Charles Bonnet syndrome (CBS) involves visual hallucinations due to eye disease, usually associated with a sharp decline in vision. The phenomenon is seen in patients with moderate or severe visual impairment. It can occur spontaneously as the vision declines or it may be precipitated, in predisposed individuals, by concurrent illness such as infections elsewhere in the body.

It is not clear why CBS develops or why some individuals appear to be predisposed to it. It is particularly noted in patients with advanced macular degeneration. It has been suggested that reduced or absent stimulation of the visual system leads to increased excitability of the visual cortex (deafferentation hypothesis). This release phenomenon is compared to phantom limb symptoms after amputation.

CBS is much more common in older patients because conditions causing marked visual loss are more common in older people. However, it can occur at any age and has been described in children.
The prevalence is hard to assess due to considerable under-reporting, perhaps because patients frequently fear that it is a sign of mental illness or dementia. However, it is thought to occur in:
About 10-15% of patients with moderate visual loss.
Possibly up to 50% of people with severe visual loss.
Presentation:
The nature of the hallucination depends on the part of the brain that is activated. The hallucinations may be black and white or in colour. They may involve grids/brickwork/lattice patterns but are typically much more complex:

The hallucinations are always outside the body.
The hallucinations are purely visual – other senses are not involved.
The hallucinations have no personal meaning to the patient.
Hallucinations may last seconds, minutes or hours.
CBS tends to occur in a ‘state of quiet restfulness’. This may be after a meal or when listening to the radio (but not when dozing off).
Symptoms also have a tendency to occur in dim lighting conditions.
Patients may report high levels of distress, with some patients reporting anger, anxiety and even fear associated with the hallucinations.

Cataract is a condition characterized by clouding of the lens of the eye. This condition most frequently occurs due to age-related degenerative processes in the lens, but can also be associated with ocular trauma, metabolic disorders, side-effects of drugs, or congenital infections. The clouding causes distortion of light, as it passes through the lens, resulting in visual impairment and glare. Initially, a cataract presents discretely and may even go unnoticed, but the visual impairment worsens as the cataract grows larger.

Diagnosis is typically established on the basis of a thorough history and direct visualization of the cataract (by means of slit-lamp microscopy). Surgery is indicated with significant visual impairment and involves lens extraction and implantation of an artificial lens. Untreated cataracts eventually lead to complete blindness.

The vas deferens is a long tube that connects the epididymis to the ejaculatory ducts. It acts as a canal through which mature sperm may pass through the penis during ejaculation.

Most men with CF (97-98 percent) are infertile because of a blockage or absence of the vas deferens, known as congenital bilateral absence of the vas deferens (CBAVD). The sperm never makes it into the semen, making it impossible for them to reach and fertilize an egg through intercourse. The absence of sperm in the semen can also contribute to men with CF having thinner ejaculate and lower semen volume.

Biguanides (Metformin):
People who take metformin alone should be able to fast safely given that the possibility of hypoglycaemia is minimal. However, patients should modify its dose and administration timing to provide two-thirds of the total daily dose, which should be taken immediately with the sunset meal, while the other third is taken before the predawn meal.

Thiazolidinediones: No change needed.

Sulfonylurea:
Once-daily sulfonylurea (such as glimepiride or gliclazide MR): the total daily dose should be taken with the sunset meal.
Shorter-acting sulfonylurea (such as gliclazide twice daily): the same daily dose remains unchanged, and one dose should be taken at the sunset meal and the other at the predawn meal.
Long-acting sulfonylurea (such as glibenclamide): these agents should be avoided.

It is important that diabetic patients to eat a healthy balanced diet and choose foods with a low glycaemic index (such as complex carbohydrates), which can help to maintain blood glucose levels during fasting. Moreover, it is crucial to consume adequate fluids to prevent dehydration. Physical activity is encouraged, especially during non-fasting periods.

Vasopressin, also called antidiuretic hormone (ADH), regulates the tonicity of body fluids. It is released from the posterior pituitary in response to hypertonicity and promotes water reabsorption in the collecting ducts of the kidneys by the insertion of aquaporin-2 channels.. An incidental consequence of this renal reabsorption of water is concentrated urine and reduced urine volume. In high concentrations may also raise blood pressure by inducing moderate vasoconstriction.

This man has a small-cell lung cancer (SCLC) and associated Lambert-Eaton myasthenic syndrome – a well-recognized paraneoplastic manifestation of SCLC. This classically affects the proximal muscles, especially in the legs, causing difficulty in standing from a seated position and climbing stairs. In contrast to myasthenia gravis, eye involvement is uncommon. Treatment with steroids is often helpful, which explains his transient symptomatic improvement during treatment for his COPD exacerbation. Steroid myopathy does not fit as the symptoms started well before his course of prednisolone. Although the patient is mildly hypercalcaemic, this would not be sufficient to produce his presenting symptoms, although it does reinforce the suspicion of lung malignancy. Motor neurone disease would be unlikely in this context and would not improve with steroids. Myasthenia gravis could produce these symptoms, but in the context of a new lung mass is a less viable diagnosis.

The most common causes of a sudden painless loss of vision are as follows:
– Ischaemic optic neuropathy (e.g. temporal arteritis or atherosclerosis)
– Occlusion of central retinal vein
– Occlusion of central retinal artery
– Vitreous haemorrhage
– Retinal detachment

Retinal detachment is a cause of sudden painless loss of vision. It is characterised by a dense shadow starting peripherally and progressing centrally.

Vitreous haemorrhage usually presents with dark spots.

Central retinal artery and central retinal vein occlusion do not usually present with progressing dense shadow.

This man’s lack of ischaemic risk factors makes ischaemic optic neuropathy less likely.

Osteoarthritis (OA) is a disabling joint disease characterized by a noninflammatory degeneration of the joint complex (articular cartilage, subchondral bone, and synovium) that occurs with old age or from overuse. It mainly affects the weight-bearing and high-use joints, such as the hip, knee, hands, and vertebrae. Despite the widespread view that OA is a condition caused exclusively by degenerative “wear and tear” of the joints, newer research indicates a significant heterogeneity of causation, including pre-existing peculiarities of joint anatomy, genetics, local inflammation, mechanical forces, and biochemical processes that are affected by proinflammatory mediators and proteases. Major risk factors include advanced age, obesity, previous injuries, and asymmetrically stressed joints. In early-stage osteoarthritis, patients may complain of reduced range of motion, joint-stiffness, and pain that is aggravated with heavy use. As the disease advances, nagging pain may also occur during the night or at rest. Diagnosis is predominantly based on clinical and radiological findings. Classic radiographic features of OA do not necessarily correlate with clinical symptoms and appearance. RA involves proximal interphalangeal joints not distal. Gout occurs as a result of overproduction or underexcretion of uric acid and frequently involves first toe. Fibromyalgia is a disorder characterized by widespread musculoskeletal pain accompanied by fatigue, sleep, memory and mood issues.

Among the given options the most appropriate management in this patient would be ethanol and haemodialysis.

Ethanol competes with ethylene glycol for alcohol dehydrogenase and thus, helps manage a patient with ethylene glycol toxicity.

Ethylene glycol is a type of alcohol used as a coolant or antifreeze
Features of toxicity are divided into 3 stages:
Stage 1: (30 min to 12 hours after exposure) Symptoms similar to alcohol intoxication: confusion, slurred speech, dizziness (CNS depression)
Stage 2: (12 – 48 hours after exposure) Metabolic acidosis with a high anion gap and high osmolar gap. Also tachycardia, hypertension
Stage 3: (24 – 72 hours after exposure) Acute renal failure

Management has changed in recent times:
Fomepizole, an inhibitor of alcohol dehydrogenase, is now used first-line in preference to ethanol.
Ethanol has been used for many years works by competing with ethylene glycol for the enzyme alcohol dehydrogenase this limits the formation of toxic metabolites (e.g. glycolaldehyde and glycolic acid) which are responsible for the hemodynamic/metabolic features of poisoning.
Haemodialysis has a role in refractory cases.

According to echocardiography findings pulmonary pressure is closer to systemic blood pressure and it is evidence of pulmonary hypertension. Because of the reversal of shunt due to pulmonary hypertension, cyanosis and clubbing have developed. So the most probable diagnosis is Eisenmenger’s syndrome.