Hypermetropia and astigmatism -> adult patients

What is hypermetropia?

• unaccommodated hypermetropic eye is too weak to suit its axial length

• eyes far point is virtual one, positioned behind retina

• if deficiency can be made up by effort of accommodation, far point can be brought with the retina + distance objects can be seen clearly

What is manifest hypermetropia?

• amount of hypermetropia exhibited through maximum plus refraction —> cycloplegic drops

• max plus lens that provides the optimum distance VA

what is latent hypermetropia ?

• hypermetropia which is masked by accommodation + not revealed by non cycloplegia refraction

• cycloplegic agent necessary to uncover full amount of hypermetropia

• may account for several D in children → cycloplegia refraction necessary to get full magnitude of refractive error

What are the symptoms of uncorrected hypermetropia?

• can be asymptomatic usually if hypermetropia <1DS

• Pre-presbyopic px with hypermetropia may report blur manifested during reading or prolonged near activities

• when stimulus at any distance exceeds available accommodation, a blur in clarity of vision results

• Headaches (frontal)

• Asthenopia → uncomfortable vision, tired eyes

What is regular astigmatism?

• meridians having max and min refractive powers separated by angle of 90 degrees

• if steepest meridian approx vertical at 90 degrees → WITH the rule astigmatism

• If steepest meridian is approx horizontal at 180 → AGAINST rule

• if steepest meridian neither horizontal or vertical → OBLIQUE astigmatism

What are the symptoms of uncorrected Astigmatism?

• Asthenopia → tired eyes

• Headaches → frontal and associated with visual task

• low amounts of astigmatism <0.75DC asthenopia symptoms at far and near

• High degree astigmatism >0.75 DC near asthenopia, reduce vision for distance and near targets

what is irregular astigmatism?

• max and minimum powered meridians separated by angle other than 90 degrees

• uncommon and found as a result of secondary cause

• E.g corneal scarring, keratoconus

What is the purpose of the Spectacle Prescription?

> Improvement of vision,

> relief of asthenopic or subsidence of headache

• Hypermetropia, Myopia and astigmatism

> Treatment of disturbances of eyes structure or visual system that might worsen or induce other anomalies

• anomalies indicated by insufficient accommodation, vergence or binocular sensory fusion

What are the considerations for prescribing spectacles?

> minimum essential info to decide which lens power to be prescribed

• uncorrected,monocular + binocular distance vision

• distance refractive correction for each eye

• best corrected monocular + binocular distance visual acuity

• details of any binocular vision anomalies

• working distance for any essential tasks

What are considerations when adapting to an astigmatic prescription

• astigmatic corrections that have any significant change in either power or axis position , or If newly initiated - increase difficulties associate with px acceptance

• px suffer disorientation due to perceived alterations of the element making up judgements of linear space

• if axis altered - px may perceive marked tilting of floor and the walls

clinical tips for astigmatism

• large changes in cyl or axis may indicate changes in corneal curvature

• e.g keratoconus