A study from Scotland suggests, After patients remove their soft contact lenses, biometry can be performed sooner than currently advised. The study findings were published in the journal Eye.
Contact lens use alters the shape of the cornea, which affects the results of biometry, an investigation that is essential before cataract surgery. There is no clear evidence about when to remove contact lenses before performing biometry to provide accurate measurements.
In our group of soft contact lens wearers, change in corneal shape after contact lens use did not significantly affect biometry; therefore, (it) has no impact on IOL (intraocular lens) choice or refractive outcome, said the authors.
Lead author Dr. Colin Goudie and colleagues calculated the change in predicted lens power for emmetropia at several time points after soft contact lenses were removed.
Their prospective study involved 14 healthy soft contact lens wearers and 13 healthy non-contact lens wearers (matched controls). The participants ranged in age from 22 to 69 (mean, 33). Eight contact lens wearers used daily disposable lenses, two used two-week lenses and four used monthly lenses.
The authors conducted biometry immediately after participants removed their contact lenses. The test was then repeated after 2, 4 and 7 days of not wearing them. All measurements were made using the Zeiss IOLMaster.
Measurements from contact lens wearers and controls showed similar degrees of variation over time. The within-subject standard deviation in predicted IOL power for emmetropia in contact lens wearers was 0.20 diopters compared with 0.18 diopters for controls.
The researchers also surveyed 89 ophthalmologists in Scotland about how they handle biometry in their patients who wear contact lenses. Responses showed wide variation in the advice they gave to patients, ranging from removing the lenses immediately before biometry to taking them out more than 2 weeks before the test.
Dr. Cecilia S. Lee said, "The study points out that we currently do not have good data to support when to remove contact lenses prior to obtaining biometry. This likely explains why guidelines vary significantly among physicians."
"However,” she noted, "the study examined only 14 contact lens wearers who had minor corrections. More importantly, the majority of study participants were under the age of 40; thus, the study results may not apply to the majority of people who are considering cataract surgery."
"The results may reduce the number of preoperative visits patients need to make prior to cataract surgery," added Dr. Clements, who also was not involved in the study. "Currently, contact lens users are often asked to come back for another visit to repeat the measurements without using contact lenses. This may be an inefficient use of time and resources."
"The authors did not specify which type of soft contact lenses were being used. These variables may influence cornea shape and should be included in a follow-up study. Care should also be used to recognize that soft contact lenses behave very differently than rigid gas permeable contact lenses, and the study did not investigate this variable."