Hyperopia: Latent, Manifest, and Cycloplegic Refraction

• Cycloplegic refraction is the process of determining refractive error in the absence of accommodation.
• It is performed using cycloplegic drugs

Information Provided by Static Retinoscopy

• It controls accommodation to some extent

Hyperopia Considerations

• Patients with significant hyperopia, latent hyperopia, or accommodative esotropia may mask much of their hyperopia during non-cycloplegic retinoscopy (dry refraction).
• Extra latent hyperopia may be uncovered using a fogging procedure or cycloplegia
• A "lag" of accommodation found through MEM retinoscopy is indicative of latent hyperopia

Hyperopia Classification

• Based on the role of Accommodation in Visual Function, types include manifest, facultative, absolute latent, and total.
• Manifest hyperopia is the sum of absolute and facultative hyperopia.
• Latent hyperopia is when the hyperopia is compensated by the tonicity of the ciliary muscle
• Latent hyperopia, common in young hyperopes, needs cycloplegia because accommodation can't be relaxed during routine refraction
• Facultative hyperopia can be compensated by accommodation
• Absolute hyperopia cannot be compensated with accommodation

Absolute vs Facultative Hyperopia

• Facultative hyperopia can be compensated by accommodation
• Latent hyperopia is not manifested in dry refraction (objective)
• Latent hyperopia needs cycloplegic refraction or fogging techniques to uncover
• In latent, patients cannot control hyperopia compensation due to the increased tonicity of the ciliary muscle

Cycloplegic Agents

• These cause paralysis of the iris sphincter, resulting in mydriasis, and the ciliary muscle, which causes cycloplegia.
• These antagonize the muscarinic action of acetylcholine (cholinergic antagonist)
• They block muscarinic receptors, leading to the inhibition of all muscarinic functions
• Cholinergic receptors are found in the iris and ciliary body.
• Atropine, homatropine, cyclopentolate, tropicamide, and scopolamine are cycloplegic drugs
• 85-90% of pupils dilate well, but not all pupils dilate with cycloplegic agents
• Patients complain of photophobia and are unable to see up close

Mechanism

• Inhibit the action of acetylcholine, blocking muscarinic receptor sites.
• Block the parasympathetic system
• This leads to the sympathetic system predominating to produce mydriasis and cycloplegia
• The sphincter muscle is innervated by cholinergic fibers, and its contraction via an agonist results in miosis, while blockade by cycloplegic or mydriatic agents results in mydriasis.
• The radial muscle is innervated by adrenergic fibers to alpha-1 receptors
• Its contraction by an agonist results in mydriasis, and its blockade results in miosis.

Effects of Acetylcholine (Ach) on Muscarinic Receptors

• Parasympathetic effects are produced from Ach stimulating muscarinic receptors
• Eyes: Miosis, lacrimation, accommodation, decreasing IOP.
• Digestive Tract: Saliva secretion, stomach acid secretion, peristalsis
• Other effects: Decreased heart rate, bronchial constriction, enhanced urination

Cycloplegics

• Anticholinergics: Inhibit muscarinic receptors of the iris sphincter and ciliary body
• These include Cyclopentolate, Atropine, Homatropine, Scopolamine, and Tropicamide
• Sympathomimetics: Stimulate adrenergic alpha receptors
• Phenylephrine and Hydroxyamphetamine are good mydriatics but poor cycloplegics

Atropine

• Used in extreme cases of uveitis to avoid post. synechiae & ua inflammation
• Naturally occurring alkaloid.
• First isolated from the belladonna plant (Atropa belladonna).
• Nonselective muscarinic antagonist.
• Most potent mydriatic and cycloplegic agent presently available.
• Mydriasis may last up to 10 days, and cycloplegia for 7 to 12 days, depending on concentration
• Commercially available as a sulphate derivative in 1% solution or 1% ointment
• Effects can take 1-2 days to work, and can take up to one week to wash of

Atropine Mode of Action

• Reduces pain from ciliary spasm.
• Prevents the formation of posterior synechia from secondary iridocyclitis.
• Increases the blood supply to the anterior uvea.
• Brings more antibodies to the aqueous humor.
• Decreases exudation by reducing hyperemia and vascular permeability

Atropine use in cyclorefraction

• Often used for cycloplegic refraction in young, actively accommodating children with suspected latent hyperopia or accommodative esotropia
• Can be used up to 1%
• Can also be used for myopia control at 0.01%, 0.02%, 0.025%, 0.05%
• Similar to placebo usage according to research
• Not typically used for routine cycloplegic refraction in school-aged children or adults because of prolonged paralysis of accommodation, which impairs near vision, and continued mydriasis, which causes photophobia
• Use in cases of esotropia with a suspected accommodative component, which may lead to a permanent deviation.
• Slow/prevent the progression of myopia by placing the ciliary muscle at rest to reduce the tension that produces elongation of the eye.
• Penalization treatment for mild and moderate amblyopia treatment by blurring the better seeing eye and forcing use of the amblyopic eye.

Atropine Side Effects

• Ocular Side Effects: Direct irritation, allergic contact dermatitis, risk of angle-closure glaucoma, and elevation of IOP in patients with open angles
• As children are not exempt from angle-closure glaucoma it is important to always check before prescribing
• Systemic Side Effects: Diffuse cutaneous flush, dry mouth, thirst and dry eyes, fever, urinary retention, tachycardia, arrhythmia, myocardial infraction, excitement, restlessness, speech disturbance, ataxia (loss of muscle coordination), seizure, personality changes
• Atropine Contraindications: Hypersensitivity to belladonna alkaloid, OAG or CAG, High IOP
• Repeated use of parasympatholytics is contraindicated because of teratogenic effects.
• Contraindicated in breastfeeding mothers because of anticholinergic and hypertensive effects.
• It should be used with caution in pediatric patients due to its low margin for toxicity
• The antidote is physostigmine.

Other Agents: Homatropine

• Can be used to treat ivitis & uveitis
• 1/10th as potent as atropine.
• It has a shorter duration of mydriasis and cycloplegia than atropine
• Not the drug of choice for cycloplegic refraction because of its prolonged mydriatic and cycloplegic effect
• Mydriasis last 1-3 days with this drug
• Not the drug of choice for cycloplegic refraction or dilated fundus exam but good for anterior uveitis.

Other Agents: Scopolamine

• Used for motion sickness
• Nonselective antagonist
• Effects: Pupi dilation and decreases motion sickness
• Maximum cycloplegic effect in 40 minutes lasting at least 90 minutes.
• Adaptation takes up to 3 days to return to a level where the average can read.
• Treat anterior uveitis in patients with sensitivity to atropine.

Cyclopentolate

• Golden child of drugs; available in 0.5%, 1%, and 2%.
• Reserved for uveitis of inflammatory purposes
• In infants and school-aged children, it is the drug of choice for routine cyclorefraction in nearly every age group
• Faster onset with shorter duration of efficacy.
• Cycloplegia happens in 30 to 45 minutes
• Mydriasis and cycloplegia are fully recovered within 24 hours
• Administer 1 or 2 gtt of 0.5% for children under age 3
• For children above age 3, administer 1 or 2 gtt of 1%

Cyclopentolate: Not recommended for use in:

• infants
• small children
• children with brain damage or spastic paralysis
• Those with Down syndrome

Cyclopentolate Side Effects

• Ocular: Transient stinging on initial instillation, lacrimation, and blurred vision
• Allergic reactions are rare
• Symptoms of irritation and diffuse redness, facial rash that develops within minutes to an hour of instillation can occur
• Systemic: Drowsiness, ataxia, disorientation, speech disturbance, and restlessness
• It can have more CNS-related effects than Atropine
• Greater use of 2% in children, although multiple instillations of 1% may have the same symptoms.

Tropicamide

• Available in 0.5% and 1% concentrations, Mydriacyl
• Short duration cycloplegic - about 30 minutes
• Recovery occurs within 2 to 6 hours.
• Considered inadequate for cycloplegia in children.
• Widely used as a mydriatic agent.
• It is common to combine it with cyclo to get a full effect in children.
• Does not take more than 24 hours for editation to go away

Common Drugs and Dosages

• Cyclopentolate 0.5%: 1 gtt repeated in 5 min (Birth - age 3).
• Cyclopentolate 1%: 1 gtt repeated in 5 min (Age 3 and up/dark iris)
• Tropicamide 0.5%: 1 gtt repeated in 5 min (Birth – age 3)
• Tropicamide 1%: 1 gtt repeated in 5 min: (Age 3 and up/dark iris)
• Atropine 1%: 1 gtt tid for 1-3 days before refraction

General Rules

• Select a drug with adequate cycloplegia and minimal toxicity risk
• Light irises are more responsive to drugs.
• Dark irises tend to need stronger doses or multiple instillation
• Low weight infants (premature) use lower doses
• Children with CNS disorders may have increased reactions to cycloplegics
• Mydriasis can be reversed with Dapiprazole(Rev-Eyes), but has no effect on cycloplegia
• Dapiprazole is not available anymore

Rules for Cyclorefraction

• Decrease markedly with age
• Paitents over 40 are less likely to have latent hyperopia
• Perform in young adults only if latent hyperopia is suspected
• Asthenopia complaint for near work but has no uncorrected refractive error or binocular abnormalities

Examples where uses are useful

• Determine refractive error, standard of care in children.
• Detect latent hyperopia, high hyperopia, small pupils for age (possibly due to accommodation)
• Differential Diagnosis, strabismus (especially esotropias or high esophorias), low AoA for age, fluctuations of accommodation or refraction, rule out pseudomyopia, and for non-responsive patients
• Use when objective and subjective findings do not correlate.

Cyclorefraction Procedure

• Always perform a dry refraction and a trial frame for maximum plus most VA before performing cyclorefraction
• Needs E&U (educated and understood) on procedure - parent must also consent and child must assent
• Before Cycloplegia every patient needs blood pressure, Van Herrick angles, IOP (Goldmann, NCT, Icare), Pupils check, VA at D and N, medicolegal aspect

Trial Frame

• Start with subjective refraction.
• Take VAs
• Conduct +/- 0.25DS for MPMVA
• Check the axis and cylinder power checks (spherical equivalents).
• Review VAs at distance and near
• Have patient walk around if they feel any discomfort
• Instill 1 gtt Proparacaine 0.5% OU as absorption increases when administering to epithelial cells , provides less discomfort
• Add Punctum occlusion for less systemic absorption
• Followed by 1 gtt Cyclopentolate 0.5% or 1 % depending on age.
• Repeat after five minutes (if necessary)
• Should be instilled only after confirming drug name, concentration, and expiration date
• After cycloplegia has been reached, perform retinoscopy with adjusted power.

Recommended Regime for a DFE:

• Adults (purely mydriatic), Phenylephrine 2.5% + Tropicamide 1%, repeat every fifteen to thirty minutes
• Children (if over three y/o), Phenylephrine 2.5% + Tropicamide 1% + Cyclopentolate 1%, repeat every 25 to 30 minutes
• Infants ( less than 3 y/o), Phenylephrine 1% + Tropicamide 0.25% + Homatropine 2% or Cyclopentolate 0.5% ( cut dose by half ), repeat in 35 to 45 minutes
• At 45 mins, its pey time for Wet rofiac

Findings

• Check near VAs but careful with myopes.
• Objective refraction with VA. Document Wet Retinoscopy
• Subjective- if necessary, without binocular balance 20/25 when cyclo is still good problem: once dilated - photophobic, reflexes are a little confusing- scissor reflex I must look e center of pupi
• Changes may occur due to spherical aberration or loss of accommodation.
• No trial frame after cycloplegic refraction
• Always trial frame first before dropping

To be noted

• Patient may not accept the full wet retinoscopy
• If a big change is seen, TF has to be repeated at least one day after cyclorefraction and SRx to MPMBVA
• SRx to MPMBVA where the patient is comfortable and can tolerate
• Acсоmmodative strabismus and anomalies indicates cyclo has had an effect
• Normal findings include and increase of +0.50 to +0.75 is latent error

Record Keeping

• If patient does not consent say why on file
• Include Pharmacological agent , amount of drops distilled, what time it was administered

Downside of Cycloplegia

• Painful, unwanted drops
• Incomplete absorption and effect.
• Prolonged exam time
• Pediatric and developmentally delayed patients often are emotionally traumatized by repeated instillation

Why is Cycloplegia Important?

• VA may be reduced at times in hyperopes, mainly at near; latent hyperopia VA tends to be more usual.
• Patients tend to have inconsistent levels of N and D VA when fatigue is present
• Patients with moderate and high hyperopia are at a significantly inceeased risk for refractive and strabismic amblyopia
• Hyperopia over +3.50D increase factors (especially in isoametropic amblyopia)
• Latent hyperopia is more predictable than cycloplegic hyperopia because most children will compensate due to accommodation

Delayed Subjective Refraction

• The goal is to maximize relaxation of accommodation and acceptance of plus
• Good for hyperopes and accommodative spasms
• It has to be administered after typical subjective refraction

Method 1 of Delayed Subjective Refraction

• Fog with +2.00DS OD and OS
• Show 20/200 letter, if its not blurry add more plus until blurry
• Repeat until binocularly focused
• Wait 5 minutes
• If patient can not focus the letters or decrease -0.25DS steps (MPMVA)
• If patient can focus the letters: go to the next line, do MPMBVA
• Test for the last letters

Method 2

• To find NRA (Negative Relative Accommodation) has value to be used in the near test Have near rod at 40cm and 20/20 line or sustained letters
• Test patients and ask the patient to look for a certain amount and range
• Test each step of accommodation and the patient should achieve a level where they have a plus of -0.25DS (called MPMBVA) and 20/20

Cyclodamia

• Mehtod of relaxing accommodation without using cycloplegia
• Use method of maximizing relaxation of accommodaton
• Maintain retinoscopy with lenses that relax accommodation
• Slowly reduce spheres BINOCULARLY
• Clock dial technique test with opposite eye being uncovered
• An estimate is obtained that will be similar to cycloplegia

Mohindra “Near” Retinoscopy

• Useful technique with children in low/medium
• Has good correlation technique with “wet” retinoscopy with low/medium hyperopia
• Poor reaction: Children with esophoria or esotropia who present with the same amount of hyperopia

Doing Mohindra “Near” Retinoscopy

• Make room lights dark as possible
• Place yourself 50cm away from the patient on the same axis of site
• Dim the retinoscope light
• Have the child fixate on light
• Focus one point on retinascope bar or lenser
• Use lenses that can cross meridians and and do an optical cross through it
• Adjust for power with 1.25D (not 2.00D) - test with different accommodations - ~0.75

Explore hyperopia, its classifications (latent, manifest, absolute, facultative), and clinical signs. Understand the importance of cycloplegic refraction, especially in children, to reveal the total hyperopic error. Learn how accommodation affects refraction results.