A Review of Scleral Depression and Scleral Indentation

Technique

Maximum pupillary dilation is important to give the best peripheral view, and this can usually be accomplished with of phenylephrine 2.5% and tropicamide 1% for 20 to 30 minutes. At times, multiple administrations of phenylephrine 10% or cyclopentolate 2% can be beneficial.

The ora serrata and equator are located 7 mm and 14 mm posterior from the limbus, respectively, and the depressor is placed between these regions.³ Standing directly 180° away from the region of examination is helpful as the depressor, condensing lens, and indirect ophthalmoscope all must be in line for visualization.

Sixty percent of retinal specialists use topical anesthesia prior to scleral depression.⁴ Scleral depression may be performed either through the eyelid or directly on the bulbar conjunctiva.³ If depression is performed on the conjunctiva, topical anesthesia should be used. When we use a cotton-tipped applicator, wetting it with artificial tears or anesthetic drops improves comfort. Placing the depressor directly on the bulbar conjunctiva is beneficial in the directly temporal and especially the nasal region due to eyelid anatomy.

Types of Depressors

Many different scleral depressors exist: Josephberg-Besser, thimble-shaped Schepens, Keeler, and Flynn (for pediatric patients) to name a few. Perhaps the two most frequently used are the double-ended Schocket scleral depressor and a cotton-tipped applicator. A survey by Shukla et al. found that 60% of vitreoretinal specialists use a metal scleral depressor, whereas 40% use a cotton-tipped applicator based on a prior survey.⁴

In our experience, there are a few advantages to a Schocket scleral depressor, or other metal depressors, over a cotton-tipped applicator. Metal depressors allow subretinal fluid around tears or holes to be more easily visualized due to the instrument tip’s smaller radius. Also, the Schocket depressor is easier to use on patients with deep orbits and for depressing on the sclera in the medial and lateral canthal regions.

Indications

Scleral depression should be considered when there are risk factors such as the following:

• Lattice degeneration, retinal holes, and tears^2,3
• Positive Shaffer’s sign (pigmented cells in the anterior vitreous) or symptoms of a retinal tear such as flashes and floaters^2,3
• Vitreoretinal tufts,¹ schisis, subtle sea fans in sickle cell retinopathy⁴
• Vitreous hemorrhage³
• Axial myopia^2,3
• Recent blunt trauma (to examine for retinal dialysis)^2,3,4
• Retinopathy of prematurity screening^5,6

Interestingly, Shukla et al. conducted a prospective study evaluating 100 eyes. No difference in peripheral vitreoretinal pathology, or even additional information about the pathology, was detected with scleral depression in any of the eyes compared to a thorough 28 diopter (D) indirect examination.⁴

Contraindications

In the postoperative period, there is concern that corneal or scleral wounds may open or leak with scleral depression.¹ We usually wait 1 month after surgery before considering scleral depression. Caution should be used in patients with scleral³ or corneal thinning,⁷ as there is a report of scleral depression causing a ruptured globe in a patient with pellucid marginal degeneration.⁷ It should be noted that with scleral depression, the mean elevation in intraocular pressure is 65.3 mm Hg and 47.8 mm Hg in the superior temporal and inferior nasal quadrants, respectively.¹

Some Contraindications to Consider:

• Immediate postoperative period^1,3,8 (cataract surgery, trabeculectomy, or glaucoma filtering device,^2,9 etc.)
• Suspected intraocular foreign body or penetrating trauma^1,2,3,8
• Hyphema^2,3,8
• Zonular instability⁸
• Advanced glaucoma^3,8
• Severe scleral thinning (eg, scleromalacia perforans)³
• Corneal thinning (eg, pellucid marginal degeneration)⁷

Side Effects / Complications:

• Ruptured globe, especially with corneal⁷ or scleral³ thinning
• Dislocated lens⁸
• Transient visual disturbances³
• Intraretinal hemorrhages during retinopathy of prematurity screening (self-resolving)^5,6
• Potential changes in electroretinogram (ERG)¹
• Discomfort⁴
• Elevated intraocular pressure¹

Discomfort

Shukla et al. identified a higher level of discomfort (0–10 scale) associated with scleral depression at 4.68 compared to 1.84 without depression.³

The authors of this review conducted a randomized prospective study (unpublished data, clinical-trials.gov NCT04115917) on 169 eyes (87 participants) to compare levels of discomfort during scleral depression. A Schocket scleral depressor was used on one eye and a cotton-tipped applicator on the contralateral eye. A visual analog scale (VAS) from 0 (no pain) to 10 (worst pain) assessed participant discomfort.

The mean VAS score was 2.02 ± 0.22 standard deviation (SD) for the Schocket scleral depressor and 1.91 ± 0.21 SD for the cotton-tipped applicator (P = .31). Linear regression analysis revealed a weak negative correlation between discomfort and HbA1c levels (R² = 0.094; P = .014). No significant difference in VAS score was found among patients with varying ages, spherical equivalents, or retinal pathology (retinal tears/holes).

We concluded that both the Schocket scleral depressor and cotton-tipped applicator were found to be associated with low levels of discomfort and no significant difference in discomfort was found between the two. Patients with elevated levels of HbA1c appeared to experience lower levels of discomfort, which may be explained by a diabetic neuropathy of the sclera.

Excess discomfort may arise from a depressor being used on the upper eyelid tarsal plate. When depressing superiorly, place the depressor superior to the tarsal plate or on the bulbar conjunctiva. Rolling the scleral depressor directly over an extraocular muscle insertion site can be uncomfortable as well.^2,3

Clinicians learning the technique should also be cautious to only use gentle pressure. Not seeing the indentation from scleral depression rarely is due to insufficient pressure, rather from inappropriate positioning.

Lens and Alternative Methods to Scleral Depression

Sixty-two percent of retinal specialists report using a 20 D lens, 22% use a 28 D lens, and 16% use another lens.⁴ A 28 D lens offers less magnification but a wider viewing angle with scleral depression.²

Castanos et al. recommend three-mirror gonioscopy as an alternative to scleral depression, especially in eyes with zonular dehiscence.⁸ Tran et al. suggested that patients with clear media and widely dilated pupils may not require scleral depression at all, and other examination methods include contact or non-contact lenses at the slit lamp, B-scan echography, and widefield fundus photography.⁹

Considerations with COVID-19

In order to help prevent the spread of infectious diseases it is important to properly clean the scleral depressor between patients, especially if depression is performed on the globe itself since COVID-19 has been detected in tears.¹⁰ One additional benefit to using a cotton-tipped applicator is that they are disposable.

Conclusions

Scleral depression is an indispensable tool for evaluating and further characterizing peripheral retinal pathology in select patients. The decision to use scleral depression should be individualized, considering patient risk factors, complications, discomfort, and alternatives for examination.