered acceptable.

The earliest signs of toxicity include bilateral paracentral visual field changes (best detected with a red test object) and a subtle granular depigmentation of the paracentral RPE.

With continued drug exposure, there is progressive development of a bilateral atrophic bull's-eye maculopathy and paracentral scotomata, which may in severe cases ultimately spread over the entire fundus, causing widespread retinal atrophy and visual loss.

Chloroquine retinopathy, also known as Bull's eye maculopathy, is a retinopathy (damage of the retina) caused by the drugs chloroquine or hydroxychloroquine, which are sometimes used in the treatment of autoimmune disorders such as rheumatoid arthritis and systemic lupus erythematosus. This eye toxicity limits long-term use of the drugs.

A maculopathy is any pathological condition of the macula, an area at the centre of the retina that is associated with highly sensitive, accurate vision.

Symptoms of congenital PSS usually appear by six months of age and include failure to gain weight, vomiting, and signs of hepatic encephalopathy (a condition where toxins normally removed by the liver accumulate in the blood and impair the function of brain cells) such as seizures, depression, tremors, drooling, and head pressing. Urate bladder stones may form because of increased amounts of uric acid in circulation and excreted by the kidneys. Initial diagnosis of PSS is through laboratory bloodwork showing either elevated serum bile acids after eating or elevation of fasting blood ammonia levels, which has been shown to have a higher sensitivity and specificity than the bile acids test.

Various diagnostic imaging techniques are used to demonstrate PSS. Ultrasonography is a rapid, convenient, non-invasive, and accurate method for diagnosis of PSS. Ultrasonographic diagnosis of congenital PSS depends on finding an anomalous vessel either in the liver or just caudal to the liver in the dorsal abdomen, usually draining into the caudal vena cava. Ultrasonography can also be used to estimate hepatic volume and vascularity, and to identify related lesions affecting other abdominal structures, such as urinary calculi. Computed tomography (CT) may be considered when ultrasound expertise is lacking or ultrasonography is considered sub-optimal (e.g. because of the conformation of the patient). Control of respiration and careful timing of CT acquisition after contrast injection is necessary for optimal depiction of PSS. Rectal portal scintigraphy using technetium pertechnetate, a technique of imaging involving detection of gamma rays emitted by radionuclides absorbed through the rectum and into the bloodstream, demonstrates the blood vessel bypassing the liver. In certain institutions, scintigraphy is the preferred diagnostic technique, but this leaves the patient radioactive for 24h, which may be inconvenient depending on nursing needs. Portal venography is the definitive method for demonstrating PSS, but is invasive, hence it is best reserved for animals with a known shunt or those considered highly likely to have a shunt that was not detectable by ultrasonography.

A portosystemic shunt (PSS), also known as a liver shunt, is a bypass of the liver by the body's circulatory system. It can be either a congenital (present at birth) or acquired condition.

Congenital PSS is a hereditary condition in dogs and cats, its frequency varying depending on the breed. The shunts found mainly in small dog breeds such as Shih Tzus, Tibetan Spaniels, Miniature Schnauzers and Yorkshire Terriers, and in cats such as Persians, British Shorthairs, Himalayans, and mixed breeds are usually extrahepatic (outside the liver), while the shunts found in large dog breeds such as Irish Wolfhounds and Labrador Retrievers tend to be intrahepatic (inside the liver).

Acquired PSS is uncommon and is found in dogs and cats with liver disease such as cirrhosis causing portal hypertension, which is high blood pressure in the portal vein.

The signs and symptoms of a ruptured AAA may include severe pain in the lower back, flank, abdomen or groin. A mass that pulses with the heart beat may also be felt. The bleeding can lead to a hypovolemic shock with low blood pressure and a fast heart rate. This may lead to brief passing out.

The mortality of AAA rupture is as high as 90 percent. 65 to 75 percent of patients die before they arrive at the hospital and up to 90 percent die before they reach the operating room. The bleeding can be or into the abdominal cavity. Rupture can also create a connection between the aorta and intestine or inferior vena cava. Flank ecchymosis (appearance of a bruise) is a sign of retroperitoneal bleeding, and is also called Grey Turner's sign.

Aortic aneurysm rupture may be mistaken for the pain of kidney stones, or muscle related back pain.

The vast majority of aneurysms are asymptomatic. However, as abdominal aortic aneurysms expand, they may become painful and lead to pulsating sensations in the abdomen or pain in the chest, lower back, or scrotum. The risk of rupture is high in a symptomatic aneurysm, which is therefore considered an indication for surgery. The complications include rupture, peripheral embolization, acute aortic occlusion, and aortocaval (between the aorta and inferior vena cava) or aortoduodenal (between the aorta and the duodenum) fistulae. On physical examination, a palpable and pulsatile abdominal mass can be noted. Bruits can be present in case of renal or visceral arterial stenosis.