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AAO studies look at ocular, systemic conditions
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SAN DIEGO – Scientific sessions here at the American Academy of Optometry meeting addressed many of the ocular manifestations of systemic diseases. The studies explored topics such as ocular responses to asthma treatment, transdermal testosterone cream for dry eye, aberrations in keratoconus and Guillain-Barré disease presenting as Miller-Fisher syndrome.
Ocular response of asthma treatment
In a study presented here, Chika Kalu, OD, concluded that salbutamol, an asthma treatment, has a quick onset of action on phoria and intraocular pressure (IOP). The study also assessed any possible gender discrimination in these ocular effects.
Dr. Kalu, a private practitioner, studied a population of 100 patients of both genders, ages 16 and older. These patients underwent two stages of eye examinations: without asthmatic chemotherapy and after 15 minutes of asthmatic chemotherapy.
According to the abstract, Dr. Kalu found that the habitual phoria, distance and near, before and after chemotherapy showed a change toward exophoria at both far and near 15 minutes after salbutamol administration. A reversal was seen at 3 hours, but with a slight variation in about 80% of patients, which gave a complete reversal at 4 hours from onset of therapy. The IOP before and after 4 hours of salbutamol treatment showed an increase after 15 minutes and a full reversal to the original IOP after 3 hours. No change in visual acuity and no gender discrimination were seen.
Transdermal cream effective in dry eye treatment
A separate study found that transdermal testosterone is effective in treating dry eye by stimulating tear production and inhibiting tear evaporation.
“The majority of dry eye patients are women,” said Charles Connor Jr., PhD, OD, of Southern College of Optometry, Memphis. Dr. Connor presented his study results at an AAO-sponsored press conference here.
“Lacrimal changes occur during pregnancy, menopause and oral contraceptive use,” he said at the press conference. “Low testosterone levels are more prevalent in women with dry eye and correlate with symptomatic severity.”
Dr. Connor’s study analyzed the records of 23 female patients who used testosterone cream for at least 3 years under clinical observation. According to the study abstract, patients ranged in age from 40 to 69 years, with an average age of 55.5. The data were analyzed for statistical significance with regard to tear break-up time (TBUT), Schirmer’s test, IOP and contact lens wear time. A two-tailed t-test was used for this analysis.
The study found that baseline TBUT increased from 3.7 seconds to 6.3 seconds, a change that was significant at the p=0.01 level. Baseline Schirmer’s rose from 7.2 mm to 10.88 mm, which was also significant at p=0.01. Baseline IOP was 13.74 mm Hg and did not vary significantly from the 13.42 mm Hg measured at an office visit 3 years after beginning cream use. Baseline contact lens wear time was enhanced, going from 8 to 13 hours. This increased wear time began a month after starting cream use and has been sustained over the course of 3 years.
The study concluded that the transdermal delivery of testosterone appears to be useful in the treatment of dry eye. This efficacy is attributed to the fact that the cream increases tear production, slows tear evaporation and enhances contact lens wear time.
“The levels of androgens are reduced during menopause,” Dr. Connor concluded at the press conference. “I suggest using transdermal androgen.”
Residual aberrations in keratoconus
A study presented here found that wavefront aberration structures exist and have an effect on image-forming qualities of the eye, even after application of an over-refraction.
The study, authored by Jason Marsack, OD, of the University of Houston, and colleagues, looked at seven gas-permeable (GP) lens-wearing keratoconus patients. According to the study abstract, visual acuity was tested for two methods of optical correction: GPs and GP plus over-refraction (OR). Acuity was tested at two contrast levels, and Pelli-Robson (PRCS) was collected for both GP and GP + OR.
The letter contrast sensitivity function (LCSF) was formed by combining LogMAR visual acuity and PRCS.
Wavefront information was gathered during GP wear. Wavefront error in the presence of GP + OR was calculated. Letter acuity charts were convolved with the residual aberrations present in the keratoconus subjects for the GP + OR condition using VOLPro v. 6.83. This was done to examine the impact of residual aberration on image formation.
The results found that best-corrected high-contrast visual acuity was decreased compared to normal subjects of the same age and was consistent with previous reports of keratoconus visual acuity. LCSFA was also reduced. Through image stimulation, it was shown that optical quality resulting from the uncorrected lower- and higher-order aberration varies widely, suggesting that the spatial distribution of these aberrations is more significant than the RMS magnitude.
Guillain-Barré presenting as Miller-Fisher Syndrome
A case study presented here concluded that Miller-Fisher Syndrome (MFS) resulted in unilateral abundance nerve paresis, which occurred prior to the onset of symptoms of Guillain-Barré Syndrome (GBS).
The study, authored by Miriam Farag, OD, of the State University of New York (SUNY), looked at the case of a 26-year-old man presenting with a complaint of horizontal diplopia. This diplopia had been present for 6 weeks and was worse on left gaze.
The study abstract said that the subject had been diagnosed with GBS a month prior during a hospitalization for leg weakness, nausea and headaches. An MRI ruled out a space-occupying lesion, and a spinal tap revealed abnormally high protein on a cerebrospinal fluid analysis.
The patient was treated with intravenous immunoglobin, which provided some relief. The exam showed a best-corrected visual acuity of 20/20 in both eyes and normal pupils with no afferent pupillary defect, and the extraocular muscles revealed an abduction-deficient left eye. The patient’s diplopia resolved with a total of 6 base-out Fresnel prism.
The study concluded that optometrists should be aware of the ocular sequelae of MFS and consider it when making a differential diagnosis of extraocular nerve paresis.