The Ishihara color test, which consists of a series of pictures of colored spots, is the test most often used to diagnose red–green color deficiencies. A figure (usually one or more Arabic digits) is embedded in the picture as a number of spots in a slightly different color, and can be seen with normal color vision, but not with a particular color defect. The full set of tests has a variety of figure/background color combinations, and enable diagnosis of which particular visual defect is present. The anomaloscope, described above, is also used in diagnosing anomalous trichromacy.

Because the Ishihara color test contains only numerals, it may not be useful in diagnosing young children, who have not yet learned to use numerals. In the interest of identifying these problems early on in life, alternative color vision tests were developed using only symbols (square, circle, car).

Besides the Ishihara color test, the US Navy and US Army also allow testing with the Farnsworth Lantern Test. This test allows 30% of color deficient individuals, whose deficiency is not too severe, to pass.

Another test used by clinicians to measure chromatic discrimination is the Farnsworth-Munsell 100 hue test. The patient is asked to arrange a set of colored caps or chips to form a gradual transition of color between two anchor caps.

The HRR color test (developed by Hardy, Rand, and Rittler) is a red–green color test that, unlike the Ishihara, also has plates for the detection of the tritan defects.

Most clinical tests are designed to be fast, simple, and effective at identifying broad categories of color blindness. In academic studies of color blindness, on the other hand, there is more interest in developing flexible tests to collect thorough datasets, identify copunctal points, and measure just noticeable differences.

Many applications for iPhone and iPad have been developed to help colorblind people to view the colors in a better way. Many applications launch a sort of simulation of colorblind vision to make normal-view people understand how the color-blinds see the world. Others allow a correction of the image grabbed from the camera with a special "daltonizer" algorithm.

The GNOME desktop environment provides colorblind accessibility using the gnome-mag and the libcolorblind software. Using a gnome applet, the user may switch a color filter on and off, choosing from a set of possible color transformations that will displace the colors in order to disambiguate them. The software enables, for instance, a colorblind person to see the numbers in the Ishihara test.

Leucism (; or ) is a condition in which there is partial loss of pigmentation in an animal resulting in white, pale, or patchy coloration of the skin, hair, feathers, scales or cuticle, but not the eyes. Unlike albinism, it is caused by a reduction in multiple types of pigment, not just melanin.

An anopsia or anopia is a defect in the visual field. If the defect is only partial, then the portion of the field with the defect can be used to isolate the underlying cause.

Types of partial anopsia:

- Hemianopsia

- Homonymous hemianopsia

- Heteronymous hemianopsia

- Binasal hemianopsia

- Bitemporal hemianopsia

- Superior hemianopia

- Inferior hemianopia

- Quadrantanopia

The term "anopsia" comes from the Ancient Greek ἀν- ("an-"), "un-" and ὄψις ("opsis") "sight".

The diagnosis of Reis-Bücklers corneal dystrophy is based on the clinical presentation, rather than labs or imaging. Sometimes it is difficult to distinguish the disease from honeycomb dystrophy.

The ring 20 abnormality may be limited to as few as 5% of cells, so a screen for chromosomal mosaicism is critical. Newer array technology will not detect the ring chromosome and the standard metaphase chromosome analysis has been recommended. A karyotype analysis examining at least 50 cells should be requested to properly detect mosaicism.

Brain MRI shows vermis atrophy or hypoplasic. Cerebral and cerebellar atrophy with white matter changes in some cases.

When seizures are present in any forms of cortical dysplasia, they are resistant to medication. Frontal lobe resection provides significant relief from seizures to a minority of patients with periventricular lesions.

Detection of heterotopia generally occurs when a patient receives brain imaging—usually an MRI or CT scan—to diagnose seizures that are resistant to medication. Correct diagnosis requires a high degree of radiological skill, due to the heterotopia's resemblance to other masses in the brain.

Treatment is aimed at managing the symptoms of the disease. A form of laser eye surgery named keratectomy may help with the superficial corneal scarring. In more severe cases, a partial or complete corneal transplantation may be considered. However, it is common for the dystrophy to recur within the grafted tissue.

Three tests are useful in confirming the presence and severity of Horner syndrome:

- Cocaine drop test: Cocaine eyedrops block the reuptake of post-ganglionic norepinephrine resulting in the dilation of a normal pupil from retention of norepinephrine in the synapse. However, in Horner's syndrome the lack of norepinephrine in the synaptic cleft causes mydriatic failure. A more recently introduced approach that is more dependable and obviates the difficulties in obtaining cocaine is to apply the alpha-agonist apraclonidine to both eyes and observe the increased mydriatic effect (due to hypersensitivity) on the affected side of Horner syndrome (the opposite effect to what the cocaine test would produce in the presence of Horner's).

- Paredrine test: This test helps to localize the cause of the miosis. If the third order neuron (the last of three neurons in the pathway which ultimately discharges norepinephrine into the synaptic cleft) is intact, then the amphetamine causes neurotransmitter vesicle release, thus releasing norepinephrine into the synaptic cleft and resulting in robust mydriasis of the affected pupil. If the lesion itself is of the third order neuron, then the amphetamine will have no effect and the pupil remains constricted. There is no pharmacological test to differentiate between a first and second order neuron lesion.

- Dilation lag test

It is important to distinguish the ptosis caused by Horner's syndrome from the ptosis caused by a lesion to the oculomotor nerve. In the former, the ptosis occurs with a constricted pupil (due to a loss of sympathetics to the eye), whereas in the latter, the ptosis occurs with a dilated pupil (due to a loss of innervation to the sphincter pupillae). In a clinical setting, these two ptoses are fairly easy to distinguish. In addition to the blown pupil in a CNIII (oculomotor nerve) lesion, this ptosis is much more severe, occasionally occluding the whole eye. The ptosis of Horner syndrome can be quite mild or barely noticeable (partial ptosis).

When anisocoria occurs and the examiner is unsure whether the abnormal pupil is the constricted or dilated one, if a one-sided ptosis is present then the abnormally sized pupil can be presumed to be on the side of the ptosis.

With posterior lens luxation, the lens falls back into the vitreous humour and lies on the floor of the eye. This type causes fewer problems than anterior lens luxation, although glaucoma or ocular inflammation may occur. Surgery is used to treat dogs with significant symptoms. Removal of the lens before it moves to the anterior chamber may prevent secondary glaucoma.

Lens subluxation is also seen in dogs and is characterized by a partial displacement of the lens. It can be recognized by trembling of the iris (iridodonesis) or lens (phacodonesis) and the presence of an aphakic crescent (an area of the pupil where the lens is absent). Other signs of lens subluxation include mild conjunctival redness, vitreous humour degeneration, prolapse of the vitreous into the anterior chamber, and an increase or decrease of anterior chamber depth. Removal of the lens before it completely luxates into the anterior chamber may prevent secondary glaucoma. A nonsurgical alternative involves the use of a miotic to constrict the pupil and prevent the lens from luxating into the anterior chamber.

Unfortunately, the number of differentials to consider for PAIS is particularly large. Prompt diagnosis is particularly urgent when a child is born with ambiguous genitalia, as some causes are associated with potentially life-threatening adrenal crises. Determination of testosterone, testosterone precursors and dihydrotestosterone (DHT) at baseline and / or after human chorionic gonadotropin (hCG) stimulation can be used to exclude such defects in androgen biosynthesis.

Approximately one half of all 46,XY individuals born with ambiguous genitalia will not receive a definitive diagnosis. Androgen receptor (AR) gene mutations cannot be found in 27% to 72% of individuals with PAIS. As a result, genetic analysis can be used to confirm a diagnosis of PAIS, but it cannot be used to rule out PAIS. Evidence of abnormal androgen binding in a genital skin fibroblast study has long been the gold standard for the diagnosis of PAIS, even when an AR mutation is not present. However, some cases of PAIS, including AR-mutant-positive cases, will show normal androgen binding. A family history consistent with X-linked inheritance is more commonly found in AR-mutant-positive cases than AR-mutant-negative cases.

The use of dynamic endocrine tests is particularly helpful in isolating a diagnosis of PAIS. One such test is the human chorionic gonadotropin (hCG) stimulation test. If the gonads are testes, there will be an increase in the level of serum testosterone in response to the hCG, regardless of testicular descent. The magnitude of the testosterone increase can help differentiate between androgen resistance and gonadal dysgenesis, as does evidence of a uterus on ultrasound examination. Testicular function can also be assessed by measuring serum anti-Müllerian hormone levels, which in turn can further differentiate PAIS from gonadal dysgenesis and bilateral anorchia.

Another useful dynamic test involves measuring the response to exogenous steroids; individuals with AIS show a decreased response in serum sex hormone binding globulin (SHBG) after a short term administration of anabolic steroids. Two studies indicate that measuring the response in SHBG after the administration of stanozolol could help to differentiate individuals with PAIS from those with other causes of ambiguous genitalia, although the response in individuals with predominantly male phenotypes overlaps somewhat with the response in normal males.

The most important factor in diagnosing a patient with vertiginous epilepsy is the subject’s detailed description of the episode. However, due to the associated symptoms of the syndrome a subject may have difficulty remembering the specifics of the experience. This makes it difficult for a physician to confirm the diagnosis with absolute certainty. A questionnaire may be used to help patients, especially children, describe their symptoms. Clinicians may also consult family members for assistance in diagnosis, relying on their observations to help understand the episodes. In addition to the description of the event, neurological, physical and hematologic examinations are completed to assist in diagnosis. For proper diagnosis, an otological exam (examination of the ear) should also be completed to rule out disorders of the inner ear, which could also be responsible for manifestations of vertigo. This may include an audiological assessment and vestibular function test. During diagnosis, history-taking is essential in determining possible causes of vertiginous epilepsy as well as tracking the progress of the disorder over time.

Other means used in diagnosis of vertiginous epilepsy include:

- Electroencephalography (EEG)

- Magnetic resonance imaging (MRI)

- Positron emission tomography (PET)

- Neuropsychological testing

The EEG measures electrical activity in the brain, allowing a physician to identify any unusual patterns. While EEGs are good for identifying abnormal brain activity is it not helpful in localizing where the seizure originates because they spread so quickly across the brain. MRIs are used to look for masses or lesions in the temporal lobe of the brain, indicating possible tumors or cancer as the cause of the seizures. When using a PET scan, a physician is looking to detect abnormal blood flow and glucose metabolism in the brain, which is visible between seizures, to indicate the region of origin.

Management of AIS is currently limited to symptomatic management; methods to correct a malfunctioning androgen receptor protein that result from an AR gene mutation are not currently available. Areas of management include sex assignment, genitoplasty, gonadectomy in relation to tumor risk, hormone replacement therapy, and genetic and psychological counseling.

Genetic testing methods such as fluorescence in situ hybridization (FISH) and chromosomal microarray are available for diagnosing Dup15q syndrome and similar genetic disorders.

With the increase in genetic testing availability, more often duplications outside of the 15q11.2-13.1 region are being diagnosed. The global chromosome 15q11.2-13.1 duplication syndrome specific groups only provide medical information and research for chromosome 15q11.2-13.1 duplication syndrome and not the outlying 15q duplications.

Leucism (occasionally spelled "leukism") is a general term for the phenotype resulting from defects in pigment cell differentiation and/or migration from the neural crest to skin, hair, or feathers during development. This results in either the entire surface (if all pigment cells fail to develop) or patches of body surface (if only a subset are defective) having a lack of cells capable of making pigment.

Since all pigment cell-types differentiate from the same multipotent precursor cell-type, leucism can cause the reduction in all types of pigment. This is in contrast to albinism, for which leucism is often mistaken. Albinism results in the reduction of melanin production only, though the melanocyte (or melanophore) is still present. Thus in species that have other pigment cell-types, for example xanthophores, albinos are not entirely white, but instead display a pale yellow colour.

More common than a complete absence of pigment cells is localized or incomplete hypopigmentation, resulting in irregular patches of white on an animal that otherwise has normal colouring and patterning. This partial leucism is known as a "pied" or "piebald" effect; and the ratio of white to normal-coloured skin can vary considerably not only between generations, but between different offspring from the same parents, and even between members of the same litter. This is notable in horses, cows, cats, dogs, the urban crow and the ball python but is also found in many other species.

A further difference between albinism and leucism is in eye colour. Due to the lack of melanin production in both the retinal pigmented epithelium (RPE) and iris, those affected by albinism typically have red eyes due to the underlying blood vessels showing through. In contrast, most leucistic animals have normally coloured eyes. This is because the melanocytes of the RPE are not derived from the neural crest, instead an outpouching of the neural tube generates the optic cup which, in turn, forms the retina. As these cells are from an independent developmental origin, they are typically unaffected by the genetic cause of leucism.

Genes that, when mutated, can cause leucism include, "c-kit", "mitf" and "EDNRB.

The most common causes in young children are birth trauma and a type of cancer called neuroblastoma. The cause of about a third of cases in children is unknown.

Limited data is available for the long-term prognosis of ring chromosome 20 syndrome since only over 60 patients with this syndrome have been reported in published literature. Optimal control of seizures appears to be the determining factor, but early diagnosis and a comprehensive management plan with multidisciplinary support is also thought be to be important.

Biotinidase deficiency can be found by genetic testing. This is often done at birth as part of newborn screening in several states throughout the United States. Results are found through testing a small amount of blood gathered through a heel prick of the infant. As not all states require that this test be done, it is often skipped in those where such testing is not required. Biotinidase deficiency can also be found by sequencing the "BTD" gene, particularly in those with a family history or known familial gene mutation.

Treatment focuses on identifying the nature of the anomalies through various imaging methods, including MRI and CAT scan, and surgical correction to the extent possible.

Patients with Dup15q syndrome feature a distinctive electroencephalography (EEG) signature or biomarker in the form of high amplitude spontaneous beta frequency (12–30 Hz) oscillations. This EEG signature was first noted as a qualitative pattern in clinical EEG readings and was later described quantitatively by researchers at the UCLA and their collaborators within the network of national Dup15q clinics. This group of researchers found that beta activity in children with Dup15q syndrome is significantly greater than that observed in (1) healthy, typically developing children of the same age and (2) children of the same age and IQ with autism not caused by a known genetic disorder (i.e., nonsyndromic ASD). The EEG signature appears almost identical to beta oscillations induced by benzodiazepine drugs that modulate GABA receptors, suggesting that the signature is driven by overexpression of duplicated GABA receptor genes "GABRA5", "GABRB3", and "GABRG3". Treatment monitoring and identification of molecular disease mechanisms may be facilitated by this biomarker.

Speech therapy is usually the most common treatment for asemia. Speech therapy allows the patient to be able to improve their speaking, comprehension, and writing skills. These patients have to learn all of these skills again since they are unable to understand or express anything. It usually depends on how long it takes for the speech therapy to work. If the condition is less severe, it will take less time, such as perhaps a couple of months to years. If the condition is more severe, it may take many years. The way speech therapy works is through speech practice as well as using special computer programs which let the patient practice their communication skills. By using simple and short sentences or writing down these phrases can aid the patients while going through therapy. Giving them enough time to communicate with their friends, family, or therapist will help them increase their skills and be able to manage them.

Complete success is usually achieved with treatment. However, sometimes only partial success is achieved and the patient cannot fully comprehend everything. With the partial restoration of some skills, the speech therapist may only focus on the skills which can be restored. In other cases, the therapist may work on the skills which may not retrieved and teach the patient how to handle those.

Treatment of Aicardi syndrome primarily involves management of seizures and early/continuing intervention programs for developmental delays.

Additional comorbidities and complications sometimes seen with Aicardi syndrome include porencephalic cysts and hydrocephalus, and gastro-intestinal problems. Treatment for porencephalic cysts and/or hydrocephalus is often via a shunt or endoscopic of the cysts, though some require no treatment. Placement of a feeding tube, fundoplication, and surgeries to correct hernias or other gastrointestinal structural problems are sometimes used to treat gastro-intestinal issues.