Myopia Review
Eye Measurement Variables and Relationships
Characteristics of Individuals
Variation in eye size and body height.
Short individuals can have large eyes.
Taller individuals may have smaller eyes.
Example data of individuals measuring 180 cm and eye lengths around 23.5 mm versus 155-160 cm individuals with eye lengths of 26-27 mm.
Predictive Ability of Height on Axial Length
Height has no predictive ability regarding axial length.
Key Determinants of Axial Length:
Vitreous chamber depth is the primary determinant.
Other parameters include anterior chamber length and vitreous.
Comparison of datasets from years 2020, 2023, and 2024 shows similar outcomes.
Emmetropia and Axial Length
Emmetropes show a narrow refractive range of approximately +/- 0.75 D.
Axial lengths for emmetropes vary from 22.5 mm to 24.5 mm, indicating variability within emmetropia.
Correlation exists between optics and axial length.
Essential relation: If the optics match the axial length, the individual remains emmetropic.
Myopia and Axial Length
Myopes show increased axial lengths correlating to refractive error severity.
Longer axial lengths (27 mm) average around 8 D myopia.
Axial lengths of around 26 mm correlate with 4-6 D myopia.
Axial length significantly contributes to increases in myopic characteristics.
Axial Length to Corneal Curvature Ratio
Defined as the ratio of axial length (in mm) to corneal curvature (in mm).
Example: Axial length of 24 mm and corneal curvature of 8 mm yield a ratio of 3.
Ratios higher than 3 indicate potential for more myopia; ratios less than 3 indicate likely hyperopia.
Graphing this data reflects correlation with refractive error, leading to better predictive values.
Ratios observed between 2.9 to 3.5 demonstrate correlation strength.
Spherical Equivalent Refraction
Examined relationship between spherical equivalent refraction, astigmatism, and anisometropia.
Data shows scattered results, suggesting high degrees of myopia can coexist with varying degrees of cylinder amounts.
On average, there is a lower proportion of high cylindrical values in high spherical refraction groups.
Some individuals demonstrate high astigmatism despite non-myopic states, indicating variance in individual eye characteristics.
Astigmatism Analysis
Correlation between refractive astigmatism and corneal astigmatism confirmed.
Corneal irregularities contribute primarily to refractive astigmatism.
Typical observation: Refractive astigmatism is often slightly less than corneal astigmatism due to lenticular compensation.
Anterior Eye Segment Considerations
Study shows no clear relationship between corneal power and anterior chamber depth; results are varied.
General trend: Larger eyes align with deeper anterior chambers and flatter corneas, and vice versa for smaller eyes.
Binocular Vision Status and Myopia Management
Study Overview
The purpose is to tie measurements to myopia or other vision treatments.
Emphasis on assessing individuals in context of binocular vision and myopia management.
Importance of Binocular Vision
Consideration of binocular vision systems crucial for effective treatment.
Treatments like progressive lenses may be advisable for specific cases.
Potential accommodation issues require examination, especially in children with existing myopic tendencies.
Classification of Myopia
Issues relating to low vs. high myopia; early vs. late onset evaluated.
Early onset generally linked to higher risk progression.
Investigate individual's ocular history, including age at first prescription and progression patterns.
Causes of Myopia
Key factors to consider:
Genetic predisposition (family history).
Near work habits (hours spent in near tasks).
Outdoor activity levels (recommended two hours per day).
Contemporary Treatment Options
Discussion on various treatments, including but not limited to:
Progressive addition lenses.
Multifocal contact lenses for myopia control.
Low-dose atropine as therapy evaluation.
Case Studies Overview
Case Study Data from Previous Year
Data utilized from students with classifications of myopia ranged from low (-0.50 to -0.75) to higher amounts.
Various measures collected, with focus on distance acuity, phoric measures, lag of accommodation, and relative accommodation variables.
Assessment of Accommodative Skills
Lag of accommodation assessed using MEM retinoscopy; considerable lag often noted.
Positive and negative other relative accommodation results documented.
Presence of Esophoria and Exophoria in Studies
Correlations between distances affecting the resultant phoria evident.
Specific examination of shifts in phoric position with correction options discussed.
Questionnaires and Data Gathering
Surveys linked to understanding causes of myopia, outdoor activity, and genetic questions crucial in profile gathering.
Examples provided from practice session analysis linking myopia status to visual outcomes and subsequent management strategies.