Irregular astigmatism is quantified by a vector calculation called topographic disparity. Focus of the principal meridian
With accommodation relaxed:

Simple astigmatism
Simple hyperopic astigmatism – first focal line is on the retina, while the second is located behind the retina. Simple myopic astigmatism – first focal line is in front of the retina, while the second is on the retina. Compound astigmatism
Compound hyperopic astigmatism – both focal lines are located behind the retina. Compound myopic astigmatism – both focal lines are located in front of the retina. Mixed astigmatism – focal lines are on both sides of the retina (straddling the retina). Throughout the eye
Astigmatism, whether it is regular or irregular, is caused by some combination of external (corneal surface) and internal (posterior corneal surface, human lens, fluids, retina, and eye-brain interface) optical properties. In some people, the external optics may have the greater influence, and in other people, the internal optics may predominate. Importantly, the axes and magnitudes of external and internal astigmatism do not necessarily coincide, but it is the combination of the two that by definition determines the overall optics of the eye. The overall optics of the eye are typically expressed by a persons refraction; the contribution of the external (anterior corneal) astigmatism is measured through the use of techniques such as keratometry and corneal topography. One method analyzes vectors for planning refractive surgery such that the surgery is apportioned optimally between both the refractive and topographic components.
Luspatercept, sold under the brand name Reblozyl, is a medication used for the treatment of anemia in beta thalassemia and myelodysplastic syndromes.The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication. Medical uses
Luspatercept is indicated for the treatment of adults with transfusion-dependent anemia due to very low, low and intermediate-risk myelodysplastic syndromes (MDS) with ring sideroblasts, who had an unsatisfactory response to or are ineligible for erythropoietin-based therapy.Luspatercept is indicated for the treatment of adults with transfusion-dependent anaemia associated with beta thalassaemia. Side effects
Possible adverse effects include temporary bone pain, joint pains (arthralgias), dizziness, elevated blood pressure (hypertension) and elevated uric acid levels (hyperuricemia). There was also an increased risk of thrombosis (blood clots) in patients who have risk factors for thrombosis who are taking luspatercept. Structure and mechanism
Luspatercept is a recombinant fusion protein derived from human activin receptor type IIb (ActRIIb) linked to a protein derived from immunoglobulin G. It binds TGF (transforming growth factor beta) superfamily ligands to reduce SMAD signaling. The reduction in SMAD signaling leads to enhanced erythroid maturation. History
Phase III trials evaluated the efficacy of luspatercept for the treatment of anemia in the hematological disorders beta thalassemia and myelodysplastic syndromes.It was developed by Acceleron Pharma in collaboration with Celgene.The U.S. Food and Drug Administration (FDA) granted approval for luspatercept–aamt in November 2019, for the treatment of anemia (lack of red blood cells) in adult patients with beta thalassemia who require regular red blood cell (RBC) transfusions.