Background of cycloplegia and mydriasis differed; agreeing with a

 Background and aims  Mydriatic and cycloplegic agents are important drugs in Optometry. Mydriatics are sympathomimetic or antimuscarinic, and are administered to increase pupil size for examination of the peripheral lens and retina1. Cycloplegics are antimuscarinics that paralyse the iris sphincter and ciliary muscles, resulting in mydriasis and relaxed accommodation. Furthermore, latent refractive errors become manifest, enabling evaluation of full refractive power1. However, ocular complications like acute angle closure glaucoma2 and systemic effects like increased blood pressure3 are associated risks.

 The cycloplegic drug cyclopentolate and mydriatic drug tropicamide are antimuscarinics that produce mydriasis and cycloplegia. This report aims to compare their cycloplegic and mydriatic effects. Methods Two subjects A and B participated in this experiment: A had 1 drop of 1.0% cyclopentolate instilled in their left eye; B was administered with 1 drop of 0.5% tropicamide to their right eye and 1 drop of 1.0% tropicamide to their left eye.

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Pupil diameter, amplitude of accommodation (subjective; via push-up method) and accommodative response (objective; via dynamic retinoscopy) were measured every 6 minutes. Measurements were taken for 42 and 60 minutes for tropicamide and cyclopentolate respectively, as cyclopentolate takes longer to achieve maximal cycloplegia4. Pupil reactions, retinoscopy and subjective spherical refraction were finally re-checked followed by measuring intraocular pressure (IOP).    Results Cycloplegic effects From Figure 1, cyclopentolate showed greatest depth of cycloplegia. Cyclopentolate is known to be more effective than tropicamide5-6.  Tropicamide achieved maximal effects faster but recovery of accommodation immediately followed. Gettes7 found similar results. All three drops positively increase refractive power.

Table 1 shows cyclopentolate had the largest change objectively and subjectively. Previous research achieved similar findings, although differences in prescription changes were not statistically significant8. Figure 2 shows that time courses of cycloplegia and mydriasis differed; agreeing with a study asserting that pupil size poorly indicates cycloplegia4.

 Mydriatic effects From Figure 3, onset of mydriasis was quicker for tropicamide. Studies agree that tropicamide’s quick action and mydriatic effectiveness is superior to cyclopentolate, thus recommending it for clinical use1,4.  Mydriasis peaked at 18 and 36 minutes for tropicamide and cyclopentolate respectively.

Previous studies also achieved similar results1.  Iris colour did not affect mydriasis, agreeing with Richardson’s9 study. Other findings From Table 1, final responses of all eyes were the same: non-equal, non-reactive to light, round, no accommodation reflex.

Both subjects had elevated IOP after the test. This was an expected outcome following mydriasis10.  Direct ophthalmoscopy was more easily performed.  Conclusions   Cyclopentolate had more effective and longer-lasting cycloplegia.

Tropicamide overall produced greater magnitude of mydriasis and was quick in producing maximal effects. Both were effective in dilating the pupil for examination of peripheral retina, but increased IOP.