Hereditary persistence of fetal hemoglobin (HPFH) is a benign condition in which increased fetal hemoglobin (hemoglobin F, HbF) production continues well into adulthood, disregarding the normal shutoff point after which only adult-type hemoglobin should be produced. Presentation
The condition is asymptomatic, and is only noticed when screening for other hemoglobin disorders. Sickle cell disease
In persons with sickle cell disease, high levels of fetal hemoglobin as found in a newborn or as found abnormally in persons with hereditary persistence of fetal hemoglobin, the HbF causes the sickle cell disease to be less severe. In essence the HbF inhibits polymerization of HbS. A similar mechanism occurs with persons who have sickle cell trait. Approximately 40% of the hemoglobin is in the HbS form while the rest is in normal HbA form. The HbA form interferes with HbS polymerization. Causes
HPFH can be caused by mutations in the β globin gene cluster, or the γ gene promoter region. In addition HbF levels are influenced by polymorphisms in the BCL11A gene and in the MYB gene enhancer. In HPFH the percentage of HbF varies from 0.8-1.0% to about 30% of the total hemoglobin, but levels as high as 100% can be seen in homozygotes for delta beta thalassemia. Diagnosis
Epidemiology
About 10% of the population has an HbF level >1.0%. HPFH may alleviate the severity of certain hemoglobinopathies and thalassemias, and is selected for in populations with a high prevalence of these conditions (which in turn are often selected for in areas where malaria is endemic).
New studies conducted on rats using perilla frutescens aqueous extract have shown to relax the ciliary muscle. Since there are no known drugs to treat this eye condition, perilla frutescens in an aqueous extract form may result in the relaxation of the ciliary muscle in humans as well. Perilla frutescens is currently used in traditional medicine in Korea, Japan, and China and a clinical study "showed that PFA (perilla frutescens extract) attenuates eye fatigue by improving visual accommodation"

Prognosis
For routine cases of spasm of accommodation, the American Optometric Association says the prognosis is fair and on average, the number of visits a patient needs will be 1-2 for evaluation and 10 follow up visits. Additionally, the AOA recommends the following management plan for spasm of accommodation: "Begin with plus lenses and VT; if VT fails, use cycloplegic agent temporarily; educate patient".For more chronic and acute cases that do not respond to vision training and cycloplegic drops, the eye muscles should weaken with advancing age providing intermittent or permanent relief from this condition. See also
Miosis
Cycloplegia
Pseudomyopia


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