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Apparent accommodation and depth of field in pseudophakia
M J Elder1, C Murphy, G F Sanderson
1Department of Ophthalmology, Christchurch Hospital, New Zealand.
Journal of Cataract and Refractive Surgery
|June 1, 1996
Summary
Pseudophakic eyes, those with artificial lenses, show similar depth of field to natural (phakic) eyes. This explains good uncorrected vision for both distance and near tasks in pseudophakic eyes without astigmatism or disease.
Area of Science:
- Ophthalmology
- Optics
- Visual Science
Background:
- The depth of field influences uncorrected visual acuity.
- Understanding depth of field in pseudophakic eyes is crucial for predicting visual outcomes after cataract surgery.
Purpose of the Study:
- To compare the depth of field between phakic (natural lens) and pseudophakic (artificial lens) eyes.
- To elucidate the reasons for good uncorrected distance and near visual acuity in pseudophakic eyes.
Main Methods:
- Depth of field was measured in 10 phakic and 10 pseudophakic eyes.
- Measurements were taken for both near and distant targets under cycloplegia.
- A constant pupillary aperture of 2.5 mm was maintained using a soft contact lens.
Main Results:
- No statistically significant differences in depth of field were found between phakic and pseudophakic eyes.
- Depth of field for near visual acuity was +/-0.85 diopters (D), with an amplitude of legibility of +/-1.94 D.
- For distance visual acuity, 85% of eyes had a depth of field between 0.25 and 0.50 D.
Conclusions:
- Pseudophakic eyes, particularly those with mild myopia (-0.75 D), can achieve uncorrected distance acuity of 20/30 and read N5 unaided.
- These visual outcomes are expected in the absence of astigmatism and ocular disease, with a pupil size of approximately 2.5 mm.