Scleral depression – do we need it?

Reassessment of Scleral Depression in the Clinical Setting

Shukla SY, Batra NN, Ittiara ST and Hariprasad SM. Ophthalmology 2016; 123: 2360-2361

This small prospective study of 100 eyes of 50 new patients presenting to a single vitreoretinal specialist examined the utility of scleral depression for detecting peripheral vitreoretinal pathology using indirect ophthalmoscopy. 50 eyes of 25 patients with symptoms of new (<3 months) floaters or flashes and 50 eyes of 25 asymptomatic patients were examined. Patients were dilated. Indirect ophthalmoscopic examination of the peripheral retina was first performed with a 28D lens and findings were recorded. The examination was then repeated using 360° scleral depression and any differences in findings between the two examinations were recorded. After each examination the patients were asked to rate the associated level of discomfort using a standard scale of 0 (no pain) – 10 pain (the worst pain the patient has ever experienced).

No difference in peripheral vitreoretinal pathology was detected by the use of scleral depression in any of the 100 eyes. Patients reported a higher level of pain associated with examination with depression when compared with examination without depression (mean, 4.68 with depression vs mean, 1.84 without depression; P < 0.001).

128 practicing vitreoretinal specialists were also surveyed using an anonymous online questionnaire regarding current opinion and clinical practice. 50 responses were received. Responses indicate that 22.2% of asymptomatic patients undergo scleral depression vs 87.9% of symptomatic patients. Respondents believed that 31.1% of peripheral retinal pathology was missed without scleral depression in patients with symptoms versus 12.4% being missed in patients without symptoms. These findings did not vary based on years of experience or practice setting (P > 0.05).

The authors note that scleral depression is useful in many clinical situations, such as when examining patients with far anterior retinal pathology. There are also situations when scleral depression may not be used in the initial detection of peripheral pathology but it is helpful in further characterizing it. The authors acknowledge the limitations of the small sample size and the single observer, and the use of the 28D lens, which provides a wider viewing angle, but less magnification, compared with a 20D lens. A sample size of n=400 would be required for a more powerful study if a 5% “miss rate” was accepted.

The authors conclude that, when a 28D lens is used, scleral depression did not provide any additional benefit to indirect peripheral retinal examination, but that scleral depression does significantly increase patient discomfort.

My comment:

This paper raises the interesting question of whether or not a current technique in practice is clinically necessary, and certainly illustrates the importance of reassessing our methods of practice as time passes. As clinicians we prefer to perform the most accurate, efficient, effective, and cost-effective techniques available to our patients during their examinations, and we like to maintain their comfort as we do this. There will always be situations where scleral indentation is necessary, but perhaps this is less often than previously thought.

For optometrists the key message is that you can do a very thorough examination without indentation. Indentation is a difficult skill to master; it took me several years, including practice during detachment surgery. I would argue that you would be better learning to do a 3-mirror fundal examination if you really want another way to pick up peripheral retinal disease.

Refractive error and glaucoma

The Association of Refractive Error with Glaucoma in a Multiethnic Population

Shen L, Melles RB, Metlapally R, et al. Ophthalmology 2016; 123: 92-101

This cross-sectional study aimed to evaluate the association between refractive error and the prevalence of glaucoma by race or ethnicity. Participants had refractive error, were aged 35 years or older, and had no history of cataract surgery, refractive surgery, or a corneal disorder. 34,040 individuals with glaucoma or ocular hypertension (OHT) were identified, and compared to 403,398 controls. Glaucoma cases were classified as primary angle closure glaucoma (PACG); primary open angle glaucoma (POAG), normal tension glaucoma (NTG), pigmentary glaucoma (PIG), and pseudoexfoliation glaucoma (PXF); or OHT. Spherical equivalent refractive error (SE) was coded as a continuous trait and also by categories. Logistic regression analyses were used to estimate the association between refractive error and the prevalence of glaucoma overall and in specific racial or ethnic groups. Main outcome measures of the association between glaucoma subtypes and refractive error were odds ratios (ORs) with 95% confidence intervals (CIs).

Results showed that in controls, the mean SE was -0.59 dioptres (D) (standard deviation, 2.62D). Each 1D reduction in SE was associated with a 22% decrease in the odds of PACG (OR, 0.78; 95% CI, 0.77-0.80) and with increases in the odds of open-angle glaucoma ranging from 1.23 (95% CI, 1.20-1.26) for PIG, to 1.07 (95% CI, 1.03-1.11) for PXF, and to 1.05 (95% CI, 1.04-1.06) for OHT. A stronger association was also observed between myopia and POAG among non-Hispanic whites (OR, 1.12; 95% CI, 1.11-1.13) and NTG among Asians (OR, 1.17; 95% CI, 1.15-1.20) and non-Hispanic whites (OR, 1.19; 95% CI, 1.15-1.22).

The authors conclude that myopia was associated with an increased prevalence of all forms of open-angle glaucoma and OHT. Any degree of myopia has a significant effect on glaucoma risk. Moderate racial differences in the association of myopia with the risk of POAG and NTG were also found. The strongest association of myopia was with PIG, NTG among Asians and non-Hispanic whites, and POAG.

My comment:

This study, like others, shows a potential relationship between refractive error and glaucoma. As the authors note, there are a number of hypotheses as to the reason for this, such as myopic nerve heads being structurally more susceptible to glaucomatous damage; thinner corneas could be linked to thinner scleras and weakened support for the optic nerve head in myopic eyes. The study suggests a role for genetic influences in glaucoma, some of which have been linked to anterior chamber depth and axial length (as have race, ethnicity, age and gender).

As the authors note, there are limitations to the study, not the least of which is the potential for over-diagnosis of glaucoma in myopic eyes given the structural differences in myopic eyes compared to emmetropic eyes, which may cause an overestimation of the relationship between myopia and glaucoma.

The take home message from this is that it is prudent to carefully evaluate the eyes and optic nerve heads of our ametropic patients for glaucoma and to consider baseline visual fields and OCT scans. It can be very difficult to diagnose glaucoma in high myopes.

Protecting against dry eye

Topical Fluorometholone Protects the Ocular Surface of Dry Eye Patients from Desiccating Stress: A Randomized Controlled Clinical Trial

Pinto-Fraga J, López-Miguel A, González-Garcia MJ, et al. Ophthalmology 2016; 123: 141-153

The purpose of this single-centre, double-masked, randomized, vehicle-controlled clinical trial was to assess the efficacy of topical 0.1% fluorometholone in dry eye disease (DED) patients for lessening the damage to the ocular surface when exposed to adverse environments. 41 patients with moderate to severe DED randomly received 1 drop 4 times daily of either topical 0.1% fluorometholone (FML group) or topical polyvinyl alcohol (PA group) for 22 days. Corneal and conjunctival staining, conjunctival hyperaemia, tear film break up time (TBUT), tear osmolarity, and the Symptom Assessment in Dry Eye (SANDE) questionnaire scores were determined at baseline. Variables were reassessed on day 21 before and after undergoing a 2-hour controlled adverse environment exposure and again on day 22. The main outcome measures were the percentage of patients showing an increase 1 point or more in corneal staining and a reduction of 2 points or more (0-10 scale) in SANDE score, after the controlled adverse environment exposure and 24 hours later.

Results showed greater improvements in corneal and conjunctival staining, hyperaemia, and TBUT in the FML group compared to the PA group (P<0.03). After the adverse exposure, the percentage of patients with a 1-grade or more increase in corneal staining was significantly higher in the PA group than the FML group (63.1% vs 23.8%; P=0.03). The FML group showed no significant changes in corneal staining (mean, 0.86; 95% confidence interval [CI], 0.47-1.25; vs mean, 1.05; 95% CI, 0.59-1.51, for visit 2 and 3, respectively), conjunctival staining (mean, 0.95; 95% CI, 0.54-1.37 vs mean, 1.19; 95% CI, 0.75-1.63), and hyperaemia (mean, 0.71; 95% CI, 0.41-1.02 vs 1.14; 95% CI, 0.71-1.58) after the exposure. However, for the PA group there was significant worsening (P < 0.009) in these variables (corneal staining: mean, 1.95; 95% CI, 1.57-2.33 vs mean, 2.58; 95% CI, 2.17-2.98; conjunctival staining: mean, 1.68; 95% CI, 1.29-2.08 vs mean, 2.47; 95% CI, 2.07-2.88; hyperaemia: mean, 1.95; 95% CI, 1.63-2.26 vs mean, 2.84; 95% CI, 2.62-3.07).

The authors concluded that three-week topical 0.1% fluorometholone therapy is effective in both reducing ocular surface signs in DED patients and in preventing exacerbation caused by exposure to desiccating stress.

My comment:

It is well known that corticosteroids are effective in treating DED but this small study is novel in that it demonstrates the protective effect of FML, enabling patients to cope with their normal daily activities that may otherwise exacerbate their DED symptoms. The use of steroid for the short three-week duration of the study and the minimal penetration of FML into ocular tissues means the likelihood of the therapy resulting in any complications is minimal.

Topical steroids are my first line therapy in patients with evaporative tear dysfunction. They might also be a very good idea for patients who are usually controlled on lubricants who are planning a long haul flight.

Atropine for childhood myopia progression

Use of Atropine for Prevention of Childhood Myopia Progression in Clinical Practice

Shih KC, Chung-Yan T, Ng AL, et al. Eye & Contact Lens 2016; 42: 16-23

This review article examines the literature surrounding the use of atropine in childhood myopia control with a focus on randomized controlled trials (RCTs) and meta-analyses. Observational studies with control groups were also reviewed to discuss the practical aspects of applying the findings to clinical practice. Future directions including possible combination therapy were examined.

Five RCTs and 2 meta-analyses were found. All the studies demonstrated beneficial effects of atropine in myopia control. The authors found that the available evidence is predominantly focused on Chinese populations, and there is currently a lack of guidance on timing of therapy initiation, duration of therapy, and treatment cessation. The authors suggest combining atropine with other forms of myopia control (such as orthokeratology) for future directions of study.

The authors concluded that atropine is a robust option for childhood myopia control, but that further evidence including RCTs in different populations as well as the upcoming 5-year atropine for the treatment of myopia 2 trial results will provide answers for wider acceptance of its use.

My comment:

It is still unknown exactly what mechanisms cause myopia to progress, and it appears to be multifactorial. The use of atropine, particularly in combination with other forms of treatment, in children with progressive axial myopia is now mainstream. Which is very reassuring given the first patient I treated was my son!

Is laser cataract surgery everything we hoped for?

A Comparative Cohort Study of Visual Outcomes in Femtosecond Laser-Assisted versus Phacoemulsification Cataract Surgery

Ewe SY, Abell RG, Oakley CL, et al. Ophthalmology 2016; 123: 178-182

This prospective, multicentre, comparative case series study aimed to evaluate the visual outcomes after femtosecond laser-assisted cataract surgery (LCS) with phacoemulsification cataract surgery (PCS). 1876 eyes of 1238 patients who underwent cataract surgery between January 2012 and June 2014 were included. Cases underwent clinico-socioeconomic selection. Patients for whom LCS was contraindicated received PCS; otherwise all patients were given the choice between PCS and LCS with an agreement to pay the difference in cost for LCS. LCS was performed on 988 eyes and PCS was performed on 888 eyes. Masked subjective refractions were performed 2 to 6 months postoperatively and main outcome measures were six-month postoperative visual and refractive outcomes.

Results showed that baseline best-corrected visual acuity (BCVA) was better in LCS compared with PCS (20/44.0 vs 20/51.5; P < 0.0003). Preoperative surgical refractive aim was significantly different between the two groups (LCS -0.28 vs PCS -0.23; P <0.0001). More patients who received LCS had toric lenses implanted compared with PCS (47.4% vs 34.8%; P < 0.0001). Postoperative BCVA was better after LCS compared with PCS (20/24.5 vs 20/26.4; P = 0.0003). More LCS cases achieved BCVA > 20/30 (LCS 89.7% vs PCS 84.2%; P = 0.0006) and 20/40 (LCS 96.6% vs PCS 93.9%; P = 0.0077). However, PCS cases gained more letters compared with LCS cases (13.5 vs 12.5 letters; P = 0.0088), which reflected the baseline BCVA differences. Mean absolute error was higher in LCS compared with PCS (0.41D vs 0.35D; P < 0.0011). More eyes in the PCS group were within 0.5D of the preoperative refractive aim compared to the LCS group (LCS 72.2% vs PCS 82.6%; P < 0.0001).

The authors concluded that femtosecond LCS did not demonstrate any clinically meaningful improvements in visual outcomes over conventional PCS.

My comment:

Femtosecond laser-assisted cataract surgery was predicted to greatly improve cataract surgery outcomes compared to conventional phacoemulsification cataract surgery, mostly through mechanisms such as reducing phacoemulsification energy required during surgery and minimizing the likelihood of mechanical trauma to the structures surrounding the natural lens. This would improve the surgical safety profile, reduce the post-operative complication rate and improve the visual outcomes for the patient. This study shows no clinically significant advantage in performing LCS over PCS, and once the cost of LCS equipment and surgery is taken into account it demonstrates that LCS is not cost-effective compared to PCS. Moreover, LCS is definitely inferior to PSC in dense cataracts.

At present LCS is a near-dead duck. Insurance companies were quick to realise it offered no great advantage and so did clinicians who had no financial interest. Who knows if there may be a better iteration in the future. The second mouse gets the cheese!