If you’ve been told you have nanophthalmos and also have cataracts, it’s natural to feel a little uneasy. Cataract surgery is one of the most successful and commonly performed procedures worldwide—but when your eyes are significantly smaller than average, the game changes. The stakes are higher, and the surgical plan needs to be precise, personalised, and prepared for potential complications.
In this article, we’re going to walk through exactly what nanophthalmos is, why cataract surgery in these eyes poses unique risks, and how modern surgical strategies are designed to avoid problems like uveal effusion and angle closure. Whether you’re a patient researching your options or a clinician refreshing your knowledge, this guide gives you a full picture of the current best practices.
What Is Nanophthalmos?
Nanophthalmos is a rare developmental condition where the eye is abnormally small but otherwise structurally normal. While the average axial length of a healthy adult eye is around 23-24 mm, nanophthalmic eyes usually have an axial length of less than 20 mm—and often as short as 16-18 mm.
This significant reduction in eye size doesn’t just affect vision. It also impacts everything from fluid dynamics to intraocular space, making even routine procedures—like cataract surgery—a lot more complicated.
Anatomical Features of Nanophthalmic Eyes
The key anatomical features of nanophthalmos include:
- Thickened sclera: The sclera (white outer layer of the eye) is often abnormally thick, which restricts fluid outflow and can predispose the eye to choroidal effusion.
- Narrow anterior chamber: The front part of the eye has much less room to work with, increasing the risk of angle closure glaucoma and intraoperative crowding.
- High lens-to-eye volume ratio: In these eyes, the lens takes up proportionally more space than it should, leading to additional pressure on surrounding structures.
All of these factors combine to create a surgical environment where small margins can have large consequences.
The Main Risks in Cataract Surgery for Nanophthalmic Eyes
Cataract surgery in a nanophthalmic eye requires more than technical skill—it demands careful planning to prevent serious complications. Here are the primary concerns surgeons aim to avoid:
- Uveal Effusion
This is one of the most feared complications in nanophthalmic cataract surgery. It occurs when fluid builds up in the uveal layer (a part of the eye that includes the iris, ciliary body and choroid), often due to poor outflow or surgical trauma.
Because of the thickened sclera and congested venous drainage in nanophthalmic eyes, the risk of uveal effusion is significantly higher. If it progresses, it can lead to choroidal detachment and even vision-threatening hypotony (low intraocular pressure). - Angle Closure Glaucoma
The narrow anterior chamber in nanophthalmic eyes predisposes patients to angle closure, where the drainage angle becomes blocked, and intraocular pressure rises dangerously. While removing the cataractous lens often helps reduce this risk, the surgical manipulation itself can trigger an acute angle closure event—especially if inflammation and anterior chamber shallowing occur postoperatively. - Scleral Buckling and Compression
Because nanophthalmic eyes are so small, even the positioning of surgical instruments or speculums can exert significant pressure on the globe. This can compromise blood flow or lead to inadvertent trauma during what would otherwise be a straightforward manoeuvre in a normal-sized eye.
Preoperative Planning: Where Success Begins
For nanophthalmic cataract cases, the pre-op phase isn’t just routine—it’s critical. A meticulous work-up can significantly reduce intraoperative surprises and postoperative complications.
- Biometric Measurements
Axial length, anterior chamber depth, lens thickness, and white-to-white measurements must be carefully recorded. These metrics help determine IOL power calculations and surgical feasibility.
High-resolution imaging such as anterior segment OCT or ultrasound biomicroscopy (UBM) can offer even deeper insight into anterior chamber dynamics and angle status. - Systemic and Genetic Associations
Nanophthalmos can sometimes occur as part of a genetic syndrome (e.g., nanophthalmos-retinitis pigmentosa complex). Knowing a patient’s full medical and ocular history helps tailor the risk management strategy, especially if there’s an associated systemic vascular fragility or co-existing retinopathies. - Surgical Team and Environment
Cases like these should only be performed by experienced anterior segment surgeons, ideally in centres with access to advanced imaging, surgical back-up (including vitreoretinal support), and a range of IOLs suitable for short eyes.
Intraoperative Strategies: Adjusting the Playbook
So how do surgeons minimise risk when performing cataract surgery in nanophthalmic eyes? Here’s a breakdown of the key intraoperative strategies that can make all the difference.
Controlled Wound Construction
Surgeons aim for a small, self-sealing incision to maintain chamber stability. An overly large wound in a nanophthalmic eye can increase the risk of hypotony and make anterior chamber maintenance difficult.
Use of High-Viscosity Ophthalmic Viscosurgical Devices (OVDs)
Maintaining a stable anterior chamber is paramount. High-viscosity OVDs help prevent collapse of intraocular structures and reduce mechanical trauma.
They can also tamponade the posterior chamber and prevent forward movement of the iris-lens diaphragm, particularly useful in very shallow eyes.
Slow, Low-Flow Phacoemulsification
Reducing fluid turbulence is key. Lowering phaco power and aspiration flow rate helps avoid intraoperative pressure spikes and reduces the risk of uveal effusion and endothelial cell loss.
Consideration of Posterior Sclerostomies
In some cases, prophylactic posterior sclerostomies (small drainage incisions made in the sclera) are created to allow choroidal fluid to escape, reducing the risk of effusion. While not routine, this method can be life-saving in select high-risk eyes.
IOL Selection and Postoperative Concerns
Choosing the Right IOL
IOL power calculation in nanophthalmic eyes is notoriously challenging. Due to their short axial length, many patients require very high-power IOLs (e.g., +30D or higher), and standard biometric formulae often underperform in these ranges.
Surgeons typically use newer-generation formulae like Barrett Universal II or Hill-RBF, sometimes cross-checked with artificial intelligence-assisted calculators for improved accuracy.
Risk of Pigment Dispersion and Iris Chafing
The limited space in these eyes means the IOL must be chosen and placed carefully. Oversized lenses or imperfect centration can lead to iris chafing, pigment dispersion, and inflammation.
Longer Healing Time and Higher Inflammation
Postoperative inflammation tends to be more intense and prolonged in nanophthalmic eyes. This is partly due to increased surgical manipulation and partly due to the eye’s reduced fluid handling capacity.
Surgeons often opt for longer courses of topical steroids and more frequent monitoring, particularly in the first few weeks after surgery.
When to Combine Cataract Surgery with Other Procedures
In some cases, cataract surgery alone may not be enough—or safe—to perform in isolation. Combined approaches can offer safer, more stable outcomes:
- Combined phaco-trabeculectomy may be recommended if glaucoma control is poor or angle closure risk is high.
- Vitrectomy support may be necessary in eyes where intraoperative instability or posterior pressure is expected.
- Laser iridotomy (either pre-op or post-op) is sometimes used to prevent angle closure in borderline cases.
The goal in each of these scenarios is to tailor the surgical plan not only to the patient’s refractive goals but also to their anatomical and fluid dynamic constraints.
Anaesthetic Considerations and Intraocular Pressure Management
Anaesthesia planning in nanophthalmic eyes isn’t just about keeping you comfortable—it’s also about maintaining stable pressure inside the eye throughout the procedure. Because of the eye’s small size and reduced fluid outflow, even minor fluctuations in pressure can lead to serious complications, such as choroidal effusion or optic nerve damage.
Choosing the Right Anaesthesia
Most cataract surgeries in the general population are safely performed under topical or sub-Tenon’s anaesthesia. However, in nanophthalmic eyes, a sub-Tenon’s block is often preferred over topical drops alone. Why? It provides more consistent globe akinesia (lack of movement), reducing the risk of trauma during surgery, while also helping to reduce intraocular pressure preoperatively.
General anaesthesia may be considered in highly anxious patients or those unable to lie still, but it must be used with caution. Anaesthetic agents that increase venous pressure can raise the risk of uveal effusion, especially in the presence of a thickened sclera and restricted venous drainage.
Preventing Intraoperative Pressure Spikes
In nanophthalmic eyes, even standard amounts of irrigation fluid can overwhelm the eye’s capacity to regulate internal pressure. That’s why modern phacoemulsification systems are set to use low flow rates, low bottle height, and minimal vacuum. Every effort is made to avoid sudden pressure surges that could cause forward movement of the lens-iris diaphragm or rupture delicate vascular structures in the choroid.
Some surgeons pre-treat with oral or intravenous carbonic anhydrase inhibitors to lower IOP ahead of the procedure. Others use intravenous mannitol when needed to temporarily dehydrate the vitreous and deepen the anterior chamber.
Long-Term Outcomes and Follow-Up
While the surgical risk is undeniably higher in nanophthalmic eyes, with the right protocols and precautions, many patients go on to have excellent outcomes. Visual acuity can improve significantly, especially if no retinal pathology is present, and the cataract was the primary source of visual decline.
That said, long-term follow-up is essential. These patients remain at risk for chronic inflammation, elevated intraocular pressure, and even secondary angle closure if the anterior segment crowding persists.
In some cases, further interventions may be needed months or even years down the line—but with vigilant follow-up, these can usually be managed effectively.
Frequently Asked Questions About Cataract Surgery in Nanophthalmic Eyes
- What makes cataract surgery riskier in nanophthalmic eyes?
The main issue lies in the eye’s size. Nanophthalmic eyes are significantly smaller than average, with shorter axial lengths, thicker sclerae, and shallow anterior chambers. This combination makes them more prone to complications like uveal effusion, intraocular pressure spikes, and angle closure glaucoma during or after surgery. Even routine steps in standard cataract surgery, such as wound construction or lens implantation, need to be adapted to avoid causing damage. - Can cataract surgery still be safely performed in these eyes?
Yes—when approached correctly. Cataract surgery in nanophthalmic eyes can be done safely, but it requires an experienced surgeon, detailed preoperative planning, and sometimes additional precautions like posterior sclerostomies or customised intraocular lenses. The key is individualised care. When the risks are properly managed, outcomes can be just as good as in larger eyes. - Will I need a special type of lens implant?
In most cases, yes. Nanophthalmic eyes typically need high-power IOLs, sometimes over +30 dioptres. Because these eyes are so short, standard IOL calculation formulae may not be accurate enough, so surgeons use specialised methods or AI-based tools to get a more precise result. The lens itself may also need to be smaller or shaped differently to avoid complications like iris chafing or crowding. - Is it true that fluid can build up behind the eye after surgery?
This refers to uveal effusion, one of the biggest concerns in these cases. It happens when fluid collects under the uvea (the eye’s middle layer), leading to potential choroidal detachment and vision loss. Because of the thickened sclera and poor drainage in nanophthalmic eyes, the risk is higher. But careful fluid management, use of high-viscosity OVDs, and in some cases surgical drainage (sclerostomy) can help prevent it. - Will I be at greater risk of glaucoma after surgery?
Possibly, especially if you already have narrow angles or a history of angle closure. The surgery itself can help by removing the bulky natural lens, which often deepens the anterior chamber. But post-operative inflammation or IOL crowding can still lead to angle issues. This is why long-term monitoring and sometimes pre-emptive treatments like laser iridotomy are used to reduce the risk. - Does cataract surgery take longer in nanophthalmic eyes?
It can, yes. The surgical steps are more delicate and often need to be performed more slowly and with lower fluid dynamics to avoid pressure spikes. Positioning instruments without touching the corneal endothelium or iris can also be more difficult in the tight anterior chamber. These eyes require a meticulous and unhurried approach to ensure safety. - How soon will I see results after the surgery?
Vision may take slightly longer to stabilise compared to standard cases. Inflammation tends to be more prolonged, and post-op medications might be needed for longer. That said, many patients with nanophthalmos experience a dramatic improvement in vision within a few weeks, especially if no other eye diseases are present. Full recovery can take several months. - Will I need more follow-up appointments than usual?
Almost certainly. Your surgeon will want to monitor intraocular pressure, inflammation, anterior chamber depth, and IOL positioning very closely in the first few weeks. If any complications arise, early detection makes a big difference. These appointments are crucial to ensure that your eye is healing as expected and to catch any issues before they become more serious. - Should I choose a specialist centre for my surgery?
Absolutely. Nanophthalmic eyes are considered high-risk for cataract surgery and should only be operated on by surgeons with experience in managing complex or small eyes. Specialist centres like the London Cataract Centre have access to the right imaging tools, lens options, and surgical strategies to ensure your procedure is as safe and successful as possible.
Final Thoughts: Tailored Surgery for Tiny Eyes
Cataract surgery in nanophthalmic eyes is not just a scaled-down version of standard cataract surgery—it’s a field in itself. These eyes require a different level of planning, equipment, and surgical finesse. Every step, from preoperative imaging to IOL selection to fluid management, needs to be adapted to fit the unique anatomy and physiology of a very small eye.
If you or a loved one has been diagnosed with nanophthalmos and cataracts, don’t panic—but do make sure you’re in experienced hands. At the London Cataract Centre, surgeries like these are carried out by cataract surgeons familiar with complex eye anatomy and backed by full multidisciplinary support.
It’s not about rushing—it’s about precision. Because when done right, even the smallest eyes can enjoy the clearest outcomes.
References
- Rajendrababu, S., Babu, N., Sinha, S., et al., 2017. A randomised controlled trial comparing outcomes of cataract surgery in nanophthalmos with and without prophylactic sclerostomy. American Journal of Ophthalmology, 183, pp.125–133.
- Agarwal, S., Balasubramanian, D., Maheshwari, D., et al., 2021. Clinical spectrum and treatment outcomes of patients with nanophthalmos. Eye (London), 35, pp.1234–1242. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8027642/ 
- Dahal, M., Cosmic, A., Bhattarai, S., et al., 2022. Cataract surgery in short eyes, including nanophthalmos: outcomes and formula accuracy. BMC Ophthalmology, 22, p.356. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8636843/ 
- Wang, P. and Liu, Q., 2022. Medical therapy and scleral windows for uveal effusion syndrome in nanophthalmos. Ophthalmology and Therapy, 11(2), pp.453–461. Available at: https://link.springer.com/article/10.1007/s40123-022-00601-z 
- Tan, G., Özdek, Ş. and Yeter, D.Y., 2022. Treatment of nanophthalmos‑related uveal effusion with two‑ vs four‑quadrant partial‑thickness sclerectomy and sclerotomy surgery. Turkish Journal of Ophthalmology, 52(1), pp.37–44. Available at: https://doi.org/10.4274/tjo.galenos.2021.33723